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2010-2011 Team 02 Project Proposal and Feasibility
Study
Brian DeKock
Brenton Eelkema
Jacqueline Kirkman
Nathan Meyer
Brandon Vonk
December 6, 2010
Calvin College; Grand Rapids, MI
Engineering 339: Senior Design Engineering Capstone
©2010 Calvin College and HydroTower: Gardening Solutions
Executive Summary
Food production, distribution and consumption have become a growing concern due to
population growth in developing countries and the movement of populations into more urban settings.
One way to mitigate the increase in costs for food production and decrease the amount of energy
expended on food production is to grow food locally. Local foods provide a more sustainable means for
consumption of produce without requiring consumers to decrease the amount of fresh produce purchased.
Sustainability is increased because the distance produce is shipped before reaching market is reduced,
thus resulting in the use of smaller quantities of fossil fuels. The HydroTower design was developed as a
means to decrease the cost of food production, decrease the number of miles necessary for producing
shipments and increase the number of people with access to fresh produce. HydroTower will accomplish
such a reduction in shipping distances and cost of food production by bringing the ability for consumers
to grow their own produce in optimized growing conditions. There will no longer be a need to have a
garden plot or ideal weather for produce to grow. HydroTower will allow consumers to grow their own
food without the need for a “green thumb,” plots of land or precious time to grow food. While
HydroTower provides numerous solutions, the overarching objective is succinctly stated as: “feed people,
more efficiently, through hydroponics.”
Initial project designs and analysis show that HydroTower is a feasible project that combines
interdisciplinary designs including biological, chemical, electrical and mechanical principles. This design
feasibility has been confirmed through hydroponic experiments along with engineering calculations and
analysis in LED Light System designs and structural designs. In addition, the HydroTower is a viable
project both economically and technically. Economically the HydroTower will produce the highest
quality food at a cost lower than that of comparable food items. Technically the HydroTower will provide
an innovative nutrient control system that combines both mechanical and electrical engineering
knowledge. Furthermore, market research has shown that HydroTower has economic competitors who do
not provide what the HydroTower will offer. A competitive price for the HydroTower of less than $200
will ensure that the HydroTower is a strong contender in the household hydroponic market.
i
Table of Contents
Table of Acronyms...........................................................................................................................iv
List of Tables ....................................................................................................................................v
List of Figures ..................................................................................................................................vi
1. Introduction ..............................................................................................................................1
1.1. Project ...............................................................................................................................1
1.2. Team ..................................................................................................................................2
2. Design Specifications .................................................................................................................3
2.1. Requirements .....................................................................................................................3
2.1.1. Functional Requirements ............................................................................................3
2.1.2. Performance Requirements ........................................................................................5
2.1.3. Interface Requirements ..................................................................................................6
2.1.4. Environmental Requirements .....................................................................................6
2.1.5. Underwriters Laboratories Requirements ..................................................................7
2.1.6. User Requirements .....................................................................................................8
2.1.7. Manufacturing Requirements .....................................................................................8
2.1.8. Delivery Requirements ...............................................................................................9
3. Hydroponics ........................................................................................................................10
3.1. Hydroponic Basics ...........................................................................................................10
3.2. Types of hydroponic systems ........................................................................................11
3.2.1. Flood and drain (Ebb and Flow) ...............................................................................12
3.2.2. Continuous drip ........................................................................................................12
3.2.3. Float .........................................................................................................................13
3.2.4. Aeroponics ................................................................................................................14
3.2.5. Deep Water Culture..................................................................................................15
3.3. HydroTower Experiments ............................................................................................15
3.4. Proposed Design...............................................................................................................20
3.4.1. Chosen Prototype Design ..........................................................................................20
4. Electrical and Computer System .............................................................................................22
4.1.1. User Interface (UI)....................................................................................................22
ii
4.1.2. Data Management and Processing ............................................................................24
4.1.4. Control Systems ........................................................................................................27
4.1.5. Lighting System ........................................................................................................30
4.1.6. Power Systems ..........................................................................................................31
5. Mechanical Systems.................................................................................................................32
5.1. Requirements ...................................................................................................................32
5.2. Size...................................................................................................................................32
5.3. Nutrient System ...............................................................................................................34
5.4. Psychrometrics.................................................................................................................38
5.4.1. Humidification ..........................................................................................................38
5.4.2. Temperature .............................................................................................................41
6. Frame Structure ......................................................................................................................42
6.1. Structure and Size............................................................................................................42
6.2. Safety/ Stability and Durability ........................................................................................43
6.3 Mobility ...........................................................................................................................43
6.4 Ease of Build ....................................................................................................................43
6.5 Aesthetics .........................................................................................................................46
7. Business Analysis.....................................................................................................................47
7.1. Market Research..............................................................................................................47
7.1.1. Customer ..................................................................................................................47
7.1.2. Overview of Market ..................................................................................................47
7.1.3. Market Survey Results..............................................................................................48
7.2. Strategies to Success .....................................................................................................49
7.2.1. Entrepreneur’s vision of the company ......................................................................50
7.2.2. Design Norms............................................................................................................50
7.3. Industry Profile and Overview .........................................................................................50
7.3.1. Industry Profile ........................................................................................................50
7.3.2. Major Customer Groups...........................................................................................51
7.3.3. Regulatory Restrictions ............................................................................................51
7.3.4. Growth Rate and Outlook.........................................................................................51
7.3.5. Key Success Factors ..................................................................................................52
7.4. Business Strategy .............................................................................................................52
iii
7.4.1. Desired Image and Position in Market ......................................................................52
7.4.2. Company Goals and Objectives: Operational ...........................................................52
7.4.3. Company Goals and Objectives: Financial ...............................................................52
7.4.4. SWOT Analysis ........................................................................................................53
7.5. Competitor Analysis.........................................................................................................53
7.5.1. Established Competitors ...............................................................................................53
7.5.2. Potential Competitors ...................................................................................................55
8. Business Financials ..................................................................................................................57
8.1. Prototype Costs ................................................................................................................57
8.2. Variable and Fixed Costs .................................................................................................57
8.3. Cash Flow Analysis ..........................................................................................................58
9. Management ............................................................................................................................60
9.1. Project .............................................................................................................................60
9.2. Work Breakdown Structure and Scheduling....................................................................61
9.3. Budget..............................................................................................................................63
9.4. Website ............................................................................................................................63
9.5. Meetings and Status updates ............................................................................................63
9.6. Resources .........................................................................................................................63
10. Design Competitions ........................................................................................................65
10.1. 2011 ASME Innovation Showcase ................................................................................65
10.2. IEEE Engineering in Medicine and Biology Society Student Design Competition ........65
10.3. 2011 IEEE Presidents’ Change the World Competition................................................65
11. Conclusions..........................................................................................................................66
Appendix A: Work Breakdown Structure/ Milestones ....................................................................67
Appendix B: Cash Flow Analysis ....................................................................................................70
Appendix C: Lighting System Design Calculations (Red LEDs) .....................................................72
Appendix D: Lighting System Design Calculations (Blue LEDs).....................................................76
Appendix E:Psychrometric Calculations for Air Flow System ........................................................80
Works Cited....................................................................................................................................84
Bibliography ...................................................................................................................................88
iv
Table of Acronyms
CPU Central Processing Unit
EC Electro Conductivity
HydroTower ©HydroTower: Gardening Solutions
LCD Liquid Crystal Display
LED Light Emitting Diode
MS Microsoft
PCB Printed Circuit Board
PPFS Project Proposal and Feasibility Study
SWOT Strengths, Weaknesses, Opportunities, Threats
UI User Interface
WBS Work Breakdown Structure
v
List of Tables
Table 1: List of Engineering 339/340 Professors and Concentrations......................................................1
Table 2: October hydroponic experiments with soybeans and radishes................................................16
Table 3: October hydroponic Experiment #2.......................................................................................17
Table 4: Different options for touch-screen devices.............................................................................23
Table 5: Maximum loads on the power supply....................................................................................31
Table 6: Hoagland's Solution .............................................................................................................35
Table 7: Electrodes and interferences ................................................................................................36
Table 8: Psychrometric calculations variable list .................................................................................40
Table 9: Summary of wick humidifier design for fan usage .................................................................41
Table 10: Full assembly of second HydroTower prototype...................................................................45
Table 11: Census Bureau 2008 population..........................................................................................47
Table 12: Prototype Costs .................................................................................................................57
Table 13: Variable and fixed costs estimations for HydroTower ...........................................................58
Table 14: Tech-Lead positions for the HydroTower Team ....................................................................60
vi
List of Figures
Figure 1.2: HydroTower: Gardening Solutions (Engr 339/340 Team 2) ..................................................2
Figure 2: Diagram of hydroponics .....................................................................................................10
Figure 3: Benefits of Hydroponics .....................................................................................................11
Figure 4: Diagram of flood and drain (Ebb and flow) system ...............................................................12
Figure 5: Top Fed Continuous Drip System ........................................................................................13
Figure 6: Float method of hydroponics ...............................................................................................14
Figure 7: Aeroponic method of hydroponics .......................................................................................14
Figure 8: Hydroponic grwoth over 3 weeks with 2 soybean plants and 4 radish plants ...........................17
Figure 9: Hydroponic growth over 2 weeks with 3 soybean plants and 3 radishes..................................18
Figure 10: Soybean plants at week 2 ..................................................................................................19
Figure 11: Radish plants at week 2.....................................................................................................19
Figure 12: soybean plant with signs of iron deficiency ........................................................................19
Figure 13: Radish plant with signs of iron deficiency ..........................................................................20
Figure 14: Initial Setup .....................................................................................................................25
Figure 15: Water Supervisor Program ................................................................................................26
Figure 16: Main UI ...........................................................................................................................26
Figure 17: Calculation for target amount of LEDs ...............................................................................27
Figure 18: Simulink Air Temperature Control System .........................................................................28
Figure 19: Schematic of control system for nutrient control .................................................................29
Figure 20: Plant light frequency response ...........................................................................................30
Figure 21: First HydroTower prototype design (circular) .....................................................................33
Figure 22: Second HydroTower prototype (rectangular) ......................................................................34
Figure 23: Survey results on likely aspects for purchasing HydroTower ...............................................49
Figure 24: Survey results on customers growing their own food...........................................................49
Figure 25: RotoGro 240 Rotating Garden ...........................................................................................53
Figure 26: Desktop Hydroponic system ..............................................................................................54
Figure 27AeroGarden Pro 200 ...........................................................................................................54
Figure 28: Biosphere Home Farming .................................................................................................55
Figure 29: Kitchen Nano Garden .......................................................................................................56
Figure 31: WBS Spring Semester.......................................................................................................62
Figure 30: WBS Fall Semester...........................................................................................................62
1
1. Introduction
The introduction provides a brief overview of the project and team. The project fulfills
requirements of the 2010-2011 Calvin College Engineering Senior Design class and specifically, the
project selected has been titled HydroTower: Gardening Solutions.
The Calvin College engineering capstone is designed to provide a “real world” experience to
engineering students in their final year of undergraduate education. Students within senior design
choose both their own teams and projects under the direction of five engineering professors, one in
each of the four concentrations (Electrical/Computer, Chemical, Civil/Environmental and
Mechanical). Table 1.1 shows the senior design professors and their corresponding concentrations.
Engineering 339 in the fall and then the subsequent Engineering 340 in the spring combine project
implementation with class lecture and discussion to prepare students to enter the workforce
following graduation.
Table 1: List of Engineering 339/340 Professors and Concentrations
Ned Nielsen Mechanical
J. Aubrey Sykes Chemical
Steve VanderLeest Electrical/Computer
Wayne Wentzheimer Chemical
David Wunder Civil/Environmental
1.1. Project
In 2008, for the first time in history, more than half of the global population lived in
cities. Furthermore, projections for urban growth and development by research completed by
Dickson Despommier (author of The Vertical Farm: Feeding the World in the 21st Century)
concluded that “by the year 2050, nearly 80% of the earth's population will reside in urban
centers”. 1 Such a situation presents a unique opportunity to feed populations in cities which
subsequently living long distances from agricultural areas. Furthermore, the idea of hydroponic
vertical farming allows those persons without access to outdoor garden areas to produce their own
food. The specific product HydroTower was developed from Disckson Despommier’s
commercial vertical farming ideas, but adapted for residential hydroponic growing use. Overall,
HydroTower will reduce the amount of fossil fuels used in food production, decrease the distance
produce is shipped to reach market and eliminate the use of pesticides and herbicides.
1 Despommier, Dickson. "The Problem." The Vertical Farm. Ed. Dr. Dickson Despommier Ph. D. Environmental Health Science
of Columbia University, n.d. Web. http://www.verticalfarm.com/
2
1.2. Team
The HydroTower Team is comprised of a mixture between electrical and mechanical
engineering concentrations and is also an interdisciplinary project combining electrical,
mechanical, chemical and biological knowledge and design. The learning experience for the
individual team members is benefitted by such diversity.
Figure 1.2: HydroTower: Gardening Solutions (Engr 339/340 Team 2). Back Row (Left to Right): Jacqueline Kirkman
(ME), Brandon Vonk (EE). Front Row (Left to Right): Brian DeKock (ME), Nathan Meyer (EE), Brenton Eelkema (EE)
Electrical concentration members include Brenton Eelkema, Nathan Meyer and Brandon
Vonk while the mechanical concentration members include Brian DeKock and Jacqueline
Kirkman. Brenton Eelkema will graduate with a BSE Electrical Engineering concentration and is
from Irvine, California. Nathan Meyer grew up in Elmhurst, Illinois and is studying Electrical and
Computer Engineering and is getting a minor in Physicsand he currently has an internship with
DornerWorks in Grand Rapids. Brandon Vonk is originally from Hamilton, Ontario, Canada, is
an Electrical Engineering Major with a Physics Minor at Calvin College. Brandon has also had an
internship with Johnson Controls Inc. Brian DeKock grew up in Salt Lake City, Utah and is
pursuing a BS in Mechanical Engineering. Brian currently has an internship with Temper in
Rockford and is also seeking a full time position after graduation. Jacqueline Kirkman will
graduate in May 2011 with a BSE Mechanical Engineering concentration and a minor in
International Relations. Jacqueline has interned at Westinghouse Electric Co in Pittsburgh, PA.
3
2. Design Specifications
2.1. Requirements
The following design requirements are assumed to be System-Level Design.2 These
requirements have an established concept development but are not fully implemented as a
detailed design. Therefore, these requirements have not been finalized and may or may not be
represented in the final prototype. However the following design requirements do represent the
current design direction and specification for HydroTower. Requirements headings are not ranked
in order of importance, however sub headings are ranked by the currently foreseen importance to
overall success and design of the product. The HydroTower will function according the
requirements stated below:
2.1.1. Functional Requirements
a. The HydroTower is designated for specific use as a hydroponic grower capable of growing
plants, vegetables, and herbs indoors.
b. HydroTower will be one base unit and two additional stackable units. The product will be
fully functional using only the base station or using the base station in combination with one
or two stackable additions.
c. Growing Ability: HydroTower will allow the growth of any plant, vegetable, or herb that is
height permitted to fit within HydroTower. HydroTower team will not specify what can and
cannot be grown, however certain plants will be suggested based on ability to grow in a
hydroponic environment.
d. Autonomous Ability: HydroTower will have the ability to function in an autonomous mode
capable of running without human intervention for seven consecutive days. Any significant
system failure within HydroTower will trigger a fail-safe automatic shutdown of the system
which must be reset by a human operator.
e. Location: HydroTower will be designed primarily for use in an indoor environment. In
addition HydroTower will be capable of handling moderate outdoor temperatures for
summertime growing. HydroTower will be able to operate in conditions between 100o F and
32o F outdoors. In an indoor environment HydroTower will be designed to operate at indoor
temperatures of between 40o and 85
o.
f. Overall Size : HydroTower must be suitable for indoor use. Therefore the product must fit
through doorways and stand upright in a room without touching the ceiling. HydroTower
must be lower than 8 feet in height and less than 34 inches wide. Preliminary design of
2 Karl T. Ulrich and Steven D. Eppinger. Product Design and Development. McGraw-Hill, New York, 1995. Print.
4
HydroTower has a height of 5 feet and a width of 34 inches. The base unit shall have a height
of approximately1 foot with each additional unit having a comparable height of 2 feet.
g. Overall Weight Unloaded: HydroTower base station must be able to be carried by an
average adult person regardless of gender capable of carrying 50 lbs. The maximum weight
for the base station without growing media or water will be less than 30 lbs. Each additional
stackable unit should weigh less than 20 lbs. when not filled with growing media or water.
The total weight of an unloaded HydroTower will be no greater than 80 lbs.
h. Overall Weight Loaded: HydroTower fully loaded should not be able to be pushed over or
toppled by a child under the height of 3 feet. The fully loaded base station should weigh
approximately 50 lbs. Each additional stackable unit should weigh no more than 30 lbs.
Therefore a HydroTower with base unit and two additional stackable units should weigh
approximately 110 lbs fully loaded.
i. Structure Supports: The structure of HydroTower will be supported by four rectangular
metal tubes capable of supporting the weight and torque forces applied to HydroTower from
standard usage as claimed by the HydroTower user manual.
j. Power Consumption: The HydroTower will not consume power greater than what is
available in a conventional 120 VAC outlet. Power on and shutoff switch will be easily
accessible and labeled near the user interface. Attachment Plugs and Receptacles along with
Fuses will be in accordance with UL standards. 3
k. Light Emitting Diodes: LEDs will be shielded by the outer shell of the HydroTower in order
to prevent retina damage from bright LEDs to users outside of the HydroTower. Warning
label will be placed on the inside of the HydroTower.4
l. Strength: HydroTower will be able to endure the climbing and pulling of a small child or
animal no more than 3 feet tall and 30 lbs. HydroTower structural design will first and
foremost focus on the supports holding together the base unit and additional stackable units.
Secondly, HydroTower structural design will focus on building a strong containment
reservoir to ensure water does not escape HydroTower. In addition, the outer shell of
HydroTower will be able to endure a moderate amount of force exerted by accidents and
normal wear such as running into HydroTower while walking or usage past the specified
design life.
3 "Ul-498.14." UL StandardsInfoNet. N.p., 16 Nov. 2007. Web. 05 Dec. 2010.
<http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0498.html>. 4 "UL | Additional Resources." Redirecting Page to Browser Language Detected URL. N.p., n.d. Web. 05 Dec. 2010.
<http://www.ul.com/global/eng/pages/offerings/industries/lighting/lightingindustryservices/articles/>.
5
m. Durability: HydroTower will be designed to last in an indoor environment for 20 years.
Additional use of HydroTower in an outdoor environment during moderate summer
conditions may increase wear and reduce the operational life of HydroTower.
n. Water Reservoir and Usage: The water reservoir in HydroTower will be located in the base
unit of the system. The reservoir will be capable of holding enough water to meet
requirements specified under Autonomous Ability. HydroTower will be designed to operate
using soft water. The prototype will not have the ability to process hard water.
o. Water Pump: The water pump will be submerged in the water reservoir and will be capable
of pumping water to the top growing level of HydroTower.
p. Plant Diseases and Insects: One of the main advantages of hydroponic growing is that
diseases and insects that live in soil are not present. Over 80% of all plant diseases come from
soil. The inside of the container will be closed to prevent insects from entering and escaping
should any insects enter HydroTower via plants or users.
q. Corrosion Resistance: HydroTower will use materials that are corrosion resistant. Corrosion
resistance will first focus on any areas in HydroTower where electrical connections and water
are near each other. Secondary focus areas will include water piping and the outer shell of
HydroTower.
r. Water Resistance: Water resistance will be an utmost issue when dealing with almost all
major components of HydroTower. Water resistance will be assumed using the water criteria
set out in the earlier section titled, Water Reservoir and Usage. Water overflow will be
considered and overflow channels will exist on each level to ensure that water does not exit
HydroTower during standard operation.
2.1.2. Performance Requirements
a. Quality: HydroTower must produce quality plants capable of delivering fruits,
vegetable and herbs that are comparable to produce found in local supermarkets.
b. Growing Time: HydroTower must be able to grow plants between 25-50% faster than
conventional soil grown plants. This growth speed will ensure that produce can be
planted and harvested in a timely manner in order to supply a family of 4 people.
c. Growing Ability: HydroTower will be limited to plants that meet height and width
requirements of the product. For example, apples cannot be grown in HydroTower due
to the fact the apples grow on trees that exceed than the volume of the entire
HydroTower unit. In addition, plants such as pumpkins cannot be grown in
HydroTower unit due to their weight and size. The HydroTower team will recommend
6
a wide variety of plants that can be grown successfully in HydroTower, but will not
specify a listing of plants as stated in Growing Ability above.
d. Air Temperature: The air temperature of HydroTower will be based on the Location
requirements specified in the previous section Functional Requirements. Further
research is required to determine the optimum temperature for plant growth. Any
temperature for a sustained period that cannot support plant growth in HydroTower will
issue a shutoff command that stops all operation in HydroTower. Any sudden
temperature increase or decrease in HydroTower will issue a warning to the user.
(Sustained period and sudden temperature increase or decrease will be defined with
further research)
e. Water Temperature: Water Temperature will follow the same guidelines set out in
the previous subsection titled, Air Temperature.
2.1.3. Interface Requirements
a. User Interface (General): The interface and interaction requirements for HydroTower
will assume a rugged design that is capable of usage with wet and dirty hands.
Emergency shutoff features and signals will be intuitive to the user without an
instruction manual. All controls for HydroTower will be located in the base unit.
Instructions on operation will not be included for the user interface on HydroTower.
These instructions will be provided separately in the user manual.
b. User Interface (Control Systems Interface): The user interface for the control system
of the project will feature a touchscreen controller that is capable of displaying
information related to growth time, chemical concentration, water usage, power usage,
and temperature controls. On the touchscreen, the size of the choice selection buttons
will be a minimum of one square inch.
c. User Interface (Power Options/Water and Nutrient Insertion): HydroTower will
feature intuitive buttons to turn on and off. In addition, an emergency shutoff switch
will be prominently displayed. Water and nutrient insertion points will be labeled and
capped to prevent accidents, tampering, or contamination from other users, children, or
pets.
2.1.4. Environmental Requirements
a. Immediate Environment: The immediate environment will be defined as the room in
which HydroTower is located.
7
i. Visual: HydroTower will have a uniform outer shell made of plastic that will be
a neutral color. An effort will be made to contain the LED light from
HydroTower to prevent the light from being a large distraction in the room
ii. Sound: HydroTower will not produce any sustained noise that is greater than 60
dB.
iii. Smell: HydroTower will not contaminate its immediate location with any smell
from inside the unit. Further research will determine if an air purifier is needed
during the operation of HydroTower.
iv. Humidity: The humidity of HydroTower will be optimized to a relative humidity
of 50%. Measurement and control of humidity will be taken care of by the
control system.
b. Outside Environment: The outside environment will be defined as any part of the
environment that that HydroTower interacts with both directly and indirectly.
i. Recycling: All attempts will be made to ensure that HydroTower is as
environmentally friendly as possible. This means further developing the already
stellar environmental achievements of hydroponic growing. Specific efforts will
be made in ensuring that recycled or recyclable materials are used in the creation
of HydroTower.
ii. Water and Nutrient Disposal: Water disposal will be based on the method of
hydroponics chosen in the second semester. Leftover water at the end of a
growing cycle will have little nutrients and will be discarded. Waste water will be
limited to, at most, half of water reservoir capacity.
2.1.5. Underwriters Laboratories Requirements
a. Electronic Gardening Appliances (UL 82):
“ 1.1 These requirements cover cord-connected, electrically-operated gardening
appliances, such as cultivators, edger-trimmers, and the like, rated 250 volts or less for
use in accordance with the National Electrical Code, NFPA 70.
1.2 These requirements also cover battery-operated gardening appliances.
1.3 These requirements do not cover sprayers, foggers, or equipment for use in hazardous
locations as defined in the National Electrical Code, NFPA 70.
1.4 These requirements do not cover electrically operated lawn mowers or garden tractors
or their attachments.
8
1.5 A product that contains features, characteristics, components, materials, or systems
new or different from those covered by the requirements in this standard, and that
involves a risk of fire or of electric shock or injury to persons shall be evaluated using
appropriate additional component and end-product requirements to maintain the level of
safety as originally anticipated by the intent of this standard. A product whose features,
characteristics, components, materials, or systems conflict with specific requirements or
provisions of this standard does not comply with this standard. Revision of requirements
shall be proposed and adopted in conformance with the methods employed for
development, revision, and implementation of this standard.” 5
2.1.6. User Requirements
a. Ergonomics: Defined as the efficiency and the usability of HydroTower:
i. Ease of use: As stated in the previous subsection User Interface, power,
emergency shutdown options, and water/nutrient insertions points will be easy to
find and use.
ii. Maintenance: Standard maintenance on HydroTower will be limited to cleaning
after plant cycles and possibly changing filters. This maintenance plan will take
no longer than one hour to complete for each plant cycle.
iii. Cleaning: All parts of HydroTower that need to be cleaned will be easily
accessible and removable when possible.
b. Assembly: HydroTower will be able to be completely assembled and disassembled in
less than one day by a select user of HydroTower.
2.1.7. Manufacturing Requirements
a. Development Time : The HydroTower prototype will be completed by May 7, 2011.
b. Project Development Cost: HydroTower development cost will be less than $2,000.
c. Development Capability: HydroTower will be mass produced based on the
documentation of the HydroTower team. This documentation will be specified in the
Delivery Requirements section.
d. Product Quality: The quality of HydroTower will be based on the design norms
chosen by HydroTower team and specified in these requirements.
e. Product Cost: HydroTower will cost less than $100 to produce.
5 "Ul-82.7." UL StandardsInfoNet. N.p., n.d. Web. 05 Dec. 2010.
<http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0082.html>.
9
f. Sale Price: HydroTower will sell for less than $200.
g. Sellable Unit: A sellable unit of HydroTower will include two versions: the base unit
and stacking unit. Included in the base unit are all components of HydroTower in
addition starting seed packages and a user’s manual. The stacking unit will include a
brief instruction guide on how to attach to the base unit. The stacking unit will not
include any seed packages or an additional user’s manual.
2.1.8. Delivery Requirements
a. PPFS: The PPFS will be completed by December 5, 2010
b. Final Report: The Final Report will be completed by May 7, 2011.
c. Working Prototype : The working prototype will be created by May 7, 2011.
d. Team Website : The team website will be created by November 25, 2011 and updated
monthly.
e. Design Competition: HydroTower team plans on entering three design competitions.
Entrance deadlines are specified outside the requirements section and are located in the
Design Competition sub section.
10
3. Hydroponics
This section details the basics of hydroponics such as various growing methods, and various
advantages and disadvantages to each growing method mentioned. Some of the advantages and
disadvantages are in regards to growth times, ease of use, portability, maintenance, and complexity.
3.1. Hydroponic Basics
Hydroponics is a method of plant growth whereby there is no soil medium. The nutrients
that the plants would get from the soil are mixed into a liquid solution that is applied to the roots
of the plants.
Hydroponic systems usually require seeds to be germinated in either a separate container
and transported to the hydroponic growing apparatus after germination is complete. Germination
describes the period where the seed “hatches” and produces a root long enough to be used for
transplantation into the hydroponic system (typically no more than an inch in length). However,
small foam blocks can be used for germination inside most hydroponic apparatuses. Figure 2
depicts a simplified diagram of hydroponic growth for plants.6
There are many advantages of having a soilless medium to grow plants. Since no soil is
needed and the replacement medium does not grip the roots like soil does, the plants can be
transported from one place to another. This will allow for easier access for conducting disease
inspection and treatment, as well as allow for repositioning during growth for greater plant
density, light access, and other minor adjustments. Another advantage of using a hydroponic
system is that the efficiency of plant growth. Nutrients can be delivered to the plant roots as is
described in the next section. Lou Albright, a Professor at Cornell University has been able to
6 "Deficiency Symptoms Of Elements | Tutorvista.com." Tutorvista.com - Online Tutoring, Homework Help for Math, Science,
English from Best Online Tutor. N.p., n.d. Web. 05 Dec. 2010. <http://www.tutorvista.com/content/biology/biology -
iv/plant-nutrition/deficiency-symptoms-elements.php>.
Figure 2: Diagram of hydroponics
11
achieve harvests of head lettuce within “35 days after seeding” and produces “58 heads per
square foot, per year (approximately 400 tons per acre per year)”7. This is compared to average
yields of head lettuce being “ready for harvesting in 70 to 80 days after seeding”8 and producing
“17 tons per acre”9 per year. While these numbers are quite significant, one must remember that
hydroponic systems allow for year-round production, and are not generally exposed to harsh
outdoor environments. Figure 310
shows the benefits of hydroponics in the area of reducing the
number or resources used in growing plants. In a conventional soil system, water reaching plant
roots is dependent upon the soil type, which at times can lead to waste of water. However, water
is controlled in HydroTower thus reducing the amount of water both used.
A brief summary of the benefits of using hydroponics is the growing time is decreased by
over fifty percent, the amount of nutrients and land used is decreased by over 75 percent, and the
total water used is decreased by almost ninety percent.
Figure 3: Benefits of Hydroponics
3.2. Types of hydroponic systems
7 "BEE Faculty - Lou Albright." Department of Biological and Environmental Engineering. N.p., n.d. Web. 05 Dec. 2010.
<http://www.bee.cornell.edu/cals/bee/people/profile-albright.cfm>. 8 Sanders, Douglas C. "Lettuce Production." North Carolina Cooperative Extension: Home. N.p., n.d. Web. 05 Dec. 2010.
<http://www.ces.ncsu.edu/depts/hort/hil/hil-11.html>. 9 Jackson, Louise, Keith Mayberry, Frank Laemmlen, Steve Koike, Kurt Schulbach, and William Chaney. Iceberg Lettuce
Production in California. Vegetable Research and Information. University of California, n.d. Web.
<http://ucanr.org/freepubs/docs/7215.pdf>. 10 "Cityscape Farms: Soilless Farming." Cityscape Farms: Home. N.p., n.d. Web. 05 Dec. 2010.
<http://www.cityscapefarms.com/soillessfarming/>.
12
3.2.1. Flood and drain (Ebb and Flow)
The flood and drain method of a hydroponic system consists of having a reservoir of the
nutrient solution that is not in contact with the plants. The plants are situated in a growing
medium (eg: rocks, marbles, perlite, tray, etc.) separate from the reservoir. At specified intervals,
water is pumped into the medium wherein the plants are situated. After a specified amount of
time, the water is then drained from the medium and flows back into the reservoir.
Figure 4: Diagram of flood and drain (Ebb and flow) system11
Some advantages of the flood and drain method are as follows: 1) aeration of the nutrient
solution is not required since the roots are exposed to air between flood cycles thus providing the
roots of the plant access to air between cycles, oxygen and carbon dioxide are abundant, and as a
result, decreasing the plant growth time, 2) the growing medium selected for plant support (eg:
perlite, sand, rocks, marbles, various action figures, etc.) can be for plants using the flood and
drain technique. For example, due to the short cycle times, it is difficult to grow strawberries in
this type of system because the corolla of the strawberry must always be moist12
.
Some disadvantages of the flood and drain method are as follows: 1) if the nutrient
concentrations cannot be controlled using a control system, the reservoir will need to be replaced
leading to wasted water and nutrients.
3.2.2. Continuous drip
11 "Dual Flow Hydroponic System Ebb and Flow NFT." Hydroponics Supplies Darlington County Durham. N.p., n.d. Web. 05
Dec. 2010. <http://www.secretgardenhydroponics.co.uk/product/Dual_flow_01-015-005>. 12 "Pros and Cons of Ebb and Flow Hydroponics | Easy Hydroponics." Hydroponics | Easy Hydroponics. N.p., n.d. Web. 05 Dec.
2010. <http://www.easyhydroponics.net/pros-and-cons-of-ebb-and-flow-hydroponics.html>.
13
The continuous drip method of a hydroponic system is one where the nutrient solution is
fed at a small rate onto the top of the roots of a plant through a drip nozzle where gravity allows
the small amount of solution to flow over the roots.
Figure 5: Top Fed Continuous Drip System13
An advantage of using the continuous drip method is that the nutrient solution does not
need to be aerated because the roots are constantly covered with a thin film that allows for air to
penetrate and reach the roots. However, a disadvantage of this system is that the drip nozzle
needs to deliver one drop at a time, it is quite possible for the nozzle itself to become clogged.
The need to manually unclog a nozzle could have a negative impact on the low maintenance of
the HydroTower.
3.2.3. Float
The float method of a hydroponic system is one where the nutrients are simply being
circulated in some type of reservoir. On top of the reservoir is a flotation device that holds the
plants. There are holes in the flotation device that allow the roots to grow into the water. The
circulation of the water is typically performed by submerged pump in the corner of the
apparatus.
13 "Build Your Own Hydroponics System | BGHydro." Hydroponics | Hydroponic Supplies. N.p., n.d. Web. 05 Dec. 2010.
<http://www.bghydro.com/bgh/static/articles /0806_byos.asp>.
14
Figure 6: Float method of hydroponics14
An advantage of using the float method is that it is one of the simplest systems to
implement because the nutrients do not need injection into the water. Instead, a slow circulation
and aeration of the water is provided by the pumps.
Some disadvantages of using this system are that the roots of the plants will not have full
access to the open air. As a result, the nutrient solution will need to be aerated to provide proper
oxygenation to the roots of the plants. Furthermore, this system is not as fast as some of the
other alternatives as a result of the aeration problems.
3.2.4. Aeroponics
The aeroponic method is where the plants are held suspended by some apparatus while
the nutrient solution is sprayed onto the roots. Some further variations of aeroponics include
spraying constantly, spraying for a few minutes per hour, etc.
Figure 7: Aeroponic method of hydroponics15
14 "Hydroponic Systems." Hydro-Unlimited.com. N.p., n.d. Web. 05 Dec. 2010. <http://www.hydro-
unlimited.com/index.php?p=2_1>.
15
An advantage of using an aeroponic system is that the roots receive more oxygen than the
other methods due to the naturally aerated nutrient spray, and the roots exposed roots. As a
result, this method yields some of the fastest growing plants in hydroponic systems.
A disadvantage of this system is that the roots of the plant need to be exposed to the open
air which means that a base medium can not obstruct airflow to the roots. Growing mediums
capable of providing sufficient airflow to the plant roots will not allow sufficient grip for the
roots in order to support the plant. As a result, separate mechanisms are needed to either suspend
the plant, or provide enough support to keep the plants from falling over.
3.2.5. Deep Water Culture
Deep water culture is a variation of the float method whereby the plants are held above a
nutrient solution reservoir by a mechanism. The plants are suspended in such a way that
approximately half of the roots are sitting in the liquid and the other half are exposed to air
above the reservoir water level. This differs from the float method in that the plant supports are
not floating in the mixture, but instead have a section of air between the reservoir and the
supports to allow for oxygenation of the roots, eliminating the need for aeration of the nutrient
solution before delivery to the plants.
Some advantages of the deep water culture system are that similar to the advantages in
aeroponics where much of the root of the plant is exposed to the air, thereby increasing the speed
of plant growth. Also, just as in the float system, the deep water culture method is very low
maintenance. No pumps are required for moving the solution to different parts of the plant.
However, unlike the float system, the nutrient solution no longer needs to be aerated.
Some disadvantages of this system is that great care must be taken to make sure that the
roots to do not lose contact with the nutrient water solution. This makes growth during the first
few weeks difficult, since the roots are very short. The amount of root in contact with the water
changes the growth speed of the plants. Too much water and the roots will not have proper
aeration, too little water and the roots could dry out. Also, if not monitored regularly, some roots
may dry out if they are not properly placed in the reservoir.
3.3. HydroTower Experiments
The HydroTower team began experiments on October 13, 2010 to test both soybeans and
radishes in a basic hydroponic environment. Soybeans and radishes were chosen because of their
15
“Hydroponics Growing Systems Explained One by One." Hydroponics Gardening - Start a Small Garden Indoors- Helpful Guide. N.p., n.d. Web. 05 Dec. 2010. <http://www.jasons-indoor-guide-to-organic-and-hydroponics-
gardening.com/hydroponics-growing-systems.html>.
16
growth speed and availability in the biology department. These seeds were first placed in a
plastic bag between a moist paper towels for five days in order for germination to occur. The
germinated seeds were then transplanted to plastic cups with a water nutrient system that is
further described in the Nutrient section of this report. Soybean seedlings were placed in two
cups and radish seedlings were placed in four cups for a total of six cups. Cups 1 and 2 used two
times the normal concentration Hoagland’s Solution. Cups 3 and 4 used 50% concentration
Hoagland’s solution. Cups 5 and 6 used the normal 100% solution Hoagland’s Solution is the
standard liquid nutrient used to feed plants in a hydroponic system. This solution consists of 12
elements dissolved into water to supply all of the plants needs and is again discussed in the
Nutrients section of this report.15
The table below tracks the growth over three weeks.
Table 2: October hydroponic experiments with soybeans and radishes
# Type/Hoaglands% Week 1 (g) Week 2 (g) Week 3 (g)
1 Soybean/200% 1.95 1.82 1.65
2 Radish/200% 1.51 1.62 2.48
3 Radish/50% 1.52 1.98 3.17
4 Soybean/50% 1.89 3.07 5.1
5 Radish/100% 1.55 2.07 2.8
6 Radish/100% 1.55 2.07 4.07
The graph below represents the hydroponic growth over three weeks. Five out of the six
plants show a quality rate of growth.
17
Figure 8: Hydroponic grwoth over 3 weeks with 2 soybean plants and 4 radish plants
In three weeks, only plant one showed no growth. The two soybean plants, numbers four
and six, showed the highest growth rates. The radishes showed a lower but still comparable
numbers between plants. The above results would indicate that 50% Hoagland’s solution is the
best choice to grow plants. However these results may be deceiving due to the fact that these
experiments were not carried out over the full life cycle of the plants. Results will need to be
confirmed during Engr 340 to show that 50% Hoagland’s solution is in fact detrimental to the
overall growth of the plants. In the second week, three more soybean plants and three more radish
plants were started. Each of these plants were placed in 100% concentration Hoagland’s solution.
The results are displayed in the table below.
Table 3: October hydroponic Experiment #2
0
1
2
3
4
5
6
Pla
nt
We
igh
t (g
)
Plant Number/Hoagland %
Hydroponic Growth (Weeks 1-3)
Week 1
Week 2
Week 3
# Type/Hoagland% Week 2 (g) Week 3 (g)
1 Soybean/100% 4.2 6.8
2 Soybean/100% 4.64 7.4
3 Soybean/100% 4.89 6.8
4 Radish/100% 4.32 5.7
5 Radish/100% 3.55 4.83
6 Radish/100% 4.26 5.93
18
Figure 9: Hydroponic growth over 2 weeks with 3 soybean plants and 3 radishes
The above graph shows that the weight of some of the soybeans nearly doubled.
The radishes showed a slightly low speed of growth. These results confirm that plants can
be grown in Hoagland’s solution and thus Hoagland’s solution will be used in
HydroTower. However, there were some signs of fatigued growth on many of the plants.
The pictures below show the soybean and radish plants, respectively. The next two pictures
following the week 2 growth pictures show the beginnings of iron deficiency. This is indicated by
the curled leaves and slightly brown color.
012345678
Pla
nt
We
igh
t (g
)
Plant Number (#)
Hydroponic Growth (Weeks 2-3)
Week 2
Week 3
19
Figure 10: Soybean plants at week 2
Figure 11: Radish plants at week 2
Figure 12: soybean plant with signs of iron deficiency
20
Figure 13: Radish plant with signs of iron deficiency
Overall, this experiment successfully demonstrated that growing plants in a basic
hydroponic system is possible. This experiment gave the HydroTower team a good idea of
the way that plants grow and how their root systems function. In addition, the team now
understands and can identify some of the nutrient deficiencies that exist in plants. This
experiment serves as a baseline to growing more complex plants and using more advanced
hydroponic systems. The use of more advanced hydroponic systems will allow
HydroTower to optimize growth. The results of this experiment could have been improved
by using appropriate lighting to grow the radishes and soybeans. The fluorescent lights
that were used in this experiment did not represent sunlight and thus future experiments
can make such a modification to improve the overall results. Specifically, wavelength
specific LEDs in the HydroTower design will solve the previously mentioned problem.
3.4. Proposed Design
3.4.1. Chosen Prototype Design
The HydroTower team is currently in the midst of researching as to which system would
be best to implement depending whether or not a control system for the specific ions in the
nutrient solution is or is not possible. A further description of the nutrient system issues is
discussed in the Nutrient section of this report.
If a control system is possible, then the Team will proceed with the flood and drain
technique. Several reasons for choosing a flood and drain system are that the system is robust in
its ability to harbor different varieties of plants. That is, all plants that fall under the
recommended HydroTower plants are able to grow in a flood and drain system. Also, a separate
21
reservoir for growing plants will be beneficial for implementing the control system. Having a
separate reservoir inside HydroTower allows for filtering of foreign materials out of the system
(eg: plant leaves or root debris). Speed of growth using this system meets the requirements the
Team set. Lastly, with the flood and drain system, little resources are wasted due to a water
recycle system.
3.4.2. Transparency, Stewardship and Trust
The requirements of HydroTower are influenced by the selected design norms of
transparency, stewardship and trust. The HydroTower team wants to be open and genuine with
customers such that customers both understand how HydroTower functions and secondly
understand the benefits of HydroTower and hydroponics (see Hydroponic Basics section). The
Team also wants to be good stewards of God’s creation by eliminating many of the fossil fuels
and costs used in transportation and other current food processes, which are also directly linked to
the transparency aspect of having users understand the benefits of hydroponics. Lastly,
HydroTower will produce food for people, making trust a design norm since customers must not
feel as though HydroTower is neither unsafe nor unhealthy.
22
4. Electrical and Computer System
In order to satisfy the requirements as established by the HydroTower team (see Requirements
section), the following section details both the design decisions and methods for the electrical and
computer system.
4.1. Design Procedure
The electrical systems have two basic categories of design. First, purchasing a prebuilt
system and secondly designing the system in house. The user interface and higher level control
systems are implemented in software that runs on prebuilt hardware. Other systems, such as the
lower level control systems, lighting, and power supply will be designed for implementation in
HydroTower. The decision to purchase rather than design the digital hardware was made because
such design work would not contribute to the operation of HydroTower inside the scope of the
initial prototype. That is, the objective for Engr 340 is to build a working prototype capable of
growing plants and demonstrating an automated nutrient distribution system along with a control
system and user interface.
4.1.1. User Interface (UI)
The user needs a way to operate HydroTower that is simple and efficient. HydroTower
will require input from the user to perform initial setup, letting the system know when plants are
added or removed plants. Furthermore, routine maintenance, such as cleaning the filter,
replenishing the water reservoir, and replacing nutrient concentrates will be a needed input to the
UI. The UI needs two features to perform the previously mentioned tasks, a display for conveying
information to the user and a method for the user to input commands to the HydroTower.
A character LCD could satisfy the needs of the display because a character LCD will
allow the HydroTower to display basic text information to the user with little formatting. To
allow input, a series of labeled buttons will control the system functions. A character LCD is the
basic solution and would be the least expensive to the overall system to implement. However, the
character LCD is not the best solution for accomplishing the overall design goals of making the
system aesthetically pleasing and simple to use.
The second solution to providing a UI is to implement an LCD touch screen. This is a
more expensive solution than a character LCD, but an LCD touch screen offers more options to
the overall functioning of HydroTower. A touch screen LCD is able to provide a dynamic
interface to the user where context menus are simple and intuitive, allowing a user to navigate the
23
program and operate basic functions of the HydroTower even if the instruction manual was not
read by the user.
HydroTower will use a touch screen interface for the UI because of the previously
described advantages. The next decision to make is on which specific touch screen LCD to
implement because all requirements must be met. Hence, cost is a large factor in selection of a
touch screen LCD. Since it was decided that the HydroTower will use an Arduino microcontroller
(discussed in the Data Management and Processing section) to run the higher level automation
and UI program code, the touch screen chosen needs to be compatible with this platform.
Outlined in the table below are three alternatives that will satisfy the needs of the touch screen
device.
Table 4: Different options for touch-screen devices
Device/
Manufacturer
Screen
Size Resolution Support Price Availability
Nuelectronics16
2.8” QVGA Datasheets $57 Sold Out
(as of 11/30/2010)
BL-
TFT240320PLUS17
3.2” QVGA Datasheets $60
Sold Out
(as of 11/30/2010)
TouchShield Slide18
3.2” QVGA Datasheets, Larger
user community $175 Good
When comparing these alternatives, it is hard to see a clear choice that is superior to the
rest. The TouchShield Slide would prove to be a more reliable option but is also the most
expensive, costing almost three times more than the competition. The TouchShield Slide device,
however, does provide the clearest documentation, providing sample code, and support to make
development easier. The BL-TFT240320PLUS is also a possible option because the the BL-
TFT240320PLUS has the same 3.2-inch screen as the TouchShield Slide but has a lower price.
16 "2.8 TFT Color LCD,touch Screen Shield V1.2 for Arduino 168/328 - £35.00 : Nuelectronics.com, Arduino Freeduino
Projects." Nuelectronics.com. N.p., n.d. Web. 05 Dec. 2010. <http://www.nuelectronics.com/estore/index.php?main_
page=product_info&cPath=1&products_id=19>. 17 "BL-TFT240320PLUS V2." Circuit Ides Design. N.p., n.d. Web. 05 Dec. 2010. <http://www.circuitidea.com/dev-board/BL-
TFT240320PLUS-V2.html>. 18
"Liquidware : TouchShield Slide." Liquidware : Open Source Electronics. N.p., n.d. Web. 05 Dec. 2010. <http://www.liquidware.com/shop/show/TSL/TouchShield Slide>.
24
Unfortunately, the BL-TFT240320PLUS overall is a less feasible option since it is more difficult
to acquire. This shield only has one listed supplier, www.thaieasyelec.net19
, who lists the product
as sold out as of November 30, 2010. The fact that Nuelectronics’ touch screen is also sold out
disqualifies it from being a viable alternative. Due to these factors, the HydroTower will include
the TouchShield Slide.
4.1.2. Data Management and Processing
A large part of the novelty in HydroTower is its ability to automatically control and
optimize the environment in which plants are grown. This requires that the system can read, store,
and operate on data. If designing for the production system, the processor and its adjacent
systems would be custom designed, however an existing board is used to reduce development
time for the initial HydroTower prototype. Several embedded processors were considered for the
HydroTower. The first option is to use an Altera DE2 development kit with a NIOS II processor.
This solution provides ample computing power and memory. The DE2 is very flexible and can
accommodate many additional subsystems. The downside to using a DE2 board is that they are
larger and have extraneous hardware. Another solution considered was to use an ARM-based
board. This would allow for an easy Linux-based programming environment and some of the
advantages that accompany a modern OS. For the HydroTower, an ARM-board would be more
expensive and overkill for the system as lesser solutions will suffice.
The third option is to use an Arduino20
microcontroller. This platform is very flexible and
easy to program. There are many different expansion “shields” for Arduino boards. These shields
contain extra hardware in a form factor that directly plugs into the standard I/O pin interface of
the Arduino. This allows us to use I/O ports for controlling external systems such as the lighting
control, pump system, nutrient control, and the temperature control systems. Also the Arduino
has touch screen shields that will easily allow development of a clean and sleek UI. The Arduino
board solution is far less expensive and adequately flexible option and therefore is the main data
storage and processing unit of HydroTower.
4.1.3. Software Model
Shown below is the software breakdown for the different actions of the HydroTower. The
first-run program is shown in Figure 14 and will require basic information from the user as inputs
19
Arduino - 3.2 Inch TFT Touch Screen with Arduino Interface V2." ThaiEasyElec.net. N.p., n.d. Web. 05 Dec. 2010. <http://www.thaieasyelec.net/index.php/Arduino/3-2-inch-TFT-Touch-Screen-with-Arduino-Interface-V2/p_68.html>. 20
Arduino - HomePage. N.p., n.d. Web. 05 Dec. 2010. <http://arduino.cc/en/>.
25
along with verifying the system reservoirs are properly setup. The next program function will be
the general function that will handle the water pumping and nutrient replenishment in the system.
This is shown in Figure 15.
Welcome
Set Date/Time
Check Nutrient
And Water Levels
Prompt to
Address
Reservoir
Levels
Low Levels
Levels OK
Prompt to Start
Plant Cycle
No Enter Sleep
mode
Begin Growth
Cycle
Program
Yes
Figure 14: Initial Setup
26
Begin
X=1
Flood Level X
Wait while
Roots Soak
Drain Level X
Check Nutrient
Concentrations
Calculate and
Inject Make-up
Nutrients
All Levels
Watered?
End
Yes
Low Nutrients
OK
Increment X
No
Figure 15: Water Supervisor Program
The User Interface on the touch screen will need to give several options and controls over
the HydroTower system. The high level view of this menu is shown in Figure 16. From here the
user can control the lighting and pumping schedule of the HydroTower. Also, the user can let the
system know that they have added or removed plants from the system. Another menu provides
the user a way to read and address maintenance alerts.
Status Screen
Scheduling EditorMaintenance Alert
ManagerAdd Plants
Figure 16: Main UI
27
4.1.4. Control Systems
HydroTower aims to automatically provide an optimal growing environment for plants
through the use of several control systems. These control systems will manage several
environmental variables that affect plant growth.
4.1.4.1. Water Flow
The first system will manage the flow of water to the plants. At the current stage in the
design, two different delivery methods are proposed. The first method uses flood and drain to
soak the plant roots in water for 15 minutes every four hours21
. The second method uses nozzles
to deliver a controlled amount of water to the roots of the plants. In both methods a pump will
drive the water through the pipes. The Arduino microcontroller will have programmed times to
drive the pump in either method. The decision for which method to use is dependent on the result
of the research currently being conducted for which nutrient injection method the HydroTower
will use, this research is discussed in Mechanical Nutrient Systems section.
4.1.4.2. Lighting System
A second control system in the HydroTower will control the light to the plants. Plants
require two frequencies of light, 650nm and 450nm. There are several common light sources used
in hydroponic systems, including LED, fluorescent, and halogen. The LEDs chosen for
HydroTower specifically match the required light for plant growth. The LEDs need to deliver
brighter light than is used in average applications of LEDs. For this reason, the lighting system
will utilize 30 1W LED’s. This number was calculated in MathCAD and is shown in Figure 5.1.
Figure 17: Calculation for target amount of LEDs
21
Resh, Howard M. Hydroponic Food Production. 6thth ed. Mahwah, NJ: NewConcept, 2004. Print
28
The microcontroller will illuminate the LEDs based on a summer daylight schedule,
allowing for a shortening day, since this is a trigger to some fruiting plants to bear fruit because a
shortening day indicates fall and the onset of the end of the growing season. The lighting system
will also allow for the LEDs to be shut-off when there is ample light being supplied externally.
4.1.4.3. Temperature Control
The next control system will be responsible for maintaining the temperature of the water
and air in the system. The microcontroller will take in voltage information from thermocouples
installed in HydroTower, and turn on and off separate heaters accordingly to regulate the
temperature required. The system will likewise enable exhaust fans installed in the HydroTower
to bring in cool air from the outside environment if the inside temperature rises above the
allowable range specified in Temperature of the Mechanical section. The Simulink model below
shows the preliminary air temperature control system.
Figure 18: Simulink Air Temperature Control System
The air temperature control system will include a thermostat that will monitor the air
temperature inside the HydroTower. The maximum temperature allowed in the system is 80°F.
Above this temperature the heater will shut off allowing for cooling from the exhaust fans. The
minimum temperature allowed is 70°F. Below this value the heaters will turn on. Influences on
this system include the conductive and convective heat transfers from outside the HydroTower
via the walls and the fans, but more analysis will be performed during Engr 340.
The water temperature control system will be nearly the same as the air temperature
control system. However, in this case, there will be no influence from exhaust fans. The desired
water temperature will be the same as the air temperature (70°F). This system will include a
separate thermostat. To control the temperature of the water, a water heater will be employed
which will turn on at the minimum temperature and turn off at the maximum temperature via
29
thermostat control. The dissipative conduction and convection will provide the cooling of the
water, and the water heater will provide heat.
The temperature control system is currently being expanded to provide a qualitative cost
analysis of running the heaters in the system. With this analysis, the microcontroller will be able
to minimize costs of the system whilst changing the thermostat maximum and minimum values to
be used in Engr 340.
4.1.4.4. Nutrient Injection
The final control system of HydroTower is to provide a nutrient-rich, yet nontoxic,
supply of water to the plants. The range of nutrients provided to plants is important since too high
of concentrations of nutrients results in killing the plants from toxicity. The nutrient control
system will provide to proper amount of nutrients to the plants, but will be designed differently
depending on which delivery method is decided upon once a final design direction is reached in
January of 2011.
If HydroTower employs the spray/drip system, Hoagland’s solution will be premixed and
no replenishment solution will be necessary. If HydroTower uses a flood and drain system, which
has water being recycled, then nutrients will need to be injected into the water to keep the
nutrients at an optimal level. This injection system will consist of six nutrient reservoirs that each
have a valve to control the release of nutrient concentrates. To measure out precise amounts of
concentrate, each valve will have an accompanying control system. Figure 19 shows the general
form of this controls system.
Figure 19: Schematic of control system for nutrient control
The Arduino microcontroller will decide when and how much concentrate to add based
on one of two methods. The open-loop method includes a schedule that is determined based on
how many plants are in the system and a predetermined rate of consumption for each nutrient.
30
The closed-loop method involves determining what the concentration of nutrients is in the
recycled water and compensating to replenish absorbed nutrients. The closed-loop method is
more accurate and represents an ideal solution for HydroTower, however currently there is no
proven method to determine the necessary concentrations in real time, and such issues are
discussed in the Nutrient System portion of the Mechanical Systems section. The first method has
the benefit of being simpler to implement, however it cannot respond to unpredictable situations.
Currently the team is pursuing both methods to determine which one is feasible for the final
design direction of HydroTower, which is also discussed in the Nutrient System portion of the
Mechanical Systems section.
4.1.5. Lighting System
The HydroTower Lighting system will consist of Light Emitting Diodes (LEDs) which
will be mounted on the ceiling levels of the HydroTower to provide light to the plants. Given the
calculation in section the Lighting System section, 30 1W LEDs will be used. As can be seen in
Figure 20 below, the wavelength of light that plants use is only in two specific electromagnetic
frequencies between 425nm and 660nm. Therefore, the two frequencies for the HydroTower
LEDs will be red and blue.
Figure 20: Plant light frequency response22
The LEDs needed were donated by SoundOff Signal Inc. The acquired LEDs will need
heat sinks to be designed to run them at 1W such that heat can be dissipated away from the LEDs
22
"PHOTOSYNTHESIS." Estrella Mountain Community College. N.p., n.d. Web. 05 Dec. 2010. <http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookPS.html>.
31
for proper operation. The best option for these LEDs is to run them at 1W with an ambient
temperature of 80°F, and maximum junction temperature of 257°F. This means that using copper,
heat sinks in the shape of a square (notches cut for leads as in datasheets23, 24
) will require a side
length of up to 4 centimeters for red and 6 centimeters for blue. Full analysis of the selected red
and blue LEDs are contained in Appendix C and D.
4.1.6. Power Systems
The power system for the HydroTower supplies each subsystem with its respective
voltage needs. The power system will take an input from a standard AC wall outlet. By operating
off either 120V at 60Hz or 220V at 50Hz the HydroTower will be more flexible in where it can
be installed and used. Table 5 below shows the current power requirements of HydroTower.
Table 5: Maximum loads on the power supply
Component Voltage Current Watts
Base (x1)
Pump 24V 3A 72W
Arduino 5V 0.5A 2.5W
Valves 25V .5A 12.5W
Heater 25V 3A 75W
Growing Unit (x3)
LED's 12V 2A 24W
Exhaust Fans 12V 0.25A 3W
Max Power 243W
The power system will supply power not only for the base unit and the first growing unit,
but also for a second growing level. The largest power draw in each of the growing units will be
the LED lighting. Each unit will need sturdy electrical connections to ensure stable operation and
stand up to repeated assembly and disassembly.
23
"LR W5SM." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010. <http://catalog.osram-os.com/catalogue/catalogue.do?favOid=000000000003f86200020023&act=showBookmark>.
24 "LD W5SN." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010. <http://catalog.osram-
os.com/catalogue/catalogue.do?favOid=000000030002a14801f30023&act=showBookmark>.
32
5. Mechanical Systems
5.1. Requirements
HydroTower mechanical components range from the structure of the housing unit to the
pumping, piping and heating of HydroTower. The specific requirements from the mechanical
systems are based upon heating/heat transfer and the structure/frame for HydroTower.
The plants within HydroTower must be in a temperature range no lower than 40°F and no
higher than 85°F wherein the optimum temperature is 70°F.25
Furthermore, the mechanical
system must maintain the interior of HydroTower at a relative humidity no lower than 30% and
no higher than 70% wherein the optimum relative humidity is 50%.26
Another aspect of the
heating/ventilation of HydroTower is in regards to the housing of the electrical components and
controls. The current HydroTower prototype design has the electrical housing contained within
the base unit.
5.2. Size
Based upon the objectives and goals for HydroTower, the unit size was developed to fit
within a residential dwelling. Thus, some design specifications were made such that HydroTower
accommodates a range of users from third world countries in villages to apartment dwellers in the
United States or classrooms in schools. Specifically, HydroTower is designed with a 2.5 foot
diameter and is no more than 6 foot tall. The current prototype of the HydroTower is fabricated
from wood provided by Calvin College. Figures 21 and 22 depict the main designs for
HydroTower. While the first built prototype is circular and has a 2.5 foot diameter, the Team has
decided to change the HydroTower structure design to a rectangular module with a short end
length of 32 inches. Figure 22 depicts the next HydroTower structure design. A rectangular
structure was chosen for several reasons. First, while circular shapes are assumed to be more
aesthetically pleasing, a rectangular shape is more functional when placed in a room. The
HydroTower Team rationalized that most likely, the placement of a HydroTower unit would be in
a corner of a room, thus making rectangular a more feasible option. Secondly, in regards to
manufacturing of HydroTower, square and rectangular components are made faster and more
easily. The dimension of 32 inches for the short end was based on standard widths of doors in
houses. Team HydroTower assumed that a HydroTower unit would be situated in a living room
25
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print. 26
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print.
33
or den area in a house and/or in a corner of an apartment or other building. Standard widths for
door frames are 34 inches, but Team HydroTower took into account extra clearances.27
Figure 21: First HydroTower prototype design (circular)
27
DoItYourself. What is the Standard Door Fram Width? Nov 30, 2010. <http://www.doityourself.com/stry/what-is-the-standard-door-frame-width>
34
Figure 22: Second HydroTower prototype (rectangular)
5.3. Nutrient System
One of the objectives of HydroTower is real-time automation of the nutrient and water
feed to the plants. The nutrient section describes the preliminary designs along with the issues and
alternative solutions to the real-time measurement and makeup of depleted nutrients.
Initial theoretical designs for the nutrient system included the nutrients shown in Table
628
. Precedence has been set by many hydroponic growers as well as other gardeners to use
Hoagland’s solution as the nutrient supplements because all of the nutrients found in Hoagland’s
solution are found in natural soil and are further known as necessary nutrients for plant growth.29
The macro-nutrients listed in the first five rows of Table 6 would be added as individual liquid-
molar concentrations and directly injected into the water feed stream before the pumping of the
water through the flood and drain process occurred. Such a method would first add the needed
nutrients to the water supply and would secondly adequately mix the water supply and nutrients
before pumping to the plants. For the initial design, the direct injection of the nutrients would be
28
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print.
29 Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth
Company, 1999. Ch 30. Print.
35
performed by low-pressure valves. However, as indicated later in this section, since the nutrient
system is still in preliminary designs specific valves and calculations regarding proper mixing
will be performed once a final design direction has been selected. Real time measurements of the
water would determine the amount of nutrient makeup necessary before the water would re-enter
HydroTower for plant feed, thus implementing a recycle stream for HydroTower. The water
measurements would occur in the base unit water reservoir to ensure a clear reading occurs
representative of the entire water system.
Recycle streams would require water analysis based on both pH and electro-conductivity
(EC)using electrodes measuring the amount of nutrients in the stream. However, electrodes
capable of measuring individual ions from within a solution do not exist thus leading to possible
design changes in the direction of the HydroTower project. As indicated previously, the initial
theoretical design had the objective of measuring and making up the absorbed nutrient in real-
time. However, the initial theoretical design also intended to use EC electrodes to measure each
individual ion, which is not possible to do for two reasons. No electrodes exist capable of
measuring the ions wherein the ions are in solution with other ion nutrients. Table 730
contains the
electrodes capable of measuring ions, but also shows the problem in that ions have interferences
30
"Ion Selective Electrodes." Consort.be. Consort, n.d. Web. 5 Dec. 2010. <http://www.consort.be/Downloads/Documentation/IonElectrodes_pg.pdf>.
Hoagland's Solution (Plant Nutrient Solution)
Stock SolutionmL Stock
Solution/1L
202g/L 2.5
236g/0.5L 2.5
15g/L 1.5
493g/L 1
80g/L 1
1 L
2.86g/L
1.81g/L
0.22g/L
0.051g/L
0.09g/L
0.12g/L
136g/L 0.5
MnCl2 x 4H2O
Majors:
2M KNO3
2M Ca(NO3)2 x 4H2O
Iron (Sprint 138 iron chelate)
2M MgSO4 x 7H2O
1M NH4NO3
Minors:
H3BO3
ZnSO4 x 7H2O
CuSO4
H3MoO4 x H2O or
Na2MoO4 x 2H2O
1M KH2PO4 (pH to 6.0 with 3M
KOH)
Table 6: Hoagland's Solution
36
Model Ion Sensor Range (M) Range (ppm) °C Interferences pH Electrolyte
ISE20B Ammonium polymer 5.10-6 - 100 0.1 - 18000 0 - 50 K+ 4 - 10 NaCl
NH4 +
ISE21B Bromide solid state 5.10-6 - 100 0.4 - 79900 0 - 50 I-, CN-, S2-, high levels 2 - 14 KNO3
Br- of Cl-and NH3
ISE22B Cadmium solid state 10-7 - 10-1 0.01 - 11200 0 - 50 Cu2+, Hg2+, Ag+ , high levels 2 - 12 KNO3
Cd2+ of Fe2+ and Pb2+
ISE23B Calcium polymer 5.10-6 - 100 0.2 - 40000 0 - 50 Pb2+, Hg2+, Cu2+, Ni2+ 3 - 10 KCl
Ca2+
ISE24B Chloride solid state 5.10-5 - 100 1.8 - 35500 0 - 50 I-, Br-, CN-, S2- 1 - 12 KNO3
Cl-
ISE25B Copper solid state 10-8 - 10-1 0.00064 - 6350 0 - 50 Hg2+, Ag+ , high levels of 2 - 12 KNO3
Cu2+ Cl-, Br-, Fe2+ and Cd2+
ISE26B Cyanide solid state 5.10-6 - 10-2 0.13 - 260 0 - 50 Cl-, Br-, I-, S2- 11 - 13 KNO3
CN-
ISE27B Fluoride solid state 10-6 - sat. 0.02 - sat. 0 - 50 OH- 5 - 8 KCl
F-
ISE28B Fluoroborate polymer 7.10-6 - 100 0.1 - 10800 0 - 50 I-, ClO4 -, CN- 2.5 - 11 (NH4)2SO4
BF4 -
ISE29B Iodide solid state 5.10-8 - 100 0.006 - 127000 0 - 50 S2-, CN-, Cl-, Br- 0 - 14 KNO3
I- S2O3 -2 , NH3
ISE30B Lead solid state 10-6 - 10-1 0.2 - 20700 0 - 50 Hg2+, Ag+, Cu2+,high levels 3 - 8 KNO3
Pb2+ of Fe2+ and Cd2+
ISE31B Nitrate polymer 7.10-6 - 100 0.5 - 62000 0 - 50 I-, ClO4 -, CN-, BF4 - 2.5 - 11 (NH4)2SO4
NO3 -
ISE32B Perchlorate polymer 7.10-6 - 100 0.7 - 99500 0 - 50 - 2.5 - 11 (NH4)2SO4
ClO4 -
ISE33B Potassium polymer 10-6 - 100 0.04 - 39000 0 - 50 Cs+, NH4 + 2 - 12 NaCl
K+
ISE34B Silver/Sulphide solid state 10-7 - 100 0.01 - 107900 0 - 50 Hg+, Hg2+ 2 - 12 KNO3
Ag+/S2- 0.003 - 32000
ISE35B Sodium glass 10-6 - sat. 0.02 - sat. 0 - 50 H+, K+, Li+, Ag+, Cs+, Tl+ 5 - 12 NH4Cl
Na+
ISE36B Surfactant polymer 10-5 - 5.10-2 1 - 12000 0 - 50 similar types of surfactants 2 - 12 KCl
X+/X-
ISE37B Water hardness polymer 10-5 - 100 0.4 - 4000 (Ca2+) 0 - 50 Cu2+, Zn2+, Ni2+, Fe2+ 5 - 10 KCl
Ca2+/Mg2+
ISE50B Ammonia gas sensing 5.10-7 - 100 0.01 - 17000 0 - 50 volatile amines 11 - 13 NH4Cl
NH3
ISE51B Carbon dioxide gas sensing 10-4 - 10-2 4.4 - 440 0 - 50 volatile week acids 4.8 - 5.2 NaHCO3
CO2/CO3 2-
ISE52B gas sensing 5.10-6 - 5.10-3 0.2 - 220 0 - 50 SO2, HF, acetic acid 1.1 - 1.7 NaNO2
Nitrogen oxides
NOx
in the Hoagland’s Solution. For an example of interference, in Hoagland’s Solution one of the ion
nutrients to measure is NO3, but one of the interferences for NO3 is ClO4. Cl2 is one of the mico-
nutrients, and when ClO4 dissociates in solution, Cl2 is left, thus inhibiting the NO3 electrode. The
mentioning of dissociation of ions in solution is what leads toseveral alternative solutions or
directions for HydroTower and measuring the nutrients in real-time. Currently, two alternative
designs are occurring t along a parallel time basis. One design alternative will become the new
HydroTower design direction by January 2011.
Table 7: Electrodes and interferences
37
The first alternative to the flood and drain system with the direct injection of nutrients is
an aeroponic/spray hydroponic technique. Such a system would change the design of
HydroTower in that the spray nozzles would direct the flow of water to plant roots and
Hoagland’s solution would be added directly into the water spray. One objective of the spray
technique would be to minimize the amount of waste water from such a process of spraying the
plants throughout the day. Despite a change in design for HydroTower, the Team is maintaining
the initial goals of providing sustainable methods for growing produce and other plants. The need
to eradicate waste water left over from watering/feeding the plants is environmentally unsound in
two ways. First, the waste water would contain the nutrients, which should not be introduced
directly into a water treatment system (eg: should not be poured down a residential drain). It is
not environmentally appropriate to implement a design which would require users to dispose of
the chemical waste through residential water/drainage systems. While the nutrients are found
naturally in soil and nature, introducing higher concentrations and having the only method of
disposal as residential drains does not align with the goals or objectives of HydroTower as being
a sustainable design. Secondly, wasting water is not efficient for the overall delegation of water
as a resource and is thus not a feasible option for the HydroTower design project.
The second alternative for the flood and drain system with the electrode analysis would
be to research solutions for analyzing individual ions in the water nutrient system. The premise
behind the second design alternative is based upon knowledge that when compounds are in
solution, ions dissociate and are thus individual elements. For example, NH3 is a compound in
Hoagland’s Solution, but in theory, the second alternative would use an electrode which measures
for N elements. Electrodes for N, Mg, Ca, K and possibly Fe would be used in research to
measure the conductivity of the water solution and analyze for specific algorithms to add the
makeup nutrients. Professor Doug VanderGriend will also be assisting team HydroTower in
researching possible ways to isolate the dissociated elements in solution using electrodes much
like the initial design intended. Furthermore, Professor VanderGriend would assist in analyzing
the data collected from the electrodes to see if any empirical relations may relate the element ions
to the amount of nutrient in the water solution. Said research will begin at the very end of first
semester and will continue into January 2011. However, a time limit on the research and design
of electrodes capable of analyzing the water solution after which the first design alternative will
be implemented fully.
A final design direction will be selected by the middle of January 2011.Currently, the
Team has been split into two sub-groups, one group looking into the first alternative of the spray
system and the second sub-group focusing on research for the electrodes. Until the final design
38
direction is selected, the team will remain working on the two alternative design options. Should
one design become very apparent as the best alternative, that design will become the new final
design direction. Delegation of time and efforts has been a 50-50 split between both design
alternatives, but as the project continues, one design alternative will become the main focus in
which case delegation of time and effort will become 90-10 (90% of the time being on the final
design direction and 10% being towards ensuring the correct design direction was chosen).
5.4. Psychrometrics
Mechanical design of HydroTower for optimal plant growth includes humidity and
temperature control of the water and nutrient system. The environmental conditions for plants are
optimal when relative humidity is about 50% and temperature is 70°F.31
5.4.1. Humidification
From a biological standpoint, if humidity is too high, and condensation forms on plant
leaves, the plants become susceptible to fungus and disease.32
Thus, the mechanical design of
HydroTower includes compensation for air flow and ventilation to regulate the humidity within
the HydroTower growing structure. Furthermore, if the relative humidity is too low, plants will
close their stomatas, which are how plants intake CO2 and release O2. Should the humidity
become too low, a humidifier will turn on via the control system for psychrometrics and will
subsequently add moisture to the air within HydroTower.
Initially, the mechanical designs were going to measure humidity with a hygrometer and
then have the regulation of air flow controlled by fans and a venting system with mechanical
flaps capable of different degrees of opening/closing. However further analysis of alternative
design options showed that a more complex and expensive humidity control system was not
necessary to meet the design requirements. For example, below is a list of the alternative designs
for the humidifiers/dehumidifiers, four humidifying systems researched and then analyzed
included the following.
1) Steam humidifiers which boil water to release steam into the air
2) Impeller humidifiers which move water through a diffuser to make very fine water
droplets in the air
31
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print. 32
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print.
39
3) Ultrasonic humidifiers which vibrate at an ultrasonic frequency to create water
droplets which are absorbed into the air.
4) Wick/evaporative humidifier which draws water out of a reservoir and allows water
to evaporate as air passes over the wick via a fan-powered ventilation system
Qualitative and quantitative analysis of the cost and implementation of each of the four
humidifying/dehumidifying systems was completed to move towards a final design on the
humidifier/dehumidifier system. Qualitative analysis of implementation and cost allowed Team
HydroTower to eliminate the steam humidifier and the ultrasonic humidifier. Both of the
aforementioned options would require more electrical and mechanical systems to control the
humidity, which would add to the overall cost of HydroTower. Furthermore, the components
necessary to have either a steam humidifier or an ultrasonic humidifier would subtract the
amount of space usable in the base unit by the electrical control systems and/or the amount of
water held within the base unit. Thus, either the controls box would move outside of the base
unit or the base unit size would need to increase. Overall, Team HydroTower decided to not
pursue further designs of implementing the steam humidifier or the ultrasonic humidifier.
The two other humidification system alternative designs were the impeller and then the
wick humidifier. Due to resources and initial thoughts of Team HydroTower and the tech lead
on the psychrometric design, the wick humidifier was pursued in quantitative analysis for
several reasons. First, the wick humidifier would require forced ventilation, and since Team
HydroTower found several CPU fans the cost for production of a prototype would be low.
Furthermore, the wick for the humidifier would be placed in the water tubing and then in the
middle of the forced air flow stream. The wick would be a water-absorbent cotton rope which
could be purchased at a fabric store for under $0.50/foot.33
A filter for the system may also be
necessary, but testing of the implemented wick design would show if a filter is needed for better
functioning. Should a filter on the wick humidifier prove necessary, the cost of the filter would
be under $10.34
Quantitative analysis of the wick humidifier system was based upon temperature changes
of the air and the amount of heat transfer from the water to the air. The amount of air flow
needed to maintain a relative humidity of 50% with an air entry temperature of 70°F and an exit
air temperature of 65°F was completed. The fan which was being used as the base case for the
flow rate of air were the fans found by Team HydroTower. The fans (two) were able to provide
33
"Cotton Rope | Twisted & Braided 1/4 - 1 Inch Sizes." KnotandRope.com. N.p., n.d. Web. 5 Dec. 2010. <www.knotandrope.com/store/pc/Cotton-Rope-c6.htm>.
34 "Wick Humidifier - Google Search." Google. N.p., n.d. Web. 05 Dec. 2010. <http://www.google.com/search?q=wick
humidifier...>
40
12cfm of air flow (cited in bibliography page DC Fan Data Sheet and NMB-Mat DC Axial Fan).
Equation 6.4.1 shows the main equation used to calculate the needed air flow rate while full
calculations are contained in Appendix E. The result of the calculation showed that one fan
capable of 12cfm would be enough to maintain the proper humidity within HydroTower since
the calculated air flow rate was 5.1 cfm based on the previously mentioned conditions.
𝑚𝑑𝑜𝑡𝑎 =𝑚𝑑𝑜 𝑡𝑤 𝑖𝑛
∗ ℎ𝑤𝑖𝑛− ℎ𝑤𝑜𝑢𝑡
ℎ𝑎𝑜𝑢𝑡 − ℎ𝑎𝑖𝑛 − 𝑜𝑚𝑒𝑔 𝑎𝑜𝑢𝑡− 𝑜𝑚𝑒𝑔 𝑎 𝑖𝑛 ∗ℎ𝑎𝑜𝑢𝑡
Equation 6.4.1
The following table shows the variables and variable names.
Table 8: Psychrometric calculations variable list
Variable Variable Name Units
𝑚𝑑𝑜𝑡𝑎 Flow rate of air Cfm
𝑚𝑑𝑜𝑡𝑤𝑖𝑛 Flow Rate of water Gal/min
ℎ𝑤 𝑖𝑛 Enthalpy of inlet water Btu/ lbm dry air
ℎ𝑤𝑜𝑢𝑡 Enthalpy of outlet water Btu/ lbm dry air
ℎ𝑎 𝑖𝑛 Enthalpy of inlet air Btu/ lbm dry air
ℎ𝑎𝑜𝑢𝑡 Enthalpy of outlet air Btu/ lbm dry air
𝑜𝑚𝑒𝑔𝑎𝑖𝑛 Humidity ratio of inlet air lbm H2O/lbm dry air
𝑜𝑚𝑒𝑔𝑎𝑜𝑢𝑡 Humidity ratio of outlet air lbm H2O/lbm dry air
Providing HydroTower remains with the flood and drain system along with the current
prototype model as the final design direction, HydroTower will implement a wick humidifier
due to the low cost and simplicity of implementing the design both in prototyping and in
manufacturing. The wick humidification system will work well for ensuring that the air within
HydroTower remains at about 50% relative humidity because as the air becomes more humid,
the water requires more energy to evaporate and the same principle applies for dry air (easier to
evaporate water when air is less humid). Thus, the wick humidification system works by natural
evaporation of water from the wick. Specific design of the wick humidifier will occur during
spring semester once the final design direction is known. However, one specific issue with wick
humidification to be addressed during the design phase is that wick humidification will be to
ensure that condensation does not occur within the HydroTower. Thus, as previously mentioned,
the two fans will be installed on each growing level on either side of HydroTower. The wick
humidifier will have a control system based on readings from a hygrometer. For the control
41
system, if the humidity is too high the fan furthest to the water input flow (hence, the fan without
the wick in front of it) will turn on. Should the humidity remain high, both fans will turn on. The
fail-safe method to ensure humidity can be lowered within HydroTower will be looked into
further during the spring semester. The table below shows a more visual summary of how the
fans will turn on and off via the control system and hygrometer readings.
Table 9: Summary of wick humidifier design for fan usage
System Reading Fan with Wick Fan without wick
Humidity too high Off On
Humidity too low On Off
Extreme ranges high
or low
On On
Fail-safe method for
humidity out of
range
To be determined in
spring semester
To be determined in
spring semester
5.4.2. Temperature
Control of the temperatures of both water and air are necessary to optimize plant growth,
however, hierarchically, the water temperature is more important. Such a decision is based on
the rate of heat dissipation from the water and the rationalization that the air temperatures will be
relative to the ambient air in a room of a residential area. The optimum growing temperature for
most plants is 70°F.35
Using the waste heat from the electrical components has been discussed as
a method to control the heat of the water. However, since the Team is still working towards
finalizing a design direction, specific mechanical design and analysis for the temperature control
system have been placed on hold until a final design direction is chosen.
35
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print.
42
6. Frame Structure
The responsibility of the frame and structure design of HydroTower is one portion of the
mechanical responsibilities of Team HydroTower and specifically falls to Brian DeKock and
Jacqueline Kirkman. The frame and structure design must fit within the objectives of a modularized
unit which is light weight and easily transported when emptied from plants and water. The frame
structure must also be sturdy enough to be operable under safe conditions. Specific quantities and
objectives on the safety regulations for HydroTower have not yet been quantified but will be
addressed once a final design direction has been chosen. Furthermore, specific requirements on the
weight and transportability of HydroTower are estimated thus far in the design process. This section
addresses the specifications of the frame of HydroTower including the size, safety, mobility,
manufacturability and appearance of HydroTower.
6.1. Structure and Size
The structure of the HydroTower is designed to fit in typical housing in urban areas, thus
the standard measurement widths of doors. Some of the more informal requirements of the
HydroTower structure established by the Team were light weight and transportable when not full
of water and plants, small enough to fit through doorways but large enough to grow plants
equivalent to that of a small garden plot, yet robust enough to have a design life of 20 years and
sturdy such that the center of gravity is low and the chance of tipping over is low for user safety
as described in Safety/ Stability and Durability section. Initial designs of the HydroTower
structure were composed of circular modularized stackable units to make HydroTower
aesthetically pleasing. Team HydroTower assumed that circular designs were more visually
appealing to consumers and would thus fit well within the marketability of HydroTower.
However, after the
Hence, while the current working prototype of HydroTower is a circular modularized unit
2.5 feet in diameter, the next working prototype will be built as a rectangular unit with the short
side a width of 32 inches, based on standard door widths for residential houses.36
Sizing constraints for HydroTower are based upon usage in a residential setting (thus, the
size of the household or apartment) and the functional aspect of growing plants (overall square
meters comparable to an outdoor garden The current height of HydroTower includes a base unit
1 foot high with each modular growing level 2 feet high. Thus, the maximum height of
HydroTower would be 5 foot.
36 DoItYourself. What is the Standard Door Fram Width? Nov 30, 2010.
<http://www.doityourself.com/stry/what-is-the-standard-door-frame-width>
43
The modular and stackable design provides the user with adaptability and portability such
that a user may choose how many plants are grown and the overall configuration of
HydroTower. For example, a user may purchase the base unit and one growing level, one base
unit and two growing levels. Many possibilities for base unit and growing levels exist, but the
constraints are that at least one base unit and one growing level are necessary for function while
the maximum is two growing levels supported on one base unit.
6.2. Safety/ Stability and Durability
Safety is a very important aspect of this project for several reasons. First, a responsible
engineering design should not place anyone in danger, thus, HydroTower must be stable and
should not tip over or break through normal usage during the design life.
Since HydroTower prototypes are built from wood and plastics, structural durability is an
issue which will be analyzed further once a final design direction is made and during second
semester of Engr 339/340. A finite element analysis will provide the necessary information on
key parameters to ensure the design stability. All HydroTower components shall be selected
such that durability and cyclical fatigue meet the design requirement of a design life of 20 years.
Analysis of such durability and fatigue will be completed after a final design selection is made.
6.3 Mobility
The HydroTower must be mobile enough to be moved by one average-sized adult person
regardless of gender. Mobility of HydroTower is very important to the overall success of the
project. HydroTower will be purchased as a fully assembled base unit with one growing level.
Additional growing levels may be purchased individually. However, all modular components
must be easily moved from the store to the user’s residence and must be easily set-up by the
user. Initial market research has confirmed HydroTower will need to produce food for a family
but will need to fit in a corner of a room. The final design of HydroTower will determine the
overall mobility of the product instead of the mobility determining the design since the Team has
chosen overall function as a higher priority than mobility. However, mobility is still a factor in
design decisions and will be used more during second semester and final design selections.
6.4 Ease of Build
The relative ease of producing HydroTower for mass production is a high priority for
both the design and prototype of HydroTower. While the measures of success for HydroTower
44
in May 2011 only define a working prototype, planning for full scale production of HydroTower
is a priority in the design and decision making processes. Hence, the design of HydroTower
must not only meet the direct requirements as established by the group for success, but must also
allow a transfer to an assembly line production method. For example, each HydroTower will be
a modular component off the base unit. Thus, each growing level will be manufactured the same
way. The growing levels of HydroTower will be stackable via interlocking metal rectangular
tubes wherein the tubes for the growing levels fit within the tubes for the base unit. Figure 10
depicts the exploded assembly version of the HydroTower. The design must be easily transferred
to an assembly line and consideration of assembly during final design selection will assist the
Team in knowing what methods to employ for manufacturability.
45
Table 10: Full assembly of second HydroTower prototype
46
6.5 Aesthetics
Part of designing in engineering is to make a product that not only serves its purpose, but
also is pleasing to the eye. Marketing for HydroTower is for in-home and residential usage, thus,
the HydroTower will be placed in the house or apartment and will need to coordinate with
interior décor. Some brainstorming has concluded HydroTower could be manufactured in
several colors or could have some patterns on the exterior such that users could select the design
which best fits their style and décor. Aesthetics will be a strong selling point for HydroTower as
a product. Successfully blending function and aesthetics will be a key component in selling the
HydroTower. While function of HydroTower is hierarchically a higher priority than aesthetics, if
HydroTower does not meet the aesthetic appeal to potential customers the overall success of
HydroTower as a product will be lessened.
47
7. Business Analysis
7.1. Market Research
7.1.1. Customer
HydroTower involves minimizing space and maximizing efficiency to grow plants in a
non-commercial environment. The market for this type of product would be anyone who does not
have gardening space to grow vegetables and plants. More specifically, HydroTower is being
targeted at women who have a family at home and need fresh produce for their children. The
table below shows the 2006-2008 statistics from the United States Census Bureau.
Table 11: Census Bureau 2008 population37
Between the ages of 25 and 39 there are over 30 million women living in the United
States. If only 1% of the population of women in the United States buy at HydroTower within the
first two years over 60,000 units could be sold each year.
Growth in this market could increase as larger questions are raised about the safety of
consumers in commercial food production. Additional growth could be driven by the growing
number of people moving into cities and living in apartments and high rise condominium towers.
HydroTower presents the perfect solution for the consumer who is looking to eat fresh produce
whose quality can be ensured all while reducing the carbon footprint of large scale food
production.
7.1.2. Overview of Market
The current hydroponics market is a growing market as perceptions shift towards the need for
new sources of food production. The hydroponic tomato market alone is predicted to grow by
37
http://factfinder.census.gov/servlet/STTable?_bm=y&-geo_id=01000US& qr_name=ACS_2008_3YR_G00_S0101&-ds_name=ACS_2008_3YR_G00_
48
over 50% from 2007 onward.38
In the past hydroponic gardening has often been associated with
marijuana cultivation. Many people are unaware that hydroponics can be used to grow many
types of herbs and vegetables indoors with incredible efficiency. Some current hydroponic
growers and designs can be seen in the competitor analysis section of this business plan. The
HydroTower creates a distinct and new niche in the market for hydroponic gardening. First by
designing a new type of hydroponic grower with the visual appeal that is unseen in the market of
previous hydroponic gardeners will be attracted to this product. The second part of the market
will attract people who have never been interested in hydroponics due to the maintenance and
complexity of the system. HydroTower’s user interface and scheduling system will now make it
easier for an individual to grow many plants comparable to that of a home garden.
7.1.3. Market Survey Results
An ongoing market research survey is being conducted during the writing of this report.
Currently there are 21 responses to the survey with 10 questions. The questions are listed
below:
1. How often do you buy fresh produce from the grocery store?
2. How much of the produce that you buy is organic?
3. Would you be more likely to buy produce labeled organic?
4. Do you have a garden at home?
5. Pleas list what fruits or vegetables you grow in your garden.
6. Would you prefer to grow more of your own food if you had enough space?
7. Are you familiar with hydroponics?
8. How likely would you be to purchase a hydroponic system for growing vegetables?
9. Please list what vegetables you would want to grow most in a hydroponic system?
10. Which of the following would make you more likely to purchase and use a
hydroponic system?
The HydroTower team is currently not ready to fully analyze the results of the online survey.
Before next semester we hope to at least double the amount of responses to the survey. In
addition we hope to increase the variety of people who take our survey from college students to
older adults and our target market, women with families. The following figure shows two slides
from the final semester presentation detailing our results. Results will be summarized in the
second half of our project during Engr 340.
38 Brentlinger, D.J. 2007. NEW TRENDS IN HYDROPONIC CROP PRODUCTION IN THE U.S. Acta Hort. (ISHS) 742:31-
33. http://www.actahort.org/books/742/742_3.htm
49
Figure 23: Survey results on likely aspects for purchasing HydroTower
Figure 24: Survey results on customers growing their own food
7.2. Strategies to Success
The key strategy to success in the HydroTower business plan is perception. A majority of
people either have no idea what hydroponics is or immediately associate hydroponics with drug
use. In talking with many hydroponic gardeners this perception has slowly begun shifted to a
positive light over the last ten years. Even though many hydroponic businesses have grown over
the past few years the largest source of hydroponic knowledge is still individuals who post their
ideas and projects online.
The second key strategy will be to convince consumers of the tradeoff that they have when
choosing hydroponic gardening options, such as the HydroTower, over other options for
50
purchasing produce. The key tradeoff for consumers to consider will be that growing food in the ir
own homes is higher quality and has a greater sustainable/environmental impact over simply
buying from the grocery store. Additionally the HydroTower presents the opportunity to avoid the
growing number of food and produce recalls that have hit multiple regions of the United States.
7.2.1. Entrepreneur’s vision of the company
HydroTower’s vision is to “Feed people, more efficiently, through hydroponics”.
HydroTower will be a standalone unit capable of producing plants for feeding a family of four.
HydroTower will reduce the amount of soil, nutrients and water used in growing plants while also
decreasing the amount of fossil fuels used in transporting produce from the farm to the market.
7.2.2. Design Norms
The HydroTower Team has chosen three specific design norms that will help drive our design
decisions and ensure a quality product. The first design norm is stewardship. The HydroTower
team strives to be good stewards of God’s creation by decreasing costs of transportation, fossil
fuels, current food processes. Sustainability and environmental impact will be some of the largest
issues in the 21st century. The second design norm is transparency. We want to be open and
genuine with our customers about the functionality and usability of this product. The third design
norm is trust. Trust is vital in any relationship between a company and a customer. However the
HydroTower Team takes this very seriously given the past perceptions of hydroponic gardening.
The HydroTower team wants to have customers trust that they can feed families with an efficient
and reliable system.
7.3. Industry Profile and Overview
7.3.1. Industry Profile
The hydroponics industry is largely based on many small businesses that each
manufactures specific parts for hydroponic gardening. Large commercial hydroponic farms exist
but are currently not feasible for large scale production when compared to traditional farming
methods. However, research on large scale hydroponic farms has been occurring more
prevalently. Articles have been published by university professors have been published over the
past twenty years. A number of textbooks on hydroponics are also available
39 40
. Alarge portion
39
Howard M. Hydroponic Food Production. 6thth ed. Mahwah, NJ: NewConcept, 2004. Print. 40
Dalton, Lon, and Rob Smith. Hydroponic Crop Production. Tauranga, New Zealand: NZ Hydroponics International, 1999. Print.
51
of the individual hydroponic gardening industry is based off of the internet according to both
Mud Lake Farms and Horizon Hydroponics. Many individuals have posted their own builds and
recommendations on many websites that cannot be found commercially.
7.3.2. Major Customer Groups
First and foremost, HydroTower is designed for the individual or family who is looking
for a gardening solution without having a backyard garden. As larger numbers of people move
into cities, growing space will become scarcer.
More specifically HydroTower’s customer is going to be families without traditional
outdoor gardening space who are looking for a way to grow the freshest vegetables. An additional
customer group would be individuals who are skeptical of grocery store produce and are looking
for the freshest and highest quality fruits and vegetables.
Future customer groups currently outside the focus of the HydroTower Team include 3rd
world applications, schools and high end restaurants. A lower cost application (roughly 10
percent of original cost41
) of HydroTower would open up the largest customer group that number
in the millions and possibly billions throughout the developing world.
7.3.3. Regulatory Restrictions
There are currently no direct regulatory restrictions pertaining to hydroponic growing.
Any regulatory restrictions in place will be on safety features of the HydroTower. The safety
concern and regulation will be in design that combines water and electrical connections. These
regulations are set by the UL, FCC, and CE. Organic farming in the HydroTower will be under
the direction of the organic growing standards set by the United States government. There are
additional local and federal regulations on the cultivation of marijuana that can be grown through
hydroponics. However these ordinances and laws pertain only to the use of marijuana and not to
the use of hydroponic gardening.
7.3.4. Growth Rate and Outlook
Over the next five years, the number of tomatoes grown in hydroponic greenhouses is
expected to rise by 50%. Lettuce and herbs are now also increasingly being grown
hydroponically. Microgreens are also being introduced as a valuable hydroponic crop. High
41
Smith, Amy. 7 Rules of Design for Low-Tech Engineering. N.p., Oct. 2009. Web. 29 Nov. 2010. http://www.popularmechanics.com/technology/engineering/gonzo/4273680
52
quality hydroponic and organic hydroponic fruits and vegetables are selling at more than 15% -
50% higher than traditional fruits and vegetables.42
7.3.5. Key Success Factors
The largest current barrier to entry is the uncertainty of hydroponics. The most common
element in conversations on HydroTower is the question, “What is hydroponics?” Many people
are initially skeptical about growing plants without any soil indoors. Success will depend on how
willing customers are to try something new. In addition, as with any emerging and growing
market, competitors will be looking to take a share of the market. Many competing products are
able to produce high quality produce. HydroTower will need an easy to use interface and
appealing design to compete where other products have fallen short. These other products are
shown in the competitor analysis below.
7.4. Business Strategy
7.4.1. Desired Image and Position in Market
The desired image of HydroTower Team is to create a new application in hydroponic
gardening using the fundamental principles of hydroponics combined with automation, easy to
use interface, and strong visual appeal. It is the desire of the HydroTower Team to shift the
perspective of hydroponic gardening away from a complex and commercial product into a simple
and consumer-based product through HydroTower. Specifically HydroTower will have an
innovative low maintenance design along with a new type of nutrient automation system.
7.4.2. Company Goals and Objectives: Operational
The operational goal of the HydroTower Team is to create a functional semi-automatic
stackable system based on the fundamentals of hydroponic gardening which grows quick and
high quality herbs, fruits, microgreens, and vegetables.
7.4.3. Company Goals and Objectives: Financial
The financial goal of the HydroTower Team is to balance the cost of automation with the cost
of usability and appeal. It is the objective of the HydroTower Team to find the balance between
valuable features and cost. The cost of the HydroTower will stay low in cost by using the most
42 Brentlinger, D.J. 2007. NEW TRENDS IN HYDROPONIC CROP PRODUCTION IN THE U.S. Acta Hort. (ISHS) 742:31-
33. <http://www.actahort.org/books/742/742_3.htm>
53
inexpensive microcontrollers while still maintaining the requirements as established by the Team
to control automation and standard parts that can be easily manufactured and mass produced.
7.4.4. SWOT Analysis
Strengths: Expanding market with many new ideas on hydroponic gardening. People are
more likely to try out ideas and product which are showing up multiple places in different forms.
Weaknesses: Quality reference research material lacking, not organic, untested ideas for
automation.
Opportunities: Many small and startup companies in the industry. This competition will
keep the HydroTower team thinking and working towards the best possible solution.
Threats: Large corporation industrial designs
7.5. Competitor Analysis
7.5.1. Established Competitors
The RotoGro 240 Rotating Garden has an innovative design with timer and rotating motors.
The design is quoted as saying, “The effect of gravity on the rotation of plants is amazing. Its
strengths are that the RotoGro is a developed product on the market and it has an innovative
design. The weaknesses of this product are that it costs $5,200 and lacks in visual appeal. Almost
nobody would want to have something like this product sitting in their living room.43
Figure 25: RotoGro 240 Rotating Garden
43
"RotoGro 240 Rotating Garden." HHydro.com. N.p., n.d. Web. 5 Dec. 2010. <http://www.hhydro.com/RotoGro-240-Rotating-Garden.html>.
54
The second established competitor is the Desktop Hydroponic System. The Desktop
Hydroponic System is a compact planter that grows small herbs on desk using sunlight or the
artificial light from an office. This product has a strong visual appeal and a low cost of $40. The
weaknesses of the Desktop Hydroponic System are that it has no additional light source and is not
big enough to feed a family. Growing options are limited.44
Figure 26: Desktop Hydroponic system
The AeroGarden Pro 200 Indoor Tabletop Vegetable Garden is a fully automated system
that is capable of growing multiple types of herbs and vegetables. For $200 the indoor garden
provides everything that is needed to start growing. The weaknesses of this product are that it
lacks growing spaces and still does not have a strong visual appeal.45
Figure 27AeroGarden Pro 200
44
"ThinkGeek :: Power Plant Herb Garden." ThinkGeek. N.p., n.d. Web. 05 Dec. 2010. <http://www.thinkgeek.com/homeoffice/kitchen/b7d7/?cp g=cj&ref=&CJURL>.
45 "The Indoor Tabletop Vegetable Garden." Hammacher Schlemmer. N.p., n.d. Web. 05 Dec. 2010.
<http://www.hammacher.com/publish/75426.asp#?cm_mmc=CJ-_-2617611-_-3682082-_-Save up to 70% on
Electronics>.
55
7.5.2. Potential Competitors
“Biosphere home farming concept generates food and cooking gas, while filtering water.
The concept supplements a family’s nutritional needs by generating several hundred calories a
day in the form of fish, root vegetables, grasses, plants and algae. Unlike conventional
hydroponic nurseries this system incorporates a methane digester than produces heat and gas to
power lights, similarly algae produces hydrogen and the root plants produces oxygen, which is
fed back to fish. CO2 is pumped into the plants. It is a closed loop interdependent system. The
system uses waste water and non-consumable household matter and delivers food in return.”46
The strength of this idea is that it is backed by Phillips which is a large company. However the
system is larger than most needs for a family.
Figure 28: Biosphere Home Farming
The Nano Garden is a design concept produced by Hyundai with a strong visual appeal.
“The Nano Garden is a vegetable garden for the apartment kitchen, using hydroponics, so users
don't need to worry about pesticides or fertilizers. Instead of the sunlight, Nano Garden has
lighting which promotes the growth of plants. The amount of light, water and nutrient supply is
also controllable, so users can decide the growth speed. It lets users know when to provide water
or nutrients to the plants, and Nano Garden functions as a natural air purifier, eliminating
unpleasant smells.”47
46
"Biosphere Home Farming by Philips." Yanko Design. N.p., n.d. Web. 05 Dec. 2010. <http://www.yankodesign.com/2009/03/17/the-ultimate-recycle-bin-nourishes-as-well/>.
47 "Kitchen Nano Garden." Fast Co. Design. N.p., n.d. Web. 5 Dec. 2010. <www.fastcodesign.com/idea-2010/kitchen-nano-
garden>.
56
Figure 29: Kitchen Nano Garden
57
8. Business Financials
HydroTower has been identified as a potential marketing and business opportunity. The business
financials section contains estimates on costs and revenue possible for HydroTower. Professor
Medema of the Business Department at Calvin assisted the HydroTower Team in beginning an
analysis on HydroTower. However, due to the issues faced in selecting a final design direction, much
of the financial analysis will occur during Engr. 340.
The current outlook for HydroTower is to sell modularized levels, the first of which would be the
base unit. Subsequent stackable units could be purchased and attached to the base unit. HydroTower
will also sell refills of the nutrient concentration bottles.
8.1. Prototype Costs
Throughout first semester, the Team has been exploring alternative design options
through testing and prototyping. Costs of the prototype are listed in the table below.
8.2. Variable and Fixed Costs
Cash flow analysis for HydroTower was completed based upon the Excel file provided
by Professor Medema in the Calvin Business Department. Appendix B contains the cash flow
analysis compiled in Excel. This outlook was used to determine whether or not starting a new
business for this product would be feasible. The cost analysis was based on concepts learned in
Business 357. The BizPlan financial template was used to analyze a three year product forecast.
Based on information from the continuous online survey, there is a predicted market that is
estimated to have sales revenue of $100,000 in the first year. The number of units sold is based on
assuming a small percent of the market will purchase it each year, gradually increasing as it gains
recognition. The fixed cost in the first year is higher than the second and third years because of
Material for Purchase # of Units Cost per Unit ($) Total Cost ($) Description
Wood (Sheets 4*4ft) 2 0 0 Provided free to Team by Engr WoodShop
Metal (Sheets 2*6 ft) 1 0 0 Provided free to Team by Engr WoodShop
Nails 12 0 0 Provided free to Team by Engr WoodShop
Perlite 1 3.79 3.79
Seeds 60 0 0 Provided free to Team by Biology Dept
Nutrients (in L of solution) 2 0 0 Provided free to Team by Biology Dept
3.79Total Prototype Cost
Table 12: Prototype Costs
58
Fixed Costs Amount
Rent on Facility 100,000
Renting Equipment for Manufacturing 200,000
Taxes 50,000
Salaries (manager, 4 employees at 40,000/employee) 290000
Labor of Design (200 hours) 20000
660,000
Variable Costs (5000 units/ year)
shipping 15 75000
LED Lights 50 250000
LCD Touch Screen 100 500000
Water Pump 30 150000
Chemicals 25 125000
Tubing 10 50000
Temperature Sensors 10 50000
Microprocessor 30 150000
Housing/Build materials 20 100000
1450000
Total 2,110,000
Breakeven Point ($) 422
repair, replacement and initial purchasing costs. The depreciation expense fluctuates because the
initial purchasing cost and interest is compiled throughout the next two years. The equipment
purchase for the second year and the third are much lower but still exist because the growth of the
company. Interest rates are based on a pessimistic view of the economy. Error! Reference
source not found.The cash flow analysis is solely a prediction and only used as a way to assess
the start up of a potential business. More cash flow analysis will be done in the second semester
when more information can be obtained. In conclusion, based on the assumed number of units
sold, the business will break even around the end of year two and turn a large profit at the end of
year three.
8.3. Cash Flow Analysis
The final design of the HydroTower is an innovative and functional design that offers a
product to the hydroponic market that is not offered on the market. This type of product has the
Table 13: Variable and fixed costs estimations for HydroTower
59
potential to be profitable. The purpose of the cash flow analysis is to analyze the costs and profit
if a business were formed to design and sell this product to the market.
For this class, the team will be designing a prototype useable in urban residential housing
areas. The cost for the prototype and the final design is expected to differ. During the
prototyping, multiple design considerations cause cost to increase. Designs are perused but later
deemed infeasible. In addition, several components were salvaged from spare parts in the
engineering building to keep the final cost within budget.
60
9. Management
9.1. Project
Since the Team is comprised of two mechanical and three electrical engineering students,
work was delegated to each member according to the strengths each member provides the Team.
Table 9.1.1 shows the work delegated to each Team member. While multiple members of the
Team work together, one member is designated as a Tech-Lead and is thus responsible for the
overall organization of their specific task area.
Specifically, below is a description of each of the Team member’s responsibilities. While
much work is done in teams, the descriptions below explain individual roles of the Team and the
specific delegation of work.
Brian DeKock was placed in charge of the overall structure and manufacturing of
prototypes. Brian has the most knowledge and passion for building in the
woodshop and finding ways to implement designs using “scraps” from the wood
and metal shop. Brian was also placed in charge of the heating/cooling system as
well as the water piping. Each of the heating, cooling and piping systems involve
Table 14: Tech-Lead positions for the HydroTower Team
Task Tech Lead
Business
Big Idea Project Nathan
Elevator Pitch Brandon
Engineering Business Plan Jacqueline
PPFS
Project Requirements Brenton
Research Brian
Feasibility Jacqueline
Design
PCB Brandon
Power System Brandon
User Interface Nathan
Automatic Plant Care Program Brenton
Air Quality Controls Brenton
Water Quality Controls Nathan
Structure Design Brian
Air Flow Jacqueline
Water Piping Brian
Heating/Cooling Brian
Chemical Distribution Jacqueline
61
integration of components into a prototype system. Thus, Brian was the best fit
for each of his task delegations.
Brenton Eelkema was in charge of developing the business overview and WBS
creation. In addition he worked to build and measure preliminary experiments in
hydroponics. Brenton took Brandon’s place as the representative of HydroTower
in the Elevator Pitch, a competition put on by the Business Department and
Entrepreneurship Club at Calvin. HydroTower took third place out of 12
competitors, earning $300 for the Team’s budget.
Jacqueline Kirkman was delegated the air flow system and the chemical
distribution system. Jacqueline has the most experience of the group members in
chemical systems and was thus the logical choice. Psychrometrics and air
ventilation were also assigned to Jacqueline’s responsibilities. Jacqueline has
further acquired the position of Project Manager due to her organizational and
detail-oriented management skills , thus other tasks are delegated to Jacqueline
which fall under team management but are not specifically listed here.
Nathan Meyer was delegated to manage the software design and implementation.
Nathan is also responsible for the design of the nutrient control logic. Nathan
presented to the Big Idea Contest judges since HydroTower was selected in the
final four applicants. The Big Idea Contest was a competition hosted by the
Enterprise Center at Calvin; HydroTower made it to the final four but did not win
the grand prize of $200. Nathan has been assigned to maintain the team website
and update it as content becomes available.
Brandon Vonk has the responsibility of designing the power systems and printed
circuit boards (PCBs) along with the lighting system for HydroTower. Brandon
has the most experience with PCBs and thoroughly enjoys working with power
systems, making him the best choice. Brandon has also been delegated the
responsibility of maintaining an updated team budget.
9.2. Work Breakdown Structure and Scheduling
The Team has selected a project schedule such that the project should be completed by
April 26 in order to yield two weeks of leeway to handle unexpected delays or obstacles in the
project. Figure 30 and Figure 31 show the current project schedule that was made using MS
Project. The full project work breakdown structure (WBS) is located in Appendix A.
62
Figure 31: WBS Fall Semester
Figure 30: WBS Spring Semester
63
9.3. Budget
Brandon Vonk is responsible for maintaining an updated budget for the team.
Maintaining the budget requires updating both the working budget and the projections for the
budget in MS Excel. Completing the necessary order forms when necessary is also contained
within the responsibilities for maintaining the proper budget. Current expenses and more cost
details are contained in Section 8.
9.4. Website
Nathan Meyer is responsible for both updating and maintaining the team website. Nathan
is the most familiar with programming and the DreamWeaver software and was thus the most
logical choice for the overall upkeep of the website.
9.5. Meetings and Status updates
Team meetings have been established as a weekly occurrence held on Wednesdays
following the conclusion of Engr 339, typically beginning at 3:30pm and lasting for either one or
two hours. Other meetings are called as necessary to ensure the team remains in clear and
focused communication. Meeting agendas are made by Jacqueline Kirkman in advance to the
onset of the meetings. Furthermore, meeting agendas are distributed before each meeting such
that all team members can review the agenda and have input on meeting topics. All meeting
topics are prioritized to ensure items of higher importance are discussed and issues of highest
importance can be addressed in the most efficient manner.
Weekly status updates for both the team members and the overall team are sent out every
week to the Team’s advisor, Professor VanderLeest. Each team member records the amount of
hours they work individually, and team hours are designated for when all team members are
present for a meeting or for team work. Team status reports are submitted on Sunday evenings to
Professor VanderLeest after each individual member reports their time, their accomplishments
for the week of submittal and their tasks for the next week. Jacqueline Kirkman organizes the
final team weekly status update.
9.6. Resources
Listed below are the key resources contributing to the success of Team 2.
Professor Steve VanderLeest, Team 2 advisor, ensuring the successful
completion of HydroTower tasks and assisting in brainstorming to solve some
design problems.
64
Professor David Wunder, assisted Team 2 in researching different ideas for
chemical analysis for the water supply.
Professor David Dornbos, taught the Team how to mix Hoagland’s solution and
gave access to the Biology department’s plant laboratory and gave Team 02
seeds to begin experimenting hydroponic growth. Has been a continuous
resource for knowledge about plant growth and optimization.
Professor Uko Zylstra, connected the Team with Mud Lake Farms (Kris and
Steve Haitsma).
Steve & Kris Van Haitsma, owners of Mud Lake Farm, provided the Team with
information about hydroponic growth and gave the Team a tour of Mud Lake
Farm hydroponic floating system.
David Plant, Werecon: Advanced Water Treatment, assisting the team in research
of electrodal analysis of the water supply and providing more alternative
solutions to nutrient system design.
Professor Robert Medema, Business Department, assisted with cash flow
analysis and was the main contact to SoundOff Signal
SoundOff Signal, donated LED’s.
Tim Theriault, Team Industrial Consultant, provided valuable advice to the team
regarding project scope and timeline goals.
65
10. Design Competitions
10.1. 2011 ASME Innovation Showcase
Deadline: January 10, 2011
“Inspiring students to be product innovators and entrepreneurs, the ASME Innovation
Showcase (IShow) provides a platform for top collegiate teams to compete for seed money to
further develop their product. While demonstrating their technical creativity, winners must
prove that they have a sustainable business model to a judging panel of successful innovators,
industry experts, venture capitalists, and intellectual property specialists.”48
10.2. IEEE Engineering in Medicine and Biology Society Student Design Competition
Deadline: June 1, 2011
“This competition involves designing and building an original device or product not
currently offered on the market that applies engineering principles and technology to
problems in medicine and biology. Other acceptable designs include a modification of an
existing product, and may consist of hardware, software, or a combination of both.”49
10.3. 2011 IEEE Presidents’ Change the World Competition
Deadline: January 31, 2011
“The IEEE Presidents’ Change the World Competition recognizes and rewards students
who identify a real-world problem and apply engineering, science, computing, and leadership
skills to solve it. The contest offers students the perfect opportunity to have their ingenuity
and enthusiasm for engineering and technology recognized by prestigious IEEE members
around the globe.” 50
48
"ASME IShow - Programs." American Society Of Mechanical Engineers - ASME.ORG. N.p., n.d. Web. 05 Dec. 2010. <http://www.asme.org/Communities/Innovates/Programs/Innovation_Showcase_IShow.cfm>.
49 "IEEE Engineering in Medicine and Biology Society Undergraduate Student Design Competition." IEEE. N.p., n.d. Web. 05
Dec. 2010. <http://www.ieee.org/membership_services/membership/students/awards/eng_medicine_undergrad_
design.html>. 50
"Presidents' Change the World Competition." IEEE. N.p., n.d. Web. 05 Dec. 2010. <http://www.ieee.org/membership_ services/membership/students/competitions/change_the_world/index.html>.
66
11. Conclusions
Overall, Engr. 339/340 and the PPFS concluded that HydroTower: Gardening Solutions as both a
project and product are feasible based upon proven technologies, analysis and testing of current
prototype designs. We have achieved many milestones throughout the course of this semester such as
building a prototype, selecting and obtaining LEDs, upload of the team website, basic analysis of air
flow design, and selection of frame structure as a of a rectangular modular unit.
Although some aspects of the final design have yet to be fully addressed, they will be attended to
next semester. This includes nutrient system, rectangular prototype, final design components, and the
finalized business plan. The team as identified a few concerns which one being the cost of the
HydroTower in a new and competitive market, another is the integration of computer/electrical and
mechanical systems, but realizing these risks will prove to help the design process and help in the
decision making process. The project is on schedule and the HydroTower team is confident that is
can complete the final design on time and according to design specifications.
For the second part of our project the HydroTower team plans to accelerate the development of
our design. We are confident that we will be able to move forward at a greater pace due to the
development of our team and the creation of a framework that will enable us to move on from our
mistakes and repeat our successes. The HydroTower team will continue to work through January in
order to hopefully finalize design requirements and ensure that financial and planning projections are
met.
We will continue our work in the second semester in order to insure that requirements and
deadlines are met promptly. We will no longer have the option to make major design changes that
could fundamentally effect how our product works. Again, fundamental decisions will need to be
made on the nutrient system in order to ensure a viable product.
The HydroTower team hopes that these decisions will help to create a high quality Senior Design
project and overall excellent project.
67
Appendix A: Work Breakdown Structure/ Milestones
68
Appendix A: Work Breakdown Structure/ Milestones (Cont)
69
Appendix A: Work Breakdown Structure/ Milestones (Cont)
70
Appendix B: Cash Flow Analysis
71
Appendix B: Cash Flow Analysis (Cont)
72
Appendix C: Lighting System Design Calculations (Red LEDs)
73
Appendix C: Lighting System Design Calculations (Red LEDs) (Cont)
74
Appendix C: Lighting System Design Calculations (Red LEDs) (Cont)
75
Appendix C: Lighting System Design Calculations (Red LEDs) (Cont)
76
Appendix D: Lighting System Design Calculations (Blue LEDs)
77
Appendix D: Lighting System Design Calculations (Blue LEDs) (Cont)
78
Appendix D: Lighting System Design Calculations (Blue LEDs) (Cont)
79
Appendix D: Lighting System Design Calculations (Blue LEDs) (Cont)
80
Appendix E:Psychrometric Calculations for Air Flow System
Assumptions:
Compressed liquid water
Enclosed space
Heat loss only from water to air (enclosed) by natural convection
<Could add heat loss from sides>
2.0 Inputs
Pressure:
P 14.696 psia <assumed>
0.1779594 psia <calculated from T_ambient> stPSAT
Temperature:
Water In 70 F <assumed>
21.11 C <calculated>
Water Out 65 F <assumed>
Ambient 50 F <assumed>
10 C <calculated>
Diameter of HydroTower and Thickness of Walls:
Thickness 3 inches <assumed>
Thickness 0.25 feet <calculated>
OD 2.5 feet <measured>
ID 2.25 feet <calculated>
Height 1 feet <measured>
Volume of Water in Base Unit:
V_gal 3.9760782 gallons <calculated>
V_m^3 0.01505109 m3 <calculated>
V_L 15.0510933 L <calculated>
Ideal Relative Humidity:
rel_hum 0.5 %
P_sat_T_ambient
Psychrometric Calculations for Air Flow Design of HydroTower
81
Appendix E:Psychrometric Calculations for Air Flow System (Cont)
Properties <Assumed Compressed Liquid>
Thermal Conductivity k 0.348895 Btu/hr-ft-F <calculated> stCDL
Heat Transfer Coeff h 1 k*Nu/ L_c
Surface Area: Water A_s 3.976078 ft^2
Density ρ 62.30856 ft^3/lbm <calculated> stVCL
Characteristic Length L_c 2.25 ft <assumed>
kinematic viscosity ν 0.000681 lbm/ft-s <calculated> stVISL
Prandtl Number Pr 0.121445
gravity g 32.2 ft/s2
Volume Expansion Coeff β 0.014286 1/F <assumed>
Thermal Diffusivity α 0.005607 <calculated>
Specific Heat Cp 0.998662 Btu/lbm-F <calculated> stCPL
Flow Rate of Air m_dot_a 12 cfm <Data Sheets for fans, see Jacq drive>
Flow Rate of Water m_dot_w 1 gal/min <Assumed based on the pump>
2.31E-03 lbm/s
Specific Volume of inlet water
0.016049 ft^3/lbm
82
Appendix E:Psychrometric Calculations for Air Flow System (Cont)
3.0 Calculations
Notes:
Procedure
Find heat given off by water in 1 level (can be scaled up later)
Assume CV is closed, thus no airflow
Find condensation tempurature
Find min flow rate to stop condensation
If too dry:
Air humidity will be controlled "automatically" by a wick humidifier
more humid, harder to evaporate the water
less humid, easier to evaporate water
wick will be placed in front of the fan blowing air into the CV
fan will be a CPU fan
Calculations:
Rayleigh Number for enclosure:
Ra_L = Pr * g * (T_water - T_ambient) * rho * L_c^3 * Pr/ v^2
Ra_L = 032 * 1.4E-02 *50.0 - 70.0 * 2.25^3 *0.12 / 0.00^2
2.74E+07 [N/A]
Nusselt Number Note: If #NUM! is shown, value out of range
Nu = 0.195* Ra_L^(1/4) For: 10^4 < Ra_L < (4*10^5)
Nu = 0.195* 27447275.0^(1/4)
14.1 [N/A]
Nu = 0.068* Ra_L^(1/3) For: (4*10^5) < Ra_L < (10^7)
Nu = 0.068* 27447275.0^(1/3)
20.5 [N/A]
Heat Transfer
Note: Negative Q is defined as heat loss. Positive Q is defined as heat absorbed.
Q_dot = k*Nu*A_s* (T_1 - T_2) / L_c
For: 10^4 < Ra_L < (4*10^5) Q_dot = 0.349 * 1.4E+01 * 3.976 * (50.00 - 70.00) / 2.25
Q_dot= -174.0 Btu/hr
For: (4*10^5) < Ra_L < (10^7) Q_dot = 0.349 * 2.1E+01 * 3.976 * (50.00 - 70.00) / 2.25
Q_dot= -252.9 Btu/hr
83
Appendix E: Psychrometric Calculations for Air Flow System (Cont)
Enthalpy of Water
h_w_1 38.09155 Btu/lbm
h_w_2 33.09723 Btu/lbm
Enthalpy of Air
h_a_1 26 Btu/lbm dry air
h_a_2 23 Btu/lbm dry air
omega_1 0.0078 lb H2O/ lb dry air
omega_2 0.0065 lb H2O/ lb dry air
m_dot_a= (m_dot_w_in * (h_w_1 - h_w_2)) / ((h_a_2 - h_a_1) - (omega_2 - omega_1)*h_a_2)
m_dot_a= 0.003797 lbm/s
density of air at 0 ft altitude 0.07647 lbm/ft3
m_dot_a= 5.062 cfm
84
Works Cited
"2.8 TFT Color LCD,touch Screen Shield V1.2 for Arduino 168/328 - £35.00 : Nuelectronics.com, Arduino Freeduino Projects." Nuelectronics.com. N.p., n.d. Web. 05 Dec. 2010.
<http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=19>.
"Arduino - 3.2 Inch TFT Touch Screen with Arduino Interface V2." ThaiEasyElec.net. N.p., n.d. Web. 05 Dec. 2010. <http://www.thaieasyelec.net/index.php/Arduino/3-2-inch-TFT-Touch-Screen-with-Arduino-Interface-V2/p_68.html>.
"ASME IShow - Programs." American Society Of Mechanical Engineers - ASME.ORG. N.p., n.d. Web. 05 Dec. 2010.
<http://www.asme.org/Communities/Innovates/Programs/Innovation_Showcase_IShow.cfm>.
"BEE Faculty - Lou Albright." Department of Biological and Environmental Engineering. N.p.,
n.d. Web. 05 Dec. 2010. <http://www.bee.cornell.edu/cals/bee/people/profile-albright.cfm>.
"Biosphere Home Farming by Philips." Yanko Design. N.p., n.d. Web. 05 Dec. 2010. <http://www.yankodesign.com/2009/03/17/the-ultimate-recycle-bin-nourishes-as-well/>.
"BL-TFT240320PLUS V2." Circuit Ides Design. N.p., n.d. Web. 05 Dec. 2010.
<http://www.circuitidea.com/dev-board/BL-TFT240320PLUS-V2.html>.
"Build Your Own Hydroponics System | BGHydro." Hydroponics | Hydroponic Supplies. N.p.,
n.d. Web. 05 Dec. 2010. <http://www.bghydro.com/bgh/static/articles/0806_byos.asp>.
"Cityscape Farms: Soilless Farming." Cityscape Farms: Home. N.p., n.d. Web. 05 Dec. 2010. <http://www.cityscapefarms.com/soillessfarming/>.
"Cotton Rope | Twisted & Braided 1/4 - 1 Inch Sizes." KnotandRope.com. N.p., n.d. Web. 5 Dec. 2010. <www.knotandrope.com/store/pc/Cotton-Rope-c6.htm>.
"Deficiency Symptoms Of Elements | Tutorvista.com." Tutorvista.com - Online Tutoring, Homework Help for Math, Science, English from Best Online Tutor. N.p., n.d. Web. 05 Dec. 2010. <http://www.tutorvista.com/content/biology/biology- iv/plant-
nutrition/deficiency-symptoms-elements.php>.
"Dual Flow Hydroponic System Ebb and Flow NFT." Hydroponics Supplies Darlington County
Durham. N.p., n.d. Web. 05 Dec. 2010. <http://www.secretgardenhydroponics.co.uk/product/Dual_flow_01-015-005>.
"Hydroponic Systems." Hydro-Unlimited.com. N.p., n.d. Web. 05 Dec. 2010.
<http://www.hydro-unlimited.com/index.php?p=2_1>.
85
"Hydroponics Growing Systems Explained One by One." Hydroponics Gardening - Start a Small Garden Indoors- Helpful Guide. N.p., n.d. Web. 05 Dec. 2010. <http://www.jasons-
indoor-guide-to-organic-and-hydroponics-gardening.com/hydroponics-growing-systems.html>.
"IEEE Engineering in Medicine and Biology Society Undergraduate Student Design Competition." IEEE. N.p., n.d. Web. 05 Dec. 2010. <http://www.ieee.org/membership_services/membership/students/awards/eng_medicine_
undergrad_design.html>.
"Ion Selective Electrodes." Consort.be. Consort, n.d. Web. 5 Dec. 2010.
<http://www.consort.be/Downloads/Documentation/IonElectrodes_pg.pdf>.
"Kitchen Nano Garden." Fast Co. Design. N.p., n.d. Web. 5 Dec. 2010. <www.fastcodesign.com/idea-2010/kitchen-nano-garden>.
"LD W5SN." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010. <http://catalog.osram-
os.com/catalogue/catalogue.do?favOid=000000030002a14801f30023&act=showBookmark>.
"Liquidware : TouchShield Slide." Liquidware : Open Source Electronics. N.p., n.d. Web. 05
Dec. 2010. <http://www.liquidware.com/shop/show/TSL/TouchShield Slide>.
"LR W5SM." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010.
<http://catalog.osram-os.com/catalogue/catalogue.do?favOid=000000000003f86200020023&act=showBookmark>.
"PHOTOSYNTHESIS." Estrella Mountain Community College. N.p., n.d. Web. 05 Dec. 2010. <http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookPS.html>.
"Presidents' Change the World Competition." IEEE. N.p., n.d. Web. 05 Dec. 2010. <http://www.ieee.org/membership_services/membership/students/competitions/change_the_world/index.html>.
"Pros and Cons of Ebb and Flow Hydroponics | Easy Hydroponics." Hydroponics | Easy Hydroponics. N.p., n.d. Web. 05 Dec. 2010. <http://www.easyhydroponics.net/pros-and-
cons-of-ebb-and-flow-hydroponics.html>.
"RotoGro 240 Rotating Garden." HHydro.com. N.p., n.d. Web. 5 Dec. 2010. <http://www.hhydro.com/RotoGro-240-Rotating-Garden.html>.
"The Indoor Tabletop Vegetable Garden." Hammacher Schlemmer. N.p., n.d. Web. 05 Dec. 2010. <http://www.hammacher.com/publish/75426.asp#?cm_mmc=CJ-_-2617611-_-
3682082-_-Save up to 70% on Electronics>.
86
"ThinkGeek :: Power Plant Herb Garden." ThinkGeek. N.p., n.d. Web. 05 Dec. 2010. <http://www.thinkgeek.com/homeoffice/kitchen/b7d7/?cpg=cj&ref=&CJURL>.
"UL | Additional Resources." Redirecting Page to Browser Language Detected URL. N.p., n.d. Web. 05 Dec. 2010.
<http://www.ul.com/global/eng/pages/offerings/industries/lighting/lightingindustryservices/articles/>.
"Ul-498.14." UL StandardsInfoNet. N.p., 16 Nov. 2007. Web. 05 Dec. 2010.
<http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0498.html>.
"Ul-82.7." UL StandardsInfoNet. N.p., n.d. Web. 05 Dec. 2010.
<http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0082.html>.
"Wick Humidifier - Google Search." Google. N.p., n.d. Web. 05 Dec. 2010. <http://www.google.com/search?q=wick humidifier...>.
Arduino - HomePage. N.p., n.d. Web. 05 Dec. 2010. <http://arduino.cc/en/>.
Brentlinger, D.J. 2007. NEW TRENDS IN HYDROPONIC CROP PRODUCTION IN THE
U.S. Acta Hort. (ISHS) 742:31-33. http://www.actahort.org/books/742/742_3.htm
Dalton, Lon, and Rob Smith. Hydroponic Crop Production. Tauranga, New Zealand: NZ Hydroponics International, 1999. Print.
Despommier, Dickson. "The Problem." The Vertical Farm. Ed. Dr. Dickson Despommier Ph. D. Environmental Health Science of Columbia University, n.d. Web.
http://www.verticalfarm.com/
DoItYourself. What is the Standard Door Fram Width? Nov 30, 2010. <http://www.doityourself.com/stry/what- is-the-standard-door-frame-width>
Howard M. Hydroponic Food Production. 6thth ed. Mahwah, NJ: NewConcept, 2004. Print.
http://factfinder.census.gov/servlet/STTable?_bm=y&-geo_id=01000US&
qr_name=ACS_2008_3YR_G00_S0101&-ds_name=ACS_2008_3YR_G00_
Jackson, Louise, Keith Mayberry, Frank Laemmlen, Steve Koike, Kurt Schulbach, and William Chaney. Iceberg Lettuce Production in California. Vegetable Research and Information.
University of California, n.d. Web. <http://ucanr.org/freepubs/docs/7215.pdf>.
Karl T. Ulrich and Steven D. Eppinger. Product Design and Development. McGraw-Hill, New
York, 1995. Print.
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999. Ch 30. Print.
87
Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth Company, 1999.728-730. Print.
Resh, Howard M. Hydroponic Food Production. 6thth ed. Mahwah, NJ: NewConcept, 2004. Print
Sanders, Douglas C. "Lettuce Production." North Carolina Cooperative Extension: Home. N.p., n.d. Web. 05 Dec. 2010. <http://www.ces.ncsu.edu/depts/hort/hil/hil-11.html>.
Smith, Amy. 7 Rules of Design for Low-Tech Engineering. N.p., Oct. 2009. Web. 29 Nov. 2010.
http://www.popularmechanics.com/technology/engineering/gonzo/4273680
88
Bibliography
Data Sheet Archive. DC Fan Datasheet - 031158 - FS12H3 Comair Rotron. 5 Nov, 2010.
<http://www.datasheetarchive.com/datasheet-pdf/078/DSAE0068583.html>.
Data Sheet Archive. NMB-MAT DC Axial Fan. 5 Nov, 2010.
<http://www.datasheetarchive.com/Indexer/Datasheet-051/DSA0027852.html>.
Douglas, J S. Hydroponics: The Bengal System with Notes on other Methods of Soilliess Cultivation. London: Delhi: Oxford University Press, 1959. 17-77. Print.
Harris, Dudley. Hydroponics: Growing Without Soil. Newton Abbot: David and Charles, 1974.
43-70. Print. Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 7th ed. New York:
W.H. Freeman and Worth Company, 2005. 645-66. Print.
