Performance Modeling of Low Cost Solar Collectors

in Central AsiaProject Presentation

Steph Angione, Zach Auger, Adrienne Buell, Suza Gilbert, Emily Kunen, Missy Loureiro, Alex Surasky-Ysasi, Amalia Telbis

Problem Definition• Goal: Design a performance model for a

solar collector in central Asia• Specifications:

– Heat water for domestic use– Be low cost– Use local materials– Be efficient– Be easily maintained – Be sustainable

Step 1:Background ResearchStep 1:Background Research• Background Research:

– Region and climate data– Materials and availability– Heat transfer– Testing and modeling process

Geography, Climate and Housing: Tajikistan

– Latitude of 34°00’N and longitude of 68°00’E

– More than half of the country lies above 3,000 meters

– Climate• Highlands similar to lower

Himalayas– Housing

• Built into the mountains• Multifamily/ multistory

– Construction• Raw bricks, plaster & cut

straw (horizontal layers)• Where available: wood used

for roof beams• Cement often used for roof

Geography, Climate and Housing : Afghanistan

– Latitude of 33°00’N and longitude of 65°00’E

– Includes three distinct areas:• central highlands, southern

plateau, and northern plains– Climate

• hottest in southwest, coldest in northern regions with waves of intense cold and temperatures below zero

– Housing • Construction Materials: stone,

coniferous wood, plaster, straw, and brick

• Terraced Housing

MaterialsMaterials• What to look for when

choosing a material:– Thermal Properties– Durability – Availability – Construction Methods– Maintenance– Costs

• Materials Specified by EWB: – Sheet Metal– Wood– Glass– Black Paint– Horsehair

• Regional Materials: – Clay, Cement, Brick, Sheep

Wool, Straw, Plaster

• Variety of metals available– Best heat capacity – Aluminum [903 J/kg*K]– Best conductivity – Copper [401 W/m*K]

• Durability and Construction Methods:– Cutting tasks only require aviation snips– Pieces are easy to bend

Sheet Metal

Copper Sheet: • Can be shaped into any form easily• Doesn’t not crack when hammered, stamped, forged or pressed• Resists corrosion and does not rust• Can be recycled• Easiest metal to solder

Aluminum Sheet:• Excellent conductor of heat• Light (about 1/3 weight of copper)• Withstands wind, rain, chemicals, pollution • Excellent durability • Can be recycled• Soldering requires specialized reaction fluxes and tools

• Wood:– Used for construction

• Easily cut – Hand-tools sufficient

– Durable insulation– Readily available

• Black Paint:– Used to absorb solar energy by

changing the absoptivity • Absorptivity = a = 94%

– Radiates back 90% of solar radiation

• Glass:– Used as glazing– Reduces losses – Has to be tempered and have high

transmittance

• Horsehair and sheep wool:– Used for insulation: lasts for over 200

years– Material readily available

• 0.3 million horses in Afghanistan • 11-14 million sheep in

Afghanistan• Other insulation:

– Bousillages – mixture of moss and clay

• Outer layer is a mixture of horsehair, water, and clay

Heat Transfer FormulasHeat Transfer Formulas• Conduction

– Fourier’s Law: dQ/dt=-kA(dT/dx)– Through a material

• Convection– Newton’s Law of Cooling:

dQ/dt=hA(Ts-Tf)– Fluid flowing past a solid

• Radiation– Stephan-Boltzman Law:

dQ/dt=εσATb4– Heat emitted by an object

Hot Material

Components of a Solar CollectorComponents of a Solar Collector

• Absorber Plate• Absorber Surface

Coatings• Glazing• Insulation• Casing

Testing and ModelingTesting and Modeling

•Determine All Variables and Constants • Visualized Design/Schematic

–CAD software:•SolidWorks, ProE

–Free-hand sketches

Calculations

• Use of MatLab or Excel• Use of possible simulations

– F-chart! – TRNSYS

Step 2: Identify the SituationStep 2: Identify the Situation• Specified Situation:

– Domestic hot water heating for average household size of 7 people

– Water use per person per day: 25 liters– Region: rural, mountainous– System output temperature: 60 °C– Year round functionality– Storage tank water capacity: 1-2 days– Delivery system: either batch or continuous flow

Step 3: Selected Designs To Step 3: Selected Designs To ModelModel

Solar Heater Types and DesignsSolar Heater Types and Designs• Passive vs. Active Solar Heaters

– Active• use pumps to circulate water or

an antifreeze solution through heat-absorbing solar thermal collectors

– Passive • The water is circulated without the

aid of pumps or controls• Open Loop vs. Closed Loop

• If the liquid that needs to be heated is also the one being circulated: Open Loop

• If antifreeze or another solution used in a heat exchanger to heat the water: Closed Loop

1.2 Closed Loop

Drain Down Drain Back

One Liquid UnreliableFreeze Protection 2 Liquids Heat Exchanger

Antifreeze Solution

Good Freeze Protection

Less Efficient

1.1 Open Loop

Use Pump Direct Water Heating Cost Less

Drain-BackFreeze

Protection

More Efficient UNRELIABLE

Possibilities and their +/- …what we ended up picking

• Active– Open Loop:

• (+) cost less• (-) pump controlled• (-) only possibility for freeze protection: manually draining X Second one OUT !!!

– Closed Loop: • Drain Down:

– (-): not reliable !!! X First one OUT !!! • Drain Back:

– (+) good freeze protection– (+) can use water/water instead of antifreeze– (-) pump and 2 different storage tanks

• Passive– Batch

• (+)easy (can even be a tank painted in black)• (+) offers freeze protection because the water is only present in the tanks and the areas

are large; the water cools off slowly • (-) takes long to heat the amount of water

– Thermosyphon• (+) no need for pumps• (+) offers good freeze protection• (-) heavy tank placed above the collector• (-) efficiency decreases when using indirect heating

• We voted between: Drain Back, Batch and Thermosyphon– Systems chosen

• Group I (Suza, Missy, Emily and Zach): Drain Back System• Group II (Stephanie, Adrienne, Alex and Amalia): Thermosyphon

Team Members:•Melissa Loureiro

•Emily Kunen•Suza Gilbert•Zach Auger

Team Drain Back

DrainbackDrainback• Solar collector located above storage tank• 2 liquid system

• Both can be water• 1liquid water and 1an antifreeze

solution• Active closed loop system

• Uses pump• Pump circulates water through collectors when

collectors are warmer than stored water• Heat exchanger used in storage tank• Heat transfer between circulating fluid and

potable water• Circulating solution drains to a 2nd tank when

pump shuts off• Tank is placed on a tilt for complete drainage

Team Drain Back System• Collector

– 28 parallel copper pipes– Copper plate– 1.13m^2 area– Soda lime glass glazing– Sheep wool insulation– Black interior

• Housing• Heat Exchanger

– Heat transfer fluid flows through exchanger

– Exchanger within storage tank containing working fluid

• Pump• Drain back Reservoir

Model •Software: Microsoft Excel

•Spreadsheets for:

-Materials

-Energy Input and Output

-Collector

-Heat Exchanger

-Sunlight

-Efficiency

Efficiency and Costs• Total Cost:

US$1167.02– Soft Copper Tubing for

Heat Exchanger: $83.26/100 feet

– Copper Sheet: $147.30/ 2 sheets

– Copper Feeder Pipes: $26.00/12 feet

– Glazing: $320.00/ 2 sheets

– Black Paint: $30/gallon

•Efficiency: Efficiency

88.40%

88.60%

88.80%

89.00%

89.20%

89.40%

89.60%

89.80%

90.00%

Jan Feb March Apr May June July Aug Sept Oct Nov Dec

Month

Effic

ienc

y

Sheep woolBousillageClayStraw

What’s Next

• Performance Modeling– Several days of testing– Slight variations in

model• Prototype

– Improve construction techniques

– Compare to performance model

Team Thermosyphon

Amalia Telbis Alex Surasky-Ysasi

Steph Angione Adrienne Buell

– Area 1.85 m^2: standardized according to available glazing– Absorber Plate: 0.02” thick copper sheet bent around the parallel pipes– Glazing: 1/8” thick single glass sheet with 0.01% iron-content– Parallel Flow Pattern: Copper piping

• Header and footer 1.5”• Parallel pipes 0.5”• Free floating array supported by wood risers every 10”

– Housing: Wood frame that slides into the mounting stand at 33o

– Insulation: • dead air between plate and layer of

plywood• boussilage clay, water, and horsehair• 1m high stand with brick walls encasing

dead air– Back flow prevention: one way valve– Pressure relief valve needed at high

antifreeze temperatures

ThermosyphonThermosyphon

Thermosyphon:

• Working fluid: 40.5% ethanol-water mixture• Boiling Temperatures: 84oC• Freezing Temperature: -24oC

• Heat exchanger:• Countercurrent • Bendable copper tubing: 1”outer diameter

– Length: 9m – 11 loops- 0.25m diameter spaced at 1.05”

• Storage tank: placed above the solar collector• Dimensions: 0.5m x 0.5m x 1.05 m steel casing• Insulation: sheep wool, boussilage and brick

Modeling:

• Software used: Excel • Governing Equations:

– Heat transfer in the solar collector– Mass flow rate calculation– Heat transfer in the heat

exchanger• Collector plate efficiencies at a

constant ambient temperature (20oC) for parallel pipes of different sizes vs. the temperature of the antifreeze

• Collector plate temperatures at a constant ambient temperature (20°C) for parallel pipes of different sizes vs. the temperature of the antifreeze

Efficiency vs Mixt Temperature

78

80

82

84

86

88

90

92

94

0 10 20 30 40 50 60 70

Mixt Temp (oC)

Effic

ienc

y (%

)

1/5inch pipe

3/4inch pipe

Temp of Plate vs Temp of Mixture

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60 70

Temp Mixt (oC)

Tem

p Pl

ate

(oC

)

1/5inch pipe

3/4 inch pipe

Results:Annual Output Temperatures of both the water and the antifreeze:

The water reaches The antifreeze reaches

▪ app. 30°C in the winter ▪app. 65°C in the winter▪ app. 58°C in the summer ▪above boiling point in summer

Annual Performance in Kabul

0

10

20

30

40

50

60

70

80

90

100

Month

Out

put T

empe

ratu

re o

f Wat

er (C

)

Antifreeze End Temperature in Kabul

0

10

20

30

40

50

60

70

80

90

100

Month

Tem

pera

ture

(C)

Daily Performance in Kabul

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14

Hour

Tem

pera

ture

at S

tart

of H

our (

C)

December Antifreeze

December Water

June Antifreeze

June Water

What’s next?

• Use computer programming software – F-chart method to analyze efficiencies– Matlab to ease the process of iteration

• Optimize design• Model different regions • Change the working fluid during the summer or use a different antifreeze solution• Make a business plan and try to implement

DRAIN BACKFreeze protection = draining system

Powered by pump

Price ~ $1167 US

Collector Area = 1.13 meters^2

Parallel pipes in collector = 28

Parallel pipe outer diameter = .625 in

Single Glazing

Length of Heat Exchanger = 3.01 meters

THERMOSYPHONFreeze protection =working fluid: ethanol-water mixture

Uses natural convection

Price ~ $1250 US

Collector Area = 1.85 meters^2

Parallel pipes in collector = 21

Parallel pipe outer diameter = .5 in

Single Glazing

Length of Heat Exchanger = 9 meters

Design ComparisonDesign Comparison

Implementation: The need for Implementation: The need for sustainable developmentsustainable development

What is Sustainable Development?

• Meeting present needs with out compromising those of the future

• Goals– Improve quality of life– Promote further economic

growth– Improve social conditions

and equality– Protect and improve

environmental and human health

How can our project be made sustainable?

• Use local resources, knowledge, and skills• Include local involvement in

– Planning– Design– Implementation

• Have education and training to foster an understanding of and appreciation for the technology

• Develop renewable energy markets to encourage further research and economic growth, making the technology competitive and desirable

What Comes Next

If only we had more time…Designing-Solar collector designs limited to those in existence that have been tested

-Overlooked Possibilities -Collector plate designs-Materials

Prototyping and Testing-Theoretical model vs. Prototype-Need to construct and TEST a real model-Compare theoretical and experimental values

-Construction techniques can be simplified

Modeling-Optimizing values of the collector using computer programs-Designing a program where a user enters desired parameters

and the output is their personalized collector

ACKNOWLEDGEMENTS• Dr. Chris Bull• Peter Argo – US Embassy in Tajikistan• Professor Chason• Professor Hurt • Professor Tripathi• Professor Breuer• EWB!