D-LAB FINAL REPORT�

MICRO HYDRO in LESOTHO�BACKGROUND

Hydropower is used to generate electricity worldwide, yet oftentimes the source of that energy (lakes, rivers, and streams) remains untapped. According to the World Energy Council, “the exploitable hydro capability in Africa is the fourth largest [energy resource] but the current utilization of this potential is very low. 1” Although the greatest beneficiaries of hydropower might be communities in under-developed countries, most applications remain a modern-world technology. For those living under $2 a day, the enormous cost of accessing grid-electricity at nearly $1000 per connection makes renewable energy one of the few viable options.

The Bethel community in Lesotho is an example of a Sub-Saharan village left in the dark. Current options for decentralized electrification include diesel generation sets, photovoltaic (PV) panels, biogas plants, small-scale wind generators, and micro hydro plants. Generally in southern Africa, PV

and diesel generation sets are the only technologies used significantly. In comparison, our micro-hydro system will offer a cheaper, environmentally sustainable, and longer-lasting option for a small village.

What makes hydropower an especially attractive technology Image removed for copyright reasons.� in Lesotho compared to other renewable energies is that

river-power is a continuous resource. Harnessing solar power requires investment in fragile, imported panels, frequent battery purchases, and high maintenance costs. Our hydropower can be made completely from local goods and can be scaled as the community grows. As economic productive rises and people demand more energy capacity, new generators and turbines can be added to fit their needs.

Figure 1: Lesotho river and city map. This semester, we focused on the turbine portion. We directed our energy towards modifying existing designs to fit the barren Sub-Saharan setting. Hence, we refined manufacturing techniques and materials to reduce cost and necessary equipment. This turbine component, which harnesses the stream flow, requires further analysis and design, and its construction will directly impact how much power we can convert. Though we’ve had successes and failures in our approach, the learning process was invaluable in our continuation with the micro-hydro project.

DEVELOPMENT PROCESS

We first developed a problem statement and then fleshed out its definition with design specifications (See below). Our highest priority was that our system would be flexible; it should handle the variable

Survey of Energy Resources 2001, Africa UDEAC 1

flow rates and river heights that typically plague micro-hydro installations. We decided to adopt a one-kilowatt supply-side system. The local residents could use this power as they saw fit, and the entire system would be scalable. We also wanted a technology that was appropriate, locally-constructed, and maintainable.

We investigated several in-stream designs based on their strengths and weaknesses in the Bethel or greater Lesotho context. (See the Pugh chart analysis in the Appendix.) The Gorlov Helical Turbine and the Darrieus Wind Turbine were both top contenders. The next step was to prototype a model of the Darrieus type turbine which we settled on because of its easier construction.

PROBLEM STATEMENT

To develop an affordable, locally serviceable, off-the-grid generating unit that will provide electricity at the village scale with minimal environmental impact. It should be easy to implement unit in low-head, variable flow, high erosion rivers using locally available technologies.

DESIGN SPECIFICATIONS

Our design constraints were developed through discussion with our community partners, and through research, common sense, and comparisons. We investigated competing technologies when our community partners could not give us specifications. For example, the cost of our system had to be low enough to be affordable by a village and equal to or lower than the cost of the main competitor, PV. Our technology also had to work in the Senqu River, so the river’s character determined the limits that the system could handle. Many of the parameters were deduced straight from problem statement: the turbine had to be locally constructed and maintained, so the materials and techniques used had to be locally available. Our final design specifications are as follows:

•� Supplies 1 kilowatt minimum •� Unsubsidized cost: 10 cents per kilowatt •� Upfront capital cost: $5000 •� Functions within velocities of 1 m/s to flood velocities •� Functions effectively in a river with high sediment load where suspended solids range in size

from fine sand to large boulders •� Easily transportable, maximum size being 4’x6’x4’ •� Easily accessible for maintenance and repairs. •� Simple implementation and maintenance in rural areas : •� Weight allows two people to install, remove, and maintain •� Limited number of moving parts for durability •� Constructed of locally available materials (steel, wood, aluminum), using locally available

tools and skills

DESIGN ALTERNATIVES

Capturing vertical potential energy has been a well-established and documented topic. However, hydro turbines rarely utilize the horizontal kinetic energy of flow due because it is cheaper to exploit falling water. The portion of rivers we were looking at in Lesotho did not have that fall, so we

looked into “in-stream turbines” that harness the horizontal kinetic energy. Unfortunately, almost every model we investigated was in the research phase; none of them had been adopted for industrial use.

Two designs showed promise for our project. One was developed by a French engineer named Darrieus in 1931; it uses straight hydrofoils attached to an upper and lower plate to capture the energy in the stream. The second was a helical design developed in 1998 by Professor Gorlov of Northeastern, and it is built on the same principle as the Darrieus turbine. The difference is that the top and bottom of the blades in the helical design are twisted, allowing the blade to constantly be extracting energy from the water and increasing the turbine’s efficiency. Both of these turbines are currently being developed for possible large-scale applications in tidal and ocean power, but neither is deployed yet.

Looking at past reliability, the Darrieus turbine was a more proven design while the Gorlov was still in the research and prototype stage. Our project will incorporate design features of these turbines into our one-kilowatt generator destined for continuous, low head rivers. The main challenge we have tackled is reducing costs and manufacturing complexity in order to make hydro power affordable and accessible for rural communities.

A combination of additional Table 1. Price Comparison of Energies “green energies” (such as

Diesel generator

PV panels

Hydropower (traditional)

Wind generators

Capital cost ($/kW)

1,0001 10,0001 5,0001 7,0001

Maintenance cost ($/kWh)

25 cents 20 cents1

10 cents1 10 cents1

photovoltaics, and possibly wind power) will best serve our community during peak hours of need. For instance, while our one kWh system would bring 10-watt

fluorescent light bulbs to a hundred households, irrigation pumps need more than four kWh per meter-squared per day. During the dry season, the village water supply would be prioritized for productivity increases and a PV system might be placed in combination to serve the need. Electricity would be used power irrigation water-pumps, grain mills, televisions and radios, and lighting. These things can help families generate more income and increase their standard of living.

During January, we investigated current small-scale hydro projects in Lesotho and found that many existing installations had failed. The Lesotho Electric Corporation mentioned four existing developmental micro-hydro projects. One is located nearest the highest waterfall in the country. One has so little documentation that we were unable to track it. The one near Tseolike had sedimentation clogs almost immediately after the project was launched. One was designed without realizing that the river changed its height because of seasonal rainfall variances, and hence only generates power four months of the year. Our design seeks to address the problems of the traditional scheme, i.e. the complicated design of the turbines, the requirement of high head, the necessity for expensive civil works, and the problems caused by sediment load and variability in the height of the river. Our “in-stream” turbine requires only sporadic maintenance from local engineers. Our focus throughout the term was developing low cost construction techniques for a low-head turbine, in order to make it available to a greater variety of people. Hence this project is a productive grassroots level generator for the typical village of 300-600 people located near a fast flowing river.

FINAL CHOICE – DESCRIPTION OF PROTOTYPE�

Essentially, our solution will be a generating “island” which is diagrammed below (Fig 1). The steel turbine is suspended by raft support. The raft, in its broadest definition, is a floater that stably supports the heavy components. Right now we are considering several raft models: wood planks, used tires, oil barrels, or plastic jerry cans with PVC pipes. Above water, a generator will convert the mechanical rotation into electrical power by having wire spin within a magnetic field, creating flux. Below water, a funneling system on the raft itself will channel the water towards the rotating turbine blades.

INNOVATION�

The engineering innovation comes from redesigning the manufacturing process rather than from reengineering the details of the turbine and generation system. Whereas high capital costs have prohibited traditional electrification development, our project must be reinvented to 1) thrive in desert type rivers, 2) deliver dependable electricity, and 3) accommodate the purchasing power of the Basotho2 people. Still, tradeoffs should not compromise the quality of social benefits we bring to the community. Here, we list four ways to streamline the manufacturing process and reduce costs.

I. MINIMIZE MOVING PARTS Simplicity in design is crucial. Not only does it reduce construction time and maintenance efforts, but it’s also easier to replicate. Our turbine designs will have no moving parts except for the spinning shaft.

Our first prototype has three identical blades connected by circular plates to the center transmission shaft. We chose a symmetric NACA 0020 hydrofoil section because it is proven effective and easy to construct. A set of diameter pipes held fixed were used as a mold to make the specific hydrofoil shape. We then constructed our blades by folding a sheet of thin steel plate around the three pipes. We anticipate testing the turbine in a nearby river by the end of April. Should our blade system fail, we have also considered several other designs like the one based on the Gorlov helical turbine3

which would require a more complex jig but have a higher efficiency. Design options are being developed in conjunction with the design for our straight bladed turbine which we are currently prototyping. Wires will carry the power from the raft to a small powerhouse on shore where the energy will be stored in a battery bank. The whole system will be anchored to shore by cable so that it can be retracted for service or even demonstrations.

Turbine blade schematic removed for copyright reasons.

II. USE LOCAL MATERIALS AND LOCAL MANUFACTURE While high-tech, mass-produced parts are cheaper, many machining techniques are not

2 Cultural name for the people of Lesotho 3 Gorlov, Alexander M. “Unidirectional helical turbine operable under reversible fluid flow for power systems.”

U.S. Patent 5,451,137. Granted Sept. 19, 1995. Accessed F

accessible for most of the third world. As such, we will reinvent turbine manufacture only with local materials. Our provisional raft design has a basic steel structure supported by empty Jerry cans, PVC, oil drums, or old tires.

Since the floating component is visible, the material needs to be more valuable as a flotation system than in any other context in order to prevent theft and to make sure that we are using scarce resources wisely. Thus, our raft designs can be made mostly with “trash” such as discarded tires or oil drums. For the generator, we would like to use a 12-volt automotive alternator. The alternator would be placed in a prefabricated plastic box that has vents, and it would be connected to the shaft by a step-up gearbox or belt and pulley system. By making the entire system out of common local materials, we can take advantage of cheaper labor and also ensure that in the event of breakage, villagers will have the means to fix their generator. This is a principle of having the consumers “own” their technology.

III. BUILD IN FAILURE MODES Although breakage is not something engineers often consider, our anticipation of where the system could potentially “fail” affects our design tremendously. The regularity of part failure means these components must be easy to access and repair. Ours include:

•� Using a belt system to connect the transmission shaft to the gearing box shaft so that overspeed of the turbine could result in a belt disconnect rather than a burning out of the alternator.

•� Creating gears with breakable pegs as teeth rather than plastic gears with machined teeth that would be impossible to repair locally.

•� Having a current regulator that bleeds excess power to a grounding rod in the case of�unusually high current in the transmission wire.�

•� Mounting bearing system so that large objects would cause a hinged, upward movement of the turbine rather than having a rigid system which would be required to absorb all of the impact.

IV. REPLICABILITY Replication reduces learning curve time and encourages propagation. In addition to paper documentation and sketch drawings, we are using Solidworks models to develop a set of jigs and templates for clear and simple communication. Our goal for the future is to make the design as easily replicable as possible.

The replicable nature of jigs encourages locals to acquire creative use technology in other areas of their lives. One goal of the project is sustainability through education, and a well-tracked small-scale project is a feasible starting point for broader social change.

Graph removed for copyright reasons. ANALYSIS

Basic analysis of the forces around the turbine is important. The Darrieus turbine alone is complex in nature, as its very spinning causes it to alternate between lift and drag forces.

Inserting the turbine into another system, the support raft, required further analysis to not jeopardize its functionality. Yet because we wanted to focus on manufacturing techniques rather than turbine optimization, we built before we analyzed, and we didn’t have an idea of how fast the turbine would spin. Our component-by-component post-analysis is detailed following sections.

TURBINE There hasn’t been many resources on the Darrieus Turbine although some key research institutions had attempted to investigate this type of turbine in the past. Most of it was based on the wind turbine, not the hydro-.

Professor David Gordon Wilson eventually showed us some similar work he had done in the field of bicycle physics approximately thirty years ago. Our first goal was to determine what rotational speed we would get on a Darrieus type unit the size of our prototype so we could determine whether or not we would have enough rotation to drive an alternator.

Let’s first look at the ratio of tip speed to wind speed in steady state. This tip speed ratio (tsr) is correlated with a coefficient of power on many preexisting charts, though it would be helpful for us to complete a towing test so that we could use our own empirical results. For this analysis, I will use the results of a wind turbine test that was completed in the 1980s:

Fig 2: Closer analysis of wind speeds near turbine blades

First, we will find the maximum tip speed ratio and the corresponding power coefficient. We are using a three bladed turbine, so the results would fall

between n = 2 and n = 4. = 4.5 c = 0.6tsrwind p

Next, we scale the results so that the wind turbine chart is applicable to water turbines. Densities are used to scale the data.

tsr water = tsrwind (ρwater ) tsrwater = (unknown – we are researching and/or ρwind

will determine empirically)�The next step is to find the velocity of the tip given the velocity of the�

surrounding water.�GIVEN: vwater = 1-2 m/s × tsrwater = ?vtip = vwater

Using these numbers, we can calculate the rotational speed (in rev/min) of the unit.

d = diameter Speed = vtip × 60

(35” or 0.1378 m) π × d

We calculated that that the rotational speed of our turbine would be --- rpm.

With some gearing, this speed can be increased to the required threshold speed that is determined by the alternator. We need to find a pre-built gearbox with a gearing ratio of --- or figure out how to make a belt system work correctly to achieve this speed increase.

The final aspect we analyzed while looking at the turbine was how exactly the blades rotate. Looking at the diagram (Fig. 2), one can see how the wind (or water) speed and blade speed play into the rotation of the turbine. The tip speed ratio shows the speed of the blade is greater than the speed of the medium through which the turbine is traveling. The relative wind component comes into

contact with the turbine blade and creates a thrust force which drives the turbine forward. Of course, the largest problem is that the turbine must be given an initial speed so that that the tip speed ratio is not zero. This required initial velocity means that the turbine is not self-starting which may prove to be a large problem during the implementation stage of this project.

RAFT SYSTEM After calculating the turbine’s rotational speed, we evaluated the raft support system that would be required. The total mass of the system was roughly calculated with the volume and density of steel. We overestimated volume to ensure the support of the generation unit, and we also inserted a safety factor into the calculations. Our final mass was about 400 kilograms (1,000 pounds). A half ton generation system is considered massively heavy. Please see the attached spreadsheet for detailed calculations.

Having estimated the mass, we calculated the drag force by finding the rough cross-sectional area of the raft using buoyancy:

Calculate the volume of water displaced by equating the weight to the force of buoyancy

g = gravitational constant (9.8 m/s2)Fbuoyancy = W

ρwaterVwaterg = mraftg pwater = water’s density (1000 kg/m3)

Vwater = mraft Vwater = volume of water displaced = 0.3939 m3

= volume of raft in water = 0.3939 m3ρwater Assume a length (L = 4 m) for the raft. Use length to calculate the cross-sectional area of the front of the raft.

VwaterA = = 0.0985 m2 c L

Use drag force calculation to determine total drag on raft created by having raft partially submerged in water.

Fdrag =�12�

υρwater C A water D c 2

= 321 N

where CD is the drag coefficient (~6.5)4 and vwater is the water’s linear velocity (1 m/s, empirical results)

This force is comparable to the weight of a 150-pound person: manageable enough for cables to anchor the raft. Still, the water velocity is squared in the drag-force equation, so as it doubles, the drag force quadruples. Such a relationship could spell disaster if the cables are not properly sized for the application.

CRITIQUING THE PROTOTYPE AND NEXT STEPS

Due to the aforementioned constraints of time, resources, and ability, our group had to make several concessions during the prototype development cycle. The simplicity of our turbine masks the amount of research and thought we’ve put into this project. However, we recognize that more thought, research, and development is needed in order to improve the prototype to bring it to a deployable stage. Below we critique individual subsystems:

Turb ine

“Drag Coefficient.” Process Associates of America. Accessed 5/10/05 at www.processassociates.com. 4

Once we have done more extensive testing, we should be able to really determine the strengths and weaknesses of the design. Some lessons learned: Our steel end plates were too difficult to machine, thus future designs will include bars rather than plates. The metal on the hydrofoil deforms when welded, thus future designs may make use of a thicker gauge of steel or even non steel materials. The jig method of constructing hydrofoils seems to work adequately, but using another method may be preferred.

As a testing prototype, the turbine was sub-optimal; it was too large and unwieldy. However, as a manufacture process prototype, the turbine was useful. (We learned good and poor construction techniques, and figured out new constraints for further prototypes.) From this point on, we focus on turbine design optimization rather than the manufacturing process optimization. We will do more extensive modeling of the forces and fluids. We will scale down the turbine in order to be able to construct rapidly many different prototypes for simultaneous testing and evaluation. Enabled by the relative ease of making scale models, we will try additional styles of vertical axis turbines. Finally, we will test the design and ultimately decide whether it is feasible for eventual implementation.

Electrical Generators and Alternators While the electrical system was not the focus of our term work, the turbine needed to be compatible with the final generation system. Following Matt Oroz’s parabolic team, we initially thought that alternators would be a cheap and convenient. But out advisors enlightened us that <600 rpm for the rotor are “non-starts” for alternators, and the alternator’s optimal range is 1800-3600 rpm. Even with gearing, an alternator would not generate a decent amount of power at a usable voltage. Output power depended on the (1) machine’s rpm, (2) the strength of the magnetic field and (3) the number of turns of wire in the coils. So to increase output power at slower spins, one could either (a) wind more coils in the alternator or (b) establish a higher magnetic field.

Option 1: A higher magnetic field can be established by incorporating strong permanent magnets in the rotor, to make “permanent-magnet (PM) alternators.” It turns out that PM alternators are often used as single drive with wind turbines that are similar to our water turbine and they fit well in the Lesotho context: their low-rpm performance is excellent, they do not require a battery, they do not need maintenance of the brushes, and they are sturdy and cheap: They can be fabricated in a machine shop using scratch material from cars.

Option 2: We could rewind an automotive alternator to increase the number of coil turns so that a stronger electromagnetic field is created when the brushes bring current to the rotor. This does not reduce the inefficiency of traditional alternators, which must use part of the output to maintain the electromagnetic field. Also, the amount of coil winding needed to achieve high power output at low rpm would make the alternator too heavy and too bulky. We will most probably consider the use of PM alternators when we start designing the electrical sub-system.

Option 3: We could take a motor from a low-speed fan and run it in reverse, as a generator. This would allow for high efficiency at low rotation speeds, but the availability of such motors in a Basotho village is doubtful.

Flota t i on It is difficult to determine the floater’s improvement without its construction. We have already iterated through a number of raft

designs in and decided on one that is a mixture of buoys (either empty oil drums or old tires or etc) and steel or PVC pipe. The streamlined design minimizes the disruption of the water flow. We also changed the initial ideas of the design in order to work in a “cage” of steel pipe that surrounds the turbine and provides added support. The next steps for the flotation system are to actually build one and test it in the river. However, the particular details of the flotation system are not integral to the nature of low-head hydropower. We intend to encourage end users to innovate on their own and use their own local materials in the raft construction, while at the same time we can give a few learned tips on raft designs that worked well for us or didn’t.

Implementat ion After sufficient testing at MIT, the first implementation would be a pilot scale project at Bethel. We would work with the staff at BBCDC and ATS to make additional improvements to the design. If the pilot project proved successful, our community partners would disseminate the technology.

Eventual Business Model Our eventual business model would involve artisan-level craftsmanship. Individuals with access to shops would produce turbines for the surrounding villages on a scale of ones to tens per year. This is consistent with our goals of enabling local production.

DESIGN LESSONS LEARNED

I. Direction of Approach If we could “encapsulate” the initial problem-solution definition process, it would focus on the two dilemmas we encountered (See below). By the first method, we had to rely heavily on incomplete information supplied by our community partner because of communication delays. By the second method, we decided we could research all available turbines, map out the entire terrain of South Africa, and overlay that map with population clusters. Then we could build something and pinpoint all the theoretical ideal locations and work out the community partnerships later. So defining the problem-solution was problematic because we were trying to come to a mid-point from both the end-user and the supply side.

Method 1. Case Application → Research (1) Defining problem for specific end-user

(2) Evaluating their constraints and parameters. (3) Devise specific solution; won’t be scaleable.

(4) Research only within this narrow scope.

Disadvantage:

Method 2. Research → Case Application (1) Finding a solution, then find for application. (2) Understand our capabilities and limitations. (3) Design a “thing” that has defined features. (4) Search for an ideal “site” to tweak and deploy.

Disadvantage:Needed Accurate River Data and Community Information Immediately.

Too Idealistic and Paternalistic. No Interaction with Community.

II. Research Methods

We spent a lot of time contacting people from different sectors. We felt that having expert opinions and outside evaluation would give us a better focus, but maintaining the lines of communication required enormous coordination and patience. Moreover, the opportunity costs might not have been worth it. In a sense, the initial momentum of the project was slowed by “idea bureaucracy” inertia—that is, juggling too much detailed information. As deadlines drew closer, however, we learned that it was critical to be decisive and proactive in the design cycle. Someone had to say, “freeze, we’ve researched and we’ve got enough information to start moving on a vision.” Our first prototype did not crystallize until we sat down and drew something based on intuition.

Method 1. Consult the Experienced (1) Contact every expert we can and get advice.

(2) Research good ideas to borrow features. (3) Distill the massive amount of information.

(4) Tailor approximate solution to Lesotho.

Disadvantage:

Method 2. Wing It and Test Later (1) Evaluate situation and invent solution. (2) Create a vision and trust intuition. (3) Test technical calculations on CAD. (4) Tweak and refine our mistakes.

Disadvantage:Extremely time consuming and difficult to maintain contacts. Massive research.

More uncertainty of success, less direction, and less credibility.

III. Prototyping and Realizing the Project Since our project was mainly about redesigning the manufacturing process so that the system could be easily constructed in rural communities, this stage of the process was very important to us. Before we had specific analysis completed on our design, we had started using what we thought were easier construction methods to make the hydrofoils. We ran into challenges while building the turbine because we found that conceptual design plan and actual machining results can differ greatly. As we finished the turbine, we realized that we did not have a clear idea of how it would perform, and we needed to retrospectively complete some more in-depth analysis. The final step in the process is to generate some experimental data by putting our turbine to the test in the large towing tank here at MIT.

Going through this prototyping process, we learned a lot about this stage of the design process. First, we needed to have better established goals when we are looking at what we want the prototype to demonstrate. For example, we had planned on using our turbine prototype to show that the generation system would work, but we instead showed that the manufacturing process worked. While this was a success in itself, it showed us that the goals and end results of prototyping can be very different if not constantly reviewed. Second, we learned that other prototyping methods, such as building several smaller prototypes or prototypes of different materials, may better suit our goals. In the end, we (somewhat unintentionally) sacrificed getting data about the characteristics of the turbine design in favor of understand the full-scale manufacture challenges.

PERSONAL LESSONS LEARNED

Victoria Tai ‘Teamwork’ can get in the way of distributing by personal strengths. We did not evaluate our strengths to the project and allocate tasks according to skill and passion rather than equally

distributed “teamwork.” I felt guilty for not contributing to the prototyping phase, but I knew that mechanical work was neither my forte nor my interest. Likewise, I felt that since my strength was in presentations, market evaluation, and reports, I might have preferred to specialize in that because to me it was not “work” but “pleasure,” but it would alienate the team’s overall input.

Matt Zedler During this project, I learned much about how important it is to properly analyze a situation before diving in and starting to design. Having incomplete information about the situation was also difficult as it meant we had to “fudge” numbers and assume certain things would function in a given way. I also felt like we finally anchored ourselves with MIT professors later in the process than was really useful, and we would have spent less time prototyping if we had done scale models. I have become a much better proposal writer and team member because of this experience, and I have learned several lessons about design and engineering.

Kaia Dekker I think that were I to do the project over again, I would be much better at managing the amount of time we spent on each step as well as the focus of the project. I feel like I learned a lot about marketing, balancing, and the “politics” of engineering by taking a single project and trying to meet the design wants of Lesotho, the class, IDEAS, the PSC, the group, and myself all at the same time. However, I also feel as though we ended up spreading ourselves a bit too thin and being a bit incoherent about goals. At the same time, I felt as though we often approached the design process as though it were linear rather than iterative. Even when we changed fairly major goals, we didn’t always go back and make sure that we fully accounted for the changes in the assumptions we had made earlier.

Marion Dumas During this term I learnt what design is about and what the tasks of a designer are. I now have a much clearer and more precise idea of what we need to know and do to make progress. I learnt that prototyping should be planned if one wishes to demonstrate something precise through the prototype. For example, we wanted to make a turbine capable of spinning, but we did not take the time to analyze what the crucial parameters of the problem were. I also learnt that prototyping can have different goals: our full scale model tests a manufacturing process, while smaller scale models would have allowed us to test the physics of the design more easily. We had not made this crucial distinction when we entered the prototyping phase.

SUPPORT NETWORK

Throughout our project development at MIT and in Lesotho, we will continue to work with a strong support network. At MIT, this includes our project mentors: Allen Armstrong, Will DelHagen, Kurt Kornbluth, Matt Orosz, Amy Smith, and Kate Steel. It also includes numerous professors in the Earth Atmospheric and Planetary Sciences, Engineering Systems Design, Laboratory for Electromagnetic and Electrical Systems, Aeronautical and Astronomical Engineering, and Mechanical Engineering departments.

In Lesotho, our primary support network is our two community partners: Appropriate Technology Services and the Bethel Community Development Center. ATS is a government-sponsored research group develops life-improving technologies for Lesotho. The director, Ntate D.S. Phakisi, has been collaborating with MIT researchers to create new solutions for Lesotho’s problems, and thus

provides local data and contacts. ATS employs a number of resident engineers and technicians who are familiar with both the cultural and technical needs of the country. BBCDC is a small technical college that emphasizes practical education regarding energy, rural construction, and permaculture farming. Their staff is committed to promoting principles of sustainable design.

MOVING FORWARD

We plan to further refine our prototype and its construction techniques during the summer. Specifically, the following team members will be working on the following aspects of the project:

MODELING During the last part of the semester, we found that analysis and modeling would really be helpful in understanding the performance of our system. Hopefully, we can tweak certain parameters to optimize the turbine and electrical systems to maximize the power conversion. While we have shown some preliminary calculations in this report, this is still much that needs to be done. The dynamics of turbine rotation are actually complex fluids problems, so we will need to come up with a more complete model this summer. Analysis will include:

• Velocity vector analysis of individual blades • Startup and shutdown performance and rotation • Effects of fluid on performance (Can we model this system in air?) • Effects of mass and inertia on performance • Effects of fluid velocity on power generation • Effects of blade precision and material

Matt, Kaia, and Marion will work on the modeling of the system, calling on the expertise of Prof. David Gordon Wilson, Prof. John Haywood, Prof. Ole Madsen, and Prof. John Brisson.

PROTOTYPING Once we understand how scaling can be used to model the situation, we hope to construct smaller prototypes which will test materials and design parameters. While the modeling can give us a baseline of comparison, this detailed prototyping will give us empirical results to compare different configurations. The specific prototypes we are thinking of making include:

-Fiberglass Darrieus turbine (different angles of attack)�-Fiberglass Gorlov helical turbine�-Raft system and connection to electrical generation�

This prototyping will require the extensive use of jigs. Machining will be done here at MIT and at General Electric in Plainville, Connecticut. Material funding will be provided through UROPs and possibly through untapped D-Lab funds. Matt, Kaia, and Marion will work on this stage of the process.

TESTING Before we all leave for various destinations, we are planning to finish construction of a steel cage and test the turbine in the large towing tank in the basement of Bldg. 48. These preliminary results will give us tip speed ratio versus power coefficient curves which we can use to calculate gearing ratios and predicted power output.

By the end of the summer, we would like to have completed or at least started on a raft system that will integrate all the different components. We are looking at testing this raft system on a nearby

river and getting some long term data results. We may also be able to test near the Charles River Museum of Industry as they are looking for a small-scale hydro unit.

FURTHER RESEARCH We hope to bring new mentors into this project over the summer to help work on specific subsystems. In addition, we will continue working closely with Matt Orosz and the solar parabola team as they work out the problems with electrical generation driven by an alternator. Also, there are several theses in Barker Engineering library and VITA pamphlets that are concerned with this type of generation system.

At the end of the summer Matt and possibly Vicky will be traveling to Lesotho. Matt is planning on spending one to two weeks in Bethel working on setting up a stream current monitoring system with BBCDC and the local high school so that accurate data can be recorded. He also will be educating the engineers and students about how hydro electricity works. The end goal of this trip is further research on the potential applications of micro hydro as well as increased communication with the local community partners.

EDUCATION One of the long-lasting ways to make a difference is to educate someone. We are hoping to develop a small curriculum on hydropower and electricity that can be used to show how both function. This guide would be a useful reference material for the natives of Lesotho as well as for other communities who have thought about using hydropower as a potential resource. This guide will take advantage of preexisting materials as well as draw on the experiences and lessons that were learned during this semester.

CONCLUDING REMARKS

The micro-hydro project gave us a vivid example of the issues and questions in designing successful appropriate technologies. We now have a much clearer idea of what needs to be done to complete our electrification project. D-lab has given us the motivation and inspiration to continue experimenting. We hope that our work will result in a small technology that will prove useful to the villagers of Bethel and possibly to other people. D-lab has convinced us that simple projects can both improve the living conditions and productivity of disadvantaged communities, as well as empower students to become the developers and innovators in the domain of development technology.

APPENDIX – MASS CALCULATIONS

TURBINE [in] [in] [in] [in] BLADE x y z thickness

(3X) 1.33 30 6 0.0329

[m] [m] [m] [m] [m^3] [kg/m^3] [kg] [N] x y z thickness volume density mass weight

0.033782 0.762 0.1524 0.00083566 0.001090403 7800 8.505145317 83.43547556

[deg] [m^2]

alpha effective area 60 0.117461491

[in] [ft] SHAFT D L

(1X) 1 6

[m] [m] [m^3] [kg/m^3] [kg] [N] D L volume density mass weight

0.0254 1.8288 0.000926667 7800 7.227999775 70.90667779

[in] [in] PLATES D thickness

(2X) 35 0.125

[m] [m] [m^3] [kg/m^3] [kg] [N] 63.48753199 D thickness volume density mass weight 622.8126888 0.889 0.003175 0.001970775 7800 15.37204813 150.7997922

RAFT [ft] [in] [ft] FLOOR x y z

(1X) 4 0.25 4

[m] [m] [m] [m^3] [kg/m^3] [kg] [N]

x y z volume density mass weight 1.2192 0.00635 1.2192 0.009438949 7800 73.62380114 722.2494892 *Assuming solid steel sheet

[ft] [ft] [in] DRUMS D L thickness

(4X) 3 4 0.125

[m] [m] [m] [m^3] [kg/m^3] [kg] [N] D L thickness volume density mass weight

0.9144 1.2192 0.003175 0.007654653 7800 59.70628981 585.718703 *Assuming hollow oil drum

PIPING [in] [ft] [in]

(8X) D L thickness 1 4 0.0625

[m] [m] [m] [m^3] [kg/m^3] [kg] [N] 317.4182102 D L thickness volume density mass weight 3110.69846 0.0254 1.2192 0.0015875 7.96354E-05 7800 0.621156231 6.093542623

ACCESSORIES [kg] [N] ALTERNATOR m weight

(1X) 10 98.1

PLASTIC BOX [kg] [N]

(1X) m weight 2 19.62

WIRE [kg] [N] (1X) m weight

13 1 9.81

127.53

TOTAL MASS 393.9057422 [kg]

TOTAL WEIGHT 3864.215331 [N]

x, y define cross-section z is depth parameter

all values taken as average over component

NOTES

Mic

ro-H

ydro

Pow

er�

Pug

h C

hart

: W

e us

ed a

com

pari

son

of f

ive

hydr

opow

er a

ltern

ativ

es w

ith th

e w

ater

whe

el to

ana

lyze

the

best

des

ign

for

Les

otho

.

CR

ITE

RIA

W

EIG

HT

WA

TE

R W

HE

EL

G

OR

LO

V

DA

RR

IEU

S /

DA

VIS

SC

HN

EID

ER

LIN

EA

R

PE

LT

ON

WH

EE

L

PR

OP

EL

LE

R

The

pot

entia

l for

uni

t to

be re

engi

neer

ed a

nd

impl

emen

ted

at a

re

duce

d co

st

5 0

+

+

+

--

Abi

lity

to h

andl

e di

ffer

ent f

low

rate

s 4

0 +

(> 2

ft/s

) +

(> 5

m/s

) +

Low

- H

igh

+ L

ow

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lity

to h

andl

e di

ffer

ent r

iver

hei

ghts

4 0

+ (C

an b

ob u

p an

d do

wn

in ri

ver a

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ight

ch

ange

s)

+ (C

an b

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ver a

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ight

cha

nges

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be

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ease

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sed

in le

ngth

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nted

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