the mango tree project: energy audit and report

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The Mango Tree Project

Energy Audit and RecommendationsAgahozo-Shalom Youth Village

THE MANGO TREE PROJECT

A joint project between students from United States Air Force Academy, Tufts University and Washington University in St Louis

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TABLE OF CONTENTSTufts UniversityMichael Sidebottom, Tufts B.S. ‘10Cody Valdes, Tufts B.A. ‘13And Contributors: Fred Huang, Tufts B.S. ’10, Dante DeMeo, Tufts M.S. ’10, Patrick Barber, Tufts B.S. ’10, Michael Vizner, Tufts B.S. ‘12

United States Air Force AcademySecond Lieutenant David Pool, USAFA ‘10Cadet First Class Leif Lindblom, USAFA ‘11Cadet Second Class David Shrift, USAFA ‘12

Washington University in St. LouisTegan Bukowski, WUSTL B.A. ‘10, Yale ‘13

National University of Rwanda/Brandeis University

B.A. Economics, NUR.

The Mango Tree Project team wishes to thank its many generous support-ers, partners, and friends who have made this endeavour, and this report, pos-

left us with tremendous insights and invaluable friendships after an entire year of collaboration. In particular, we wish to thank the Agahozo-Shalom Youth Vil-lage, whose staff, youth, and leaders warmly invited us into their community and their homes for the duration of our three-week assessment trip in January 2010. Anne Heyman, Nir Lahav, and Alain Munyaburanga deserve special thanks for their generous time and patience with us as we navigated our way through the humbling process of understanding a new community in an unfamiliar country.

The individual groups of the Mango Tree Project wish to thank their own support-ers as well. The United States Air Force Academy Mango Tree Project members would like to thank the Dean of Faculty, Brigadier General Dana Born for her sup-port and encouragement in the beginning stages of the project, the Civil and En-vironmental Engineering Department for providing engineering guidance and resources, the Department of International Programs for generously funding

-port, and Ms. Leslie Christensen for her help navigating the approval process.

The Tufts Mango Tree Project members wish to thank the Institute for Global Leadership, its Director Sherman Teichman, and Assistant Director Heather Barry for their unwav-ering support of this student-led initiative from its conception in September 2009. Their guidance and enthusiasm for our project, which attempted to bring together students from three universities and multiple departments to work together towards a single

The Washington University in St Louis team want to express gratitude to the Washington University Sam Fox School of Design & Visual Arts School of Architecture for their im-mense generosity in providing not one but two travel grants to travel to and from Rwanda.

Also, Tegan Bukowski wishes to thank the Ghepardt Institute for their Civic Engagement Scholarship. Without these contributions, the project would have been impossible.

THE TEAM TO OUR SUPPORTERS

I. Executive Summary II. Rwanda 16 Years OnIII. Village Energy AuditIV. Recommendations A. Renewable Power Production B. Strategic Areas for Reduction and EducationV. Conclusion

VI. Appendices A. Hourly Electricity Usage by Building Type B. Phase 1 Energy Model Assumptions C. Phase 2 Energy Model Assumptions D. Energy Use by Appliance E. Experimental Data Phase 1 & 2 F. Biogas Production Chart G. Biogas Production Calculations H. Thermosyphon Analysis I. Thermosyphon Energy Savings J. References

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The Mango Tree Project is an endeavor among a multidis-ciplinary team of university students to understand and im-prove upon the current patterns of electricity consumption of the Agahozo-Shalom Youth Village (ASYV), a youth re-habilitation and education community located near the town

initiative of partners in the United States, Rwanda, and Israel to provide a safe living and learning environment for vulner-able and orphaned Rwandan youth, is home to 250 youth and approximately 100 staff, a number which will double to a full capacity of 700 in two years. It is currently facing consid-

of high electricity and fuel costs, both of which were antici-pated symptoms of Rwanda’s developing national energy infrastructure at the village’s conception, but nevertheless remain substantial obstacles now and even more so in the immediate future as the village expands. As a team of stu-dent researchers with practical experience in building design, sustainable systems design, renewable energy and curricula design, the Mango Tree Project (MTP) team set out with the goal of providing the village with a comprehensive under-standing of its current (and, where possible, future) electricity consumption patterns, and then to provide guidance towards implementing new systems for achieving cost-savings in the near future.

Renewable energy technologies have advanced in sophis-tication and affordability in the global energy market to the point where they are currently the only reliable and afford-able route to achieving long-term energy independence for many developing communities. Until Rwanda’s quickly ex-panding national electricity infrastructure has reached the state where it can provide economical and reliable service to energy-intensive ventures such as the ASYV, renew-able energy sources will offer a secure and cost-effective means to sustaining the village’s operations, provided that

-nanced through a relatively large up-front injection of capi-tal. Our energy audit has shown that at the current rates of electricity consumption and purchase exchange from Elec-trogaz, Rwanda’s national supplier, the village will be paying roughly $55,000USD per year in two years time. The MTP

-taic power generation system, able to produce electricity for various scales of need, to be designed and maintained in partnership with local partners such as Great Lakes Energy Ltd. and the Solar Electric Light Fund (SELF).

EXECUTIVE SUMMARY

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As a uniquely transformative healing and rehabilitation com-munity, ASYV is ideally placed to become a truly state-of-the-art educational space for Rwanda’s most vulnerable youth by specializing in these renewable technologies, which represent the future for its under-25 generation. The MTP team aims to provide ASYV with its expertise in as-sessing and sourcing renewable technologies in order to

-pirations. The recommendations contained within this pro-posal are thus intended to be practical and actionable while remaining modest in light of our position as students, as out-siders, and as individuals who will have minimal stake in any action taken as a result of this report.

This report is intended to be read by any and all individuals living or working in the village, those people who have a stake or interest in the village from abroad, and, in particu-lar, any individuals who may have an interest in support-

steps into renewable technologies and other energy-related cost savings measures over the immediate and near-term

-tory notes on Rwanda’s immediate history and the context in which ASYV has established itself, followed by the MTP’s energy audit of the village, after which we present our rec-ommendations for the production of energy, the reduction of energy use, and the concomitant implementation of edu-cational systems and materials surrounding the technology.

tragedy that brought it infamy in April 1994, when in just 100 days more than 800,000 Tutsis and Hutu moderates were systematically slaughtered by extremist Hutus, marking the nadir of a decade of instability within the heart of the Afri-can continent. The scars of the genocide and its preceding years of civil war have settled deep in the fabric of Rwandan society, both physically and spiritually. While these scars are stored most viscerally in the minds of the men, women, and children who partook in or were victim to the genocide’s inescapable violence, the most saddening manifestation of the pogroms’ destruction was the unknowable number of in-nocent children who came of age in its aftermath. For these

absence of familial support, or the well-intentioned efforts of

Today, Rwanda has an estimated 860,000 orphans of a total population of nearly 10 million. What many see as Rwanda’s saddest statistic presents a gargantuan barrier to unlocking the immense human potential of the country’s under-25 gen-eration. According to UNICEF, Rwanda is believed to have the highest concentrations of orphans in the world. Many of these children were orphaned during the genocide, while others have lost parents to HIV/AIDS, the rates of which have increased since the Hutu militias of 1994 used mass rape as a systematic weapon of war.

At the same time, Rwanda has developed at a remark-

in neighboring Democratic Republic of the Congo and vi-olently-contested elections marring the Republic of Kenya in 2007/8, it has fast risen from nothingness to emerge as somewhat of an exemplar for the Central and East African region. According to the World Bank’s 2007 World Gover-nance Indicators, the country has surpassed expectations of political stability, government effectiveness, and control of corruption, and has rebuilt its governance structures with remarkable speed. Rwanda has gained a reputation as a leader in the continent in the reduction of corruption and promotion of government accountability, having “built up a culture of good governance, transparency and evidence based policy making,” according to the Millennium Develop-ment Goal Monitor1. With Africa’s largest solar power farm now situated just seven kilometers from the capital city of Kigali, Rwanda is also positioning itself to become a leader in Africa’s renewable energy sector. And as part of its con-tinued commitment to developing its core infrastructure, the Rwandan government has endeavored to make its capital

broadband coverage.

Nevertheless, the future of the country’s leadership in its public, private, and cultural institutions faces considerable challenges. Some have characterized the post-genocide generation as a lost one, made passive and pliant by an overabundance of paternalistic aid that has created a

1. Marie Chene, “Overview of Corruption in Rwanda,” Transparency International Anti-Corruption Resource Center. Available online at (http://www.u4.no/helpdesk/helpdesk/query.cfm?id=164). Accessed December 13, 2009.

AGAHOZO SHALOM YOUTH VILLAGE RWANDA 16 YEARS ON

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lacuna where Rwandan self-empowerment need take root. This is unlikely, for the extraordinary demands imposed on the individual – particularly parentless youth – in the wake of the country’s civil war have often been beyond fathom. Others would argue, more convincingly, that President Paul Kagame’s 16-year tenure (extended in August 2010 for an additional 7 years) has only ingrained the passivity-

and which continues to extend beyond the country’s closed political forum, into the classroom and the purviews of the youth. No matter how much truth these broad characteriza-tions contain, the reality is that hundreds of thousands of Rwanda’s post-genocide youth have been forced to come of age as heads of households, street orphans, manual laborers, and by various other stunting means of survival that have diminished their prospects for positive social in-tegration and personal development. While the country has

reconciliation, these developments have succeeded despite the persistence of the genocide’s most glaring underlying causes, including a lack of positive youth engagement. With nearly ten percent of its national population orphaned and a greater number considered to be vulnerable, Rwanda ur-gently requires a sustained, concerted, and caring effort to help this generation reclaim its vitality, trust, and entrepre-neurial spirit.

This is the context in which ASYV has established itself as a true leader in the rehabilitation and leadership develop-ment of Rwanda’s youth. Of the challenges currently fac-

as a primary barrier to longevity and sustainability in pur-

of its electricity supply. Through our direct research into the village’s primary points of electricity consumption and our conversations and interactions with the directors and youth of the village, we have gained a detailed understanding of the village’s current electricity use patterns as well as an informed projection of its future demand. We have shared

http://www.mangotreeproject.org.

The scope of our energy audit was to accomplish the following:

consuming devices in the village

particlarly with respect to those which are

how long lights are kept in use

a model of the village’s current (Phase 1) energy use over a typical 24-hour period (See Figures 2 & 3)

future (Phase 2) energy use, factoring in future buildings and a population at maximum capacity (See Figure 4)

Our research as it related to the energy consumption of the village had a straight forward goal. This was to produce a complete energy model by structure and by hour-of-day for all energy usage in the village, which could inform any future steps taken to develop a renewable energy power generation system by the village and its partners. Prior to our assessment of the village, its administrators had only a rough idea of how much energy the village was using and which points were drawing on the most energy in compari-

much money was being spent on each new block of energy credits from Electrogaz, Rwanda’s national energy supplier, and where this money was being used. (See Figure 6 for Electrogaz Purchase Record). We have produced a working model of energy use in the village that the village adminis-trators will now be able to reference when talking about their current energy use to potential funders, solar photovoltaic systems experts, and other relevant parties.

The ultimate goal of our assessment is to provide the vil-lage with sustainable energy design alternatives from which to develop a strategic plan for increasing its independence from the national grid. The funding and implementation of our recommended systems will allow the village to become more sustainable, both economically and in terms of its en-vironmental impact.

III. VILLAGE ENERGY AUDIT

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the quantity and energy usage rating of all the appliances

layouts that would each serve as a model for multiple build-ings. We recorded as much information about each energy-consuming device as possible, particularly the manufacturer information, model number, and wattage of each, so that we could create a physical layout of energy-consuming devices by structure. Although it took us several days to completely map out the village, this process entailed the strictly techni-

was addressed when analyzing the behavioral observations we recorded. This data is available in Figure 1 and Appendix D.

Experimental Data

The third task of the on-site assessment was to collect ac-tual energy usage data. Prior to our assessment of the vil-lage, the only estimate that village administrators had of how much energy the village was using was based on how often they needed to buy more energy credits. Because Electrogaz sells electricity via a pre-paid, credit-based sys-tem, the village had been purchasing a certain number of

kWh.

ON SITE ASSESSMENT BEHAVIORAL OBSERVATIONS

The second task of the on-site assessment was to observe the behavioral energy usage patterns of the children and

The need to observe behavior and to hold focus groups with the community members was the most critical reason for travelling to Rwanda to perform an on-site assessment. While in the village, we spoke with new students, return-ing students, administrators, and house mothers about their energy usage. Some sample questions we asked were the following:

they normally go to bed?

ing electric kettles? What do they use them for?

Which ones? For how long?

hours? Which ones? For how long?

What we learned from our time spent with the village youth al--

gram depicting how many of each type of energy-consuming device are in use for each hour of the day. (See Figure 2) This schedule became the backbone for the energy usage model, which we could then compare against the experimental data we had gathered.

Unfortunately, under this service model, the village did and does not receive a monthly electricity usage statement, as is common practice for post-paid utility service providers. Therefore, we gathered this data on an hourly basis from the village’s electricity meter to create a more accurate measure of how much energy is being used every hour and ensure that our model accurately represented the village’s energy usage. (See Appendix E and Figure 5 below for ac-tual data)

Figure 1 Children’s Home Energy Usage by Appliance

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organized the village’s structures into eight units based on their usage and their similarity to one another. (See Figure 2 and Appendix A)

The eight structures are as follows:

The label “Typical” indicates a structure that is representa-tive of two or more near-identical structures and is used to model all such structures. Each of these structures was or-

any time of the day, which gave us the precise control nec-

experimental data that we had gathered. (See Appendix B for the assumptions we used in modeling for Phase 1’s en-ergy usage)

ENERGY MODELPHASE 1

Figure 2 Hourly Energy Usage Model by Building

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We used our gathered data to create a high and a low estimate of hourly energy usage and used the average of these two as-

generation system is the time at which village power usage spikes. From 18:00 to 23:00 hours the village uses the greatest relative amount of energy during a given day, but as solar power generation systems can not produce energy at this time (after sunset), the village will still be forced to draw upon electricity from the grid or electricity stored in independent batteries from the day’s solar production. This, of course, will incur additional costs for the village on top of solar power production systems.

The next task was to extrapolate the Phase 1 model to the size of the village when it becomes fully operation with 500 children and 150 – 250 staff and several new structures in 2012. There were several key assumptions that allowed us to do this effectively. (See Appendix C for Phase 2 Assumptions) In particular were the following:

double (16 houses to 32 houses).

children’s houses, so the increase in total energy consumption will be nearly proportional to the percent increase in children.

the increase in children or staff members using that particular type of structure.

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of occupants.

In order to check this extrapolated model, we scaled up the experimental data we had gathered.

Figure 3 Hourly Energy Usage Phase 1

Figure 4 Hourly Energy Usage Model Phase 2

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Because we had assumed that the increase in total energy consumption would be nearly proportional to the increase in the number of children, we decided to scale up the experimental data by a factor of two. When we compared this Phase 2 experi-mental data with the Phase 2 model we had created, the two sets of data matched up well. We decided to keep the assumption

There are several key points and conclusions to glean from our energy audit, some of which have directly informed our decision process while assessing various sustainable en-ergy systems, and others that will support the village in un-derstanding and curtailing its own energy usage.

content of the audit itself. The village now has a concrete model of how much energy it uses, both on an hourly and a

uses and the cost associated with that energy use, both cur-rently and when the village begins operating at full capacity in roughly two years time.

The second is that the majority of the energy use is due to lighting, primarily in the children’s homes and primarily dur-

important insight for the village’s staff and students, inform-ing them about which hours of the day contribute most to the village’s energy spending. (See Appendix A in particu-lar) It also gave us guidance regarding where to focus our energies in the reduction portion of our report, which led us to concentrate particularly on making the village’s lighting

Based on the extrapolated model, when the village is fully operational, we predict the cost for energy will be nearly 31,000,000 RWF (55,000 USD) per year. (See Figure 6 for Cost Summary) With the ultimate goal to foster as sustain-

entirely to Rwandan hands, the current and projected costs are economically unsustainable. Therefore, by using this foresight and data to craft potential solutions, the village and its partners can help implement smart solutions that will re-duce the yearly energy cost to a level that the village can sustain on its own for many years to come.

CONCLUSIONS AND RECOMMENDATIONS

Figure 5 Hourly Energy Usage Phase 2

Figure 6 Cost Summary Phase 1 & 2

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Problems ApproachIn order to provide the most objective and holistic renewable energy recommendations to ASYV, the Mango Tree Project team considered multiple forms of renewable energy pro-duction and evaluated each on their economic, social and engineering value. The renewable energy methods as-

solar), solar hot water, geothermal, wind, and biogas energy production. Our recommendations for the production of renewable en-ergy will be limited to the direction we believe the village should take when and if it decides to implement a power generation system, at which time it will behoove the village to obtain a realistic cost-quotation from a local partner with

Ltd. While presenting an accurate price for the landscap-ing, ground preparation, designing, constructing, and main-tenance of a solar array farm in the village grounds is out of

-able and consistent supply of solar electricity to the village and that our energy audit will greatly inform the design pro-cess that accompanies it.

Design FactorsThe Mango Tree Project Team considered several design factors to rate each renewable energy method. Among these, sustainability was determined to be the most impor-tant factor.

A high level of sustainability ensures the production meth-od will produce enough energy to reduce or eliminate the village’s reliance upon outside sources of energy. Sustain-ability also prescribes cradle-to-cradle system and material design. The system must utilize local materials and techni-cal support, as well as provide adequate supply of energy to the village. The economic feasibility of each system was also consid-ered while evaluating each of the energy production meth-ods. This factor did not serve as a decisive factor because the team believed it best to leave this design constraint for the village and its funders to assess, balancing the weight and scope of this requirement with the long-term security and cost-savings that such systems would provide. Finally, each production system was evaluated for educa-tional and social value. Again, the team did not deem this design constraint a controlling requirement but kept it in mind while determining all possible solutions. This is consid-ered to be the social sustainability of the system. It must be

the village. We have supplemented our recommendations here for the production of energy with a series of recommen-dations for educational materials and systems adjoining the production system, which will help bring the systems ‘to life’ for the youth, the primary stakeholders of the technology. Each of these design constraints was applied to each power generation system to evaluate the overall sustainability and effectiveness.

IV. RECOMMENDATIONS

A. RENEWABLE POWER PRODUCTION

Figure 7 ASYV Purchasing History

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RESULTS

The Mango Tree Project Team has considered several dif-ferent design solutions for ASYV. These design solutions comprised of vastly different energy production methods that would be implemented in different ways. The most eco-

production. Solar PV has the greatest potential for payback within the next 20 years, has lower front-end cost, and is easier to install and maintain in Rwanda. Based on the anal-ysis provided, the solar photovoltaic energy production sys-tem has the lowest estimated payback period of all available

of conjecture.2 Importantly, similar photovoltaic systems are

for the photovoltaic system. 3

SolarConcentrated solar is not a viable option due to the lack of expertise and maintenance ability already established in Rwanda (or surrounding countries). The long-term main-

made by the system. Our consultations with Antony Simm of Stadtwerke Mainz, implementing partner of Kigali So-laire, the largest operational Sub-Saharan photovoltaic so-

maintaining a concentrated solar power-production system in a country like Rwanda, where the topography and climate prohibit sustained periods of direct sunshine over the course of an entire day. While concentrated solar systems produce intensely under direct sunshine, they fail to deliver sustained

cloud cover that frequents Rwanda’s skies in the way that solar photovoltaic systems do. This factor, coupled with the highly advanced technical skills and materials needed to maintain concentrated solar systems in the likely even-tual case of overheating or breakdown, tipped the scales squarely in the direction of solar photovoltaics.

GeothermalGeothermal energy production was determined to be cost prohibitive due to the inability for a reasonably sized (ie: small) system to provide adequate energy for the village. The end-goal of the village is to be energy neutral and a geother-mal system simply would not be able to produce enough en-ergy to provide for all energy needs of the village. Six factors exclude geothermal electricity production: lack of available equipment, high resource temperature requirements, low

power requirements, and high capital cost. Only commercial equipment (>100kW) for geothermal electricity production exists, and the in situ resource temperature must be greater than 220°F (104 C), while lower resource temperatures yield

for cooling, feed and well pumps. Additionally, a geothermal electricity plant costs roughly $1,500-3,000 per kW capacity. Due to low in situ resource temperatures in Rwanda, geo-thermal electricity production is not a viable production op-tion for ASYV. 4

Wind-

cient wind data to determine whether wind electricity produc-tion would be a feasible option for ASYV. Because this data is inconclusive, the Mango Tree Project Team encourages ASYV to follow closely as 3E, the European-based energy

-ergy potential to the Rwandan Ministry of Infrastructure in December 2010. A full wind data survey will adequately de-termine wind energy production potential, and while it may prove unfeasible for the village to obtain the bulk of its en-ergy needs through wind power given its topographical loca-tion, a single wind turbine located at the top of the village’s upper-most hill, adjacent to the children’s school, would cer-tainly serve as an invaluable source of educational material and skills-development for the youth, if not a valuable but modest source of energy for the school as well. This, how-ever, may only be advisable as a secondary aspiration for the village, given the unknowability of the economic return such a wind turbine would provide.

2 Interview, Antony Simm, Stadwerke Mainz & Kigali Solaire, Kigali, January 2010.3 Interview and email correspondence, Sam Dargin, Great Lakes Energy Rwanda, Kigali, January 2010. 4 Rafferty, Kevin. “GEOTHERMAL POWER GENERATION.” GeoHeat. Geo-Heat Center, Jan. 2000. Web. 8 Sept. 2010. <http://geoheat.

oit.edu/pdf/powergen.pdf>.

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Biogas-

ergy to provide electrical energy to the village but may con-

strain on village staff of non-stop wood burning in the kitch-en facilities.5 ASYV is planning to acquire 40 head of cattle, from which biogas may be produced with the construction of relatively simple biogas digesters located near to the kitchen space in outdoor pits. (See Figure 9 below) According to the Biogas Production Estimates given in Appendices F & G, 40 average weight dairy cows will yield approximately 0.13 kWh electrical power production or 49.6m3 of biogas per day in a system such as that pictured in Figure 8. Questions for the village to consider before pursuing a biogas genera-tion system include, What systems will be erected to collect and consolidate all bovine waste into the biodigester, What will be done with the treated slurry after the waste has been digested, and Can the space required for one or multiple biodigesters (multiple smaller digesters providing the great-

provide accurate estimates of what ASYV could expect to produce from 40 mature cows, a guiding principle for con-sidering a biogas system should be that “biogas is a site-

Energy Ltd. (a private-sector enterprise based in Kigali) or the Kigali Institute for Science and Technology, a leader in

design and implementation of any biogas system.6

IMPLEMENTATION METHODS

In addition to engineering and economic sustainability, the Mango Tree Project team also desires socio-cultural sustain-ability. The team is conscious of ensuring equal investment by the community, which will augment the sustainability and

of new designs. For this reason the team believes multiple solutions should be presented to ASYV by the Mango Tree Project team. From these options the village will decide what solution best suits their needs and desires. These solutions include a modular solar photovoltaic system for each house, a larger system incorporating multiple (16 to 32) houses, a

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both Phase 1 and Phase 2 (future) construction. Addition-ally, the MTP will facilitate the education of ASYV throughout the entire process including: concept, design, construction, and sustainment.

Environmental Studies in Israel, a report by Aashish Meta titled “The Economics and Feasibility of Electricity Generation Using Manure Digesters on Small and Mid-size Dairy Farms,” University of Wisconsin – Madison, January 2002, and calculations based on the provided information by the Mango Tree Project team. Potential respitory

Project to consider. 6 Email correspondence, Mazen Zoabi, March 2010.

Figure 9 Plastic Tube Biodigester, Lowest-Cost on Market

Figure 10 Thermosyphon Design Principles

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B. STRATEGIC AREAS FOR REDUCTION & EDUCATION

Separate from independent power generation systems con-structed by the village, there are measures that the village’s youth and staff can consider undertaking to reduce their use of energy on a day-to-day basis. These include infrastruc-ture augmentation of each children’s home using solar hot water devices as well as behavioral changes that will serve as much as an educative process in the spirit of environ-

opportunities presented by any action taken to reduce elec-tricity use and, in particular, to produce renewable energy on-site, are many and invaluable to the four problem areas

usage can be realized: water heating in children’s homes, phantom loads of plugged-in appliances, external house lighting, and dining hall lighting. Each of these areas has been addressed below.

Water HeatingWater heating for tea and coffee (and perhaps for hot show-ers and clothes cleaning, but these were only uses iden-

-proximately 11% of the electricity used by a single children’s home in a given day. (See Figure 1 above) Solar hot water is a viable technology using local materials and may serve as simple way for family homes to invest in a sustainable energy project and reduce their daily energy consumption. This method requires relatively little initial cost, infrequent

maintenance, and serves as a great way to educate the village in energy savings while reducing energy use from in-home water heating devices. According to our technical report conducted by US Air Force cadet Leif Lindblom, a simple thermosyphon for each home may be constructed using local materials and labor. (See Figure 10 and Appen-dices H & I for diagrams and calculations) A thermosyphon is a simple water heating device located on the roof of a home that uses the different densities of water at different temperatures to separate hot from cold water. Assuming water enters an ASYV house at 16C, a thermosyphon that increases the water source to 65C will result in a 50% de-crease in energy consumption for heating water (i.e. for tea).

100C while the same amount of electricity can heat 20, 1L

This method cannot provide electrical energy production but

water usage on a house-by-house and daily basis. More-over, if it is true that the village youth and guests frequently use the Black & Decker boilerplate for heating water for use in showers and clothes-cleaning buckets, a large enough water tank built into a thermosyphon system would more than compensate for this ‘extra’ hot water demand.

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Phantom Loads

load electricity is completely wasted. The village currently loses an estimated 6518 watts per day due to phantom loads – this includes desktop computers and fully-charged laptop computers plugged in over night, radios and water heaters plugged in throughout the day, and printers, fax machines, and other large but infrequently used appliances. This costs the village over 314,000RWF per year. Where appropriate, the recommended course of action should be the investment in power strips that can be unplugged and/or turned off when appliances are no longer being used and the education of youth and staff about the importance of unplugging their home appliances immediately after use. The numbers provided

increase their awareness and passion about this particular cause of energy waste.

Figure 11 Phantom Loads by Device and Building

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External Light Fixtures

While the MTP team remains cognizant of the security mea-sures in place in the village to protect the youth and staff after

children’s homes, the dining hall and school, we have pre-sented two options for reducing the electricity waste of out-door lights that the village can consider and weigh against the potential security implications of both. The homes have 8 lights turned on at all times when the sun is down until the children go to sleep at around 10pm-12am, when the homes diligently turn off their outside lights and retire. Some of these lights are redundant, for example when two lights face each other on the sides of two different homes, and others are simply unnecessary for the purpose of illuminat-ing ‘social space’ for the youth, as they fall on the wrong side of the building. It is problematic that all lights are turned on

congregate on only one side of the home if and when they decide to go outside at night, which is not always frequently. The installation of either motion sensors that automatically operate the external lights in the presence of people or mul-tiple independent switch-to-light circuits that allow the youth

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ing consumption during these peak hours.

Watt Stopper and similar companies manufacturing remote sensor light attachments offer sound products in the range of $13-20USD and upwards of $75USD for the mounting of motion-sensor lights. 7 Given the potential range of each sensor, a single home may have one sensor activated for multiple lights (or across multiple homes, for that matter). For the outsides of the school and dining hall and security

when no motion is sensed and returns to 100% when motion is detected, and with a range of between 25’ and 50’, could provide a safe and ideal alternative to the current lighting system, which has all lights on at all hours of the night. Con-sidering these middle-ground alternatives while keeping in mind necessary security measures, the village may wish to investigate and invest in a system of motion-sensor bi-lumi-naire lights for the outsides of its buildings. The replacement of the current outdoor lights with bi-luminaire motion sen-sor lights would represent less of a loss to the village than imagined, as all DOP 36-Watt lights taken from the outsides of the children’s homes, dining hall, and school could serve as eventual replacements for the internal lights in the dining hall and school.

http://www.wattstopper.com/products/details.html?id=39&category=63&type=Commercialand http://www.wattstopper.com/products/details.html?id=108&category=64&type=Commercial (Accessed July 2010) In America, Home Depot offers a sound range of items in

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Dining Hall Internal Light Fixtures

Finally, inside the dining hall are over 100 36-Watt lights that illuminate the interior as the youth take their dinner and that remain on well after most have left for their homes after night-fall. Because the walls of the dining hall are painted white,

undertakes an experimental period of two weeks whereby a full half of the main hall’s ceiling lights are disconnected and

half that remain in use after dark and take appropriate steps given the feedback of the youth and kitchen staff. Given that

overall consumption of 58KWh/day (7650RWF/day), the vil-lage might expect to realize a daily cost savings of approxi-mately 3800RWF/day during this experiment.

The educative value of steps – both tangible and behavioral – taken to reduce the energy consumption of each home

line. The MTP team observed an extraordinarily high sense of stewardship and commitment to the village’s collective well-being among the students during its assessment trip in January 2010. This, with little surprise, extended to the task of turning off all home lights at bed time, which was a topic of conversation during an all-village meeting during our as-sessment trip.

With self-initiated and competitive initiatives to reduce daily energy consumption, which can and should be devised by the students as much as possible, the vil lage as a whole would realize equal parts cost savings and education ex-periences worthy of its investment. Strategic investments in this area might include energy-use monitoring systems for each home that can display data in live time and feed data to the ASYV website which all youth and staff can see, and monitoring systems for solar photovoltaic power generation systems such as the WEB Log device offered by the Ger-man company Meteo Control, which are used by the Kigali Solaire solar-panel farm to aggregate and show data on the farm’s electricity production.

Creating educational curricula around the renewable power generation systems and energy saving systems (such as the photovoltaic solar farm and thermosyphon systems) will be crucial to generating life-long passions for sustainability and familiarity with renewable technologies. Next to a pho-tovoltaic solar farm could be a wooden billboard display with LED indicators of the level of electricity being produced by the panels and the amount of electricity being drawn from the grid, if any. Such an LED display would contextualize the overall contribution of the solar panels to the village’s energy supply, and further incentivize the youth and staff to reduce their electricity use in the hours when the village is consistently relying on the grid as a supplement to its pho-tovoltaic array. This wooden billboard would also contain a static informational display about the inner-workings of solar photovoltaic energy systems.

Figure 13 WEB Log Metering Device at Kigali Solaire

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VII. CONCLUSIONS

of its energy use and from the data collected during the Mango Tree Project team’s energy audit conducted in Janu-ary 2010. We have considered the most relevant renewable energy technologies for power generation in the village, informing our analysis with insights gained through interviews and consultations with four leaders in Rwanda’s renew-

for Science and Technology (KIST), whose collective knowledge draws upon private sector experience (Great Lakes), -

ing research (KIST). Our conclusion is that a solar photovoltaic array situated on the face of the village’s hill above its dining hall will be the smartest option for generating power and reducing dependency on the unreliable and uneco-nomical national grid. Most importantly, the local capacity for quoting, building, and maintaining such a solar array is in abundant supply given the presence of the above four organizations and institutes.

Finally, we have recommended various strategic measures the village can take to reduce its energy consumption

the children’s homes and bi-luminaire motion-sensor lights on the exteriors of the village buildings, in addition to an experimental removal of 50% of the interior dining hall lights. In order to familiarize the village youth and staff with all renewable technologies, concepts, and systems implemented by the village in its pursuit of energy savings, we have offered our ideas for the education of all community members whose physical living space will be altered by the above recommendations and whose understandings of the social, habitual, and cultural factors that impact their community’s

APPENDICES

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Appendix A Hourly Electricity Usage by Building Appendix A Hourly Electricity Usage by Building

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Appendix A Hourly Electricity Usage by Building

APPENDIX B Phase 1 Assumptions

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The Mango Tree Project Appendix D Energy Use by Appliance

APPENDIX C Phase 2 Assumptions

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Appendix E Experimental Data Phase 1 & 2

Appendix D Energy Use by Appliance

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Biogas Production

Sorted by Biogas/kg animal

Animal

Type Duck Broiler Layer Pig Turkey Horse Sheep Beef Dairy Veal

Weight per animal

3 2 2 70 8 400 60 500 500 40 kg

Manure

Total 0.33 0.19 0.13 5.88 0.38 20.40 2.40 29.00 43.00 2.48 kg (per day)

TS 0.09 0.05 0.03 0.77 0.10 6.00 0.66 4.25 6.00 0.21 kg (per day)

VS 0.06 0.04 0.02 0.60 0.07 4.00 0.55 3.60 5.00 0.09 kg (per day)

Total Manure /kg animal

0.110 0.085 0.064 0.084 0.047 0.051 0.040 0.058 0.086 0.062 kg/kg animal (per day)

Output

T.Biogas 0.0267 0.0167 0.0110 0.3338 0.0330 1.62 0.1975 1.56 1.24 0.0230 m3 per day

T.Power 0.0072 0.0045 0.0030 0.0904 0.0089 0.44 0.0535 0.42 0.34 0.0062 kW

Biogas/kg manure 81.04 89.43 86.09 56.77 87.86 79.44 82.28 53.91 28.91 9.29 l/kg manure (per day)

Power/kg manure 21.95 24.22 23.32 15.38 23.80 21.51 22.28 14.60 7.83 2.52 W/kg manure (per day)

Biogas/kg animal 8.91 7.60 5.51 4.77 4.13 4.05 3.29 3.13 2.49 0.58 l/kg animal (per day)

Power/kg animal

2.41

2.06

1.49

1.29

1.12

1.10

0.89

0.85

0.67

0.16

W/kg animal (per day)

Biogas Equivalents (Numbers of animals "down" equal to one animal "across". Eg. 12.5 ducks = 1 pig)

Duck 1.00 0.63 0.41 12.48 1.24 60.59 7.38 58.46 46.49 0.86 Number of Animals

Broiler 1.60 1.00 0.66 19.96 1.98 96.90 11.81 93.49 74.35 1.38 Number of Animals

Layer

2.43 1.52 1.00 30.30 3.00 147.06 17.92 141.89 112.83 2.09 Number of Animals

Pig 0.08 0.05 0.03 1.00 0.10 4.85 0.59 4.68 3.72 0.07 Number of Animals

Turkey 0.81 0.51 0.33 10.10 1.00 49.05 5.98 47.33 37.63 0.70 Number of Animals

Horse 0.02 0.01 0.01 0.21 0.02 1.00 0.12 0.96 0.77 0.01 Number of Animals

Sheep 0.14 0.08 0.06 1.69 0.17 8.21 1.00 7.92 6.30 0.12 Number of Animals

Beef 0.02 0.01 0.01 0.21 0.02 1.04 0.13 1.00 0.80 0.01 Number of Animals

Dairy 0.02 0.01 0.01 0.27 0.03 1.30 0.16 1.26 1.00 0.02 Number of Animals

Veal 1.16 0.73 0.48 14.49 1.43 70.34 8.57 67.87 53.97 1.00 Number of Animals

Appendix F Biogas Production ChartAppendix G Biogas Production Calculations

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Appendix H Thermosyphon Analysis Appendix H Thermosyphon Analysis

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Appendix I Total System Load by Appliance Full Village

the mango tree project: energy audit and report

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