Dartmouth Humanitarian Engineering – DHElios
Solar Thermal Water Heater
Case Study: Engineering
WHEN
Fall 2021 - Now
User Research
Product Development
Systems Engineering
Tags
Overview
Designing and engineering a solar-thermal water heater for rural schools and communities in Sub-Saharan Africa to meet their needs and reduce firewood consumption by over 40%
Skills
Image of the system our team installed in Uganda in Summer 2022
Experience Summary
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Balancing user needs, business and logistical constraints, and technical limitations of building a high-tech system in a developing nation
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Analyzing performance and financial data to mitigate costs and optimize return on investment
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Leading and organizing a large team to execute complicated operations overseas
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Adapting and building on existing technology to meet specific needs of the user
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Working with interdisciplinary considerations, bridging the gap between design, electrical and mechanical engineering
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Developing partnerships with foreign entities, global communication
My Role
While I was involved in most aspects of the project, I was specifically involved in the following tasks:
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Adapting to Conditions: Engineering Alternative Components
In order to meet the needs of our users, we needed to design a product that could be built in our user's environment. This meant it needed to be made out of parts available in Kampala, Uganda, or in smaller rural cities. I can not over emphasize the constraints that our location provided. Many complicated parts were either completely unavailable or incredibly expensive. Even simple parts, such as certain pipe jointing etc that you would expect to find in any hardware store, were not available. Which components could we develop alternatives for, and which ones would we need to buy/ bring with us? Perhaps the simplest example is our variable resistance heater. It was much easier/ cheaper to find resistive heaters with fixed resistances, but these would not optimize the heat output of the system. We created models of the system where we used a configuration of fixed resistance heaters configured at the optimal level of resistance to see how much heat would we lose, but determined that the variable resistance heater had a big enough advantage to justify its cost.
We determined that the variable resistance heater was financially justified.
Voice of the User: Keeping the End Goal in Mind
One of my biggest behind the scenes contributions was keeping the team focused on our specific objective. Our users had a lot of unique needs that dramatically changed how we needed to design our system. For example, the schools do not constantly draw water, but rather they use a big batch of water early in the morning to make breakfast and a big batch in the middle of the day for lunch. This meant that certain metrics, such as overnight heat loss, were of heightened importance while others, such as maximum heating rate (which occurs in the afternoon) was less important. I worked to keep people focused on the specific problem we were trying to solve and how our product could best meet the needs of the user.
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Optimizing Solar Thermal Panels
The heating effects of solar thermal panels decreases exponentially as the water gets warmer. Accordingly, it was important to design our system in a way where the coldest water was always going through the panels. This led us to a continuous flow system, where the coldest water in the tank is always flowing into the panels and the warm water is flowing into the tank constantly, as opposed to getting a bit of water very hot and then mixing it in with the cold water. I worked on the tank insulation and structure of the plumbing configurations.
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Leadership and Logistics
As our team grew, it became increasingly complicated to be organized and communicate efficiently. One solution that I spearheaded was setting up project sub-teams to divide people based on the tasks they are interested in. This created accountability, made work more efficient, allowed people to bond more in small groups and take ownership of a part of the project, and made communication more efficient as whoever was taking charge of the project team could report the progress to the whole group. Additionally, a big part of this project was getting funding and approval for our tasks. I worked on the documents and gave presentations to different boards at Dartmouth in order to secure approval for our travel, safety certifications, and funding.
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Future Planning
This summer was a pivotal time for our club and leadership. We had been working towards our trip to Uganda, and now that that was done, our new leadership team had to navigate how to move forward after the initial accomplishment and what to do next. I established our path forward: synthesizing and implementing what we learned from the first trip, monitoring and optimizing the existing system, developing a structure for the club moving forward, working to develop a second generation design project and developing detailed plans and deadlines for future development.
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Evaluating Photovoltaic Alternatives (see "Considering PV" below)
Finally, I worked on a lot of electrical engineering problems related to the PV system and was a key decision maker in the consideration, economic analysis, and judgement about what was feasible and what met the community's needs the best. See more of this in the considering PV section above
Background
The DHElios project began when teachers at Beacon of Hope (BOH), a Ugandan primary school, contacted DHE through a former Dartmouth professor who was working as a missionary in Sub-Saharan Africa. They had observed the incredible cost of the firewood they were using and looking for a solution. This school and many schools and rural communities in Sub-Saharan Africa rely on firewood as their primary fuel source.
Due to the logistical challenges of building a prototype system in rural Uganda, where the nearest store for parts may be a half a day away, our team decided to partner with Ugandan Christian University (UCU) as a middle step to begin testing the system in Uganda and work out any potential kinks there before taking it into the country.
After months of user research, prototyping, engineering, testing, analyzing, modeling, and planning, we were able to send a team of Dartmouth Students to Ugandan Christian University (UCU) to install the first generation of our Solar Thermal Water Heater that is able to effectively reduce the school's firewood consumption by over 40%.
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​Over 90% of schools use firewood to cook with and heat water
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Roughly 60% of rural school firewood consumption is used to heat water
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Cooking is done primarily in the morning on staple foods that necessitate boiling large quantities of water (i.e. maize, porridge...)
Problem Background
​​Environmental
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Solid-fuel cooking in SSA is a major driver of deforestation and it is responsible for 1.2% of global CO2 emissions
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90% of Ugandans use charcoal and firewood as their main source of energy and Uganda is on track to lose 100% of their forest cover by 2040.
Health​
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Cooking smoke-induced diseases → 4.3 million deaths annually - more than HIV and malaria combined (WHO)
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800 million people in Sub-Saharan (SSA) do not have access to clean cooking fuels
Cost
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UCU purchases nearly 45 tons of firewood per year for boiling water (~700,000 liters)
The Challenges
Team
Student Leaders:
Anna Hugney – President
Josh Vorbrich – Vice President
Rujuta Pandit – Vice President
Noah Daniel – Former President
Ethan Aulwes – Former Vice President
​ Veronica Yarovinsky – Former Vice President
Emily Liu – Project Director
Jack McMahan – Project Director
And others who contributed to varying degrees
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Advisors:
Professor Stephen Doig
Professor Charlie Sullivan
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In collaboration with a team of students at UCU (pictured below)
UCU student team
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Engineering a system that could be built using parts available within Uganda
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Developing system, charge controllers, and batteries to optimize heating in varying lighting conditions
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Logistical challenges of sending a group of students on a multi week trip to Uganda to install a solar thermal system at the Ugandan Christian University (UCU), facilitate relations with schools, and teach people about the system
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Increased consequences of logistical mistakes and missing parts due to time required to source and transport equipment
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Water usage is heavily concentrated at the very beginning of the day and around mid day
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Overnight heat loss
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Heating large batches of water during times when the sun's strength is reduced
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Developing competing solar thermal and photovoltaic system prototypes
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Conducting functional and economic analysis to determine which system to build in Uganda
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The Product
Our solar thermal water heating system is able to heat enough water to reduce a community's total firewood consumption by over 40%. At UCU, our system is actively reducing their firewood consumption by over 100kg per day.
The Process
While solar panel systems already exist and are readily available, they are not an effective solution to the communities problems for many reasons (see "Considering PV" section below for an example). Rather than developing a complicated and unaffordable all inclusive solar energy system to solve all of their energy problems, we sought to develop a specialized system able to meet the specific requirement of heating water, which was responsible for 60% of their firewood consumption.
Flow Chart: Morning Batch (Breakfast)
Prototyping
Hanover weather ≠ Uganda weather
Prototyping took place over many months as we tested the optimal solar panel, pump, plumbing, circuit, and tank insulation designs. We spent time figuring out how to best rig the system with sensors and an arduino in order to have the tank in Uganda report data back to us in Hanover so that we could analyze it to optimize future designs (this is what we are working on now).
We developed many different iterations with various different resistive heaters, solar panel arrangements, plumbing structures, pressure escape valves, etc. We worked our way up from a small scale system to a continuous flow system large enough to model the batch heating system we would need to use at UCU. we experimented with continuous flow and multi-tank systems. We used modeling and analyzed data from various different tank insulation prototypes to determine values such as the overnight heat loss and optimal insulation techniques.
Working with students from UCU, we were able to get a sense of the communities specific needs as well as gather reasonably accurate information about the pricing and availability of certain parts in Uganda. One challenge we encountered is that unlike in the United States, where you would buy pipes at a big store like Home Depot and if you checked the price a month ago, you could expect the price to remain rather constant over the course of a month, most of the parts had to be bought from local vendors in the market in Kampala, where, depending on your bartering and the availability, the prices could fluctuate quite a bit. Further, specialized parts were difficult to find, evaluate, and transport, so we had to work around what parts we would be able to find locally.
Considering PV
Traditional solar energy systems use photovoltaic panels to generate electricity require solar panels, a battery, an inverter, and a charge controller to regulate the voltage and current coming from the panels, among other things. However, implementing this technology in Uganda posed significant problems. One example problem is that commercial charge controllers are designed in a way that they need to be connected to a battery (even for their DC load terminal output to function). However, charge controllers with a DC load terminal are limited to 100v/20a or smaller, so we would need to have 6 different charge controllers, adding complexity. The only solution is to "trick" the charge controller by wiring a battery in parallel with the low voltage DC resistive heating ellement and then wire the charge controllers in parallel. This was barely cost competitive and, given the limitations of installing and fixing a system in rural Africa, the maintenance risk was too high to pursue without further research and testing.
PV system diagram
Final System
Final System Diagram
Our final system installed outside the UCU's kitchen in Uganda
Moving forward
Our end goal is not just to install this system at universities, but to develop an open source design that can be used at all types of rural schools and communities. From our first trip, we gained invaluable information. We learned that building in Uganda is even more unpredictable and difficult than expect (but also cheaper), that there is a significant leap in the logistical requirements necessary for UCU trip compared to Beacon of Hope and more rural schools that should not be underestimated, and that moving forward we should plan more time to facilitate relationships with UCU and build their club in order to ensure longevity and buy in.
