Team Lead and Members
Shomik Verma (P '19, Lead), Virginia Pan (P '20), Tenzin Yangkey (P '20), Jaydeep Sambangi (P '18), Angus Li (P '20), Ryan Briggs (P '20), Karyn Saunders (P '18), Lisa He (P '18).
The mission of the Smart Shelters project is to implement engineering solutions to solve the important humanitarian issue facing us today - the refugee crisis. Specifically, we want to improve the quality of life of refugees by providing them with electricity and hot, clean water.
Our Smart Shelter design contains three major elements: solar panels to provide electricity, a solar water heater and tank to heat water during the day and store it for heating use at nighttime, and a passive biosand filtration system to turn rainwater into clean, drinkable water.
Because typical shelters are not structurally solid, installing heavy solar panels presents a problem. For this reason, we designed a ground mount structure to hold the solar panels about 5 feet high. We designed the mount to fit over a 2 person tent 7 ft. x 5 ft. at the base and 4 ft. tall. However, this ground mount can fit over or next to a variety of shelter types, since it is held in place on the ground. A 3D CAD model of our design is shown above. The final design was a result of an iterative process using finite element analysis (FEA) to analyze stresses and prevent any significant deformation. The FEA results prompted us to include supports in the frame to increase stability. The displacement results showed a maximum of .2 mm of displacement, and the Factor of Safety calculations showed applied forces were well above 3 times the failure load. Another important portion of the solar panels was electrical planning and design. Our design included 2 100 W solar panels. These are connected to a 12/24 V charge controller, which charges a 12 V battery. Some of the power from the battery gets converted to 5 V DC power, for a USB output. The rest remains at 12 V to power a 1-m, 30-LED light strip. Much of the electronics were similar to the Solar Benches project.
Solar Water Heater
The next component of the Smart Shelter is a solar water heater. The purpose is to heat water during the day for use for heating at night. In contrast to conventional solar water heaters, our team aimed to construct a cheap and accessible one. Therefore, while many commercial water heating techniques involve expensive solar thermal panels, our design consisted of a single pipe and parabolic mirror supported by plywood, shown above. The parabolic mirror focuses incident light to a single line, therefore concentrating light from a large area to a smaller one. Experimental analysis shows the pipe can reach temperatures up to 160 °F due to the concentration of solar light and heat. We created the mirror surface using a Mylar reflective film mounted on an acrylic plastic sheet. Our original design did not include the two plywood supports, instead relying on the plastic itself to retain its shape. We tried different methods to ensure this, including backing the mirror with wood and heat forming the acrylic, but none of these results were satisfactory. Therefore, our final design involved creating grooves in the plywood to help create the parabolic shape of the mirror.
Rainwater Collection and Filtration
Our design is a passive biosand filtration system, used with collected rainwater. We designed a support structure to angle a tarp in a funnel-like shape, maximizing surface area of rainwater collection. After collection, the water would pass to a water treatment system, consisting of bucket of activated carbon and biosand, to purify the water. Following purification, it would pass to the solar water heater, where it would be heated and stored in a well-insulated tank. Then, it could either be used by the inhabitants for washing hands or bathing, or could be stored in the tank for heating purposes at night.
Although the goal of the project was initially to build a tent to be used during tenting season in K-Ville, the mission was changed to have more of a social impact. We are hoping to implement the project in an actual refugee camp over Summer 2017 or in the 2017-2018 academic year.
For the solar panels, the team realized there are some disadvantages to using the two 100 W panels. They are large, expensive, heavy, and produce more power than necessary. Therefore, a consideration for the future is to use individual solar cells, which can cut the cost by as much as half. These could be mounted on a stronger base such as plywood or acrylic, and then woven into fabric to be placed directly on the tent. This reduces the cost and makes the solar panels safer as there is less risk for collapse.
There is also a lot of room for future improvement for the solar water heater. To achieve optimal heating, we would have to apply an absorption coating to the pipe. Right now, we coat the pipe in black spray paint to increase absorptivity. However, black spray paint also emits a lot of light, so the temperature decreases rapidly. An absorption coating would increase absorptivity and keep emissivity low, to optimally heating the pipe. Another improvement is enclosing the pipe in a vacuum tube, to reduce conductive and convective heat losses, since only radiative heat losses can occur through a vacuum. Finally, a tracking system could be implemented to allow automated movement of the pipe and mirror to ensure the focus always is at the pipe location.
The team has made significant progress in designing, manufacturing, and testing components of the Smart Shelter. Through iterative design, we have improved the design while attempting to reduce cost and optimize the components for their intended use. Now, we have concrete ideas of how to proceed and improve our project in future iterations.