Solar Oven Solving
Housing Needs

by Carol Milano

Right to left: Andrea Schultz, mechanical engineering major, with Ryan Tanaka (civil engineering) in front of solar oven, Photo Courtesy of Rose-Hulman Institute of Technology.

"Haiti. Disaster Relief. Go." Those were the only instructions given to eight undergraduates in the summer 2014 Grand Challenges of Engineering course, remembers Ashley Bernal, assistant professor of mechanical engineering at Rose-Hulman Institute of Technology in Terre Haute, IN. Their assignment: identify a problem through research, then develop a project to solve it.

They soon discovered during their six weeks of thorough investigation: thousands of Haitians live in unsafe housing, due to weather-related catastrophes or government crises. From many proposed solutions, the group chose "making plastic bricks to build low-cost shelters," says sophomore Andrea Schultz, one of three mechanical engineering majors.

The students set out to extract usable materials from Haiti's abundant plastic trash. "Gluing hard plastics together didn't work," Schultz remembers. "We then tried melting plastic, with a solar oven – a current technology that produces lots of heat. We tried cutting up plastic bottles, which took too long, then tried cutting Walmart bags, making them easy to melt." A melted blend could be placed into molds shaped like bricks or planks for building inexpensive housing, able to withstand storm winds of 12 to 30 mph, while improving Haiti's environment.

"It's unusual to use a solar oven this way. People melt plastic for things like toys, but not for construction." After studying heat transfer and conservation, Schultz's team determined specs for dimensions and insulation layers, "in order to get the temperature where we want it."

A Student's Perspective

Schultz chose the ten-week elective partly for its 12 credits. "The hands-on experience interested me – I had no idea what we'd be doing." Her challenging co-project manager role meant getting involved in scheduling and assigning specific tasks, besides her own creative activities. Though she hadn't expected management experience, she considers it valuable for any engineering field.

Plastic Samples. Photo Courtesy of Rose-Hulman Institute of Technology.

Other skills Schultz appreciated involved heat transfer components and the design process itself. "The bricks are still in prototype phase; we'll develop them further this summer. We'd like the viscosity to be more fluid so that when it hardens, it will be more uniform. Then it would adhere better, with fewer stress points. Before we try implementing these, we want to make sure it works to our expectations. I hope to travel to Haiti someday," says Schultz. "I'd never done anything this complex before. I'd take this class again – it was definitely worthwhile!

The Professor's View

To Bernal, the students' main challenge was developing a solar cooker that could focus enough energy to melt plastic. "Differing melting points for various plastic recyclables requires sorting to find materials with similar points. Their biggest success was taking risks, pushing the envelope. " Their solar solution's unusual design's "hinged, angled panels capture more of the system's solar energy, due to being more semi-circular than single flat panels would be," she explains. "Their entire oven is quite large, like a nine-foot swinging pendulum! They figured out where the center of the solar cooker's mass is, to more easily rotate and pivot the device to follow the sun." The mechanical engineering students' understanding of heat transfer, thermodynamics, radiation and conduction was especially helpful.

The course's technical writing component improved students' communication skills. "Identifying different audiences, they changed their jargon to suit each group, to explain why their design is the better choice or why this is the next step," says Bernal.

Depending on their specific focus, students learned ways "to manufacture something more efficiently, or to design drawings that more effectively communicate a particular plan," Bernal found. These could be valuable in fields like Project Architecture, or in Solar Energy, designing solar cells. Project management skills are sought everywhere.

A different mindset, and experience that's unusual for engineers, are great assets in job-hunting. Beyond classwork, consider volunteering, for example, for a local project addressing poverty-related problems. Highlight your unique background in your resume, interviews, and cover letters.