Solar-Powered

UCI’s Henry Samueli School of Engineering was recently granted one of two annual $100,000 endowments from the Bill and Melinda Gates Foundation during the most recent round of funding for designing a viable solar-powered stove.

Under the oversight of Dr. John Garman, an experimental design specialist at the Samueli School, a multi-disciplinary batch of four engineering seniors sharpened a prototypical green stove design, making it more cost-effective, practical and low-emission.

“This project has been the collective effort of students who have enrolled in this project since it started two years ago,” Lineker Phuong, one of the four collaborating students and senior studying mechanical engineering, said. “As every new quarter starts, we would build on the progress and work done by the previous quarter.”

Resembling a hyper-polished satellite dish, the device is comprised of a parabolic solar energy collector, a salt capsule, and the stove itself — an insulated, aluminum apparatus — which encases the salt pocket. The salt vessel contains a mixture of three parts sodium nitrate to two parts potassium nitrate. Within three hours of absorbing solar radiation, the salt mixture is heated to 215 Celsius (about 420 Fahrenheit). The energy released as the molten salt concoction cools powers the stove.

“What happens is that once all the salt is melted and it is taken off the solar reflector, it begins to cool and solidify from the outside surfaces inward toward the core. We want to use heat fins to tap into the core so the cooking surface remains more constant at a higher temperature,” Phuong said. “We cooked up two batches of bacon easily, but by the third, the bacon didn’t fully cook.”

With the grant money, Phuong and his collaborators hope to modify the internal heat fins, streamlining the heat transfer from the molten salt core to the stove-top.

“It works as a solar stove, but does not work as a ‘heat storage’ stove,” mechanical engineering senior and project collaborator Greg Tamashiro said.

The designers’ next goal involves maximizing the stove’s heat storage potential, so it can operate long after the sun dips below the horizon.

“We are continuously searching for different materials to improve the thermal storage, but so far our current salt mixture provides the best combination of performance and environmental consciousness,” Phuong said. Increasing the amount of sodium and potassium nitrates will increase heat output, but the designers concede that tweaking the heat fins or the box-to-salt ratio is a more feasible next step.

“By the end of the upcoming June, we believe that we should have some good results in our hand to show to the foundation to bring this project to another stage,” Tamashiro said.

The Gates Foundation’s Grand Challenge Exploration initiative prides itself in tackling the most immediate, intractable global health and development concerns. Open to anyone and everyone, the application process is acutely both accessible and competitive. Applicants are allotted just two pages to impress the Gates.

“Currently, the typical family in Rajasthan burns between 400 and 600 kilograms of firewood per month for cooking. This project aims to provide a convenient and safe way for these villagers to cook at night and to reduce the environmental impact and safety risks associated with their current cooking methods,” the engineering project’s 2012 report stated. This mission aims to reduce, and eventually eliminate, the comorbidity between villagers’ survival and rampant deforestation. A practical solar stove would also, socially, eliminate safety concerns for village women who must venture far outside their municipalities to collect firewood.

Called Phase I of funding, the initial $100,000 grants recipients eight months to investigate and refine their solutions. Should the eight months prove fruitful, recipients become eligible for a $1 million stipend — Phase II — from the Gates Foundation, during which the product (whether it be solar stove or HIV vaccine) assumes its ultimate iterations.

Dr. Derek Dunn-Rankin, professor and Chair of the Samueli School’s Department of Mechanical & Aerospace Engineering, served as advisor to the enterprising students.

“What this grant money allows us to do is continue working on an effective thermal mechanical design to create a solution to an important global health and environmental degradation problem,” he said.