Update Nov. 20, 2013: The emission-free solar stove won a $100,000 grant from the Bill & Melinda Gates Foundation.
UC Irvine engineering professor John Garman and his design students have invented a cooking stove that runs on reusable salts and solar power – even at night – for use in developing nations.
Women in less developed countries often face dangers, such as rape, when they leave their villages to collect firewood because of a lack of nearby wood. In addition, smoke from cooking indoors with firewood poses a health risk for families and the local environment.
"There are deforestation issues, emissions and health issues of burning wood fires indoors. This would circumvent all those," said Christopher Gay, a student who worked on the project.
"Most solar stoves require you to use the sunlight directly, but this one will store the energy and allow you to cook at night, which is a cultural thing for the region of India that this is designed for," Gay said.
"It wouldn't require them to break with cultural traditions, but it would significantly improve their quality of life."
HOW IT WORKS
1. A Mylar-coated reflective metal disk acts as a sunlight collector, and the disk's parabolic geometric shape allows it to concentrate the light on a single point: the stove.
2. The focused light heats two salts – potassium nitrate (used to make fireworks) and sodium nitrate (a preservative in processed meats) – that are sealed inside the stove box.
3. As the salts are heated, they change from a solid to a liquid, which stores (absorbs) heat energy. As the salts turn from a liquid to a solid, heat energy is released. By using a specific ratio of the salts, the melting point is designed to be 420 degrees.
4. The heated stove is flipped for the cooking surface. Though the stove itself reaches 500 degrees, the handles are insulated to keep people from getting burned while flipping the box. The cooking time is three hours. It's the same as having a 1,000-watt microwave on for 30 minutes.
5. The heated salts gradually return to a solid state. A day later, the stove is still at about 100 degrees. The salts are reusable.
The 30-pound aluminum stove costs about $300 to make, but the team is working to make it less expensive to mass produce.
"There are other approaches, but I think ours is the one," Garman said.
Others fill the stove with sand or rocks. But these don't provide a steady cooking temperature; it's cooling down the whole time. For example, if you're making pancakes, you're cooking on a 400-degree surface for the first batch and 300 for the next batch.
The stored energy solar stove design allows for a stable cooking temperature for three hours.
Garman was inspired two years ago by an intercollegiate challenge by ClimateHealers.org to create a stored energy cooker.
When people think of a stored energy stove, they think of using photovoltaic energy, which converts solar rays into electricity, he said.
The stored energy solar stove is intended for developing countries without electricity. Batteries go bad. Electronics fail.
"This is far more efficient because it's simple," he said.
Christopher Gay, Joe Chen, Lineker Phuong and Ananya Habtemariam.
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