Four recent graduates who majored in aerospace and mechanical engineering lined an old satellite TV dish with hundreds of squares of aluminum-coated Mylar.
At the end of a 3-foot pipe that rises from the center of the dish, they clamped a box made of a steel bottom and furnace insulation bricks for the sides and top.
In the heat of a spring Cleveland sun, the reflected light striking the steel panel pushed temperatures inside the box a past 1,100 degrees Fahrenheit.
“We’re shooting for 700 degrees Celsius on a really nice day,” said Chris Lau, from Houston. That would be 1,292 degrees on your backyard thermometer, if it registered that high. Or, to put it in another perspective, easily enough heat to melt aluminum.
Lau, Jesse Lee of Dublin, Ohio, Robert Abban from Columbus and Jason Presutti of Pittsburgh, built the solar furnace as their senior project.
They built on the cheap, on purpose, taking the first step toward creating a model that could be used in developing countries. For less than $500, they’ve produced a prototype: 75-square-feet of mirror aimed at a vessel that can safely handle the heat. Aim the mirror at the sun and the temperature in the box climbs rapidly.
For everyday use, the sunlight concentrated from the 10-foot-diameter dish could be used to cook by hanging a black pot where the brick box is, or to distill water – a key feature for areas where water and power supplies are poor.
“Simply boiling water can take care of biological contamination but may not remove chemical pollutants,” Lee said. “But if you boil water and catch the steam, that’s 100 percent pure water.”
He suggested a reflective trough, which could concentrate heat on a water pipe running down the center, would likely be more efficient and less expensive for water uses.
But, this set up may be a better option for generating electricity. Aim the energy at a heat engine, such as a Stirling engine, which turns a generator. The result could be as much as 2,000 watts of power, or enough to keep four standard refrigerator-freezers running while the sun is bright, they’ve calculated.
Beyond household uses, the solar furnace was meant to prove the maximum temperature that could be reached simply by concentrating and storing the energy, Lee said. It's more of a "green" and "sustainable" approach to high temperature materials processing.
In the last month, the group has found how clear the day is, the wind and the outside temperature all affect how much heat can be generated, Abban said.
Some members of the team may continue to fine-tune the design and experiment more this summer. After that, they’ll leave the project for succeeding classes willing to improve the furnace.
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