Greg T. Spielberg | October 2010 issue
A Stirling engine uses internal gas that’s alternately heated and cooled to produce energy. Hydrogen, for instance, is sealed in a chamber connected to a series of pistons. When the hydrogen is heated, it expands, driving the pistons through the chamber. When the hydrogen is cooled, it contracts, creating space for the next expansion. When attached to a flywheel or crankshaft, the pistons produce mechanical power, which can be used to generate electricity or pump water.
In the 19th century, Stirlings were powered mostly by kerosene, coal or wood. At its peak, the Rider-Ericsson Engine Company produced up to 40,000 engines, exporting them as far as Egypt and Australia. At one point, John Ericsson even designed a Stirling-powered ship, which made a round trip from New York City to Washington, D.C., but sank soon after in a storm in New York harbor.
Today’s SunCatcher Stirlings use solar rays to heat hydrogen. At the end of the SunCatcher’s stamen is a power conversion unit, which includes a four-cylinder Stirling engine filled with hydrogen gas and a radiator for cooling. The enormous silver dish reflects sunlight into an eight-inch (20-centimeter) aperture, which collects and transfers the heat onto the Stirling’s hydrogen chamber. The expansion and contraction of the hydrogen powers the pistons that generate the electrical power. “All of us who like the engines and collect the engines are just waiting for the day they become commercially successful again,” says Stirling fan Brent Rowell.