Christopher Helman:

For the new issue of Forbes Magazine I wrote an article about David Crane, the visionary CEO of NRG Energy NRG -0.7%. When I met Crane for lunch a couple weeks ago, no sooner had we sat down than he began singing the praises of this new contraption he had in his basement. The machine — which can generate 10 kilowatts of continuous power, fed by Crane’s natural gas line — is a new iteration of an old creation, the Stirling engine. This version, called the Beacon 10, was created after a decade of engineering by famed inventor Dean Kamen.
 I caught up with Kamen (who is best known for creating the Segway scooter) over the phone last week to ask him about the device. “We’ve turned his basement into an extension of our laboratory,” said Kamen. “It’s certainly not a machine made for the typical home, but he has a gigantic swimming pool and a huge house.”
 With the Beacon 10, says Kamen, “you don’t have to feel guilty heating up the pool.” That’s because of the highly efficient nature of the Stirling engine. First conceived in 1816 by Scottish minister Robert Stirling, the device in its simplest form consists of applying an external heat source to a closed cylinder where the cyclical expansion and compression of air inside the cylinder drives the pistons up and down. Unlike your car, where fuel is combusted inside the engine, the Stirling is an external combustion engine; it can work with any external heat source.