Dean Kamen – inventor of the Segway Personal Transporter – has been working on commercialising a new, efficient design of the 200-year-old Sterling Cycle Engine for much of the last decade. CED Magazine covers the most recent developments:
The Stirling engine…is in essence a heat engine, operating by cyclic compression. They have several drawbacks, including practical limitations to how big (in terms of energy output) they can be. Though Stirling engines have been successfully used, no Stirling engine has ever been successfully commercialized – not for long, anyways. In most circumstances, energy from Stirling engines will be far more expensive than energy from almost every other extant power generation system. Most circumstances, but not all.
Stirling engines are highly efficient generators and can be run not only with any energy source, but they can be run with different energy sources changed on the fly – kerosene, diesel, alcohol, it doesn’t matter, Kamen said, because it relies on external combustion.
A small, model Stirling Engine can be purchased at Jaycar throughout New Zealand for those who are fascinated by these devices. The link takes you to a page that also includes a video of the engine in operation.
Jaycar describes it as follows: A Stirling engine is a machine that converts heat into mechanical energy by alternately compressing and expanding air. The expanding air acts on a piston to provide mechanical force: you simply heat up the air chamber, give the flywheel a whirl and away she goes. The only source of energy is heat and as long as heat is applied, the engine will keep running and running.
CED Magazine goes on to note how Dean Kamen’s Sterling Engine can run continuously without wearing out:
Kamen’s Stirling engines have no pistons, and therefore no seals. They act as brushless DC motors, with wires the only thing inserted in the cylinder chamber to draw off the electricity generated, he explained to a group of journalists after his keynote at Cable-Tec Expo.
His company Deka Research builds the engines on a custom basis today for about $250,000 but Kamen believes that with volume they could be made for about $10,000 each. So he has been searching for large-scale applications that exploit the advantages of the engine:
And that’s where the cable industry might – might – come in. Cable has to have backup power; the very biggest companies have literally thousands of generators (typically diesel engines), most of them sitting idle 90 percent of the time. What if those generators were replaced with Kamen’s 10 kW Stirling engines?
A cable operator could run the generator on whatever fuel was the cheapest available at the time. Furthermore, they don’t rely in any way upon the grid – they will be absolutely reliable in a power outage, as long as the fuel holds out – and remember, it can run on any fuel, even alcohol.
When backup was not required (i.e. most of the time) the engine could be run to feed electricity back into the national grid to help provide for peak-time loads.
Now about all that waste heat. Kamen has built a Stirling engine into a water purifier that requires heat to purify water. If he can get enough volume on Stirling engines to reap economies of scale, his water purifiers could end up becoming practical in Third World countries where pure water is at a premium and a variety of water-borne illnesses and diseases are endemic.
“Coca-Cola is interested in these,” Kamen noted. If Coca-Cola finds a practical way to distribute these machines in Third World countries, it could be directly responsible for reducing the occurrence of well over half of all diseases in the world. The soft drink manufacturer currently has an order in with Deka for 50 of the machines. “Coca Cola has the potential to be the largest health care provider in the world.”