19 May 2009

Dean Kamen's Magic Stirling Engine

...the Stirling, was invented in 1816 by Scottish clergyman Robert Stirling. He found that alternately heating and cooling gases in a closed system could create power to do work, such as drive a piston. But...the Stirling was mostly forgotten, even though its simple concept is “elegant, it’s brilliant,” Kamen says. But its time to shine might be now. All-electric cars still suffer from wimpy batteries that limit driving range and refuel slowly. “The energy you can carry around in a liter of gasoline is 100 times higher than you can carry in the same size and weight of a battery,” Kamen says. “And that’s going to be true for a long time.” _CSMonitor_via_Keelynet
The Stirling engine has long been a solution looking for a problem. But inventor Dean Kamen seems to have found more than one good use for the venerable heat engine.

Mr. Kamen, an inventor and entrepreneur perhaps best known for the two-wheel Segway Human Transporter, doesn’t want to get into the car business himself. He just wants to see the Stirling engine that helps power the REVOLT be mass produced for vehicles. That would drive down the price, he says, and allow it to be cost-effective in another role: as a miniature electric plant for villages in the developing world.

A Stirling can run on just about anything that creates heat, from gasoline, kerosene, and ethanol, to natural gas, propane, hydrogen, and, yes, the methane given off by animal manure.

In a recent test, two villages in Bangladesh ran Stirling engines to create electricity for 24 weeks – using only cow dung for fuel. “We’re pretty excited about that,” Kamen says. _CSMonitor
The best power plant for a hybrid automobile will be a fuel cell running on a simple liquid fuel like methanol. The next best power plant may very well be a Stirling engine -- which can be available in quantity now, unlike the fuel cell which will take a few more years of development to perfect. Hybrid cars need a constant power source for charging the batteries. Stirling engines can plug away at constant speed, day after day, year after year, without complaint.

Using a sophisticated internal combustion engine in a serial hybrid automobile is expensive and unnecessary. A turbine engine would be ideal except for the expense, the noise, and its sensitivity to teenage driving habits. The Stirling makes sense, until low cost methanol powered fuel cells are perfected for autos. Even then, cost factors may well favour the Stirling.

These issues will not be settled in the US auto market, due to the massive amount of regulation crushing the US auto industry. But the rest of the world may begin to gain confidence, as the Obama depression wears on, killing the US economy and US credibility in world markets.

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