Super Soaker Inventor Develops Mega-Efficient Solar Energy Engine

Lonnie Johnson, a nuclear engineer who just happened to have invented the Super Soaker water gun, is talking up a new invention he's calling the JTEC, for "Johnson Thermoelectric Energy Conversion system." He's claiming up to a 60% energy generation efficiency in converting heat—specifically solar heat concentrated from parabolic mirrors—into electricity in a completely closed, solid-state system. If it works as well as claimed I'll finally be happy to be named "Johnson."

From Popular Mechanics' write-up:

Here’s how it works: One MEA [membrane-electrode assemblies] stack is coupled to a high- temperature heat source (such as solar heat concentrated by mirrors), and the other to a low-temperature heat sink (ambient air). The low-temperature stack acts as the compressor stage while the high-temperature stack functions as the power stage. Once the cycle is started by the electrical jolt, the resulting pressure differential produces voltage across each of the MEA stacks. The higher voltage at the high-temperature stack forces the low-temperature stack to pump hydrogen from low pressure to high pressure, maintaining the pressure differential. Meanwhile hydrogen passing through the high-temperature stack generates power.

...

Johnson envisions a first-generation system capable of handling temperatures up to 600 degrees. (Currently, solar concentration using parabolic mirrors tops 800 degrees centigrade.) Based on the theoretical Carnot thermodynamic cycle, at 600 degrees efficiency rates approach 60 percent, twice those of today’s solar Stirling engines.

Super Soaker Inventor Aims to Cut Solar Costs in Half [PopularMechanics.com]

[#1 posted by Tom , January 8, 2008 9:12 AM]

The theoretical efficiency of a Stirling engine is also the Carnot efficiency. This used to be one of their claims to fame, before everyone found out how incredibly difficult it is to get anywhere close to that theoretical maximum with a practical engine.

So it isn't clear why the article mentions the Carnot efficiency, unless there is some reason to believe that the new technology will have a practical efficiency that is better than the best Stirling engine working across the same temperature difference. No moving parts is nice, but as we know from photovoltaics, no moving parts does not high efficiency make.

[#2 posted by paul beard , January 8, 2008 9:59 AM]

I should have known someone would get to this: capturing heat seems easier than capturing sunlight, especially here in the soggy northwest. Wonder when I can tuck one of these in my attic?

[#3 posted by halfsquatch , January 8, 2008 10:06 AM]

You should already be happy to be a Johnson. Have you heard of William S. Burroughs' "Johnson creed"?

“The Johnson family” was a turn-of-the-century expression to designate good bums and thieves. It was elaborated into a code of conduct. A Johnson honours his obligations. His word is good and he is a good man to do business with. A Johnson minds his own business. He is not a snoopy, self-righteous, trouble-making person. A Johnson will give help when help is needed. He will not stand by while someone is drowning or trapped under a burning car.

[#4 posted by Joel Johnson , January 8, 2008 10:09 AM]

I am so close on this one! Minus the burning car thing! And most of the others!

[#5 posted by dogrocket , January 8, 2008 1:06 PM]

This is so pickayunish that I hesitated to say it at all, but: Centigrade was replaced by Celsius in the late 1940s or so. Amazing how long these things stick around, eh? People still say "Palm Pilot" too...