Tuesday, January 08, 2008

JTEC: Johnson Thermoelectric Energy Conversion

This heat engine, based on the "Ericsson cycle", has been discussed on multiple websites yesterday and today, including Brian Wang's.

It is based on the "Ericsson Cycle", and incorporates aspects of heat engines and fuel cells. It has no moving parts, it does not burn fuels or depend on chemical reactions (other than simple oxidation and reduction of H2 gas), and it is not at all obvious to me how it can be made to work efficiently. Anyway, here is the company's spiel:
The JTEC is an all solid-state engine that operates on the Ericsson cycle. Equivalent to Carnot, the Ericsson cycle offers the maximum theoretical efficiency available from an engine operating between two temperatures. The JTEC system utilizes the electro-chemical potential of hydrogen pressure applied across a proton conductive membrane (PCM). The membrane and a pair of electrodes form a Membrane Electrode Assembly (MEA) similar to those used in fuel cells. On the high-pressure side of the MEA, hydrogen gas is oxidized resulting in the creation of protons and electrons. The pressure differential forces protons through the membrane causing the electrodes to conduct electrons through an external load. On the low-pressure side, the protons are reduced with the electrons to reform hydrogen gas. This process can also operate in reverse. If current is passed through the MEA a low-pressure gas can be "pumped" to a higher pressure.

The JTEC uses two membrane electrode assembly (MEA) stacks. One stack is coupled to a high temperature heat source and the other to a low temperature heat sink. Hydrogen circulates within the engine between the two MEA stacks via a counter flow regenerative heat exchanger. The engine does not require oxygen or a continuous fuel supply, only heat. Like a gas turbine engine, the low temperature MEA stack is the compressor stage and the high temperature MEA is the power stage. The MEA stacks will be designed for sufficient heat transfer with the heat source and sink to allow near constant temperature expansion and compression processes. This feature coupled with the use of a regenerative counter flow heat exchanger will allow the engine to approximate the Ericsson cycle.

You can find an animation of the device in action at the link above. It is a bit of a puzzler for me at this point.

Lonnie Johnson, the inventor, was formerly an engineer at NASA's JPL, before he made millions from inventing a glorified water gun. Some of his other inventions are quite intriguing, so check out his websites.

To be honest, I am more excited about the nano-antenna and the nano-spray silicon particle PV windows, than I am about the JTEC. But if the inventor gets a working prototype with better than 1 or 2 % efficiencies, I may start to perk up.

Heat conversion is one of the best ways to utilise solar energy, and it is the only way to utilise geothermal energy. Solar and geothermal are the two most abundant sources of energy on this planet, so we had best learn to use them every way we can.

Labels: ,


Post a Comment

Subscribe to Post Comments [Atom]

<< Home

Newer Posts Older Posts