Thermoelectric Devices Could Improve Overall Efficiency by Recovering Waste Heat
Thermoelectric Devices Could Improve Overall Efficiency by Recovering Waste Heat

Aside from energy efficiency, energy recovery could be the next best way to reduce carbon dioxide emissions. Thermoelectric devices use waste heat to generate electricity.

Depending on whether you are looking at an internal combustion engine or a manufacturing plant, up to 60% of the energy that goes into these, whether chemical or electrical, is wasted as heat. Thermoelectric devices can recover some of that energy and feed it back into the system.

In an automobile, it can reduce the load on the alternator, improving engine efficiency and reducing fuel consumption. In a factory, thermoelectric devices can recover heat normally lost to the cooling system to reduce overall electrical consumption, reducing related carbon dioxide emissions.

Part of the problem with current thermoelectric devices is they only work at higher temperatures, typically over 1,000°F. This is alright for something like automobile exhaust, which can be as high as 1,600°F, but is still significantly higher than temperatures coming out of a factory cooling tower.

Osmoblue, a startup founded by Harvard graduate Elodie Dahan, has come up with a thermoelectric device that should work at temperatures as low as 85°F, which should greatly improve the amount of energy recovered from waste heat. Dahan estimates “that 10 megawatts of heat could produce between 100 and 600 kilowatts of electricity, the consumption of one hundred homes.”

The electricity in Osmoblue’s technology isn’t generated by the heat, but instead by the flow of water through a membrane by osmosis. In a simple demonstration of osmosis, salt water and freshwater on two sides of a membrane will try to balance concentrations. Freshwater will flow into the saltwater side. If this flow is tapped by a turbine and generator, electricity can be generated.

Osmoblue’s thermoelectric device uses waste heat to unbalance the concentration on a continuous basis, so the flow continues as long as the concentrations are unbalanced, generating electricity. A prototype of the device could be installed on a regional waste incinerator by 2014 for testing.

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