April 10, 2009 Until now, most systems that use heat to generate electricity have only been economical on a scale greater than 1MW using high temperatures, but the technology behind a range of appliances from Ener-G-Rotors allows the generation of electricity from waste water using much lower temperatures. Specifically designed for industrial customers to fit into hazardous environments, the patented Trochoidal Gear Engine (TGE) technology converts waste heat to electricity by way of a simple expander used in an organic Rankine cycle.

The Rankine cycle is a thermodynamic cycle, which converts heat supplied externally to a closed loop into work, and is the system used in virtually all solar thermal, biomass, coal and nuclear power plants around the world. The TGE employs the same technique, albeit on a much smaller scale. It is a positive displacement device that works like a genrotor pump running backwards and a variety of improvements to the basic genrotor technology allows the TGE to significantly lower frictional losses. This not only results in higher efficiency in turning heat into work, but also lowers maintenance costs thanks to less gear wear.


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The TGE system is also unique in recycling heat from wastewater sources as cool as 150°F and the design of the engine is very simple with only two moving parts. Ener-G-Rotors also says the low friction and simple design of the TGE makes it the most efficient, durable, and cost effective expander at low temperatures (150°F to 400°F) and small sizes (less than 200kW). The appliances using the TGE are internally lubricated and couple directly to a generator, are internally lubricated which keeps the costs of the expander and system low. Ener-G-Rotors specifically designed their products to be economical, providing a payback as short as two years. They are also modular, so they can fit in any industrial setting, and non-disruptive, with minimal maintenance needs and attendance free operation.

The company claims the TGE allows them to keep their costs low and create cost-effective systems as small at half a kilowatt or as large as 150kW. “We can now make electricity from waste heat at a price that is cheaper than burning coal. The size of the opportunity is staggering and should usher in a new era of energy efficiency,” says Mike Newell, CEO of Ener-G-Rotors. Although Ener-G-Rotors are concentrating on industrial markets, appliances employing the TGE technology are available in a range of sizes and energy outputs providing possibilities for everything from residential solar thermal, geothermal applications and even within hybrid vehicles to capture some of the heat from the internal combustion engine to generate electricity.

The company has just announced their first order for the 50kW TGE50 unit and proving that Ener-G-Rotor’s claims aren’t just hot air, the technology received the “Most Promising Technology” award at the recent Cleantech Forum XXI in San Francisco.

Darren Quick

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