US company tapping waste heat for electricity generation

A US company is in the process of harnessing waste heat, which is produced as a result of some other process and is not utilised, for electricity generation.

Ener-G-Rotors, based in Schenectdy, New York, is in the process of developing technology that will harness this waste heat that is usually generated in relatively low temperature ranges between 65 and 150 degrees centigrade.

The company says that most existing heat-harvesting technologies are efficient at temperatures only above 150 degrees centigrade. Therefore, it plans to replace the turbine that generates electricity in a typical generator with a device called a gerotor.

The company claims that this device is "near frictionless." The technology is based on the Rankine cycle, in which heated fluid flowing through a tube heats a pressurised fluid in a second tube via a heat exchanger.

The second tube is a closed loop. The working fluid flowing through it, in the case of Ener-G-Rotors, a refrigerant with a low boiling point, vaporises and travels into a larger space called an expander, where it expands, exerting a mechanical force that is converted into electricity.

The expanding vapour in Ener-G-Rotors' system turns the gerotor, which are two concentric rotors. The inner rotor is attached to an axle, while the outer rotor is like a collar around it. The rotors have mismatched gear teeth, which the vapour passing between forces apart, causing the gears to mesh, and thereby turning the rotor.

The company says that since the rotor design is simpler than that of a turbine, it would be potentially easier and cheaper to manufacture, while being much more durable. It says it has also come up with a proprietary way of mounting the rotor on rolling bearings that makes movement nearly frictionless, allowing it to turn more easily so the gas doesn't need to exert too much force to generate electricity.

Altogether, the system combines its synergies to work at lower temperatures, imparting less energy to the gas.

According to the company's CEO Michael Newell, it would be able to convert 10 to 15 per cent of low-temperature waste heat into electricity, delivering a payback in two years or less in most cases. Ener-G-Rotors plans to market its systems to customers directly, as well as operate its own systems and sell power.

On its initial marketing plan are industries such as chemicals, paper, oil, and food that use a lot of energy, and in the process also generate large amounts of waste heat. Thereafter, the company plans to participate in solar-thermal and geothermal projects, and target end consumers with a one-kilowatt system.

The company's first beta unit, a five-kilowatt system, is destined for a combined heat-and-power plant at Harbec Plastics. It is also installing beta systems at a steam plant for New York utility Consolidated Edison and at a landfill-gas-burning plant for the New York State Energy Research and Development Authority.

In need of funding, Ener-G-Rotors has managed to raise "a few hundred thousand" in grants and angel funding, and is now seeking $5 million for the first tranche of a $20 million venture-capital round.

The going too is getting tougher, with competition in the space heating up as a clutch of companies, both large and small, work on similar lines. United Technologies is one of them, which makes aircraft, aerospace systems, and air conditioning. Another is a smaller companies called ElectraTherm, with systems already installed.

CEO Newell says his company can stand out, as its technology is more efficient and simpler than ''anything else out there right now." He says that there are not many technologies that are going to work, and his company has the ''lowest cost of any of the technologies out there."