Heat Recovery System by Echogen Power Systems
Echogen Heat Recovery System
Echogen Power Systems in Akron, Ohio has developed a heat recovery system capable of capturing as much heat energy as ordinary systems two or three times its size. Echogen officials say one of their waste heat systems capable of producing 8 MW of electricity would be about the size of a desk. An oridnary system generating that much energy would typically be about the size of a standard room.
The key to Echogen’s system is the use of CO2 as the working fluid. The system uses a supercritical CO2 (ScCO2), the same type of CO2 used by the beverage industry to propel soft drinks into glasses at soda fountains. The ScCO2 is used in the heat recovery system because its smaller molecules can easily travel through smaller heat exchanger channels to allow greater heat exchange per square inch of available space. The key is the use of ScCO2 as a liquid rather than a vapor.
The system works by heat energy being transferred to the ScCO2 working fluid through a waste heat exchanger. This waste heat exchanger can be installed into a smokestack, boiler or turbine exhaust duct, hot process gas or liquid line, or solar thermal concentrator. From there, the heated ScCO2 passes through a turbo-expander where enthalpy gain from heating gets converted into mechanical shaftwork to produce electricity. The regenerator then recycles residual heat while unconverted heat is discharged from the system through a water or air-cooled condenser.
While in operation, Echogen’s system can harvest heat at 400 degrees F, a significantly lower temperature than what typical steam-cycle systems operate efficiently. The company developed a particular prototype of the system that can produce 250 kW of electricity and have installed it at the research center run by American Electric Power Co.
For more information about this product and others developed by Echogen Power Systems visit: www.echogen.com.