Supercritical CO2 Power Cycle Developments and Commercialization: Why SCO2 Can Displace Steam

by Author Michael Persichilli, Alex Kacludis, Edward Zdankiewicz, & Timothy Held
Echogen Power Systems LLC

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The U.S. DOE estimates that 280,000 MW discharged annually in the U.S. as waste heat could be recycled as usable energy to provide 20 percent of U.S. electricity needs while slashing GHG by 20 percent and saving USD $70-150B per year on energy costs. Waste heat can be considered as the other green energy because it is a renewable energy equivalent resource that improves energy efficiency from existing fossil fuel usage, while reducing grid demand by converting the recovered heat into usable electricity, heating and/or cooling. While various sources of independent data suggest that this waste heat recovery opportunity is valued at over USD $600B for the U.S. market, similar large opportunities exist worldwide.

Echogen Power Systems LLC (Akron, OH U.S.A.) is developing power generation technologies that transform heat from waste and renewable energy sources into electricity and process heat. The thermal engine technology; the Thermafficient® Heat Engine converts waste heat to power using a breakthrough supercritical CO2-based power cycle.

Compared to organic and steam-based Rankine Cycle systems, supercritical CO2 can achieve high efficiencies over a wide temperature range of heat sources with compact components resulting in a smaller system footprint, lower capital and operating costs. The Levelized Cost of Electricity (LCOE) is calculated at an average USD $0.025 per kWh for the CO2-based heat engine and averages at USD $0.065 per kWh for a complete combined cycle gas turbine system utilizing the supercritical CO2 heat engine for bottom cycling.

This paper presents an exemplary trade study comparison between the CO2 and steam-based heat recovery systems. An update is also provided for the Echogen 250 kW demonstration thermal engine which completed initial testing at the American Electric Power’s research center during 2011. Also presented is current status of long term testing with this system at a commercial district heating organization, and a multi-megawatt heat engine that will be installed at a U.S. customer host site during 2013.