Triple Cycle Power Generation Gets 70% + Efficiency

Start with a solid oxide fuel cell (SOFC). Use the waste heat from the SOFC to drive a gas turbine. Then use the waste heat from the gas turbine to drive a steam turbine. Et, voila! A triple cycle power generation system that can achieve over 70% in fuel to power efficiency.

Mitsubishi Heavy Industries Ltd. is developing the necessary technologies to put such a system together.

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In a triple combined cycle power generation system, an SOFC power generation system is placed before the GTCC system. By generating power at three stages—the fuel cell, gas turbine, and steam turbine—the resulting fuel cell combined cycle (FCCC) system achieves outstanding efficiency in generating power from natural gas. The FCCC system is expected to achieve the world’s highest power generation efficiency exceeding 70% (LHV) for several hundred MW class power generation and over 60% (LHV) efficiency for several tens of MW class power generation.

MHI sees FCCC triple combined cycle power generation as a revolutionary technology that will result in 10% to 20% improvements in power generation efficiency over existing natural gas-fired power generation systems. The company plans to pursue development based on the results of the basic technologies study, with the ultimate goal of commercializing the technology. _GCC

The idea is to milk as much power out of natural gas (and eventually methane hydrates) as possible. Japan desperately needs to improve efficiency in generation, transmission, and utilisation, in the aftermath of a rash governmental decision to shut down reliable nuclear plants.

Triple cycle power generation is also likely to be used with new generation nuclear power plants, which operate at even higher temperatures than SOFCs. Additional power gen cycles can be added to the cascade at either end, depending upon the starting temperature.

In fact, even with SOFCs, an additional power gen cycle could be added at the low end below the steam turbine cycle, utilising the lower temperature waste heat from the steam turbine.

There are many uses for waste heat besides generation electrical power. And we have only begun to discover a few of them.