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SwRI and collaborators receive $12.3M from DOE to develop turbo-expander and turbine combustor for more efficient concentrating solar plants

Southwest Research Institute and its industry collaborators have been awarded a total of $12.3 million through two contracts from the US Department of Energy’s (DOE) SunShot Initiative. The first is an $8.5-million contract to develop a high-efficiency supercritical CO2 hot gas turbo-expander for concentrating solar power (CSP) plants. The second is a $3.8-million contract to develop a novel gas turbine combustor for a CSP hybrid gas turbine system.

Turbo-expander. Because of the highly cyclical nature of concentrating solar power (CSP) plant operation, a supercritical CO2 (sCO2) hot gas turbo-expander must be able to operate at high temperatures and pressures over a wide range of load conditions while maintaining a high efficiency, handle rapid transient heat input swings and have very fast start-up capabilities to optimize the plant’s online availability.

Over a three-year period, SwRI, General Electric, Bechtel Marine Propulsion Corporation and Thar Energy LLC will design and develop a highly efficient, single or multi-stage sCO2 hot gas turbo-expander that will advance the state-of-the-art from laboratory size (TRL—technology readiness level—3) to a full TRL6 mega-watt scale prototype, said SwRI’s Dr. Klaus Brun, project manager for the effort.

A second objective of the project is to optimize novel, printed circuit heat exchangers for sCO2 applications to drastically reduce their manufacturing costs. The scalable sCO2 expander design and improved heat exchanger will address and close two critical technology gaps required for an optimized CSP sCO2 power plant and provide a major pathway to achieving CSP power at $0.06 per kilowatt hour, increasing energy conversion efficiency to greater than 50%, and reducing total power block cost to below $1,200 per kilowatt installed.

The project, which will be conducted in three phases, is expected to begin August 2012, and will continue through 2015. In phase 1, researchers will design the expander and heat exchanger. Phase 2 will involve component fabrication and phase 3 will include performance testing.

Turbine combustor. The majority of today’s commercial CSP plants generate steam to support steam turbine electric power generation. The steam generated by these state-of-the-art commercial CSP plants is limited to a maximum temperature of 400 °C, yielding approximately 40% thermal efficiencies. Even for developmental CSP technologies, these efficiencies are well below those achievable with gas turbine combined cycle plants, which can be well above 55% thermal efficiencies and as high as 62% for state-of-the-art combined cycle power plants.

This second project aims to combine the advantages of highly efficient gas turbine power plants with concentrating solar power systems by operating the gas turbine at up to 1,000 °C combustor air inlet temperatures.

SwRI and industry collaborators Solar Turbines Inc., Oak Ridge National Laboratories, German Aerospace Center and San Diego State University will develop a novel external gas turbine combustor, which can be integrated with a hybrid CSP gas turbine power plant, said Dr. Brun.

The project, to be conducted in three phases, is expected to begin in August 2012, and will continue through 2015. In phase 1, researchers will evaluate combustor concepts and develop the design. Phase 2 entails fabrication of the combustion system, which will then be tested in phase 3.



It's not clear what this second project aims to do.  Could it be using solar heat to pre-heat the combustion air, reducing the required fuel input to achieve the same turbine inlet temperature?  There's no link in the article.

Reduced fuel addition means a higher ratio of specific heats in the turbine inlet gases, so temperatures will drop more in the expansion and thermal efficiency should be slightly higher.

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