San Antonio, Texas-based Southwest Research Institute (SwRI) and two groups of partners received a total of $12.3 million for two unique projects designed at improving concentrating solar power (CSP) technologies. One is to develop a supercritical carbon dioxide (sCO2) hot gas turbo-expander for CSP, the other to develop a CSP combustor for a hybrid gas turbine system. Both awards were granted under the same solicitation from the Department of Energy’s SunShot Initiative.
The institute partnered with General Electric, Bechtel Marine Propulsion Corporation and Thar Energy LLC for the turbo-expander project, which received an $8.5 million contract. sCO2 is being considered for energy generation for a number of its properties because it has high thermal efficiencies. “The CSP cycle is close to the supercritical CO2 cycle, with CO2 as a working fluid. In that cycle you use a hot gas expander [to generate electricity],” said Dr. Klaus Brun, a program director in SwRI’s Mechanical Engineering Division.
The project has two goals, to create a megawatt-scale sCO2 hot-gas turbo-expander by 2015 in three phases and to create printed circuit heat-exchangers sCO2 applications. Meeting the two goals of the project will help reduce the cost of CSP to 6 cents per kilowatt hour.
The other award, $3.8 million, is to develop a gas turbine combustor for a CSP hybrid gas turbine system. On that award SwRI partnered with Southwest Research Institute and industry collaborators Solar Turbines Inc., Oak Ridge National Laboratories, German Aerospace Center and San Diego State University.
That system will take advantage of CSP’s and the gas turbine’s efficiencies. “We will use CSP to heat air before it goes into the combustor,” Brun said. By preheating the air before it hits the gas turbine it will increase the turbine’s efficiency. The project could result in a turbine operating at 1,000 degrees Celsius, which could help push the thermal efficiency beyond the 62 percent efficient high-end combined cycle gas turbines, according to the institute.
“It’s kind of nice because it allows you to use a standard gas turbine. Plus you can use it as a gas turbine even after the sun goes down,” Brun said. Conversely the system could also be run without gas, using just the CSP aspect of the device, he said. Like the other project, Brun and his colleagues plan to have a megawatt-scale prototype by 2015.