Supercritical carbon dioxide technology can effectively improve the efficiency of photothermal power generation system

CSPPLAZA Solar Thermal Grid news: The U.S. Department of Energy's plan for solar thermal power under the SunShot program is to bring the cost of solar thermal power down to 6 cents per kilowatt-hour by 2020, which will require a huge technological advance. Tex Wilkins, founder of the American CSP Alliance, says technology has to come down to cost. The CSP industry is continuing to innovate, and the energy Department's goals will require a major breakthrough in CSP technology if they are to be met.

The emergence of solar thermal power generation system with supercritical carbon dioxide as working medium may bring down the cost of solar thermal power generation greatly. The excellent heat transfer and flow properties of supercritical carbon dioxide have great potential to improve power generation efficiency. The research was supported by the U.S. Department of Energy. The U.S. Department of Energy's $56 million research support program for solar thermal power under the SunShot program benefits 21 projects. The NATIONAL Renewable Energy Laboratory NREL received an $8 million grant to demonstrate a multi-megawatt generation cycle using supercritical carbon dioxide as a working medium.

Craig Turchi, leader of NREL's solar thermal power project, said: "Our previous studies have shown that supercritical carbon dioxide (SCCO2) solar thermal power systems can perform well in temperatures up to 600 to 700 degrees Celsius. Supercritical carbon dioxide power generation can achieve efficient thermal energy utilization of about 45% at more than 500 degrees Celsius and 20 megapascals atmospheric pressure, which will effectively improve power capacity. The U.S. Department of Energy is supporting the development of the technology because it sees great potential to improve the efficiency and reduce the cost of power generation.

Supercritical carbon dioxide power generation systems are smaller, lighter and have less heat loss. Its application in solar thermal power generation system can achieve significant efficiency improvement. The system only needs low heat to start the generator, it can adjust quickly to cope with load changes, support rapid start and stop, these advantages are incomparable to the ordinary power generation system. Bill Gould, SolarReserve's chief technology officer, says the technology is a useful remedy for solar-thermal power stations that start too slowly.

NREL expects to complete testing in two phases. First, a Brayton cycle is established, coupled with a thermal power plant with molten salt as heat transfer medium. Supercritical carbon dioxide would then be used as a heat transfer and working medium, analogous to a direct steam generation system. The trial, which will be conducted on a 10MW solar thermal plant, will cost an estimated $16 million, of which $8 million will be funded by the U.S. Department of Energy.

The idea of using carbon dioxide, a common gas, as a working medium for photothermal power generation cycle has been proved feasible by theory. Compared with conventional steam power generation, this system has significantly higher conversion efficiency and can also save a lot of water, which is very beneficial in areas with good sunlight resources but water shortage. However, this research is still in the experimental, there are many technical difficulties to be broken through.