Coupling supercritical carbon dioxide Brayton cycle with spray-assisted dry cooling technology for concentrated solar power

Supercritical carbon dioxide (sCO₂) based Brayton cycle integrated with concentrated solar power applications is a promising technology to exploit solar energy for electricity production. To reduce the energy cost of this solar power plant, spray-assisted dry cooling technology is developed, which makes electricity more affordable for isolated and arid regions. However, pure dry cooling technology suffers from low efficiency under high ambient conditions and a spray cooling system has been proposed to address this problem. Due to the high cost and great complexity, experimental test of a designed spray cooling system on a natural draft dry cooling tower is never reported. Here a spray cooling system consisted of multiple nozzles was tested on a 20 m high experimental tower. This is, to our knowledge, the world's first attempt to practice spray enhancement of NDDCT at full scale. It is found that the introduced spray cooling can effectively precool the inlet hot air and consequently reduce the circulating water exit temperature. The promising application of this new technology in solar power plants was firstly revealed by integrating the tower into a 1 MW concentrated solar thermal sCO₂ Brayton cycle. As spraying water flowrate increases, cooling tower dissipates more waste heat, lowering the compressor inlet temperature and consequently improving the efficiency of thermal cycle. Power cycle simulations also show that cycle efficiency can be higher than 40.5% at the optimal circulating water flow rate, i.e., 4–5 kg/s, depending on the sCO₂ flow rate.