An integrated solar-cryogen hybrid power system

This paper reports a new integrated solar-cryogen hybrid power system that uses solar thermal energy and cryogen as the feedstocks. The system consists of a direct expansion (open cycle) of cryogen from an elevated pressure and a closed-loop Brayton cycle operated at a medium to low pressure. The expansion occurs sequentially in three stages (high pressure, medium and low pressure turbines) using solar heat as the superheating source. The open cycle uses all the three turbines, whereas the closed cycle only uses the medium and low pressure turbines. A solar thermal power system and a cryogen fuelled power system are used as the benchmarks to evaluate the performance of the newly proposed hybrid system and the three systems are optimised using a sequential quadratic programming (SQP) method. The results show that the integrated hybrid system gives a far better overall system efficiency and provides over 30% more power output that the summation of the power outputs of the two other systems.

► Solar-cryogen hybrid power system enables an efficient utilisation of solar radiation in the form of low to medium temperature heat.
► Solar-cryogen hybrid power system could efficiently recover the cryogenic energy.
► The optimal hot end temperature of the heat carrier heated by the solar collectors is about 600 K for the hybrid system.