Power Cycle

The major objective of operating CSP plants at higher temperatures is to enable the usage of higher efficiency heat engines to generate the electricity, which can ultimately result in lower LCOE. Depending upon whether the energy is stored as heat or fuel, there could be different options for how the energy is converted to electricity. For example, if sensible heat above 1000°C is available it can be advantageous to use a combined cycle, which is a high temperature cycle that rejects heat at a sufficiently high temperature to still enable further conversion of the wasted heat through a bottoming cycle. For example, today’s natural gas combined cycles consist of a natural gas driven Brayton cycle that rejects heat to steam based Rankine cycle and can convert heat to electricity with up to 60% overall efficiency [see link]. On the other hand, if hydrogen and oxygen are stored as fuel, one could use a solid oxide fuel cell as a topping cycle, and the waste heat can be used in a supercritical steam Rankine or CO2 Brayton cycle to potentially achieve > 70% overall efficiency.

Power Cycle