Impact of ambient temperature on supercritical CO2 recompression Brayton cycle in arid locations: Finding the optimal design conditions

Abstract

In this paper, we present a new method to determine the optimal design conditions of a supercritical CO2 recompression Brayton cycle with dry cooling based on plant location. These power cycles are gathering high interest in concentrated solar thermal power technologies, which are most likely to be deployed in arid areas where dry cooling is a strategic choice. However, the usual high ambient temperature associated with these locations affects negatively the cycle performance. The key selection of two design parameters, the recompression fraction and the compressor inlet temperature, can minimise this negative effect. The method presented here allows the adjustment of these two parameters maximising the annual generation of electricity and cycle efficiency simultaneously. The optimisation process analyses the drop in the cycle performance due to the yearly variation of ambient temperature at the specific location. To reduce the computational effort required, polynomial regressions extrapolate the results from a reduced set of design-point and off-design cycle simulations in a wide range of ambient and compressor inlet temperatures. As an example, the method is applied to three different locations demonstrating the existence of optimal design conditions and justifying the need to adjust these two key parameters for each specific location.