Benchmarking supercritical carbon dioxide cycles against steam Rankine cycles for Concentrated Solar Power

• Steam vs. supercritical CO2 power cycles on cost and efficiency for commercial CSP.
• Economic evaluation performed over the entire central receiver CSP facility.
• Steam Rankine cycles are more cost effective and more thermally efficient.
• High cost of equipment for CO2 cycle due to its corrosiveness at severe conditions.

Research into concentrated solar power (CSP) technologies has increased significantly due to environmental and energy security concerns. In particular, central receiver CSP technology is considered to be a viable option for large scale electricity generation. However, electricity cost associated with current commercial central receiver CSP technology is not yet competitive with conventional fossil-fuel based electricity generation technologies. In order to reach cost parity with conventional technologies, it is necessary to reduce capital requirements and increase efficiency. In order to meet these requirements, alternative power cycles to the current commercial steam Rankine cycle need to be considered.Supercritical carbon dioxide (S-CO2) has been considered as an alternative working fluid for power cycles in operation within a central receiver CSP plant. In this study, three different S-CO2 power cycle layouts are compared against a steam Rankine cycle at both superheated and supercritical conditions. The power cycle concepts are compared on a consistent basis in terms of both cost and thermal efficiency. Results show that S-CO2 power cycles are not competitive against the current steam Rankine technology. Therefore, based on the results of this study, research into power cycles for CSP application should target the steam Rankine cycle over S-CO2 power cycles.