S-CO2 for efficient power generation with energy storage

Abstract

Supercritical CO2 (s-CO2) power cycle has gained interest for concentrating solar power (CSP) application in the last decade to overcome the current low efficiency and high costs of the plants. This cycle is a potential option to replace the steam Rankine cycle due to its higher efficiency, more compact turbomachinery and possibility of including heat storage and direct heating. The purpose of this project is to determine the suitability of integrating s-CO2 power cycle into CSP plants with energy storage. With this aim, recompression and partial cooling cycles were identified as appropriate s-CO2 cycle configurations for CSP application. They were modelled, optimised and compared for scenarios that represent different types of CSP plants and operating conditions. The selection of scenarios includes current technologies (parabolic trough and central tower), as well as a direct heating modular system with wet and dry cooling. The partial cooling cycle presented advantages for CSP applications in the four scenarios considered, therefore, it was implemented as the power cycle in the CSP plant. The simulation of the s-CO2 cycle CSP plants corresponding to each scenario revealed that s-CO2 cycle plants could exceed the efficiency of existing Rankine cycle plants when using central tower or direct heating technologies, but not with parabolic trough. In addition, it was demonstrated that the use of wet cooling with s-CO2 power cycle results contrary to the requirements of water consumption minimisation in CSP plants since a higher amount of cooling water than in current plants was demanded. Therefore, the highest potential was shown by CSP plants that use direct heating of s-CO2 and dry cooling, obtaining a high efficiency close to 45% and reducing greatly the utilisation of water.