Thermal performance analysis on steady-state and dynamic response characteristic in solar tower power plant based on supercritical carbon dioxide Brayton cycle

Abstract

Supercritical Carbon Dioxide (S-CO2) Brayton cycles and Concentrating Solar Power (CSP) plants are gaining increasing attention due to environment pollution problems and their higher efficiencies. At present, there is a lack of researches on the dynamic thermal analysis of CSP plants based on S-CO2 Brayton cycle, which needs to be resolved urgently. Therefore, a one-dimensional dynamic model of the printed circuit heat exchanger (PCHE) is developed, which is incorporated into transient model of the solar tower power plant. And the Modified Euler or Fully-implicit Runge-Kutta Method is used to complete the dynamic solution. The results indicate that the pressure ratio equaling to 3.5 and the zigzag PCHE regenerator with a diameter of 2 mm will be the best choice for our designed power plant to achieve the balance between larger net output work and power efficiency improvement, which provides the reasonable design parameter for more complicated three-dimensional transient models. By taking the binary nitrate working temperature limitation and common influences of temperature and pressure on S-CO2 thermophysical properties into consideration, as the direct normal irradiance (DNI) decreases, the S-CO2 heat transfer coefficient will increase. When DNI value changes between 780 W/m2 and 970 W/m2, the cold side S-CO2 outlet temperature of PCHE regenerator and S-CO2 Brayton cycle power efficiency will produce 114.65 K and 8% fluctuation in no more than 15 minutes.