Dynamic modeling and evaluation of a novel evacuated tube solar collectors-assisted supercritical carbon dioxide Brayton cycle with intercooling and reheating

The transcritical CO2 Rankine cycle is increasingly recognized as a promising option for power generation in low-grade solar applications. However, there is a liquefaction problem in the condenser due to the CO2's low condensing temperature. It is very difficult to condense CO2 with the surrounding environment or water. Various approaches, such as implementing a self-condensing transcritical CO2 Rankine cycle, utilizing liquid natural gas, or incorporating CO2 mixtures, have been proposed to address this issue, but these solutions add complexity to the system. A more effective and simpler alternative is to adopt the supercritical CO2 Brayton cycle for low-grade applications. In this study, a novel solar energy-based supercritical carbon dioxide Brayton cycle with reheating and intercooling is proposed. For the heating and reheating process, two collector groups comprised of a total of 20 evacuated solar collectors are utilized. The plant is analyzed in terms of energy and exergy, taking into account Isparta, Turkey's meteorological data. From the analysis, it is determined that the carbon dioxide temperature could reach a maximum of 265.32 degrees C. The annual solar energy that falls on the solar collector is determined to be 17,697 kWh, while the annual power generation by the cycle is found to be 547 kWh. The results show that the input heat and the net power are greater than 1.5 kW and 0.3 kW, respectively, for most of the year. Moreover, the solar-based supercritical carbon dioxide Brayton cycle's energy efficiency is calculated as 3.1%, and only the Brayton cycle's energy efficiency is found as 11.4%.