The Supercritical Carbon Dioxide Power Cycle: Comparison to Other Advanced Power Cycles

This paper consists of three parts. The first part presents a mostly thermodynamic comparison of the supercritical carbon dioxide (S-CO₂) cycle to helium Brayton, superheated steam, and supercritical steam cycles. Issues that contribute to plant cost are discussed. The second part presents an economic comparison of a gas-cooled reactor coupled to S-CO₂ direct, helium Brayton direct, and superheated steam indirect cycles. The results indicate savings of up to 30% if the steam indirect cycle is replaced with the direct S-CO₂ cycle. Compared to the helium direct cycle, the savings can reach 15%. The third part describes the optimization and potential of the indirect S-CO₂ cycle and the effect of reheating. The indirect cycles of helium to S-CO₂ and lead bismuth to S-CO₂ are studied to assess the performance of gas-to-gas and liquid metal or liquid salt indirect cycles, respectively. It is shown that although the indirect cycle of helium to S-CO₂ is feasible, it poses challenges in the intermediate heat exchanger design and suffers efficiency losses due to the large power consumption of the main circulators. Gas indirect cycles are well suited for liquid metal or liquid salt reactors. Further, the study indicates that employing reheat is economically unattractive for the indirect cycle of helium to S-CO₂ because of efficiency reduction from pressure losses in reheaters and interconnecting ducting and additional capital cost. A similar conclusion was also reached for the indirect cycles of liquid metal or liquid salt to S-CO₂ even though pumping power is very small. This is because of the additional cost of an intermediate liquid metal (or liquid salt) loop, which needs to be added since it is not possible to place all heat exchangers for reheat inside the reactor vessel.