Sandia National Laboratories (SNL) is researching a thermal-to-electric power conversion technology in a configuration called the recompression closed Brayton cycle (RCBC) that uses supercritical carbon dioxide (s-CO2) as the working fluid, rather than steam, thereby dramatically increasing conversion efficiency compared to the steam Rankine cycle.
The primary reason for improved power conversion efficiency is simply that the use of s-CO2 as the working fluid in a Brayton cycle requires less work to convert a given thermal input to electricity. In general, increased efficiency represents increased output for the same thermal input, regardless of the thermal source (natural gas, nuclear, solar or coal). Where fuel costs are a significant portion of overall costs (coal and natural gas fired plants), the benefit is reduced fuel costs. Where capital investments are high (nuclear and concentrating solar power), the benefit is increased output for the initial investment.