A common thread in the evolution of the configurations of supercritical CO2 power systems for waste heat recovery

Several configurations of supercritical CO₂ (sCO₂) power systems have been recently proposed as promising solutions for power generation from medium-temperature heat sources (300 °C – 700 °C). The paper exploits the potential of a methodology called "HEATSEP" to review and analyse critically the conceptual development of these configurations, when applied to waste heat recovery. The goal is to find a common thread in the evolution of all sCO₂ configurations proposed in the literature for waste heat recovery, and search for new, more performing ones. As required by the HEATSEP method, the study is performed by separating each configuration in two parts: a part, named "basic configuration", including all components that are necessary to realize the "basic concept" on which the system is based on, and the remaining part associated with the internal heat transfers and the heat exchanger network that realize them. The paper shows that all the "basic configurations" of sCO₂ power systems presented in the literature are created by including one or more splitters after the compression process, and then re-joining the separate streams in different manners. All these configurations are included in a general evolution tree, showing how they have evolved logically and why. Starting from the most performing configurations in the literature, the HEATSEP method enables to identify possible power output improvements by exploiting heat transfers not yet considered. Results show that the possible power gains are very small (4 kW out of 480 kW) demonstrating that the literature configurations have negligible margins for improvements.