Novel thermoelectric generator enhanced supercritical carbon dioxide closed-Brayton-cycle power generation systems: Performance comparison and configuration optimization

Supercritical carbon dioxide (S-CO2) closed-Brayton-cycle (CBC) has been considered as one of the most promising thermodynamic cycles for power generation, but its simple recuperated layout has serious pinch point problem in the recuperation process and its recompressing layout has great difficulty in the compressor aero-dynamic design and system control. Considering thermoelectric generator (TEG) is a potential approach for CBC performance improvement, this research proposes five TEG enhanced CBC configurations based on simple recuperated layout, and the corresponding models consisting of zero-dimensional CBC modules and quasi-one-dimensional TEG modules are established for performance assessment and comparison. Results indicate that the configuration with split flow, in which TEG is cooled by S-CO2 at compressor outlet, has significant enhancing effect on power generation efficiency through increasing the highest cycle temperature and the full utilization of S-CO2 heat-absorption capacity, and there is an optimal number of thermoelectric modules. Based on this configuration, an improved TEG enhanced CBC scheme, in which an additional TEG is applied as pre-cooler, is proposed. Even if the compressor and turbine isentropic efficiencies are relatively high (eta C = 0.89 and eta T = 0.93), the improved TEG enhanced CBC still has higher power generation efficiency than the recompressing CBC (41.57 % vs. 40.94 %).

Automated summary

Supercritical carbon dioxide closed-Brayton-cycle (CBC) is a promising thermodynamic cycle for power generation. However, the traditional layouts of simple recuperation and recompression have their respective problems. This research proposes five thermoelectric generator (TEG) enhanced CBC configurations based on simple recuperation layout, and showed that a configuration with split flow has a significant enhancing effect on power generation efficiency. An improved TEG enhanced CBC scheme with an additional TEG as a pre-cooler is also proposed and it achieves higher power generation efficiency compared to the traditional recompressing CBC, even with relatively high compressor and turbine efficiencies.