Publications

ntentAdvanced Nuclear Power Program

Supercritical CO2 Brayton Cycle for Medium Power Applications

P. Hejzlar, M.J. Driscoll, J. Gibbs, Yifang Gong, and S.P. Kao

MIT-ANP-PR-117 (July 2007)

Abstract

This final report summarizes the results of the study of a supercritical CO₂ (SCO₂) power cycle for medium power application. The objective of these investigations is to establish a 5 – 30MWe power conversion system for an indirect cycle that (1) achieves high net efficiency in conversion from thermal to electrical energy, (2) is compact with minimum volume and weight, (3) is robust, resilient to accidents and has high long term reliability and performance, and (4) exhibits good controllability and fast response to requested power changes.

Two alternative SCO₂ cycle designs for medium power applications were developed using the optimization computer code and Solid Edge software. The first design is a recompression cycle derived from the 300MWe design developed at MIT for Generation IV reactors. The design employs two compressors (main and recompression) working in parallel and two recuperators (HTR and LTR) and maximizes cycle efficiency while striving for small plant footprint. The second design is a super-compact simple SCO₂ power cycle, which has only one compressor and one recuperator. The main focus of the simple SCO₂ design is cycle compactness and simplicity while achieving still attractive efficiency.

The 20MWe SCO₂ recompression cycle achieves, at a turbine inlet temperature of 650°C, and highest cycle pressure of 20MPa, pressure ratio of 2.6 and main compressor inlet temperature of 32°C (critical temperature is 30.98°C) the very attractive net electrical efficiency of 47.2%. The PCS is very compact with the overall dimensions of 5.5m x 2.9m x 3.4m (Length x Height x Depth). The simple compact cycle achieves for the same cycle parameters as the recompression cycle net electrical efficiency of 40.2%, which is 7% less than the recompression cycle. It exhibits even higher compactness with the overall PCS dimensions of 3.25m x 5.0m x 1.68m (Length x Height x Depth). The report also discusses PCS performance sensitivity to various parameter changes, maintenance considerations and R&D needs.