Overview

Challenges
  • Centrifugal compressor working close to CO₂ critical point, where thermodynamic properties show large gradients
  • Direct implications on turbomachinery design, manufacturability, controls. and performance prediction
  • Maximize sCO₂ cycle efficiency at 100% load and ensure electric cycle load between 20% and 100%
  • System scalability up to 100 MW Critical dry gas seal (DGS) system: possible phase transition during operation
Results
  • Designed two centrifugal compressors and one turbine expander for extreme power density
  • Highest density ever for a centrifugal compressor: >600 kg/m³ at suction
  • 5.4 MW prototype compressor tested up to 6.2 MW; full operating map explored with respect to rotating speed and inlet guide vane (IGV) position
  • Compressor prototype tested in off-design conditions including dual-phase and liquid conditions at suction
Case study details

sCO2-flex is an EU-based consortium of 10 key industry organizations and academic institutions. Its main objective is to make fossil-fuel-based electricity production more flexible to foster integration of renewable energy sources. Its use of supercritical CO2 (sCO2) technology will increase the efficiency of conventional power plants—enabling significantly smaller footprints while reducing greenhouse gas emissions, residue disposal, and water consumption.

The proposed new thermodynamic closed-loop cycle, with turbine driven by supercritical CO2, is based on the Brayton cycle and includes an axial expander and two centrifugal compressors working in parallel. It will provide 25 MWe at 100% load and have the flexibility to reduce load down to 20%.

Baker Hughes designed two compressors and one turbine expander for the project. In early 2021, we built and tested a full-scale prototype of the more innovative one, with suction close to CO2 critical point.

 

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The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement 764690 sCO2-Flex