Demonstrating supercritical CO2 power cycles at scale

Why is this gap important?

Supercritical CO2 power cycles (sCO2) in principle allow for, in addition to higher plant efficiencies compared with conventional pulverised coal plants, lower pollutant emissions, higher power density (which could reduce capex) and easier CO2 capture. In some cases they could also allow for reduced water consumption. Plant sizes, which can vary from 1 MWe to 600 MWe, could be adjusted to specific electricity demand requirements.

Technology solutions

Several technologies are being developed that use supercritical CO2 (sCO2) as the working fluid.

  • Closed-loop sCO2 cycles have already been proven through research projects in the Czech Republic, France, Japan, South Korea and the United States (TRL 5). These systems are generally more suited for syngas and natural gas plants.
  • Semi-closed SCO2 cycles promise superior flexibility in terms of plant configuration and therefore would be ideal as alternatives to traditional turbines in fossil fuel plants (TRL 5).
  • The Allam Cycle is a specialised sCO2 system in which sCO2 produced from natural or synthetic gas (from coal gasification) is fired with pure oxygen under pressure (TRL 6). It is currently being tested by NET Power and has contributed largely to the renewed interest in supercritical CO2 systems.

Closed-loop sCO2 cycles Readiness level:

Semi-closed SCO2 cycles Readiness level:

Allam Cycle Readiness level:

Colored bars represent the Technology Readiness Level (TRL) of each technology. Learn more about TRLs

What are the leading initiatives?

The advantages of sCO2 systems are significant, and hence substantial interest in the process exists.

  • NET Power is testing Allam Cycle technology on natural gas. The technology could also be run with coal. NET Power has suggested that coal-based Allam Cycle plants could achieve efficiencies of 47.8–49% (HHV) with 100% CO2 capture.
  • Initiatives in the United States include Sandia National Laboratories (SNL) which is working for the US DOE and operating two experimental systems.
  • Bettis Atomic Power Laboratory has a 100 kWe Integrated System Test (IST) recuperated closed-loop sCO2 system to evaluate advances in components and system performance.
  • There are also sCO2 projects in Japan (e.g. at the Tokyo Institute of Technology), Korea (e.g. at the Korea Institute of Energy Research), Australia, Canada.

For more information, see IEAGHG (2015) and IEA CCC (2019).

Recommended actions

Industry/companies

Academia

Next 5 years:

  • Develop collaborative research programmes or networks among companies, equipment suppliers, research institutes and governments to pool technical and financial resources for RD&D on CCUS, including through private-public partnerships.

Next 5-10 years:

  • Overcome technical, engineering and materials science challenges related to plant components such as turbomachinery, recuperators, and combustors.

Finance/economy ministries

Next 5 years:

  • Mitigate risks of investing in CCUS through investment stimulus mechanisms that leverage private funding for innovative low-carbon technologies and through promoting private-public partnerships.

NGOs and think tanks

Next 5 years:

  • Raise awareness of the longer-term need for CCUS to reduce emissions.