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23. Supercritical Carbon Dioxide (sCO2)

Maximum Phase I Award Amount: $250,000

Maximum Phase II Award Amount: $1,600,000

Accepting SBIR Phase I Applications: YES

Accepting STTR Phase I Applications: YES


Power cycles based on a supercritical carbon dioxide (sCO2) working fluid have the potential for higher thermal efficiencies and a lower capital cost when compared to state-of-the-art steam-based power cycles. These potential benefits, combined with the compounding performance benefits from a more efficient cycle on balance of plant requirements, fuel use, emissions, water use and cost-of-electricity (COE), are creating broad interest in sCO2 power cycles. The indirect sCO2 recompression Brayton cycle has the advantage of using a wide range of thermal heat sources (e.g., nuclear, concentrated solar, fossil, waste heat). This results in the power plant design being dependent on the temperature of this thermal heat source with the overall efficiency usually increasing with temperature. System analysis studies by many research organizations including NETL have projected efficiency improvements of 2 – 6 percentage points when compared with Rankine cycles operating at similar process conditions.


Grant applications are sought in the following topics:


a.      Supercritical Carbon Dioxide Resistant Coatings for Turbomachinery

Thermal barrier coatings (TBC) and anti-friction coatings are known to provide benefits for turbomachinery in power cycles, including higher use temperature, greater erosion resistance, toughness, and improved sintering resistance, increased wear-resistance and component lifetime. However, the use of TBCs and anti-friction coatings is not as well-investigated for sCO2-based power cycles, where the working fluid is supercritical CO2. Applications are being sought for the research and development of optimum thermal barrier and anti-friction coatings for large-scale sCO2 Recompression closed Brayton cycle (RCBC) turbomachinery applications. Applicants should identify and investigate TBC and/or anti-friction coatings that are sCO2-resistant with appropriate application methods for large-scale turbomachinery at conditions relevant to the sCO2 RCBC. The high density of the CO2 and small turbine pressure drop creates compact turbomachinery with unique temperature gradients. The proposed coating must be tolerant against delamination, erosion (surface requirement) resistant to corrosive gas, support thermal gradients / cycling and offer a thermal barrier. Testing should be designed to identify optimum coatings. The applicant team should have access to an sCO2 testing facility. Applicants should clearly describe the coating materials, technology, and expected benefits to turbomachinery for indirect sCO2 power cycle applications. Applications should also include a description of preliminary results of the proposed coatings showing promising performance under sCO2 conditions. Collaboration with an OEM is encouraged. The proposed materials or coating techniques are preferred to be at a later-stage in the research and development process so they will be ready for commercial potential in Phase II.


Questions – Contact: Richard Dalton,


b.      Advanced Coolers for Supercritical Carbon Dioxide Base Power Cycles

A pathway to achieving higher sCO2 power cycle efficiencies can be enabled by operating under condensing sCO2 cycle conditions. The pressure drop through the cooler plays a large factor in the sCO2 cycle efficiency. These coolers are typically modular and to meet the desired heat duty multiple modules are used in a system, typically with heat duties ranging from 1 – 3 MWth per module.


Applications are being sought for the research and development of such advanced coolers to directly cool and condense CO2 while minimizing the pressure drop and associated fan power. Applicants should focus on the conceptual design of the cooler, integration with the sCO2 power cycle, and modeling performance. Controllability of the cooler to rapidly and accurately achieve the desired outlet temperature must be considered, due to the proximity of this operating point to the CO2 critical point and its resulting implications for downstream compressor performance. Cooler module designs resulting in a reduction in metal mass should be considered to enhance controllability and response transients. Applications may also include basic experimental work (cooler tubing geometries, heat transfer) to validate the concept. The applicant must clearly describe how the cooler technology will be integrated into the sCO2 power cycle to improve the cycle performance. Applicants must also describe how the proposed cooler technology can reduce cost compared to commercial technologies. The phase I effort should include development of a plan for building and testing a cooler prototype.


Questions – Contact: Drew O’Connell,


c.       Other

In addition to the specific subtopics listed, FE invites grant applications in other areas that fall within the scope of topic description provided above.


Questions – Contact: Mark Freeman,


References: Subtopic a:

1.      Clarke, D.R., Oechsner, M., and Padture, N.P. “Thermal-barrier coatings for more efficient gas-turbine engines,” MRS Bulletin, Vol.37, No. 10, Oct. 2012, pp. 891-897,


2.      Pint, B. A., Unocic, K. A., and Haynes, J. A. “The Effect of Environment on TBC Lifetime.” J. Eng. Gas Turb. & Power, 138 (8) (2016) 082102,


3.      Kung, S. C., Shingledecker, J. P., Thimsen, D., Wright, I. G., Tossey, B. M., and Sabau, A. S. “Oxidation/Corrosion in Materials for Supercritical CO2 Power Cycles.” The 5th International Symposium – Supercritical CO2 Power Cycles, March 28-31, 2016, San Antonio, Texas,


References: Subtopic b:

1.      Pidaparti, Sandeep R., White, Charles W., O’Connell, Andrew C., and Weiland, Nathan T. “Cooling Technology Models for Indirect sCO2 Cycles.” 2019, Report NETL-PUB-22604


2.      Pidaparti, Sandeep R., White, Charles W., O’Connell, Andrew C., and Weiland, Nathan T., “Cooling System Cost and Performance Models for Economic sCO2 Plant Optimization of Cooling Technology and Cold sCO2 Temperature,” 3rd European Supercritical CO2 Conference, Paris, France, September 19-20, 2019,  NETL-PUB-22387


3.      Pidaparti, Sandeep R., White, Charles W., and Weiland, Nathan T., “Cooling System Cost and Performance Models to Minimize Cost of Electricity of Direct sCO2 Power Plants,” The 7th International Supercritical CO2 Power Cycles Symposium, San Antonio, Texas, March 31 – April 2, 2020, NETL-PUB-22738


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