GTI Energy and its partners, Southwest Research Institute (SwRI) and GE Research, have announced that the Supercritical Transformational Electric Power (STEP) Demo project, sponsored by the US Dept of Energy, has successfully achieved supercritical carbon dioxide fluid conditions at its 10 MW sCO2 pilot plant facility in San Antonio, Texas.

Supercritical CO2 (Closed Brayton cycle) power turbine technology enables next-generation indirectly heated plants (such as concentrated solar and nuclear energy) as well as directly fired natural gas electric power plants to be more efficient and help meet the global demand for a low-cost, environmentally friendly, resilient energy transition. The aimed at thermal efficiency of sCO2 units is around 40%, compared to the conventional Rankine cycle efficiency of 33%. “This milestone represents significant progress toward readying the facility for system-level testing,” says Don Stevenson, VP of Energy Supply and Conversion at GTI Energy.”

Supercritical CO2 technology can be coupled with a broad variety of low- and zero-emission heat sources, including waste heat from industrial sources, geothermal, biomass, concentrated solar, and natural gas, with and without carbon capture. The cycle lends itself to compact turbomachinery, resulting in lower capital costs and reduced power plant size and footprint. It is said to improve grid stability and resiliency with quicker response to changes in power demand, while water consumption for cooling can also be significantly reduced or even eliminated with the cycle.

“The sCO2 power cycle is a breakthrough clean, compact, and high-efficiency power generation technology that can deliver significant environmental performance. We look forward to continued operation of the current test to demonstrate control and operability of this power cycle while validating system performance over long periods of time,” noted Bhima Sastri, director of Energy Asset Transformation, US DoE Office of Fossil Energy and Carbon Management.

The $155M STEP Demo project is funded by an industry consortium and a $124.5 million Co-operative Agreement from DOE’s National Energy Technology Laboratory. The STEP pilot plant, built at SwRI’s campus in San Antonio, is among the largest demonstration facilities for sCO2 technology anywhere. It is intended to demonstrate the efficiency and performance potential of the indirect fired, sCO2 Brayton power cycle. Its flexible design means that the facility can be reconfigured as a test bed for future sCO2-cycle-based power systems and component development. 

Image: John Klaerner, lead turbine engineer, and Dr. Jeff Moore, principal investigator of the STEP Demo project, with the recently assembled sCO2 turbine for the 10 MWe demonstration plant under construction at SwRI (courtesy of SwRI)