A turbine the size of a regular office desk could soon power 10,000 households, as per a press release from the Southwest Research Institute (SwRI), which has set up a pilot plant in San Antonio, Texas. Called the Supercritical Transformational Electric Power (STEP), the demo pilot plant has seen the SwRI collaborate with GTI Energy, GE Vernova (GE), and the US Department of Energy.
The steam turbines used in power plants worldwide are entirely a dated technology. The origins of the steam turbine go back to the 19th century and have not seen radical improvements in technology, even as one can find steam turbines in varying sizes and applications.
The turbine’s job is to use water as a thermal medium in power cycles. However, if one were to change the medium itself, the turbine could be much smaller in size. Enter carbon dioxide as a working fluid, and the turbines can be significantly downsized.
Supercritical CO2 turbines
Carbon dioxide exists in a gaseous form, but it can also be concentrated using high temperature and pressure, where it behaves like a gas but with the density of a liquid. Called supercritical CO2 (sCO2), this gas form has been on the US Department of Energy’s (DOE) radar for a while since it allows the turbines to be as much as 10 percent more energy efficient than conventional turbines.
Moreover, a three-foot (one-meter) turbine using sCO2 can perform the same job as a 65-foot (20 m) steam turbine, paving the way for a significant downsizing of the turbine. From the bus-sized turbines used today, one could transition to a golf cart or even a desk-sized sCO2 turbine. The STEP aims to make that possibility a reality, and a 10 MW demo pilot is being developed with $155 million in funding at SwRI’s headquarters in Texas. That would be enough to power 10,000 homes.
Working with solar concentration
An added advantage of using sCO2 is the ability to take the gas to its supercritical state using concentrated solar power. This approach uses a system of mirrors to focus solar energy and use it for various purposes ranging from heating to power generation.
A stock image representing concentration of solar power
Kim Grosz/iStock
According to CleanTechnica, the DOE has been working over the years to reduce the cost of concentrating solar power systems with limited success. Using sCO2 could drastically reduce the costs, providing a win-win situation for the two approaches.
The STEP program has been in the works since 2018 and is the world’s largest demonstration facility for sCO2 technology. The pilot plant achieved the first operation of its compressor with CO2 reaching supercritical fluid conditions earlier this year. The goal of the project is to improve the efficiency, economics, operational flexibility, space requirements, and environmental performance of this new and upcoming technology.
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