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Supercritical carbon dioxide ‘could boost concentrated solar plant efficiency by more than 10%’

Professional Engineering

Stock image. The supercritical carbon dioxide could boost the efficiency of concentrated solar power plants and other renewable energy technology (Credit: Shutterstock)
Stock image. The supercritical carbon dioxide could boost the efficiency of concentrated solar power plants and other renewable energy technology (Credit: Shutterstock)

Supercritical carbon dioxide (sCO2) power systems could boost the efficiency of concentrated solar power (CSP) plants by an impressive 10 percentage points, according to engineers behind a new demonstration.

The Southwest Research Institute in Texas (SwRI) developed and demonstrated full-scale turbomachinery for the project, which combines sCO2 power cycles with integrated thermal energy storage.

Held above a critical temperature and pressure, sCO2 acts like a gas while having the density of a liquid. It is a highly efficient fluid for generating power, thanks to its high density, low viscosity and favourable heat transfer properties. These properties make it a promising alternative to using water or steam to turn turbines in power cycles.

The project was supported by the US Department of Energy’s Apollo programme, which was created to improve performance and reduce the cost of electricity from CSP plants, which use mirrors or lenses to concentrate a large amount of sunlight onto a receiver. The receiver converts the light into heat, which is typically used to generate power using steam turbines. The new system uses sCO2 instead, to improve efficiency and reduce operating costs.

“Advancing grid-scale energy storage is an important step to enabling full penetration of renewables into power generation,” said Dr Jason Wilkes, manager of SwRI’s rotating machine dynamics section.

“Utilising sCO2 as a working fluid can increase the efficiency of a CSP plant by as much as 10 percentage points. The high efficiency of the sCO2 cycle also allows the turbomachinery to have a smaller footprint — it is one-twentieth the size of a standard steam turbine, allowing for improved installation in most environments.”

SwRI and Hanwha Power Systems, a global energy equipment company with headquarters in South Korea, developed and demonstrated the new integrally geared sCO2 turbomachinery, which was trialled in full-pressure, full-temperature testing at megawatt-scale conditions of up to 720°C and 275 bar. The system will be integrated into a CSP pilot plant in future.

“sCO2 power cycle technology is a fraction of the size of conventional turbomachinery, offering improved performance for numerous applications,” said Dr Tim Allison, director of SwRI’s machinery department. “The successful megawatt-scale demonstration of sCO2 technology at full-cycle conditions is an exciting milestone.”


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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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