Southwest Research Institute successfully developed and demonstrated full-scale turbomachinery for one of the world’s first supercritical carbon dioxide (sCO2) power systems for a concentrated solar power (CSP) plant with the help of government and commercial collaborators.

The system integrates sCO2 power cycles with thermal energy storage.

The project was funded by the US Department of Energy’s APOLLO program, which aimed to improve CSP plant performance and lower electricity costs.

In a closed-loop environment, the 10MW sCO2 turbomachinery has passed performance and endurance tests.

Carbon dioxide is held at a temperature and pressure above a critical point, causing it to behave like a gas while having the density of a liquid.

It’s also nontoxic and nonflammable, and it’s been used in dry cleaning, low-GHG refrigeration, and decaffeinating coffee.

Because of its high density, low viscosity, and favorable heat transfer properties in its supercritical state, sCO2 is a highly efficient fluid for generating electricity.

“Advancing grid-scale energy storage is a critical step toward allowing renewables to be fully integrated into power generation.”

“Using sCO2 as a working fluid can boost a CSP plant’s efficiency by up to 10%,” according to Dr.

SwRI’s Rotating Machine Dynamics Section is managed by Jason Wilkes.

“Because of the sCO2 cycle’s high efficiency, the turbomachinery has a smaller footprint — it’s 120th the size of a standard steam turbine, allowing for better installation in most environments.”

CSP technology focuses a large amount of sunlight onto a receiver, which then converts the concentrated light into heat and extracts thermal energy to generate electricity using steam turbines.

The energy is stored as heat in the system, which can then be converted to on-demand energy using sCO2 power cycles, resulting in increased efficiency and lower operating costs.

“sCO2 power cycle technology is a fraction of the size of traditional turbomachinery, allowing for better performance in a variety of applications.”

“The successful MW-scale demonstration of sCO2 technology under full-cycle conditions is a significant achievement,” Dr.

SwRI’s Machinery Department director, Tim Allison.

SwRI and Hanwha Power Systems, a South Korean-based global energy equipment company, developed and demonstrated the new integrally geared sCO2 turbomachinery, which was tested at full-scale compressor conditions and full-pressure full-temperature turbine testing at unprecedented MW-scale conditions of up to 720 °C.