Fossil-free, renewable energy sources are often fluctuating and difficult to use consistently. Take solar power: in certain parts of the globe there is an abundance of sunshine, but if the excess cannot be saved it can’t be used when night falls.
Australia-based solar power experts RayGen are rising to this challenge. They have developed a cutting-edge energy storage system at a pilot plant in Carwarp, Victoria, that employs both solar photovoltaic and solar thermal energy to deliver renewable energy to the local electricity grid.
Electricity when the grid needs it most
RayGen is collecting solar energy using a large field of mirrors and converting it into electricity with photovoltaics. The mirrors collect sunlight, which is then redirected to a solar tower, which in turn generates electricity. This electricity is then used to supply the grid in the usual way, or to chill a body of water to near-freezing as a form of energy storage.
So, how can cold water store solar power? As the solar cells are highly concentrated, they generate a lot of heat, which can be used to heat a second body of water to near-boiling point. With this temperature difference, the use of an organic Rankine cycle (ORC – see separate box) and turboexpander technology from Atlas Copco Group unlocks the possibility to generate electricity at any time – also after sunset.
“When you talk about energy storage, people think about batteries first, but storing energy for 12 to 24 hours gets very costly. Our expanders convert the thermal energy into electricity for when the grid needs it most,” says Louis Mann, Manager of Marketing and R&D at Atlas Copco Mafi-Trench in California.
“There aren’t many applications in the world that use energy storage in the way that this plant does,” adds Louis’s colleague, Sales and Application Engineer, Ysabel Murguia.
Left image: Turboexpander technology unlocks the possibility to generate electricity at any time.
Right image: RayGen’s pilot plant in Australia employs both solar photovoltaic and solar thermal energy to deliver renewable energy to the local electricity grid. (Photo courtesy of RayGen Resources Pty Ltd.)
Scaling it up
Atlas Copco was approached by RayGen due to the former’s long experience of ORC turboexpander technology, stretching back to the 1980s. The pilot plant began operation in 2022, and the initial success and growing interest from utility companies in various parts of the world has led to a scaling up of ambitions.
“For the pilot plant we built a frame four expander generator that’s integrally geared to the gearbox,” Ysabel explains. “A frame four is a mid-sized machine, while the commercial system will require a newly developed largest frame size. We’re now developing a full-scale solution together with RayGen.”
A far-sighted solution
The real demonstration is on the commercial scale; to show the world that this type of energy storage is not just technically possible, but commercially viable too.
“There’s a trend towards larger machines in the energy transition in general to make these technologies work through economies of scale,” says Louis.
Thus, this partnership is helping usher in a transformative technology that can give the energy sector more reliable and consistent renewable energy with minimal waste.
“Energy storage like this isn’t common, but it has the potential to change the world’s view on renewable energy supply,” says Ysabel.
Interested in this solution or turboexpander technology in general? Learn more in this blog post.
