An innovative solar-hydro plant has opened giving a glimpse into the potential for green energy

RayGen generates solar electricity during the day and stores heat which then powers a turbine at night.

AGL Energy chief operating officer Markus Brokhof. Picture: Jonathan Cami

A facility that generates energy from solar and simultaneously uses the heat generated to produce electricity after dark has opened in Victoria.

It’s an innovative design that developer RayGen says will aid Australia’s transition away from fossil fuels.

RayGen, which is backed by heavyweights such as AGL Energy, Norwegian giant Equinor and US oil behemoth Chevron, uses rows of giant mirrors to reflect sunlight on to its own solar panels that generate electricity to be sold into the grid.

The innovative add-on, however, comes when RayGen uses the heat generated through solar electricity generation to heat water which is then stored in a neighbouring dam.

When the sun goes down and wholesale prices spike, RayGen can then use the hot water to heat ammonia which has a lower boiling point than water, creating stream to spin turbines and create power.

RayGen said the facility was capable of producing 4MW of high-efficiency solar energy and 2.8MW and 50MWh of long-duration storage, which the developers said was enough energy for about 1700 homes and would save about 7000 tonnes of carbon dioxide being emitted each year.

The technology is appealing to renewable energy developers such as AGL Energy, which has the advantage of being able to use retiring fossil fuel power stations that have existing transmission lines.

RayGen world-leading solar power testing station.

AGL signed an offtake agreement with RayGen in 2021.

AGL chief operating officer Markus Brokhof said the company was working with RayGen to determine whether to roll out the technology at its former Liddell coal power station, which was shuttered earlier this year.

“This plant will supply synchronous power with a view to increasing the capacity and flexibility of the local electricity grid,” Mr Brokhof said.

“We believe this technology has the potential to be deployed at greater scale and we are progressing our plans for a similar solar-plus-thermal storage plant with RayGen at our Liddell site in the Upper Hunter, NSW.”

The technology would be particularly useful in Australia where companies struggle to build enough storage capacity to smooth out renewable energy peaks and troughs.

Australia has had an increase of solar generation particularly, and on sunny days the wholesale electricity price is often zero or even in negative territory.

But without batteries, solar generators are unable to easily turn off generation.

Australia is also struggling to build enough transmission capacity so in some regions, solar generation is curtailed even when the wider grid needed additional energy to prevent outages.

On-site solar-hydro generation would avoid the need to build prohibitive batteries, which along with pumped hydro are the only other means to store excess electricity.