Rondo Energy’s 100 MWh heat battery powered by 20 MW of onsite solar

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Rondo Energy has announced that a 100 MWh heat battery it installed in California, powered solely by 20 MW of onsite, off-grid solar, has entered daily automatic operation.

The heat battery provides continuous high-pressure heat and steam to a Holmes Western oil facility, and is the first large-scale commercial project of its kind, the company said. The heat battery operates alongside gas-fired boilers at the facility.

Rondo’s heat storage medium uses “only brick and wire,” the company said, and stores heat at over 1000°C with a claimed round-trip efficiency above 97%.

The bricks used in a heat battery, known as firebricks, are developed from common materials, said a paper by Stanford University researchers, and may be heated to high temperatures with electric resistance heating.

The image below shows the process of charging and discharging a heat battery, where the source of electricity can be off-grid renewables or grid electricity.

Rondo’s heat battery charges “using only the six lowest-cost hours of electricity per day,” the company said in a statement, “whether from off-grid solar or from the grid.” In electricity systems around the world, “low-cost hours of electricity are becoming available, thanks to the deployment of solar and wind.”

The Stanford researchers projected that firebrick heat storage technology will be used to store energy for industrial process heat in a 100% renewable energy system, because of its cost advantages over battery storage for that use case. In the 100% renewable scenario, the researchers expected that firebrick system capacity for industrial process heat would reach 2.6 TWh in the U.S., with a peak discharge rate of 170 GW.

Andy Lubershane, a partner at Energy Impact Partners, which has invested in Rondo Energy, said heat batteries “will open up” a large new market for renewably generated electricity, namely industrial heat, which he said accounts for about a quarter of global energy consumption.

Last year the U.S. Department of Energy engaged in negotiations with Diageo North America for an award of up to $75 million to install Rondo heat batteries at two sites, to be powered by onsite renewables. DOE’s Office of Clean Energy Demonstrations said the projects could provide “a highly replicable blueprint” for other industrial facilities to achieve direct decarbonization. Rondo and Diageo are still in discussions about the projects, said a Rondo spokesperson.

Rondo is developing three projects in Europe and one in Southeast Asia, the spokesperson said.

The 100 MWh facility in California has 10,000 times the capacity of a typical home heating system, the company said.

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