Investors including Microsoft and oil giant Saudi Aramco have thrown their weight behind a California start-up that wants to help industry slash its emissions by storing excess renewable energy in superheated bricks.

California-based Rondo Energy announced that it has raised $60m in a new financing planned to speed the rollout of its Rondo Heat Batteries worldwide.

Rondo has attracted heavyweight investors including Microsoft's Climate Innovation Fund, Aramco Ventures and Anglo-Australian multinational mining group Rio Tinto – the latter two of which have also joined its advisory board. American venture capitalist John Doerr has also backed the company.

The Rondo system uses electric heating elements, like those in a toaster or oven, to heat thousands of tons of brick up to temperatures of 1,500°C. Rondo says the bricks maintain the heat with less than 1% energy loss daily.

When heat is wanted, air flows up through the brick stack and is superheated to over 1,000°C, before being delivered to the end point as superheated air or steam.

Rondo says its system is designed to drop into existing facilities or power new-builds, and offers a fast, low-cost pathway to decarbonisation and reduced operating costs.

The bricks can both “charge” and deliver heat simultaneously. Other claimed benefits include the abundant nature of the key materials and the safety of having no moving parts or flammable materials. The batteries boast a 50-year lifespan.

Rondo plans to target its thermal batteries at industrial processes, everything from producing steel to baby food. It says these are powered by high-temperature heat that consumes a quarter of all world energy and emits a quarter of global carbon pollution.

Rondo says its tech can turn energy from cheaper but intermittent renewable power sources into the “continuous, high temperature clean heat that industry requires, and opens the door to industrial decarbonisation at a fraction of the cost of other technologies.”

Earlier this year Rondo partnered with Siam Cement Group to expand the production capacity for its system at a facility owned by the Thai conglomerate to 90GWh per year. Rondo said this would be “larger than any current battery manufacturing facility worldwide.” Mass production is already underway with a capacity of 2.4GWh per year online.

Other types of thermal battery in development include one pioneered by a Norwegian start-up that pumps heat into a concrete-like material.

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