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Thermal storage company Rondo plans 90GWh ramp up of ‘Heat Battery’ gigafactory


Rondo Energy, which counts Bill Gates’ Breakthrough Energy Ventures among its investors, intends to scale up annual production capacity of its thermal storage tech to 90GWh.

The California-headquartered company’s Heat Battery is a type of refractory brick that can be heated to as high as 1500°C (2732°F) and retain the heat to be used either in that form, or to generate electricity. The heat can be discharged over durations that span several hours or even days.

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‘Refractory’ means it is made of material that retains its strength and form even at high temperatures, and is resistant to heat, pressure or chemical decomposition. In Rondo’s case, the materials used are oxygen, silicon and aluminium.

Targeting applications for decarbonising heat-intensive industrial processes, Rondo Energy has claimed it is a heat storage medium with more than 90% efficiency, rising to as much as 98% as system sizes scale up. In addition to aiding decarbonisation, it could offer industrial customers a way to lower and manage energy costs.

Rondo made the Heat Battery commercially available in 2022, making its first deployment for California biofuels producer Calgren under a heat-as-a-service contract at no upfront cost to the customer. The 2MWh system would enable Calgren to utilise high temperature heat at a much lower cost than equivalent gas-fired generation, it was claimed earlier this year when the project was announced.  

Alongside Breakthrough Energy Ventures’ VC-funding, other investors in the startup include sustainable energy investor Energy Impact Partners, and Siam Cement Corporation, a major Thailand-based conglomerate which is also Rondo’s manufacturing partner.

When it made the investment into the thermal storage company in September last year, Siam Cement Corporation (SCC) said the technology could be applied to many of SCC’s own industrial operations in sectors as diverse as cement, chemicals, paper and packaging. The pair planned to offer large-scale renewable energy-based Heat Battery solutions to industrial customers across Southeast Asia, working up to a global offering.

SCC executive VP Thammasak Sethaudom said the company “can leverage our 70 years of technical expertise in the refractory business and supply chain to support Rondo’s mission to decarbonise industrial process heat” and that it was “happy” to be increasing production to meet expected rising demand.

Working out of an undisclosed location in Southeast Asia, Siam Cement Corporation’s Rondo Heat Battery (RHB) manufacturing line already has annual production capacity of 2.4GWh, but there are plans afoot to scale that up massively. However, a timeline for the ramp up was not given in a release by Rondo Energy.

Ramp up announced as activity in thermal storage heats up

Interest in thermal energy storage around the world has been gradually ramping up too: Breakthrough Energy Ventures has invested in a number of others, for example. Spanish utility major Iberdrola just made a modest VC investment into one, Sweden’s Kyoto Group, which reported a few days ago.

The government of Spain a few weeks ago announced a €160 million (US$170 million) grant programme to support the deployment of 600MW of energy storage by 2026 in the European country, and included thermal storage among eligible technology options.

One startup, Israel’s Brenmiller Energy, recently broke ground on what it claimed was the first thermal storage ‘gigafactory’, with 4GWh annual production capacity for bGen, the company’s technology that involves rocks that can be heated to 750°C.

A report published in late 2022 by the Long Duration Energy Storage Council (LDES Council) global trade association found that meeting global decarbonisation goals will require several terawatts of thermal energy storage deployments.

With nearly half of global emissions coming from heating or cooling processes, and industrial applications representing a significant portion of that, the economic case for thermal energy storage for industry is very strong, the LDES Council report claimed.

LDES Council CEO Julia Souder offered an overview of some thermal storage technologies and providers in a recent article for our quarterly journal PV Tech Power (Vol.35), which you can read in full with an Premium subscription, or read an extract of it on the site here.

Read more of’ coverage of the thermal energy storage space here.

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