Thermal Batteries: A Clean and Sustainable Alternative to Lithium-Ion Batteries

The discussion about electric batteries has long been centred around lithium-ion batteries, which use lithium resources in their development. The large-scale rollout of these batteries relies on the development of vast mining projects to source the lithium and other metals and minerals required for their production. Due to the limitations of these types of batteries, scientists have been exploring the viability of alternative materials for battery construction to increase the number of energy storage options. While some companies are testing gravity batteries, others are assessing the potential for thermal batteries. The thermal batteries industry is in the nascent stage of development, but it is gaining increasing attention, as governments and companies worldwide look for alternative green solutions. These batteries work by heating a substance to store thermal energy, which can be converted into heat or electricity. Energy from renewable sources, such as solar and wind farms, can be stored to use when energy is not being produced on-site, to ensure a stable flow of electricity to the grid. f According to Pitchbook Venture Capital, thermal battery startups have seen a substantial increase in their median post-money valuation over the past year, as well as growth in capital investment. In the U.S., this has been aided by greater government funding into clean technology, supported by tax breaks and other financial incentives for private investors. Antora Energy, Fourth Power, and Malta are some of the key players in the U.S. industry at present. One Norwegian firm, Kyoto Group, is developing its Heatcube technology, which uses vertical tanks filled with salt. The company installs these tanks on sites where heat is needed, charging them with electricity. The tanks can hold heat at temperatures up to 500oC. The CEO of Kyoto, Bjarke Buchbjerg, explained, “With all the excitement about battery technology for electric vehicles, people have forgotten about the massive demand for heat for industries that can’t be produced from electrical batteries. Industrial heat is a big deal – we can’t afford to ignore it.” Similar technology has been being used for over a decade in Spain. The Spanish firm Iberdrola uses molten salt to store heat that can be discharged at sunset to produce steam, which can be transformed into electricity overnight. Malta, which is based in Massachusetts, also uses salt to store heat. The firm believes that thermal battery technology can complement other forms of energy storage, rather than replace them, to support the green transition. The benefit of using salt is that is widely available and easy to extract. Salt is good at storing heat and does not produce toxic by-products. It is also thought that salt tanks can be recharged thousands of times for a period of up to 40 years, around three times longer than other existing storage solutions. Dr Robert Barthorpe from Sheffield University believes “Molten salt is going to be an important part of the energy mix. It’s a fantastic technology, offering high temperatures at industrial scale.” However, salt is not the only substance being used to store heat. One company in California, Rondo, is using bricks to store energy, which it says costs around half the amount of green hydrogen or chemical batteries. The bricks can be heated to extremely high temperatures of up to 1,500oC and can store thermal energy for days with a loss of less than one percent per day. A 2022 report by McKinsey emphasised the advantages of thermal storage. It estimated that it would cost between $65 and $100 per megawatt hour to produce steam heat from hydrogen, around $45 to $55 for gas with carbon capture and storage technology, but just $15 to $25 for a heat pump using thermal storage. Thermal storage technology could therefore significantly reduce consumer energy bills when they become more widely available. In the U.K., the government has paid greater attention to the potential for thermal batteries in recent years, investing £9.25 million into a thermal battery trial by Sunamp in 2022. The company planned to use the funds to trial first-of-a-kind thermal battery technology in 100 homes across the country. Sunamp hopes its system will replace boilers powered by fossil fuels with a heat pump and thermal storage, which will provide both heating and hot water. The energy input will mainly come from offsite wind energy. Other companies in the U.K. are exploring the potential for compressed air and super-cooled liquid air energy storage. Meanwhile, the Norwegian firm EnergyNest is heating a specially formulated concrete and Lumenion, a German company, is storing heat energy up to 650oC in steel modules. This shows the significant potential of thermal energy storage. Greater investment in the sector will likely spur more innovations and lead to the wider global rollout of the technology in the coming years.