Material Insights · Understanding the Material World

Sensible heat storage: Impact and additionality

Attacking the fuel burned for heat, a neglected emissions giant

What this tab covers The impact and additionality lens: what it displaces on the grid, who gains and who bears the burden along the supply chain, and what happens at end of life.

Thermal stores attack fuel burned for heat, a large and neglected slice of emissions. Additionality depends on the host: replacing oil in a town heating network is clear-cut; supplying steam to an oil field is not.

Grid decarbonisation versus fossil displacement

Favourable

These stores displace boilers burning gas, oil, coal or biomass, not power-station peakers. At Pornainen, the operator says the sand battery lets the network drop oil entirely, cut wood chip use by about 60% and cut heating emissions by nearly 70%, about 160 t CO2e a year. In the US, industrial fuel burning emitted 727 Mt CO2 in 2020, about a fifth of national CO2, and 84% of that fuel is burned for heat. Buildings themselves can store heat or cold: on a modelled summer day in a US office, pre-cooling the structure cut cooling costs by about 12% with heavy thermal mass and 5% with light mass, though total energy use rose by 12% to 18%. Rondo's first 100 MWh unit, however, makes steam for an oil producer, which cuts the emissions of extracting oil but also supports it.25172325

Pornainen, emissions cut about 160 t CO2e a year; nearly 70%2 US industrial fuel combustion, 2020 727 Mt CO2, about a fifth of US CO2; 84% burned for heat23 Office pre-cooling, heavy / light mass (one modelled day) cost about 12% / 5% lower; energy use 12-18% higher25 LDES Council estimate heat is about 45% of energy-related emissions, much of it addressable by thermal storage17

Just transition and local community impact

Favourable

Materials can be sourced locally and some come from waste, and building stores uses local civil trades: Pornainen involved about 40 subcontractors and over 100 workers. Manufacturing is spreading: Rondo has a 2.4 GWh a year line in South-East Asia with Siam Cement and says it plans 90 GWh (no date given), and Antora makes its units in San Jose, California, and raised USD 550 million in 2026 to expand (company data). There are no mining frontiers to manage.262028

Pornainen construction about 40 subcontractors, over 100 workers2 Rondo production capacity 2.4 GWh a year; 90 GWh planned (company plan, no date)6

Circular economy and end of life

Favourable

The media are inert and can be reused, crushed or landfilled with little harm, and several products start as waste: steel slag at Kraftblock, soapstone offcuts at Pornainen. Steel tanks, heaters and insulation are recyclable. No recycling statistics specific to thermal stores were found. Life-cycle studies find small footprints: storing solar power in molten salt added about 0.031 kg CO2e per kWh, about a quarter of a vanadium flow battery's (calculated), and concrete stores had lower impacts than molten salt because they need less material and equipment.472426

Recycled content, Kraftblock up to 85%7 Life-cycle GHG, molten salt vs vanadium flow (PV charging) 0.0306 vs 0.121 kg CO2e per kWh24

Sources

  1. World's largest Sand Battery now in operation (Pornainen press release, company data) Polar Night Energy, 2025
  2. New industrial Sand Battery filled with soapstone equal to 1,000 fireplaces Polar Night Energy, 2024
  3. Rondo Energy's 100 MWh solar-powered heat battery now operational (news report of company claims) ESS News, 2025
  4. Thermal storage company Rondo plans 90GWh ramp-up of heat battery gigafactory (news report of company plans) Energy-Storage.news, 2023
  5. Kraftblock thermal energy storage from upcycled industrial by-products (ACerS Bulletin feature) American Ceramic Society Bulletin, 2023
  6. Long Duration Energy Storage Council report spotlights opportunity for thermal energy storage (Net-Zero Heat report, press release) LDES Council, 2022
  7. Antora Energy announces U.S. thermal battery manufacturing facility Business Wire, 2023
  8. Industrial Thermal Batteries: Decarbonizing U.S. Industry While Supporting a High-Renewables Grid (Rissman) Energy Innovation, 2023
  9. Life cycle assessment of compressed air, vanadium redox flow battery, and molten salt systems for renewable energy storage (AlShafi and Bicer, Energy Reports 7, 7090-7105) DOAJ / Elsevier, 2021
  10. Large-scale simulation-based parametric analysis of an optimal precooling strategy for demand flexibility in a commercial office building (Lu, Adetola and Bhattacharya, Energy and Buildings) PNNL / OSTI, 2024
  11. Comparative life cycle assessment of thermal energy storage systems for solar power plants (Oró et al., Renewable Energy 44, 166-173) University of Lleida repository (Recercat), 2012
  12. Antora Energy closes US$550 million Series C to scale US thermal battery deployment (news report of company data) Energy-Storage.news, 2026