TheStorage raises €3.6M seed to scale sand-based thermal energy storage

Finnish cleantech company TheStorage has raised €3.6 million in seed funding to commercialise its sand-based thermal energy storage system for industrial heat. The round was led by Voima Ventures, with participation from existing backers Superhero Capital and 2C Ventures and new investor Momentum Partners. It brings the Tampere-based company’s total funding to €5.8 million.

Heat is the hard part of decarbonisation

Industrial heat accounts for roughly a fifth of global energy consumption, and about 80% of it is still produced by burning fossil fuels. Unlike electricity, it has no easy substitute: a brewery, a paper mill or a chemicals plant needs steam at a specific temperature, on demand, whatever the wind is doing. That mismatch — cheap renewable electricity that arrives when it arrives, against processes that need heat continuously — is the gap TheStorage is built for.

Sand in motion

TheStorage’s approach is what the company calls sand-in-motion. Two insulated silos sit either side of an electric heater: cool sand is drawn from the cold silo, heated with renewable electricity when power is cheap, and banked in the hot silo. When the plant needs heat, the sand is circulated through an external heat exchanger and discharged as saturated steam, pressurised hot water or thermal oil.

Pilot systems run up to 800°C, with later designs targeting above 1,000°C. Systems scale from 20 to 500 MWh of storage, with charging power of 1 to 20 MW depending on the site. Moving the sand rather than storing it statically is the technical bet: the company claims up to tenfold higher heat transfer efficiency than static storage, and headline savings of up to 70% on energy costs and up to 90% on emissions versus fossil-fired heat.

Because charging can be timed to the electricity market, the storage also lets industrial operators buy power when it is cheapest and participate in reserve markets — a second revenue line on top of the fuel savings, and useful flexibility for the grid.

Already brewing

The technology is not theoretical. Since February 2026, a pilot installation has been running at Nokian Panimo, Finland’s second-largest craft brewery, producing fossil-free steam for the brewing process. Target sectors beyond food and beverage include textiles, pharmaceuticals, pulp and paper, cement, non-ferrous metals, chemicals and plastics.

What the money is for

The seed capital funds commercial expansion, hiring and the company’s first full-scale industrial plant.

“The new funding gives us real momentum in commercialising our technology. Interest in thermal energy storage is growing enormously across industry,” said Timo Siukkola, CEO and co-founder. “Now there is no reason for industry to keep using fossil fuels.” The company aims to double its team by the end of 2026.

“TheStorage operates at the centre of two major transitions — the electrification of industry and the shift to renewable energy,” said Pontus Stråhlman, Partner at Voima Ventures. “Exactly the kind of deep tech opportunity we look for.”

The company and the field

TheStorage was founded in 2023 in Tampere by Olli Hannula, Timo Siukkola, Heikki Hannula and Esko Kulju. Ville Pentti joined recently as Head of Business Development from Rondo Energy.

Thermal storage is a crowded field with a clear Nordic accent. Finland’s own Polar Night Energy put the first commercial “sand battery” into a district heating network, while California’s Rondo Energy and Antora Energy use brick and carbon blocks respectively. TheStorage’s differentiation is the moving-sand architecture and a deliberate focus on steam for process industries rather than district heat.

Round at a glance

• Company: TheStorage (Tampere, Finland, founded 2023)
• Round: €3.6M seed, announced 23 April 2026
• Lead: Voima Ventures
• Participants: Superhero Capital, 2C Ventures, Momentum Partners
• Total raised: €5.8M
• Use of funds: commercialisation, hiring, first full-scale plant