In a significant step towards sustainable energy storage, global composites manufacturer Exel Composites has joined forces with geothermal energy company QHeat to support long-term heat storage at the Lounavoima waste incineration plant in Salo, Finland. The collaboration has resulted in the development of custom glass fibre reinforced polymer (GFRP) tubes capable of storing up to 14 GWh of thermal energy in bedrock two kilometres underground.
Previously, the plant faced a seasonal challenge: excess summer heat was released into the air, while cold winters necessitated the use of oil burners to meet demand, increasing emissions. The new system allows stored heat to be reused in colder months, saving energy equivalent to heating 700 detached homes annually.
“This project underscores the potential of electrification in heating,” said Erika Salmenvaara, CEO at QHeat. “60 per cent of all EU heat production comes from fossil fuels and the remaining 40 per cent is still mostly combustion. In the context that half of global energy use is for heating, we see the environmental gains that electrification of heating can provide.”
While acknowledging challenges with electrical infrastructure, Salmenvaara highlighted the efficiency of heat pumps. “Heat pumps deliver up to 600 per cent more energy efficiency than using electricity directly,” she noted.
Exel Composites and QHeat worked closely to tailor the GFRP tubes to the demanding underground conditions, focusing on thermal insulation, mechanical strength, and ease of assembly. “Heat preservation combined with the right mechanical performance was the biggest criterion,” said Tiina Uotila, technical sales manager at Exel Composites.
The partners also developed a sustainable end-of-life plan for the tubes. “Instead of going to landfill, these pipes will be co-processed into cement,” Uotila explained.
Salmenvaara praised the collaboration: “I was impressed that Exel Composites’ head designer came on site with us in Salo… I understood its expertise, its design capabilities and the quality of its products.”
This project could shape the future of energy storage and heating solutions, particularly in regions with significant seasonal temperature variations. By demonstrating the feasibility of large-scale, long-term heat storage, it may encourage further investment in similar technologies, reducing reliance on fossil fuels and improving energy efficiency. The focus on sustainable end-of-life solutions also sets a precedent for responsible material management in the energy sector.