Lappeenranta replaces fossil fuels with a new kind of thermal battery

News 2022-08-03 at 17:57

The City of Lappeenranta is testing a new type of energy storage system at the Mustola heating plant, where energy is stored directly as heat. The equipment is charged with electricity, after which the thermal energy is released to the district heating network in Mustola. The equipment helps to mitigate climate change by replacing fossil fuels with a thermal battery.

The thermal battery in Mustola is a pilot to test whether it is profitable to store electricity directly as heat. “The idea of the thermal battery was based on solar-powered cookers which were planned for use in Africa, for example. The idea of the cookers never really took off, but the same method of operation was used to create the thermal battery is now in use,” says Aleksi Porkola from Elstor Oy.

The construction of the thermal battery was started at the end of 2019, and it was commissioned in June 2021. In 2021–2023, the use and functionality of the thermal battery will be tested. The thermal battery is built and operated by Lappeenranta-based startup Elstor Oy, which was founded on the basis of the project. The pilot will be implemented in cooperation with Lappeenrannan Energia Oy.

Thermal battery meets the challenge of electricity storage

The development of the thermal battery meets the challenges of electricity storage and production. Renewable electricity production is hampered and made more uncertain by varying weather conditions, such as wind and sun, meaning new methods are needed for storing and utilising energy. Solutions such as the thermal battery are important as they enable more efficient use of energy in varying conditions of production.

“Society becoming electrified, which creates pressure for new ways of producing heat and, at the same time, reducing emissions. The developed thermal battery meets this need,” says Porkola. “As much as one third of Finland's total energy consumption is used as heat, so it is most profitable to store electricity directly as heat. It is also unwise to start storing electricity because the batteries needed for it are often expensive, short in life and problematic in terms of raw materials.”

“The heating sector plays a major role in climate change, and there have not been good carbon-neutral solutions in the production of industrial steam, for example. In this case, a new type of thermal battery will play a significant role, as the device can reduce carbon dioxide by up to hundreds of tonnes each year,” says Porkola.

The thermal battery in Mustola is also significant in terms of its cost-effectiveness. Especially if the electricity tax class of district heating companies changes as planned, the thermal battery in Mustola brings exceptionally significant financial savings.

COVID-19 threw a spanner in the works, but only for a moment

The coronavirus pandemic delayed the completion of the thermal battery by stretching the delivery times of the components. However, the battery was completed and put into service without major changes to the original plan.

The development of the thermal battery was a pilot project, which always brings its own challenges. “Pilot experiments are important because they will then provide lessons for the next stages of work,” says Porkola. “The lessons learned from the pilot phase could be used in the manufacture of the second thermal battery, which has then been manufactured and commissioned very neatly.”

The second version of the thermal battery differs from the first in that it produces steam instead of heat. The battery is being used by a Lappeenranta industrial company. “The commissioning has gone surprisingly smoothly, and the customer has been pleased to have been able to use the device,” Porkola says.

A third version of the battery is already being made. “There are many expectations and hopes associated with the thermal battery, because steam in industry is mainly produced with fossil fuels, and no substitute method has yet been found for them,” Porkola says.

The global market as an opportunity

The thermal battery has a lot of potential both in Finland and internationally. In Finland, the invention is important especially for heating, but in other parts of the world, the possibility of producing steam in particular is significant.

“Finland is exceptional because there is such a great need for heat production here. In other parts of the world, however, the device could be used to produce industrial steam, for example, so that the device is charged with solar power during the day and released as steam during the night,” Porkola says.

“The goal at the moment is to invest in developing the device into a mass-produced device here in Finland. After that, it will be possible to tailor it for the international market,” says Porkola.

Learn more

Further information

  • product development engineer, Aleksi Porkola, Elstor Oy, tel. +358 (0)44 095 1124,
  • environmental director Ilkka Räsänen, City of Lappeenranta, tel. +358 (0)400 815 284,
  • climate coordinator Petri Kero, City of Lappeenranta, tel. +358 (0)40 6530 508,

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