Finland’s largest electric boiler and thermal energy storage combination launched in Vaasa

New electric boilers with a capacity of 120 megawatts and an extended thermal energy storage (TES) facility have just been put into operation in Vaskiluoto, Vaasa. This brings the total capacity of the electric boilers at the Vaasan Voima plant to 160 MW, which places the boilers in Vaasa among the most powerful in Finland in terms of capacity. Together with the extended TES facility, this solution will bring much-needed flexibility and cost-efficiency to the system, while reducing emissions from district heat production.

The new electric boilers and the extension of the thermal energy storage facility were commissioned in October in Vaskiluoto, Vaasa. The new heat generation solutions will perfectly support EPV’s strategy and promise of emission-free and flexible energy generation and consumption. Together, the electric boilers and TES facility will contribute to the clean heat production system of the future and will be an essential part of the company’s peak load reserve. In addition to demand response, these new investments will reduce CO2 emissions from production.

Vaasan Voima, a wholly owned subsidiary of EPV, already had one 40 MW electric boiler in use in Vaskiluoto, as well as a thermal energy storage facility of roughly 8 GWh. This year, the company has installed and commissioned 120 MW of additional electric boiler capacity as part of its heat production system. At the same time, the technology of the existing TES facility has been modified, increasing its storage capacity to 11 GWh.

“The solutions in Vaskiluoto represent sector coupling at its best and will take us rapidly towards zero-emission heat production. A clean heat production system is a long-term, emission-free solution that will secure heat supplies for the regions it serves and also support the needs of the new weather-dependent electricity system. The energy system of the future will need more and more flexibility of production and energy storage facilities,” says Vaasan Voima’s CEO Janne Österback.

With the energy transition, the share of renewable energy in the grid is increasing dramatically, often leading to situations where there is either too much or too little electricity available.

“With the heat the electric boilers produce, and using the thermal energy storage facility, we can optimise the heat and electricity production of the Vaasa power plant better than ever. Additionally, the electric boilers allow the power plant longer shutdown periods. Together with thermal energy storage optimisation, this creates significant benefits and improves the usability of the power plant system’s heat generation. By using electric boilers, we can help to make use of electricity in situations where there is a great deal of renewable and weather-dependent energy in the system. This is a big step towards emission-free heat production,” Österback says.

Correspondingly, the energy produced by the electric boilers will reduce fuel consumption. As the need for fuel decreases, the company can reduce the area in which bioenergy is sourced, which will result in fewer transport kilometres. In addition, the most challenging fuel fractions in the available fuel range can be eliminated. This will free up bioenergy fractions for further processing, to a higher degree of refinement, and promote sustainable development also in other sectors. By replacing combustion with electric boilers, climate emissions in electricity generation are reduced, thus contributing to achieving Finland’s and the EU’s climate targets.

“This autumn, for example, there have been periods when the entire Vaasa region has been heated using only electric boilers and the TES facility.”

The underground caverns currently used for thermal energy storage are, in principle, everlasting. The technology built on site can be easily maintained and also upgraded and adapted for new uses. This makes the facility a great tool for future energy generation. Thanks to the TES facility, Vaasan Voima will be able to meet the response needs of the electricity market regardless of heat demand.

The electric boiler and energy storage solutions built at the Vaskiluoto power plant site in Vaasa are extremely significant in scale in Finland.

“With three electric boilers and a large thermal energy storage facility, we have an excellent heat production package at Vaskiluoto. This is a great example of making the most of our own power plant site. Vaskiluoto will continue to be a key operating site for Vaasan Voima,” Österback concludes.

Facts about the Vaskiluoto electric boilers:

  • one of the boilers has a capacity of 40 MW and two others 60 MW each, totalling 160 MW
  • Electric boiler measurements: height 6.5 metres and cylinder diameter 3 metres
  • Maximum temperature of the supply water 120°C
  • Electric boilers are very quick to adjust and easy to use
  • Control capability of boiler capacity 0–100% in 50 seconds

Facts about the Vaskiluoto caverns:

Watch the video on how The Vaskiluoto thermal energy storage facility works

The Vaskiluoto thermal energy storage facility is one of the largest energy reserves in use in Finland. The TES facility has been in operation since 2020. The facility can be used into the future regardless of the production mode, making it an excellent example of sector coupling.

  • The thermal storage caverns have a capacity of 150,000 m³ and 60,000 m³ (210,000 m3 in total)
  • The TES facility has a charge and discharge capacity of 110 MW, which is enough for about 4–20 days depending on the discharge needs
  • The TES facility’s capacity is 11 GWh
  • Location: 30 metres below the ground in Vaskiluoto, Vaasa
  • Size: height 22 and 30 metres, length 178 metres and 313 metres
  • Built in the 1970s for oil storage
  • The caverns were drained of oil and cleaned in the late 1990s

For more information contact: Janne Österback, Managing Director, Vaasan Voima Oy, tel. +358 10 5055 235, janne.osterback(at)