Wind power to efficient use
Nurmijärven Sähkö will start utilising carbon-dioxide-free, low-cost electricity in its district heating production at its district heating plants. An electric boiler will be built in connection with the Rajamäki heating plant, and a procurement decision has already been made for a similar electric boiler for the Kirkonkylä plant.
Finland’s electricity production has largely shifted to wind power, which in practice means carbon-dioxide-free, often particularly cheap electricity. Now Nurmijärven Sähkö is starting to take advantage of the situation with the help of electric boilers.
“A couple of years ago, a thesis examining electric boiler alternatives was written on the Kirkonkylä heating plant. We compared a heat storage combined with an electric boiler and mapped waste heat sources. In the end, we ended up with an electric boiler,” says Pekka Roivainen, District Heating Director at Nurmijärven Sähkö.
At the same time, Nurmijärven Sähkö was looking into joining the electricity balancing market. Electricity production or consumption must be adjusted all the time, as production must always correspond to consumption. An electric boiler is well suited for this purpose.
Towards heat produced with fully renewable energy
In accordance with its strategy, Nurmijärven Sähkö is gradually striving towards non-combustible district heating production, which can partly be implemented with electric boilers.
“At the moment, we produce district heating with 97 per cent renewable wood fuels. Our specific emissions are significantly lower than the average for other energy companies’ heating plants. With the help of electric boilers, we can launch a completely carbon-free product in the future,” Roivainen says.
Nurmijärven Sähkö is still investigating the possibility of utilising waste heat that could potentially be generated in industrial plants or data centres, for example. For the time being, waste heat is not yet used in district heating production in Nurmijärvi.
An electric boiler heats water with electric resistors
An electric boiler works like a giant kettle: it heats water when there is a lot of electricity available and its price is low. This happens especially in situations where wind power production is at its peak and electricity is cheap on the market. The water heated with an electric boiler is led to the district heating network and used as heat for residents and properties.
The use of electric boilers is becoming more common, as they enable flexible and cost-effective heat production. They can be used to take advantage of price fluctuations in the electricity market and reduce the use of fossil fuels and biomass in district heating.
Wind power produces a significant amount of electricity, which can now be utilised in new ways. For example, half of the 144 GWh of electrical energy sold by Nurmijärven Sähkö in 2024 came through Suomen Voima, i.e. in practice from wind or solar power plants.
The output of the Rajamäki electric boiler is three megawatts and its cost estimate is approximately EUR 1.5 million. The electric boiler will be placed in a container measuring approximately 12 m x 3.5 m x 3 m in connection with the Rajamäki heating plant. Below is a video of the installation of the boiler container. The electric boiler will be commissioned during the end of 2025.
Automation controls the electric boiler
The solid fuel boiler of the Rajamäki heating plant is large, so its efficiency is poor in the summer. An electric boiler can significantly improve the situation.
The use of an electric boiler depends on the cost of the solid fuel. When the cost of using an electric boiler is lower than the cost of using solid fuel, the automation starts the electric boiler according to the programming. The price of electricity on the market alone does not determine the start-up, as the costs depend on many other factors, such as the electricity balancing market.
