23.6.2026
Article originally published in 5.9.2024
A 40 MW electrode boiler has been recommissioned in Lappeenranta, Finland, to provide emission-free heat to the district heating network. The electric boiler supports the flexibility of the energy system and enables renewable electricity to be utilized for heat production.
The commissioning of the electric boiler is part of Lappeenranta Energy’s long-term efforts toward carbon-neutral energy production.
The Lappeenranta Energy Group develops environmentally friendly and cost-effective energy and water utility services in the South Karelia region of Finland. Its subsidiary, Lappeenrannan Lämpövoima Ltd., which is responsible for energy and water production, has spent the past two decades investing in solutions that reduce the reliance of heat generation on combustion.
The company’s goal is to become a carbon-neutral energy and water utility by 2026.
The Mertaniemi 1 gas turbine power plant, located on the shores of Lake Saimaa, was completed in Lappeenranta in 1975. In 1982, a 40 MW electrode boiler manufactured by Sulzer (now VAPEC) was installed at the site.
The electrode boiler operated primarily during nighttime hours, while a gas turbine combined-cycle power plant was used during the day. This arrangement continued for approximately ten years, after which the use of the electrode boiler gradually declined and became only occasional. By the 1990s, the boiler was no longer operated at all. It was preserved using protective chemicals and remained largely unused thereafter.
Periodic test runs and electrical system checks were conducted over the years. The automation system was upgraded during the modernization of the Mertaniemi 1 gas and oil boilers. Regulatory inspections were also carried out as required, eventually revealing that certain safety systems no longer complied with current regulations. As a result, dismantling the boiler was considered, and justifying its continued preservation became increasingly challenging.
The boiler was ultimately never dismantled. Instead, it remained out of service until 2021, when it was brought back into operation in connection with the commissioning of the Olkiluoto 3 nuclear power plant. During this period, the boiler served as a system protection resource for Olkiluoto. In spring 2023, it underwent an extended outage during which additional protective automation systems were installed.
Before the final recommissioning, a comprehensive assessment was conducted to determine whether a new electric boiler should be purchased or the existing one modernized. Inspections showed that the existing boiler and associated equipment remained in good condition.
The recommissioning project included:
The 40-year-old boiler is now back in operation, supplying heat to the district heating network in the Lappeenranta region. The boiler has a maximum output of 40 MW. Its output is regulated using control rods, which adjust the length of the electrical current path between the electrodes.
An electrode boiler is an electric boiler that generates heat without combustion. Heat is produced when an electric current passes through water between electrodes. The boiler’s output is controlled by adjusting control rods, which alter the current path between the electrodes. This allows for rapid and precise power regulation.
Key advantages of electrode boilers include:
These characteristics make electric boilers particularly well suited for balancing district heating networks.
VAPEC (formerly Sulzer) is a Swiss boiler manufacturer. VAPEC electrode boilers provide a reliable and emission-free method of producing heat or steam. They are suitable for efficient steam and hot water generation in applications such as district heating and industrial processes.
Their long service life and reliability are based on high manufacturing quality, technical innovation, and annual inspections. As a result, they offer exceptional operational reliability, long maintenance intervals, and low maintenance costs. The compact design, excellent control characteristics, and high efficiency of VAPEC electrode boilers make them ideal for a wide range of energy production and industrial applications.
What is an electrode boiler?
An electrode boiler is an electric boiler that produces heat by passing an electric current through water without any combustion process.
Is an electric boiler emission-free?
Yes. An electric boiler produces no direct emissions, provided that the electricity used is generated from renewable energy sources.
What are electrode boilers used for?
They are primarily used in district heating systems and industrial applications for producing heat and steam.
Why are electric boilers becoming more common?
They enable the use of renewable electricity, can participate in electricity balancing and reserve markets, reduce emissions, and support the flexibility of modern energy systems.