Can heat stores in buildings help balance our energy systems so that we can save excess green energy until it is needed? A new demonstration project in Lolland wants to find out.

Lolland is known as a green energy island, where three times as much power is produced as is consumed on the island – in fact, more than eight times as much power is generated than is used, if you count the offshore wind turbines that surround Lolland. But sustainable energy production also presents a challenge: How do we use green energy in a sensible way when we have plenty of it? And can energy be stored for cloudy, windless days?

These are some of the questions we are hoping to answer in a new demonstration project taking place in Lolland. Here we will look investigate involving citizens and companies’ own buildings in the work of balancing the electricity grid and using green power when it is available.

More specifically, this will be done by connecting an individual heat store (based on salt or water) to a heat pump. This makes it possible to use electricity from renewable energy sources to heat the heat store and then store that heat until it is needed, so that the heat pump’s consumption can be lowered during the periods when green power is more scarce.

If the test is successful, this solution will benefit both consumers and our climate. At the same time, this solution would help to balance the electricity grid, which is increasingly needed as more and more of our electricity is derived from renewable energy sources, which are reliant on how much the sun shines and the wind blows.

The test will include 10-12 test buildings (including private households, public buildings and those used by businesses). As part of the solution, a digital control system will also be installed, enabling the project partner DTU to control the heat pumps as needed. The test results will be used to assess the impact of flexible energy use in buildings and potential business models. The demonstration project will also help to present viable alternatives to the almost 2,000 oil furnaces that are still in operation in Lolland.

One of the companies involved in the project is Lolland Airport. They have decided to replace an almost 45-year-old oil furnace with an air-to-water heat pump that is connected to a water-based heat store. This allows you to save what corresponds to 24-hour heat consumption. At the same time, the heat pump provides both a financial saving of 14,000 DKK annually and offers a more reliable solution than the old oil burner.

If you live in Lolland and would like to participate in the project, you can read more about how to apply here:

Participate in testing future heat pump solutions (in Danish)

You can see more about the project in here (in Danish):


Project supported by:






The project is part of Future – a project under Interreg ØKS

The solution will be tested during the warm season 2019-2020. Results are expected to be presented at the end of 2020 or in January 2021.

Project partners

SEAS-NVE, REFA Energi, DTU Department of Civil Engineering, HeatPlan, Neogrid Technologies, Kalundborg Kommune, Renewable Energy Lolland (Gate 21)