Karlskrona municipality had an ambicious objective to meet: the heating systems of all the municipal real estates would be fossil fuel free by 2016.
The Ringöhome is a nursing home with four different buildings that offers accommodation. It also has a kitchen and a pool. The building area is 2.130 m2 BTA (gross area). In order to meet their target, the municipal housing company Karlskronahem implemented several projects to replace oil heating with other energy sources. In many cases, geothermal heating was used, but in the case of Ringöhemmet, the company used the proximity to the sea instead of having to dril in the ground. Therefore, a marine heating system was installed with 3.5 km of tubes in the sea. The tubes contain refrigerants in the form of ethanol. When there is a need for heat or hot water, heat from the sea water is exchanged via one to two heat pumps.
The tubes are located 2-3 meters deep at the seabed and are kept in place with concrete weights. The Lyckeby river has its outlet just upstream the Ringöhome, it brings new water that rinses over the plant throughout the year. It also contributes to the rare occurrence of ice on the bay.
The experience from the plant, shows a higher heat efficiency compared to the corresponding geothermal installations.

Resources needed

Economically, the cost for this kind of installation is about the same as a geothermal installation. The cost saved by not drilling is used to finance the diving works.
The total amount invested for this project was 220.000€.

Evidence of success

Energy savings reach 400 MWh /per year.
Carbon dioxide emissions have decreased 62.100 kg per year.
Nevertheless, a new building with accommodation has been built in the area since the seawater plant was introduced. Energy efficiency measures have been implemented by switching to more energy efficient lighting and replacement of a more efficient ventilation unit.
The amount of energy consumed may vary slightly over the years, depending on how much the pool is used.

Difficulties encountered

The main objection came from the Swedish Maritime Administration, it was dubious wether the permission to build the facility would be granted. But when the property was bought, an area of 150 m from the shoreline was included in the sea, so due to the property rights they got the license to build.

Potential for learning or transfer

The seawater plant has worked very well and has a greater thermal efficiency than the corresponding district geothermal heating systems in Karlskronahem. If Karlskronahem had had several beachproperties areas, they would have invested in more marine heating plants. This technology is highly recommended.
The potential for transfer is high, as long as there is a water resource near, technology can be used in both seas and lakes.

Please login to see the expert opinion of this good practice.

Main institution
Energy Agency Southeast Sweden
Sydsverige, Sweden (Sverige)
Start Date
September 2010
End Date
January 2011


RACHEL CLAIRE TULLY Please login to contact the author.