Geothermal in Sweden

Sweden’s utilisation of deep geothermal heat is on a very limited scale. however, Lund, in the far south of Sweden, has two heat pumps totaling about 47 MWt  providing base-load heat to a district heating network. The plant was connected to the network in 1984 and started heat production in 1985.

There are many small ground-source heat pumps installed in the country. It is reported that  more than 350 000 small heat pumps have been installed in residential and official buildings, providing an estimated 10% of heat demand.

The Swedish Deep Drilling Program began in 2007. The purpose of the Program is to ‘study fundamental problems of the dynamic Earth system, its natural history and evolution’. In 2009 a grant was awarded for a mobile truck-mounted drillrig that is capable of reaching a depth of 2 500 m. Supported by the International Scientific Drilling Program, drilling is planned to begin in 2011.

The majority of the heat pumps are small and typically used in single houses. There are currently around 230,000 installations with about 25,000 units installed annually. Bedrock-soil-water is the most common source for heat pumps using geothermal energy with about 12 TWh of energy extracts or about 15% of the national heat demand covered. A number of systems used underground thermal energy storage UTES), either as aquifer thermal energy storage (ATES) orborehole thermal energy storage (BTES). The former was implemented in the mid 1980s and current there are approximately 100 plants using this system, mainly large scale with average capacity of 2.5 MWt.

Water wells are used and serve a dual function, both as production and injections wells, with the flow direction being reversed from summer to winter. The BTES systems consist of a number of closed spaced boreholes, normally 50 to 200 m deep. These are equipped with borehole heat exchanger, with the holes filled with ground water and not grouted. It has been shown that water filled boreholes are more efficient than grouted ones. These are typically used for combined heat and cooling of commercial and institutional buildings. The reported total for UTES is 90 MWt and 504 TJ/yr for heatings and 90 MWt and 612 TJ/yr for cooling.