Geothermal energy use in Sweden is dominated by shallow and low-temperature resources. The majority of geothermal installations are based on the ground source heat pump (GSHP) technology used for space and domestic hot water heating, mainly in residential areas. Around a fifth of all buildings in the country use GSHP technology, making Sweden a world leader in the shallow geothermal application. It is reported that overall, more than 350,000 small heat pumps have been installed in residential and commercial buildings, with approximately 27,000 units installed annually, providing an estimated 10% of overall heat demand. The market for large-scale geothermal energy systems has been increasingly expanding over the recent years. The shallow geothermal energy systems provide approximately 23 TWh of heating and cooling in Sweden, of which around 17.5 TWh is renewable heat from the ground and approximately 1.1 TWh is a free-cooling from the ground. The total installed heating and cooling capacity is approximately 6.8 GW.
Fig. 1. Shallow geothermal drilling for borehole heat exchanger at a Swedish household (source: news.cision.com)
The low-temperature shallow geothermal technology became popular in Sweden as a result of the oil crisis in the 1970s and 1980s and the following nationwide efforts to achieve independence from fossil fuel import and has been growing in acceptance ever since. The 1979 development of polybutylene pipe greatly increased the heat pump’s economic viability. A number of systems used underground thermal energy storage (UTES), either as aquifer thermal energy storage (ATES) or borehole thermal energy storage (BTES). The former was implemented in the mid-1980s and currently, there are approximately 100 plants using this system, mainly large scale with an average capacity of 2.5 MWt.
Fig. 2. Left: Aquifer Thermal Energy Storage (ATES); Right: Borehole Thermal Energy Storage (BTES) (source: Geotec)
Swedish geology is characterized by the massive Baltic shield and its diverse crystalline eruptive and metamorphic rocks. In the southern parts, sedimentary rock formations of significant thickness are located, spot-wise containing porous sandstones at considerable depths and with good hydraulic properties. The geothermal gradient reaches 28-30°C/km in south Sweden and 15-16 o C/km within the Baltic shield regions. The crystalline rocks consist mainly of granites and gneisses, which are stable during drilling operations. Sweden’s utilization of deep geothermal heat is on a rather restricted scale, mainly due to the lack of favorable geological conditions. However, Lund, a city in the south of Sweden, has two heat pumps amounting to about 47 MWt, which provide base-load heat to a district heating network. The plant was connected to the network in 1984 and started heat production in 1985.
This concludes our #GeothermalCountryOverview on Sweden. We encourage you to read our blog and check back regularly as we post weekly on a wide variety of #geothermalfactsandstats. You can also find our posts on any of the major social media platforms.
Author: Michal Kruszewski