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Renewable energy sources in Sweden

Biofuels

The most important domestic renewable source of energy is biofuels, i.e. fuels from the plant kingdom. These are mainly obtained from forest or farmland, although organic wastes from households and industry also make up an important share. In their various forms, biofuels can be used to produce electricity and heat, or as vehicle fuels.

To achieve an expansion of energy forestry, account has to be taken of the chemical and physical properties of soils, availability of water and nutrients, ground conditions and accessibility. And if more energy crops are to be grown on farmland, greater care needs to be taken to prevent contamination of the soil and protect groundwater.

Electricity production and other energy conversion processes already generate around a million tonnes of ashes in Sweden every year. These ashes have to be put to use or disposed of with adequate long-term environmental safeguards. They can, for example, be recycled as aggregate or fill, or in building materials. Another alternative is to return the nutrients they contain to forests.

SGU’s maps and databases of Quaternary deposits and soil geochemistry contain valuable information of relevance to an intensification of production on forest and arable land.

Geothermal energy

Geothermal energy is heat that is obtained from the Earth’s interior, deriving from the radioactive decay of certain heavier elements.

In the bedrock beneath Sweden, the temperature rises by 10–30°C for every 1 km increase in depth (the ‘geothermal gradient’). In volcanically active regions, the temperature increase can be much greater than that. In Sweden, the best potential for geothermal energy is considered to exist in areas where there are large bodies of groundwater at considerable depths (2–3 km), i.e. areas with thick layers of sedimentary bedrock or fault zones such as the Lake Vättern graben. Areas where meteorites have given rise to fractured bedrock at great depths are also judged to be of interest, including the Siljan Ring, the Dellen lakes and Björkö on Lake Mälaren.

Sweden’s largest commercial geothermal plant at present is in Lund. Drawing water at 20°C from sedimentary strata at a depth of some 700 m, the plant meets 30 per cent of the city’s district heating needs (i.e. 250 GWh). The heat contained in the water is heat-exchanged to achieve the required temperature.

Geophysical information, in this case gravity and magnetic maps, can be used to identify areas with potential for geothermal energy.

Ground source heating

Another way of obtaining heat from the Earth’s crust is to use the energy in the portions of it closer to the surface. While it is not as warm here as at greater depths, it is perfectly possible to extract the heat that is present, for example using heat pumps. The temperature in the layers of soil and rock from which the heat is taken is usually roughly the same as the annual mean air temperature.

There are now over 300 000 ground source heat pumps in Sweden, mainly serving individual houses. They have the advantage of enabling a house to be heated using less electricity than if the electricity were to be used directly. The rock or soil normally delivers twice as much energy as needs to be supplied in the form of electricity. Gradually, the coefficient of performance (heat output per unit of electricity) tends to decline, partly because insufficient energy is being transferred through the rock to the borehole, resulting in a fall in temperature in the hole and its immediate vicinity. In Sweden, a total of around 5 TWh of energy is extracted from rock and soil using this technology every year.

Most local authorities require a minimum distance of 20 m between heat pump boreholes. Other factors also have to be taken into account when constructing such systems, and installations have to be notified to the local authority.

SGU provides training for well drillers, leading to certification. It has also drawn up standards for the construction of wells and boreholes for heat pump and water supply purposes. Information on well/borehole depths etc. can be found in SGU’s Wells Archive.

Wind energy

Wind energy currently accounts for only a small share (less than 1 TWh) of the electricity produced in Sweden, but the sector is growing rapidly. For environmental reasons, development of this energy source is increasingly shifting towards large offshore wind farms. A number of shallow waters and offshore banks within Sweden’s territorial sea and exclusive economic zone are of interest for the establishment of such installations.

There is consequently a need for information on the marine geology of these areas – to guide decisions on the siting of wind farms and the types of foundations they require, but also as a basis for assessing how marine habitats could be affected.

Marine geological information is also important in conjunction with other types of marine construction, and when gas pipelines or cables (for electricity, telecommunications etc.) are to be laid on the sea floor. Among other things, it can tell developers where erosion, transport and deposition of sediments occur.

Fuel peat

In an energy context, peat is primarily used in the industrial generation of heat and power. Sweden has one of the highest proportions of peatlands in the world, with peat covering some 15 per cent of its surface. Peat for use as a fuel is currently extracted from around 12 000 ha of the country’s roughly 6.4 million ha of peatlands.

At SGU, peat is classed as a slowly renewable biofuel. Peat for energy purposes falls within the scope of the emissions trading scheme, but when used to generate electricity it qualifies for renewable certificates, which are awarded for electricity produced by renewable technologies. A certain proportion of the electricity consumed has to be supplied from sources holding such certificates.

In Sweden, extraction of fuel peat requires a concession. The main legislation that applies is the Act and Ordinance concerning Certain Peat Deposits, along with several chapters of the Environmental Code. Concessions are issued by county administrative boards, which are required to consult SGU on applications received. SGU primarily assesses whether the peat in the deposit is of a suitable quality for fuel production and whether the project is appropriate from a wider public interest point of view.

Detailed data from earlier surveys of peatlands are available in a special Peat Archive at SGU. Outline information on wetland types and their distribution and extent can be found in our Quaternary geology databases and in older map-sheet descriptions.

The energy content of the country’s peat resources (on a dry matter basis) is estimated at around 57,000 TWh. Only a small proportion of this gross resource is recoverable, however, once technical, economic and conservation factors are taken into account.

SGU’s Quaternary geology data provide a picture of the distribution of peat in Sweden. In addition, our Peat Archive includes reports, maps, documents and publications from various agencies and institutions, covering virtually the whole of the 20th century.

Hydroelectric power

Sweden’s hydroelectric resources are generally considered to be fully developed. However, questions of dam safety, improvements in efficiency, and the development of ‘green’, small-scale hydro will continue to arise. In the longer term, as a result of increased and more intense precipitation, new issues relating to erosion and flooding may need to be addressed. Information on Quaternary geology is used to assess erosion risks.



Geological Survey of Sweden, Box 670, 751 28 Uppsala, tel: +46 18 17 90 00, fax: +46 17 92 10, e-mail: sgu@sgu.se