Geothermal energy

Date: 14 January 2013

District heating in Iceland
Situated on the Mid-Atlantic Ridge, Iceland is one of the most geothermally active areas in the world.  At a northern latitude that keeps summer temperatures moderate and winters cold by most standards, using geothermal energy for heating is a fitting solution. 

From humble beginnings, pioneering development of technology for harnessing geothermal energy over the past 70 years has made Iceland a global leader in geothermal energy and heat production.  Modern use of geothermal heating involves pumping hot water over great distances into a network of homes and businesses and back to the source.  The technology was not always so sophisticated.

One hundred years ago, organized use of geothermal energy in Iceland was just beginning.  In 1908, Stefan B. Jonsson began using hot water for space heating in his farm; soon after, other farmers began to independently create their own systems to heat their farms, and by 1930, at least 10 farmhouses in Southern Iceland were heated with geothermal energy. 

Alongside this private development, government began organizing public and private resources toward geothermal development and began drilling wells near Reykjavik with used equipment purchased from mining companies.   In November 1930 the first public building to be heated in Reykjavik was the elementary school Austurbaejarskoli.  The hot water used to heat the school came from Pvottalaugar and required water to be pumped to the school through a pipe 3 km long.

Enterprising Icelanders quickly built on this success and expansion of the project included connecting the heated water supply to the National Hospital and 60 private homes.  Bouyed by success, further drilling was ordered.  Over the next several decades, geothermal district heating became widespread, as a collection of local initiatives.  After the oil price increases of 1973 and 1974, the importance of large scale geothermal energy and heat production became increasingly clear to Iceland´s future.  The larger scale demands of energy production, along with advancements in drilling and equipment meant deeper wells, higher temperatures and more sophisticated technology.

Deeper wells provided higher levels of energy in the form of hotter water, but also supplied water with high levels of salinity and mineral content.  Modern equipment keeps the high-salinity water separate from the water used to transfer heat to homes and businesses.  Heat is transferred from the groundwater to the fresh water in three stages: Direct-contact heat exchangers heat water first, steam coming from exhaust turbines increases the temperature further and steam from high-pressure geothermally heated water provides the third stage of heat. 

Currently, well over 90% of homes in Iceland are heated by geothermal energy, the highest percentage in the world.  Most of the district heating in Iceland comes from three main geothermal power plants, producing over 800 MWth:

• Svartsengi combined heat and power plant (CHP)
• Nesjavellir CHP plant
• Hellisheidi CHP plant

In addition to contributing to Icelanders quality of life and economy, Geothermal District Heating has had a strong positive impact on Iceland´s image, both as a member of the global community and as a leader in green technology.

Geothermal District Heating provides an effective, inexpensive and environmentally responsible method of heating.  Geothermal engineering technology developed in Iceland by Mannvit is poised to lead the way to expanded use of this green and renewable energy source across the globe.

Source: Manvitt