Geothermal Temperature Fields

We categorize geothermal areas in Iceland as either low temperature fields or high temperature fields.

Low temperature fields have water at a depth of 1km between 30-150°C (86-302°F). From these areas, hot water can be directly sourced for things like space heating, snow melting, agriculture, swimming pools, and hot tubs.

Low temperature fields are much more common than high temperature fields, and are typically found in areas with older bedrock.

High temperature fields have water at this same depth that is 200°C (392°F) or higher. High temperature fields can be used to produce hot water for the same purposes as low temperature fields, but they can also be used to produce electricity.

When hot water is sourced from high temperature fields, it cannot be used directly for the same purposes as hot water from low temperature fields because it has a much higher mineral content.

The Blue Lagoon is a perfect example of the type of water that comes from a high temperature field. The water in the lagoon comes from a nearby geothermal power plant and is especially rich in silica.

Silica and other minerals found in the water from high-temperature fields will cause scaling, or build-up, in pipe systems, so hot water from high temperature fields is instead used in a heat exchange process to heat up fresh cold groundwater that is brought in from another location.

The heated fresh water is then used for all the same purposes as water sourced directly from low temperature fields.

For electricity production, all geothermal power plants in Iceland are located within high temperature fields, because you need the higher temperatures to produce electricity.

High temperature fields are typically found closer to active volcanic areas and tectonic plate activity. Iceland is also situated above a hot spot, and the combination of tectonic plate activity and this hot spot causes a significant amount of geothermal activity on the island.

The saying we use in the exhibition is if the ground is older, it’s colder, which corresponds with the temperature of the water in the ground as well.