Energy supply in Iceland

Iceland is one of only a few countries that cover its electricity requirements by renewable forms of energy. In addition to power from hydroelectric power plants, electrical energy has been produced by geothermal power stations for a while now. One of these geothermal power stations was constructed in the Krafla-region in the north of Iceland. In 1974, the first trial boreholes were started and electrical energy has been produced since 1978.

Geology of the Krafla geothermal field

Iceland is part of the ocean floor wich has been forced up above sea level by special geological conditions. The "hot spot" located beneath Iceland has played a major role in this process, and one of the places it breakes forth is the Krafla geothermal field, where it is accessible for energy production. Nature's forces are still locked in the battle and their conflicts take various forms: Steam from seething hot springs, volcanic craters of all shapes and sizes, large and small and rough and smooth stretches of lava, the land split into fault blocks.

This area is a central volcano. Primeval forces tug the Earth's crust apart and split it with fissures that can be seen on the surface. Roughly 100 km long, this fissure zone runs almost due north to Öxarfjördur fjord and south to Mt Bláfjall. The land to the west and the east of the fissures is continuously spreading apart in its respective directions, by an average of 2 cm a year. Stóragjá chasm is a clear example of such tectonic plate drift. Some fissures have slipped to create a fault landscape; Mt. Dalfjall, for example, was formed in this way.

How is the electricity produced?

Drilling a borehole at a side as rich in energy as the Krafla geothermal field releases steam under enormous pressure, containing thermal energy. Steam pressure varies from one borehole to the next, depending upon how deep they have been drilled.

A steam generation plant harnesses thermal energy by using the steam to drive a turbine wheel, after all the moisture has been vaporized from it. Steam is piped to the turbine at different pressures: low-pressure steam is used to drive its larger wheels and high-pressure steam the smaller ones. The steam condenses as it supercools under the turbine, causing a drop in pressure and the resulting suction draws the steam down from above, increasing the rotary force of the wheel.

The turbine wheel drives a magnetized rotor inside the generator. Surounding the rotor is a copper coil in which an electrical current is induced by the motion of the magnet. This electrical current is then carried along high-voltage transmission lines to the transmission system.