Iceland is a world leader in the generation of geothermal energy, and of the six geothermal power plants in Iceland, Hellisheiði is the newest and largest. The plant has been operational since 2010, and is located on the Hengill volcano in the south-west of the Iceland.
To access the potential energy under the surface, wells are drilled thousands of metres into the ground, penetrating reservoirs of pressurised water. Heated by the Earth’s energy, this water can be more than 300C in temperature, and when released it boils up from the well, turning partly to steam on its way. At Hellisheiði, the steam is separated from the water to power some of the plant’s seven turbines, while the remaining water is further depressurised to create more steam, used to power other turbines. At its maximum output the station can produce 303MW of electricity, making it one of the three largest single geothermal power stations in the world.
What makes Hellisheiði particularly innovative is that, as well as electricity, it produces a hot water supply for the city of Reykjavik. Once the steam has been extracted, the remaining geothermal water is diverted to a heat exchanger, where it is used to heat up a supply of fresh, mains water. There is a 26km pipeline down to Reykjavik which transports hot water at around 80C. The natural incline of the mountain means the water travels naturally, and the pipe is so well insulated that it arrives in the city having only lost a degree or so in temperature.
The station is open to the public, and although state of the art, the design of the m station resembles art in itself. There are guided tours, educational installations and even a souvenir shop. “you can look over the turbine hall and hear the roar of the turbines,” says Karlsdóttir, “nothing is burning, there’s no mess, and we have walking paths all over the mountain.” According to Karlsdóttir, a major proportion of the plant’s thousands of annual visitors are British schoolchildren, witnessing a vision of clean, sustainable power dramatically different from the murky, fossilised industry they are used to.
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Photograph: Pedro Alvarez for the Observer and the guardian.com