Today we visited Hellisheiði Power Station, which is the largest geothermal power plant in Iceland, and is the 8th largest one in the world. It uses boreholes dug deep into the ground to capture geothermal fluid, which is then brought up to the surface and used to generate electricity in a double flash cycle. That means that steam is extracted twice: First, some of the water is already steam when it’s brought to the surface, so that steam gets extracted. Then, the hot water is subjected to a drop in pressure, which turns more of it to steam, which is extracted the second time. The flashers below collect the steam and separate it from the water. The geothermal fluid is then used to heat water that goes to the cities and towns before it’s reinjected into the ground.
Hellisheiði is unique because aside from generating less carbon than a conventional power plant, it also helps to sequester carbon underground. Hellisheiði is partnered with ORCA, a facility that removes up to 4,000 tons of CO₂ per year from the atmosphere. After capturing the gas, ORCA adds it to the power plant’s wastewater, which is then injected into the ground, where it forms calcium carbonate deposits in the basalt bedrock. This was really unique to visit, since ORCA is the only plant of its type in the world.
Swanson School of Engineering 