Nesjavellir power plant

The Nesjavellir geothermal power plant is the largest cogeneration plant in Iceland. The plant is located about 30 km east of Reykjavík, on the Mid Atlantic ridge which crosses Iceland. The area has great geothermal potential, rating amongst the largest high temperature geothermal fields in Iceland. The site is also a well-known and popular recreational area. The cogeneration plant produces hot water for district heating in Reykjavík and electricity for the national grid.

Construction of the first phase of the plant began in 1987 and operation commenced formally in 1990. Today, the cogeneration plant generates 120 MWe and produces 300 MWth of hot water for Reykjavík, the capital of Iceland. Collecting mains for the geothermal fluid, i.e. hot water and steam, are steel pipes situated above ground. The area experiences harsh winter conditions with expected temperatures of as low as -20°C so the effect of thermal expansion played a key role in the design of the pipes. To counter this, pipelines were installed with expansion joints, loops and specially designed supports, allowing the pipes to move. Verkís also designed and conducted full-scale tests of pressure surge devices which suppress damaging water hammer effects in the transmission pipeline to Reykjavík.

The main electrical equipment consists of generator sets, main power transformers, a 145 kV substation, 11 kV distribution systems and distribution transformers, 400 V main distribution and motor control centers and 110 Vdc centers for control and emergency power, as well as stand-by diesel generators and control and protection equipment for all systems.

In all design work, particular attention was given to the special site requirements stemming from seismic activities as well as the protection of electrical equipment and building structural elements against corrosive H2S gas from the steam supply.