Connecting a new geothermal field to an established power plant: Expansion of production at Hellisheiði.

Abstract

Hellisheiði power plant, SW Iceland, was commissioned in 2006 and it reached full electric capacity in 2011. In 2012 and 2013, it became evident that the original production filed was not be sufficient to be able to maintain the powerplant’s full capacity in the long run. The Hverahlíð geothermal field is located around 5 km away from the Hellisheiði power plant. Originally, there were plans of building a separate 90 MWe power plant there. However, to maintain production capacity at Hellisheiði the Hverahlíð field was instead connected to the Hellisheiði power plant, resulting in the longest steam pipeline that has been built in Iceland. In this paper the challenges of connecting the Hverahlíð field are described.

A separation station was constructed at the Hverahlíð site as well as two pipelines, one for geothermal brine and the other for steam. For the steam a DN1000 pipe was selected with a transport capacity of 100kg/s at the pressure of 8-10 bar. For the geothermal brine a DN600 pipe with a transport capacity of 220 kg/s at 206°C. One of the main challenges was that the pipes needed to cross one of the busiest highways in Iceland. Due to the proximity of the pipes to the highway, efforts were made to minimize their visual impact as well as the impact on the surrounding flora/environment.

The pipes were built in 2014 and 2015 and commissioned in early 2016. Since then, drilling in Hverahlíð has been very successful and plans have been made to construct a second set of pipelines from the field to provide steam and brine for the power plant. Hence, extending lifetime of the Hellisheiði power plant and providing flexibility in operation.