Hellisheiði hot water main

From Hellisheiði geothermal plant to Reykjavík - Iceland

  • Hellisheidaraed

Verkís services was project management, design, tender documents and procurement, geotechnical work, piping systems, mechanical equipment, structure, site construction supervision.

 Sizes: 19,5 km long
 Project time:  2008 - 2010

Project overview:
The Hellisheiði hot water main carries hot water from Hellisheiði geothermal plant to transmission tanks on Reynisvatnsheiði. The main's capacity is up to 2,2 m3/sec of approx. 130°C hot water. Maximum flow in the main and 105°C hot water equals around 700 MWth geothermal power for district heating. Preparations for the construction of the hot water pipeline started early in 2008 and it was formally put into service at the end of 2010.

Hellisheiði hot water transmission pipeline is a 19,5 km long supply main for hot water from Hellisheiði geothermal plant to Reykjavík city.
The first five kilometers of the pipeline have a nominal width of 1.000 mm but it narrows to 900 mm thereafter. By gravity flow only, 1.450 l/s of hot water can be transferred from a tank by the Hellisheiði power plant to tanks on Reynisvatnsheiði located just east of Reykjavík. By pumping at the plant the discharge pressure can be raised to 10 bar which increases main´s capacity to 2.250 l/sec. The main lies at a height of 97 m to 265 m above sea level. Water is pumped from the geothermal plant (259 m.a.s.l.) through a 1.000 mm wide and 360 m long pipe into a tank (water surface 271 m.a.s.l.) west of the powerhouse. The tank's capacity is 950 m3, but once full capacity of the main is required, an additional tank will be built adjacent to the present one. The Hellisheiði hot water main is designed to withstand up to 2,5 MPa maximum pressure. This enables significant capacity increase by pumping at the Hellisheiði geothermal plant. The flow in the main is controlled with control valves located in a control building at Reynisvatnsheiði, with the aim to maintain a fixed water level in the hot water tank by the plant. 

By gravity the flow rate is 1.450 l/s and the water from the Hellisheiði power plant reaches Reykjavík city in 2,5 hours. At full capacity, 2.250 l/sec at 10 bar pressure rise, the travel time is reduced to 1,5 hours. At maximum gravity flow the temperature drop is only half degree Celcius, which is due to good thermal insulation and high volume of water running through the main.
The main is constructed of pre-insulated steel pipes (heating pipes), insulated with polyurethane foam in a plastic protective cover. The main is wholly laid in ground and has five valve manholes with 900 mm ball valves. At Reynisvatnsheiði connection facility, Hellisheiði and Nesjavellir hot water mains may be joined to mix hot water from both geothermal plants before it flows into accumulation tanks on Reynisvatnsheiði.