Geothermal water for district heating in Reykjavík, Iceland

Category Petrology
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Gunnlaugsson, Einar; Ivarsson, Gretar
Holding Date 04 October 2008

The main use of geothermal water in Iceland is for heating houses. The District Heating Utility in Reykjavík is the largest geothermal district heating service in the world. The harnessed power of the geothermal areas is about 780 MW thermal. Annually, 60 million cubic meters of hot water flow through the Utility’s distribution system. The district heating in Reykjavik utilizes geothermal water from four low temperature geothermal fields, Laugarnes and Ellidaar are located within the city limits, but the third, Reykir and Reykjahlid lay some 20 km northeast of Reykjavík. Exploitation of the Laugarnes field began in 1930 by pumping 14 l/s of 87 °C water from wells and surface springs. Water from Reykir field was first piped to Reykjavik in 1943 and exploitation of the Ellidaar field began in 1968. Initially only artesian flow from springs and relatively shallow drill holes was used for district heating in Reykjavik but in the sixties and early seventies deep production wells were drilled in all the fields and downhole pumps installed, multiplying the flowrate from the fields. The use of high-temperature geothermal energy for heating in Reykjavík started 1990 when the Nesjavellir power plant started operation. Pumping in the low-temperature geothermal fields has lowered waterlevel and geothermal surface manifestations have disappeared. With opening of the Nesjavellir field it was possible to reduce the pumping frm the low-temperature fields. Then the waterlevel rose again and equilibrium has been attained indicating that the geothermal energy is sustainable. Extensive monitoring programme of the exploitation has been carried out for the last decades and records have been kept on fluid production, fluid temperature, water level variation and fluid chemistry.
The water from the low temperature fields is used directly for heating and as tap water. Due to high content of gases and minerals at the high temperature area, water and steam are used to heat fresh water. Today geothermal energy is used to heat the entire city and five neighbouring communities. From 1998 electricity has been co-generated from geothermal steam at Nesjavellir. About 70% of the energy used for district heating comes from low-temperature geothermal fields the other from high-temperature geothermal resources.The use of geothermal energy for heating in Reykjavik has massively reduced the City’s dependence on fossil fuels, making it one of the cleanest cities in the world. The CO2 emission has been reduced from 1944 to 2006 by up to 110,000,000 tones, delivering savings of up to 4 million tons CO2 every year. The cost of the geothermal energy is low comparing to other alternatives. The financial savings form 1944 to 2006 would amount to about 4,290 M US$. The use of geothermal for heating houses in Iceland has therefore contributed to Iceland’s transformation from one of the poorest nations to one that enjoys a very high standard of living.