Krafla Geothermal Power Plant

Krafla geothermal power plant is located in NA Iceland.  The plant has 2 x 30 MW units, the turbines have double pressure inlet and dual flow, 5 steps on each side. Mannvit has been involved in the design and preparation of the power plant from the beginning. In total, 33 boreholes were drilled, including 17 high pressure production wells and 5 low-pressure production wells. The plant uses 110kg/second of 7.7 bar saturated high-pressure steam and 36 kg/sec of 2.2 bar saturated low-pressure steam and has been in operation at 60MW since 1999. The plant is owned and operated by Landsvirkjun (National Power Company).

Krafla geothermal power plant timeline:
1974 - First exploration wells 
1975 - Beginning of seismic and volcanic impacts threaten continued development of the plant 
1975 - Production wells and construction of power plant despite seismic activity
1977 - Power Plant begins operation
1978 - Power production starts
1984 - Significant decline in seismic and volcanic impact
1996 - 2nd steam turbine installed and beginning of additional drilling
1999 - Producing 60 MW 

The construction work started in 1974 / 1975 with drilling and a contract for the two units was signed with MHI.  Unfortunately volcanic activities started in the area at the same time giving a lot of difficulties in drilling and harnessing the geothermal field.  For a while it was uncertain whether Krafla would ever actually enter operation when, early on, large-scale volcanic eruptions occurred only two kilometers away from the plant, posing a serious threat to its existence. Work continued, however, and phase one of the power plant went on line early in 1977.

With respect to this situation, the progress was adjusted in the way that the first unit was installed and commissioned in 1978 but only with partial load.  In the coming years further drilling was carried out and in the middle of the eighties the first unit was operating on full load when the effect of the volcanic activities on the geothermal fluid started to decline. In the middle of the nineties the chemistry of the fluid had still improved and it was decided to start further drilling and to install the second unit, purchased almost 20 years earlier. This time everything went according to plan and the second unit was installed and commissioned in 1997.  Since then Krafla has been in operation without problems.

During this development many complicated problems arose and were solved in due course.  For instance the steam gathering system had to be redesigned and refurbished to meet the requirements of the double pressure inlet to the turbines and the overall control and safety system was refurbished to meet modern requirements and specifications.  Mannvit and Verkís have been responsible for all the engineering in Krafla from the very early beginning to the present. In 1996 Landsvirkjun decided to finalize the installation of the second turbine and provide enough steam to make it possible to run the power plant at maximum output and efficiency.

One of the wells (IDDP-1) in the "Iceland Deep Drilling Project" was drilled in 1999 in Krafla geothermal reservoir and reached magma (molten lava). That particular well had a bottom hole temperature measured at 430°C and became the world’s hottest geothermal well. The engineering to harness the well is under the responsibility of Mannvit.