Hydropower: 12,910 GWh
The total energy generation of Landsvirkjun’s hydropower stations was approx. 12,910 GWh in 2016.
Landsvirkjun operates 14 hydropower stations all over Iceland, divided into four areas of operation. There are six power stations in the Þjórsá area, with a total of 18 generating units and a number of waterway structures. The area spans from the Hofsjökull Glacier and down to the Búrfell Hydropower Station. There are three power stations in the Sog area with a total of eight generating units and several waterway structures by the Þingvallavatn Lake and Úlfljótsvatn Lake.
There are two power stations in Laxá, with two units in operation and a few waterway structures. The stations are operated in the Blanda area. The waterway at the Blanda Hydropower Station spans a length of 25 km and the station has a total of three units.
The fourth operational area is the Fljótsdalur Hydropower station, the largest hydropower station in the country, with six generating units and extensive waterway structures including tunnels 70 km in length. The Station generated 5000 GWh this year or approximately 37% of Landsvirkjun's total generation.
Operation of power stations
The operation of Landsvirkjun’s power stations was successful throughout the year. There were 82 unforeseen interruptions in 2016, compared with 106 in 2015. Landsvirkjun's goal is to ensure that generating units in the power stations are available 99% of the year, not accounting for routine maintenance periods. Units were available 99.9% of the time this year which is the same availability as in 2015.
Investments in operating power stations
Maintenance is an integral part of Landsvirkjun’s operations. Two large refurbishment projects were carried out this year, at the Búrfell and Laxá Hydropower Stations. A total of 87 investment and renovation projects were carried out at power stations in 2016.
Reconditioning generating unit 4 at the Búrfell Hydropower Station
Generating unit number 4 at the Búrfell Hydropower Station was reconditioned in the beginning of February 2016. The project was successful and the turbine came online, as scheduled, at the end of April. The runner, wicket gates, wicket gate bearings, main shaft seal and various smaller components were replaced. The stators for the generators were reconditioned, stator bars were replaced and the isolation and support systems were significantly improved. The turbine cooling system was also renewed.
Measurements show that the efficiency of the turbine was increased by 3–4% as a result of the reconditioning project and the generating unit's capacity thereby increased by 12 GWh/ year.
The Búrfell extension history
The Búrfell Hydropower Station began operations in 1969. Proposals were put forward for an expansion of the station in 1990 alongside plans to expand the aluminium smelter at Straumsvík.
The design and tendering process was completed for an expansion of 100 MW (at another powerhouse in the same area) but the project was delayed as a result of the postponement of the expansion of the smelter.
During the same time period an assessment was carried out on the condition of the turbine equipment at the existing station as it was badly damaged by sand erosion - after twenty years of continuous operation. The damage was so extensive that the efficiency of the turbines had decreased substantially. Landsvirkjun decided to recondition the turbines and to renew the runner and wicket gates. Tenders for the project were released in 1995 and the most feasible bid was accepted. The most feasible bid included a substantial increase in turbine capacity which meant that the station could be upgraded by replacing other equipment in the power train.
Increased capacity 1996–1998
The capacity of the station was increased between 1996 and 1998, when runners, wicket gates, stators for the generators and other related equipment was renewed. The installed capacity of the station increased from 210 MW to 270 MW and energy generation rose from 1,800 GWh to 2,300, an increase of 500 GWh, which is similar to the capacity of the Búðarháls Hydropower Station. This was the most economical project the Company had ever undertaken. The station has since then been running over its estimated capacity (up to 300 MW). This however resulted in cavitation damage to the turbines which has been repaired by welding.
In 2013, an annual inspection of turbine 4 revealed a crack in the turbine runner and a similar crack was discovered in turbine 5 in the following summer. The inspection revealed that the damage was caused by repeated welding work. Various solutions to the problem were subsequently assessed and a decision was eventually made to renew the runners as well as reconditioning the rest of the turbine parts. The opportunity was also used to carry out reconditioning of the generators.
Turbines reconditioned in 2018 and 2019
A window of opportunity will open for reconditioning work in the first few years after the expansion of Búrfell is completed in 2018. However, turbine 4 was reconditioned in 2016, due to its poor condition. The other turbines will be reconditioned in 2018 and 2019.
Laxá III, work carried out on the intake structure and turbine
The first Laxá station began operations in 1939.
Construction work began on the intake structure and turbine at Laxá III in May, 2016 and is expected to reach completion by February 2017.
The scope of the work on the intake reservoir, dam and tunnel intake, is extensive. The intake reservoir was deepened to reduce water velocity. A specialised sediment trap was installed in front of the tunnel intake structure, designed to flush out sand and gravel. Specialised ice skimming equipment was installed to remove ice from the intake reservoir, and the trash rack was modified to prevent stones and ice from entering the headrace tunnels for the station.
Repairs were carried out on the dam and intake tunnels. The runner, wicket gates, wicket gate bearings, main shaft seal and various smaller components were replaced in the turbine. Other parts of the turbine were repaired and surface treated.
History of the development
The Laxá River runs from the Mývatn Lake and is 59 km in length. The river is usually divided into upper and lower river stretches; the upper stretch is 33 km in length and stretches from the lake to the canyons by Brúarfoss where the Laxá Station is located. The youngest station, Laxá Station III, began operations in 1973 and is located underground. The Laxá stations generate approx. 170 GWh per year (Laxá III generates 93 GWh of this energy). The design of the station initially included a substantial increase to the height of the intake reservoir dam. The current dam was built in 1939 for Laxá I but was never altered because of the environmental impact.
A number of problems have been associated with the operation of Laxá III as a result of the lower dam height. Ice problems and damage to the turbines have occurred because the head is different to the head that the station was designed for. The small size of the reservoir has also led to substantial sedimentation from the river entering the station’s turbines. These combined factors have resulted in damage to the turbine which has been repaired annually with welding work. The runner was replaced in 1993, after 20 years of operation.
Knowledge dissemination a key factor
There were clear indications several years ago that the runner from 1993 would not last for much longer. An assessment was completed on the possibility of reconditioning the turbine and carrying out modifications to the dam and intake structure (without a height increase) at the same time, with the aim of reducing the sand and ice problems. Norwegian and Icelandic experts on sediment traps were consulted. Design work was completed in the middle of 2015 and a decision was made to begin construction in 2016. Special attention was paid to presenting and discussing the project with the local community and those involved.