Greenland is a large country with a small population. The distance between the many small communities is counted in hundreds of kilometres. Sea traffic and a well established network of inland flights bind the country together. A young, growing population must be supplied with heat and electric power for greater prosperity. It is not possible, as in Sweden, to supply each community through a nationwide network. The local scale is evident. Each community must have its own power and heat production.
Because of this, every major community has its own oil fired power plant while the smaller ones have power plants and private oil fired boilers. It is easy to supply the plants with oil through tankers and then locally distribute electricity through cables and heat through district heating pipes. Because of the higher cost of oil and the climate threat, however, Greenlanders want to replace their dependence on fossil fuels by sustainable energy.
Solar energy is not an option for countries situated around the Pole Circle where the temperature may drop to -40°C over long periods during the long and dark winter. What remains are wind power and hydroelectric power. Unfortunately, wind power also is no option since it necessitates an equally large power production during periods when wind power cannot be used. On Greenland, this is over much of the time since the wind is seldom moderate but is either too much or too little.
Hydroelectric power, on the other hand, is a reliable source that is easy to regulate and sustainable. As in all construction, however, some encroachment on nature must be accepted. It must be made as small as possible and acceptable.
On Greenland there has been a large expansion of hydroelectric power generation. The first plant which now provides the capital with pure energy came into production in 1993. At the turn of 2009, hydroelectric power accounted for sixty per cent of publicly produced energy in the country, both for power and heat. This is a proportion people are still actively endeavouring to raise.
Hydroelectric plant at Sisimuit. Sisimuit, a community of about 5,500 population, is situated on the west coast and north of the Pole Circle. It is Greenland's second largest town and has a large prawn and fish industry and a university. Over the period 2007 – 2010, the Greenland power company Nukissiorfiit built an underground hydroelectric plant of 15 MW to replace the existing oil based power and heat plants. The transmission line with Sisimuit in the background. (The photograph was taken by Lind Foto and is owned by Nukissiorfiit).
The hydroelectric plant at Sisimuit
Sisimuit, a community of about 5,500 population, is situated on the west coast and north of the Pole Circle. It is Greenland's second largest town and has a large prawn and fish industry and a university. Over the period 2007 – 2010, the Greenland power company Nukissiorfiit built an underground hydroelectric plant of 15 MW to replace the existing oil based power and heat plants.
The plant is situated about 25 kilometres north of Sisimuit on the inside of the fjord Kangerluarsuk Ungalleq. It consists of an underground power plant and a transformer station. On the surface there is only a portal building at the entrance tunnel. Water enters the plant through a 4.6 km long penstock tunnel. Water is then discharged into the bottom of the fjord through a 200 m long tailrace tunnel. The water comes from the lake Taseruaq and its upland. The head is ca 80 m. A longitudinal section of the plant and its components is shown on p. . The intake and discharge have been placed at such a depth that they are not affected by the ice formed in the winter. There is thus no risk of freezing.
The energy produced is taken from the machine hall to the transformer station and a 60 kV overhead line to a transformer station in Sisimuit for further distribution over the local network. The transmission line is about 27 km long and passes over two ridges and a fjord between these. The transmission line with Sisimuit in the background is shown below.
From the portal building that has a workshop, store and office for ten people with overnight facilities there is a road down to a helicopter pad and a quay for small vessels. In principle, the plant is to be unstaffed and remotely controlled from Sisimuit. The area is undeveloped apart from a holiday house a little further out in the fjord.
The area is used for hunting and fishing. A footpath winds its way from the fjord up to the lake through a somewhat unpenetrable terrain, with large boulders from an old rock slide.
The contractor for the construction was the Danish firm Pihl & Son who passed the job on to its Icelandic subsidiary ISTAK, a company wth extensive experience in power plant constrution in a cold climate. All infrastructure for the construction had to be created from scratch. Housing for the workers, office, workshps, store and roads on the site had to be built. All transport between Sisimuit and the site was by boat. Owing to ice conditions the fjord is only navigable from December to May. All this imposed stringent demands on planning and logistics. Rockworks were carried out by drilling and blasting, see Fig. 3. All concrete was produced on site. Turbines, transformers, electrical installations and mechanical components were made in different places in Europe and transported to Sisimuit by boat for transshipment and local transport to the site. Work was completed within the stipulated time frame in spite of a small tunnel fall and a major fire in the workshop.
The plant is being run in and has begun delivery of power to Sisimuit as planned.
The very small and local damage to the terrain caused by the works shall be reparied prior to completion. (Photograph by Lind Foto and owned by Nukissiofiit).
Deep underground. Longitudinal section through the plant with intake from Lake Taseruaq at left and discharge into the fjord Kangerluarsuk Ingalleq at right. (not to scale)
Sensitive environment
Great efforts have been made to reduce the impact on nature. The area consists of sandy soils and till that are covered by vegetation some way up the steep hillsides. The low vegetation which forms a dense mat consists of Salix, Betule Nana and different varieties of heather. The humus layer is very thin. Further into the valley there are large boulders left behind by rockslides which makes the terrain very difficult to penetrate. The nature of the area and the local encroachment are shown in the photograph above.
Hydroelectric plant at Sisimuit. Sisimuit, a community of about 5,500 population, is situated on the west coast and north of the Pole Circle. It is Greenland's second largest town and has a large prawn and fish industry and a university. Over the period 2007 – 2010, the Greenland power company Nukissiorfiit built an underground hydroelectric plant of 15 MW to replace the existing oil based power and heat plants. The transmission line with Sisimuit in the background. (The photograph was taken by Lind Foto and is owned by Nukissiorfiit).
Generally speaking, all temporary roads and buildings had to be demolished and the nature reinstated. Where possible the thin humus layer was removed and later replaced. In many cases this was not feasible. New surfaces were fertilised twice and if necessary sown with annual grass to bind the surface. No alien vegetation has been allowed.
A total of 240,000 m3 of rock has been blasted and laid in the specified place for disposal. Rock masses have been landscaped to fit into the surroundings. The surface has been fertilised and sown. Concrete redidues have been buried and covered with ca 2 m of naturally occurring soil.
All oils and other environmentally harmful products were handled under strict control and spill has been collected and transported to Sisimuit for destruction.
The transmission line was built with great care to avoid making tracks in the sensitive environment as far as possible. Regrowth in Arctic regions takes a very long time. Materials were therefore transported largely by helicopter. Certain tracks made by tracked vehicles were however unavoidable in conjunction with foundation works for the transmission masts.
Hydroelectric power is in many respects a superior form of energy. Environmental disruption can be limited. Much smaller areas are architecturally affected than in the case of wind power. Underground stations can be given a design that harmonises with nature. Open and clear communication with those affected is essential.
Author
:
Håkan Stille
is professor of soil and rock mechanics at KTH