Four years passed from the beginning of construction work at Kárahnjúkar in 2003 until the Fljótsdalur Power Station reached full operational capacity in 2007. Concurrent with the construction work at Kárahnjúkar, an aluminium plant was built in Reydarfjördur. Most of the energy generated is sold to the Reydarfjördur plant.
On its long journey from the reservoirs in the highlands to the station’s intake, the water drops approximately 200 m. Two-thirds of the total head runs through an approximately 400 m high vertical pressure tunnel near the Fljótsdalur Station.
The water’s total drop therefore, is more than 600 m. The water drives six powerful turbines in the powerhouse and then flows through a tailrace tunnel and canal into the river Jökulsá in Fljótsdalur, east of Valthjófsstadur Mountain, at an altitude of 26 metres. The underground powerhouse is located inside Valthjófsstadur Mountain and is accessed through an 800 m tunnel. Electricity is transmitted from the station through a separate cable tunnel to the switchgear house and from there through high-voltage lines to Alcoa’s aluminium plant in Reydarfjördur.
Fljótsdalur Station came on-line in 2007. The Station’s catchment area covers over 2200 km2 and the station’s reservoirs are formed by five dikes that are over five kilometres in length. The water is diverted to the Fljótsdalur Station’s turbines from the reservoirs in the highlands north of the Vatnajökull Glacier, through a tunnel system that is approximately 72 km long.
Kárahnjúkar Dam is the tallest concrete-faced rockfill dam in Europe and among the largest of its kind in the world. The River Jökulsá á Dal is dammed at Fremri Kárahnjúkar with the largest of the Kárahnjúkar dams. Most of the rockfill was quarried just upstream of the dam within the reservoir area and placed in compacted layers. During construction, the river was diverted through two diversion tunnels under the dam on the western bank. Two smaller saddle dams were built at Kárahnjúkar, Desjará Dam to the east and Saudárdalur Dam to the west. Together, the three dams form the Hálslón Reservoir which covers an area of 57 km2, and reaches all the way to the Brúarjökull Glacier.
Most years, Hálslón fills up in late summer. When this happens, the spillover is diverted through a chute down to the canyon edge, where it becomes the waterfall Hverfandi (Vanisher). Almost 100 metres high, Hverfandi can, at times, become more powerful than Dettifoss, its neighbour to the north and one of Europe’s most powerful waterfalls. The water from all the reservoirs comes together in the headrace tunnel, which runs almost level at 100-200 metres depth under the Fljótsdalsheidi Moor. The headrace tunnel ends in two pressure shafts, where the water falls 400 metres vertically into the Fljótsdalur Station’s Powerhouse, about 1 km inside the mountain.
Fljótsdalsstöð | |
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Uppsett afl Kárahnjúkavirkjunar: | 690 megavött |
Tryggð orkuvinnslugeta: | 4.600 gígavattsstundir á ári |
Hverflar: | Francis, lóðréttur ás |
Fjöldi: | 6 |
Hönnunarrennsli: | 24 rúmmetrar á sekúndu hver |
Stærð: | 115 megavött hver |
Hálslón | |
Flatarmál lóns þegar það er fullt: | 57 ferkílómetrar |
Lengd lóns þegar það er fullt: | 25 kílómetrar |
Miðlunarrými: | 2.100 gígalítrar |
Vatnsborðshæð þegar lón er fullt: | 625 metrar yfir sjávarmáli |
Lágmarkshæð vatnsborðs við rekstur: | 575 metrar yfir sjávarmáli |
Vatnasvið: | 1.806 ferkílómetrar |
Áætlað meðalrennsli í Hálslón: | 107 rúmmetrar á sekúndu |
Kárahnjúkastífla | |
Mesta hæð stíflu: | 198 metrar |
Lengd stíflu: | 700 metrar |
Fyllingarefni í stíflu: | 8,4 milljón rúmmetrar |
Desjarárstífla | |
Mesta stífluhæð: | 68 metrar |
Lengd stíflu: | 1.100 metrar |
Fyllingarefni í stíflu: | 2,9 milljón rúmmetrar |
Sauðárdalsstífla | |
Mesta stífluhæð: | 29 metrar |
Lengd stíflu: | 1.100 metrar |
Fyllingarefni í stíflu: | 1,6 milljón rúmmetrar |
Ufsarlón | |
Flatarmál lóns þegar það er fullt: | 1 ferkílómetri |
Vatnsborðshæð þegar lónið er fullt: | 625 metrar yfir sjávarmáli |
Vatnasvið: | 430 ferkílómetrar |
Áætlað meðalrennsli í Ufsarlón: | 31 rúmmetri á sekúndu |
Ufsarstífla | |
Mesta stífluhæð: | 37 metrar |
Lengd stíflu: | 600 metrar |
Fyllingarefni í stíflu: | 0,5 milljón rúmmetrar |
Kelduárlón | |
Flatarmál lóns þegar það er fullt: | 7,5 ferkílómetrar |
Vatnsborðshæð þegar lónið er fullt: | 669 metrar yfir sjávarmáli |
Miðlunarrými: | 60 gígalítrar |
Kelduárstífla | |
Mesta stífluhæð: | 26 metrar |
Lengd stíflu: | 1.700 metrar |
Fyllingarefni í stíflu: | 0,7 milljón rúmmetrar |
Jarðgöng: | Alls um 72 kílómetrar |
Aðrennslisgöng frá Hálslóni (þvermál: 7,2-7,6 metrar): | 39,7 kílómetrar |
Aðrennslisgöng frá Ufsarlóni (þvermál:6,5 metrar): | 13,3 kílómetrar |
Þrenn aðgöng vegna aðrennslisganga (þvermál: 7,2-7,6 m): | 6,9 kílómetrar |
Tvenn hjáveitugöng og aðkoma við Kárahnjúkastíflu: | 2,4 kílómetrar |
Bergþéttingargöng undir Kárahnjúkastíflu: | 500 metrar |
Sveiflugöng (þvermál: 4,5 metrar): | 1,7 kílómetrar |
Tvenn göng í Hraunaveitu (þvermál: 4,5 metrar): | 3,7 kílómetrar |
Tvenn fallgöng að stöðvarhúsi (þvermál: 4,0 metrar): | 800 metrar |
Aðkomugöng að stöðvarhúsi (þvermál: 7,5 metrar): | 1,0 kílómetri |
Frárennslisgöng (þvermál 9,0 metrar): | 1,3 kílómetrar |
Strengjagöng (þvermál 4,0 metrar): | 1,0 kílómetri |
Frárennslisskurður í Fljótsdal | |
Lengd: | 2,1 km |
Grafið rúmmál: | 700.000 rúmmetrar |
Heildarfallhæð frá Hálslóni í stöðvarhús í Fljótsdal: | 599 metrar |
Hönnunarrennsli (mesta mögulega rennsli): | 144 rúmmetrar á sekúndu |
Meðalrennsli: | 110 rúmmetrar á sekúndu |