Landsvirkjun

Fljótsdalur Power Station

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.

115 MW
Hydropower
115 MW
115 MW
Hydropower
115 MW
115 MW
Hydropower
115 MW
115 MW
Hydropower
115 MW
115 MW
Hydropower
115 MW
115 MW
Hydropower
115 MW
690 MW
690 MW
Installed capacity
6 x 115 MW
6 Francis turbines
4.800 GWh p.a.
Generation capacity
599 m
Total head
144 m3/s
Maximum flow
2007
Brought online

Catchment Area

Fljótsdalur Station’s Catchment Area

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.

Specifications

Fljótsdalsstöð
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