Mjólkávirkjun – Hydroelectric project

The Mjólkárvirkjun hydroelectric project, is situated in Arnarfjörður fjord in the Westfjords of Iceland. The project harnesses the fresh water rivers Mjólká and Hofsá.

The power plant was first operated in 1958 and harnessed energy from Borgarhvilftarvatn reservoir. It is owned by the Westfjord Power Company.

At full reservoir and overflow, the Mjólká river falls into its natural riverbed down a steep cliff above the current powerhouse in many white waterfalls. Steel pipes convey the water from two intake ponds to the common powerhouse of Mjólká I and II. The horizontal double jet Pelton turbine and generator of Mjólká II was replaced by a five jet vertical modern high efficiency vertical Pelton unit in 2011. A new power station, Mjólká III, was constructed upstream of Mjólká I in 2010 and harnesses the remaining water in the river Mjólká as well as water diverted from the river Hofsá. Mjólká IV power station is a future plan drawing water from the same intake reservoir as Mjólká II and releasing the water to the intake pond of Mjólká III. Electro-mechanical equipment of Mjólká I was replaced in 2016. All units are centrally controlled in the main power station. The energy is delivered via 33/66/132 kV switchgear and transmission lines to the Westfjords main transmission lines.

Verkís’ involvement began in 1985 with the refurbishment of the electrical equipment of Mjólká I. In 2005, Verkís conducted a feasibility study for the refurbishment of the existing plants (Mjólká I and II) and further options for harnessing the rivers in the Gláma highland (Mjólká III and IV). Verkís also provided extensive consultation with an economic and technical study as well as completing the final design and the tender documents for all the civil, electrical and mechanical works related to the refurbishment and the new projects. In 2015-16, Verkís was the consultant for the electro-mechanical refurbishment of Mjólká I and in charge of the design the layout, preparation of the technical specification for the equipment and design review.

Current plant description:

Mjólkávirkjun I  

Commissioned: 1958

Refurbishment of electro-mechanical parts: 2016

Installed capacity: 3,2 MW

Horizontal Francis turbine

Rated speed 1000 min-1

Was previously a 2,4 MW horizontal Pelton turbine, 2 jets

Rated speed: 500 rpm

Generator: 3,4 MVA, 6,3 kV

Annual energy prod.: 13,5 GWh

Gross head: 210 m

Rated discharge: 1,7 m3/s

Mjólkávirkjun II

Commissioned: 1975

Refurbishment of electro-mechanical parts: 2011

Installed capacity: 7,0 MW

Vertical Pelton unit, 5 jets

Rated speed 1000 min-1

Was previously a 5,7 MW horizontal Pelton turbine, 2 jets

Generator:  8,5 MVA , 6,3 kV

Annual en. prod.: 42 GWh

(49 GWh)

Gross head: 488 m

Rated discharge: 1,9 m3/s

Mjólkávirkjun III

Commissioned: 2010

Installed capacity: 1,15 MW

Francis turbine, horizontal

Rated speed: 1000 min-1

Generator: 1,35 MVA, 0,4 kV

Annual energy prod.: 6,5 GWh

Gross head: 99,5 m

Rated discharge: 1,4 m3/s

Mjólkávirkjun IV

Commissioning: In planning

Installed capacity: 1,0 MW

Planned a vertical Pelton turbine, having 4 jets

Rated speed: 600 min-1

Generator: 1,1 MVA, 0,4 kV

Annual energy prod.: 1,5 GWh

Gross head: 176 m

Rated discharge: 0,8 m3/s

Technical information


Westfjords, Iceland

Project period:

1985 – 2016


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