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Hydropower stations harness the power of falling water in order to drive turbines which then generate electricity. Precipitation and meltwater from glaciers is accumulated in main reservoirs that are mostly located in the Icelandic highlands. The reservoir water levels are at their highest towards the end of the summer period and store approximately 4,600 gigalitres or 4.6 cubic metres of water. This storage capacity enables us to generate electricity at a stable rate, year around.

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Water management in a closed hydropower system

Is the number of AA batteries that would be needed to store all the energy in Landsvirkjun’s reservoirs.

Landsvirkjun generates all its electricity from renewable energy resources such as water, geothermal energy and wind energy. The natural water cycle is utilised for energy generation and production is therefore dependent on weather conditions at any given time.

The hydropower system is set up in such a way that it accumulates glacial meltwater in the reservoirs during the summer period and the water is then utilised over the winter period. Weather conditions in Iceland are unpredictable, whereas electricity usage remains stable throughout the year. The potential supply capability of the electricity network is based on water availability during ‘dry’ years which means that there is substantial spillover in an ‘average’ year.

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Utilised catchment areas within Landsvirkjun’s operations

Landsvirkjun operates 13 hydropower stations within 5 operational areas all over the country. The figure shows the percentage of hydro energy according to water catchment areas.

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The energy generation system in Iceland is isolated and is not connected to other energy systems. This highlights just how important it is to ensure the water storage in reservoirs is enough to supply energy to the electricity system, even during poor water years.

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What defines a water year?

Landsvirkjun’s water year begins on the 1st of October and finishes on the 30th of September in the following year. The water year follows the fluctuations in the reservoirs. Generally the water year commences with full reservoirs. They reach their lowest level in the middle of the year and fill up again in the second half of the year. The water year is divided into four quarters and each has its own characteristics. The period from October to December is characterised by autumn rainfall (in good years). The period from January to March is characterised by the winter cold and low flow with the exception of periodical thawing. The period between April and June is characterised by snow melt and spring floods and the period from July to September is characterised by glacial ablation.

Reservoirs are effective storage systems for electrical energy. Landsvirkjun’s reservoirs can store 5.150 GWh. The highest storage capacity reached was 4.864 GWh in the beginning of October, 2014.

The inflow to Landsvirkjun’s operational areas in the water years 2013- 2014 was 7% under the average for the last ten water years. The year is therefore categorised as under average without being categorised as dry. There has been one low inflow water year in the last ten years. The hydrology status this year is the result of a combination of a very dry year between 2012 and 2013 and a low inflow rate from October, 2013 and up until April 2014. This resulted in reductions to the energy supply last winter. In this case the term reduction refers to the reduction of energy supply to certain clients (in accordance with Landsvirkjun’s contract conditions). More information on energy generation and water status can be found in the chapter on energy generation 2014.

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