On days with little wind, Europe may have to rely on Norwegian reservoirs to keep its wheels running smoothly in the future. On the Continent, the concept of Norway as Europe's green battery has caught on -- but is it feasible in practice?

The Centre for Environmental Design of Renewable Energy (CEDREN) -- one of Norway's Centres for Environment-friendly Energy Research -- is carrying out the HydroPEAK project to study whether Norway could truly provide Europe's balance power.

When electricity production is based on intermittent sources such as the sun and wind, the power delivered to the grid will vary greatly from hour to hour and from day to night. Consumers, however, expect a constant supply of electricity on the grid, whether during periods of peak demand in the morning and afternoon or periods of low demand at night.

Flexible hydropower

The imbalance between the supply of power and consumer demand is becoming more and more of a problem for energy companies and grid operators, as fossil fuel-based power plants are gradually being replaced by wind farms. Norway's main energy source, hydropower, is unique in that production can easily be adjusted by releasing more or less water through the turbines.

Since Norway has Europe's largest hydropower resources, the Continent's energy companies and grid operators are keenly interested in gaining access to Norwegian reservoirs. The question is, will Norway be able to help Europe with its balance power needs?

Demand exceeds supply

A recent study by the German Advisory Council on the Environment reports that Germany's target to produce all of its electricity from renewable sources by 2050 hinges upon access to a whopping 60 000 MW of balance power.

The study identifies Norway as the only country that could supply such a volume. This amount, however, is several times greater than Norway's potential as estimated by the Norwegian Water Resources and Energy Directorate (NVE). According to NVE, Norway's potential for balance power production in 2030 will total some 20 000 MW. By way of comparison, Norway's total installed capacity is currently 29 000 MW.

Rapid changes in the power system

The greatest challenge, however, is not the scale of Europe's balance power needs, but rather the rapid changes that are putting Norway's entire power system under pressure, from changes in the reservoirs' biological environments to voltage fluctuations in the grid.

Reservoir levels can vary by as much as 10 metres in a single day, and voltage fluctuations in the grid can overload consumers' electrical devices. This is where Norwegian researchers enter the picture.

Numerous challenges

The HydroPEAK project addresses eight areas of research:

scenarios for Europe's balance power needs; hydrological effects; models for the power system; pumped-storage hydroelectric stations; frequency variations in the grid; physical effects on hydro tunnels; physical effects on rivers; impacts on river ice

The first area listed above provides a basis for all of the HydroPEAK sub-projects. Researchers are drawing up scenarios for how the Norwegian energy sector could satisfy the balance power demands of a European power system that will be increasingly based on renewable energy.

"The scenarios determine how much balance power will be needed, so that the other research areas can be scaled according to the most likely scenarios," explains Professor Killingtveit.

Changes in Norwegian watercourses

Norway has in-depth expertise in the environmentally-responsible operation of hydropower plants. So far, changes have mostly occurred gradually over long periods of time. However, the power system of tomorrow will have to absorb rapid change, which may lead to some unpleasant surprises.

One consequence will be more difficulty in delivering electricity with stable voltage and frequency. Also, hydro tunnels for transporting water from the reservoir to the turbines may be exposed to a higher risk of rockslides and landslides due to greater variation in water pressure in the rock.

"Using the Norwegian power system for balance power will lead to changes in Norway's watercourses. How much are we willing to tolerate?" ask the professor and his colleagues.

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