Planning for winter

Winter challenge

Electricity is always available in Switzerland. Around the clock, 365 days a year. But we must not take that for granted. Particularly in the winter months, energy producers are confronted with special challenges. The demand for energy increases considerably during periods of snow, ice and low temperatures. The problem here is that domestic electricity generation cannot cover this increased demand, which means that Switzerland relies on imports during the winter months.

Energy supply and consumption in Switzerland

1Electricity generation in Switzerland:
energy from nuclear, run-of-river and storage power plants
4Net imports

But why is it that some places in Switzerland do not generate enough electricity during winter? The answer is that electricity generation is heavily dependent on the weather. For example, if water levels in rivers are low due to long dry spells, run-of-river power stations produce less electricity. The same applies to storage power plants: a dry summer or autumn means that the water levels in dams are low and water reserves are limited.

The potentially challenging energy and grid situation in the winter can only be overcome by working together.

The particular challenge is that Switzerland cannot simply import an unlimited amount of electricity. In the winter months, around 80 percent of electricity is imported at the highest voltage level (380 kV). To supply Switzerland with the energy it requires, this imported electricity must first be transformed to a lower voltage level (≤ 220 kV). However, the capacity for transforming electricity is limited. A greater number of high-capacity transformers is required.

1/2: Imports / Exports
2/2: Transformation

Winter situation 2015 / 2016

In the autumn of 2015 it became apparent that the energy and grid situation in winter could become strained. Energy reserves in Switzerland were scarce at that point due to a series of specific circumstances:

  • Due to the dry weather in summer and autumn the rivers were carrying significantly less water compared to the long-term average, which affected electricity generation from hydroelectric power plants.
  • The level of the reservoirs was found to be below average based on a long-term comparison.
  • The nuclear power plants Beznau 1 and 2 were both out of service. As a result, a feed-in of 720 MW into the 220-kV grid was lacking in northern Switzerland.

The lack of constant energy from hydroelectric and nuclear power had to be compensated for with other types of generation, particularly from storage power plants and imports. Since the capacity for the transformation from 380 kV to 220 kV is limited, imports were only usable to a limited extent to compensate for the lack of constant energy.

The «Winter 2015-2016 Report» highlights the difficult initial situation, the steps taken to ease the pressure and the measures taken to avoid a recurrence of it in future. The working group «Responsibility for the Security of the Electricity Supply» documented the results of its work in the report of the same name.




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