Opinion: Winter Electricity is a Question of Power Source

Switzerland's energy future, particularly concerning winter electricity supply, hinges on a critical reassessment of its current strategy, which heavily favors photovoltaic expansion. A closer look at the physics of energy systems reveals that solar power, while valuable, is ill-suited to reliably meet the consistent, high demand of winter.

The nation's dominant energy source, hydropower, faces seasonal limitations. Run-of-river plants produce significantly less power in winter due to lower water levels. While Alpine storage hydropower can partially compensate, the overall contribution from all Swiss hydropower plants in winter is only 43 percent of their annual output, creating a substantial deficit.

Currently, nuclear power plants bridge this winter electricity gap, operating at nearly 100% capacity and acting as a crucial insurance policy. However, Switzerland's planned phase-out of nuclear energy, coupled with an increased reliance on photovoltaics, poses a significant challenge. Solar energy's inherent intermittency, it ceases production daily, contrasts sharply with the need for stable baseload power.

Moreover, photovoltaic generation experiences a dramatic seasonal decline. In the least productive winter month, solar installations generate only one-ninth of the power produced in the peak summer month. This extreme winter weakness, with capacity utilization dropping to a mere 2% in the worst winter month, highlights the inadequacy of solar power as a sole replacement for nuclear and baseload hydropower during periods of high demand.