Energieerlebnis Schönau EN » 12. Storing hydro power (Always in motion)

12. Storing hydro power (Always in motion)

Pumped storage - the ideal solution to the energy storage problem?
Actually, pumped storage plants are an ideal solution to solve the problem of unsteady solar and wind power. And indeed they are supposed to play an important role in the exit from nuclear and fossil-fuel energy. Thus, not far from Schönau, the pumped storage Atdorf near Wehr was planned. With a pump/drop height of 600 meters and 1.4 GW (gigawatts) output, it would have become the most powerful in Europe. All German pumped storage units together provided an output of approx. 7 GW in 2017. But in the course of the planning approval in 2017 the investor pulled out.

On one hand, there was resistance from the population. The large, artificial reservoir on top of the mountain near Herrischried would have been a big alteration of the landscape. From the opponents' point of view, habitats for rare plant species would have been lost and drinking water sources endangered. Again, there was a conflict between the goal of a CO2-neutral power supply and the conservation of landscape and nature.

Lack of economic efficiency
For the utility companies, however, there was another reason to withdraw from the project: due to the energy transition, new pumped storage plants in Germany are not very profitable anymore. The investment is worthwhile if the price difference between cheap night-time electricity for pumping and high-load and peak-load electricity during the day is as great as possible. But with the shutdown of nuclear power plants, the supply of cheap night-time electricity has deceased. At the same time, photovoltaic plants produce the most electricity around noon, so that electricity at peak-load times has become much cheaper.
In addition, pumped storage power plants are treated as end consumers by German legislators. Network charges apply twice: for electricity purchased for pumping and for the delivery of electricity to end users. And this although pumped storage plants deliver the important control energy to ensure grid stability.

CO2 neutral?
High-load and peak-load power from pumped storage power plants can be highly damaging to the climate. Specifically, when the pumping power is sourced from lignite-fired power plants. Although pumped storage power plants have a high efficiency of 75 to 85%, the intermediate storage loses energy again. Therefore, CO2 emissions per kilowatt hour are extremely high if lignite is used to power the pumps.
However, the latest by the time 60 to 70% of the electricity in Germany is generated from wind and sun, large-scale storage will be needed. At this point pumped storage plants may become more important again. The problem: planning, approval and construction will take about a decade. It might be easier to equip Scandinavian reservoirs with additional pumping options. Today, we do not yet know which storage technologies will prevail in the future.

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