How can renewable energy be stored? One possibility is offered by pumped storage power plants – a kind of huge battery. Inexpensive, flexible – but not without controversy.
As much energy as possible should come from renewable energies in the coming years – but what happens if additional energy is needed on a day with little sunshine or a lull in the wind? Then pumped storage power plants can help out – they can be used as storage.
The power plant switches to turbine operation for this purpose. Gravity forms the basic principle: the water falls from above through a kind of giant faucet and flows through the turbines on its way to the lower basin. These drive the generators and generate electricity.
The whole thing happens impressively quickly: a power plant can be brought from standstill to full capacity in around a hundred seconds. This flexibility makes these storage systems particularly valuable for the energy world.
This is how pumped-storage power plants work: The water falls from above through a kind of huge water tap and flows through turbines on its way to the lower reservoir. These drive the generators and generate electricity.
How exactly pumped storage power plants function
Pumped storage power plants use water to store and also generate energy. The facilities consist of two pools at different altitudes. They are connected by a pressure shaft and a cavern. The heart of the system is located in the cavern, an underground room: pumps, turbines and generators.
If there is a surplus of energy generated by wind power or solar power, the power plant’s pumps are used. Here, the excess electricity is used to transport the water against gravity into the upper reservoir and store it for the next need. It can easily be stored for hours, days or weeks in the higher upper basin. The higher the water level in the reservoir, the higher the capacity of the available energy.
Germany’s largest pumped storage power plant has been in Goldisthal in Thuringia since 2004. The full output is around 1,060 megawatts. After all, this corresponds to almost half of the installed power plant capacity from conventional energy sources in all of Thuringia. In the event of a power failure, the pumped-storage power plant can step in for several hours at short notice.
Cavern of the Goldisthal pumped storage plant in Thuringia: This is where pumps, turbines and generators are located.
intervention in the nature
The construction of such systems often requires major interventions in nature and the landscape: rivers are dammed and large areas of land are flooded. In order to minimize the impact on the environment, some power plants have their waterways and energy distribution completely underground.
Nevertheless, the further expansion of pumped storage power plants in Germany is met with massive resistance from residents and those looking for relaxation.
The economic framework conditions also pose a challenge: “High feed-ins of electricity from photovoltaic systems at midday mean that the typical midday peaks in the electricity price on the electricity exchange level off and thus the yields of pumped storage power plants decrease,” according to the Federal Environment Agency.
Stable and sustainable power supply
Nevertheless: Pumped storage power plants are significantly involved in the energy transition: they can be implemented relatively inexpensively, have low operating costs and a long service life. They contribute to a stable and more sustainable power supply, particularly due to their ability to react quickly. These power plants currently store the largest amount of energy in the world.