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Hydraulic pumping: water as a potential energy storehouse
Hydraulic pumping: water as a potential energy storehouse
This method allows the storage of large amounts of energy in the form of dammed water in two reservoirs located at different heights.
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Hydraulic pumping is a proven technology, which today represents almost 85% of the available storage capacity in the world
Hydraulic pumping, which today provides almost 85% of the installed electricity storage capacity in the world, is "one of the most viable and efficient solutions for large-scale energy storage over long periods. The pumping provides exceptional flexibility to the electricity system in the management of fluctuations inherent to wind and solar generation to ensure a reliable and continuous supply," explains Carlos Gutiérrez, Repsol Renewables Technology Manager.
This method allows the storage of large amounts of energy in the form of dammed water in two reservoirs located at different heights. At times of high demand, water is released from the upper reservoir and flows down through some pipes, moving turbines that generate electricity. And when there is excess renewable electricity generation, it is used to pump the water back from the lower reservoir to the highest reservoir and reuse that potential energy when it is needed again. The storage capacity of a pumping station largely depends on the size of its upper reservoir, with some facilities being able to store energy for a few hours of continuous electrical supply, while those that have larger reservoirs are capable of retaining enough energy for several weeks.
It is also a more than proven technology, since the first pumping facilities date back to the 1890s in Italy and Switzerland, and there are numerous stations around the world that have been operating for decades, such as the Niederwartham plant, of 119.4 MW and located in the Silberbach river (Germany), inaugurated in 1930, and which today remains in operation. This very long useful life "represents an advantage compared to other storage alternatives such as, for example, current batteries, which have an approximate duration of 15 years because of the degradation they suffer," Gutiérrez continues.
These facilities must be situated at locations with enough water availability and which allow the two reservoirs to be located at different levels, so "in those areas where there is the possibility of expanding already existing pumping stations and making new ones, it seems quite reasonable to opt to make the most of it." In Spain, one of the most notable hydraulic pumping projects is that of Aguayo II, in Cantabria. The aim is the repowering of a 360-MW hydroelectric plant (Aguayo I), active since 1983, where new underground water pipes and equipment that would allow the increase of the capacity of both plants to 1,360 MW would be installed.
"In this expansion, we will not only make the most of the upper and lower reservoirs, but also a large part of the existing infrastructures, thus minimizing the environmental impact of the project," explains Luis González, assistant manager of this project at Repsol. In this way, the joint facility of Aguayo I and Aguayo II will become one of the largest pumping facilities in Europe, with a capacity to generate per year the electricity equivalent to the average consumption of over 500,000 homes in Spain, and "a key infrastructure for the integration of the growing volumes of renewable energies that are expected by 2030 in the Spanish electricity system."
