Existing and potential capacity for a scenario of one existing water reservoir for selected EU and EFTA countries. (Credit: EU, 2013)

One of the major drawbacks of the solar and wind power stations is the unstable power output (solar plants generate no power at nighttime). One way to compensate for that is to use pumped-storage hydroelectricity for load balancing. A new JRC report assessing Europe’s potential for pumped hydropower revealed that for a set of countries for which comparable data are available, the current storage capacity could be increased by up to 10 times when new plants are based on one existing reservoir.

A larger capacity to store energy would allow a higher penetration of renewable energies and would support the EU’s efforts to reach its goal of 20% of energy from renewables by 2020.

The fastest growing renewables — solar and wind — depend on natural resources that are not necessarily available when electricity is most needed. Therefore, the possibility to use the generated energy during times of increased demand becomes extremely important. Pumping water from a low to a higher elevated reservoir during off-peak electricity demand periods transforms electricity into potential energy, which in turn can be re-converted to electricity in periods of high demand. This system, known as pumped hydropower storage (PHS) is currently the only widespread, large-scale electricity storage technology.

In its report Assessment of the European potential for pumped hydropower energy storage, JRC researchers used two scenarios to calculate the potential storage capacity: topology T1 refers to two existing reservoirs with adequate difference in elevation, close enough to be linked by a new penstock and electrical equipment, while topology T2 is based on one existing reservoir, with a suitable site nearby where a second reservoir could be built. The latter scenario is only considered for sites sufficiently away from populated areas, protected natural parks and transport infrastructure.

According to the report, a comparison with the existing PHS, reported in 14 countries, suggests that the T1 theoretical potential is 3.5 times the existing capacity, whereas the T2 potential is 10 times as much the existing capacity. Further work should aim at facilitating the actual implementation of the potential by providing stakeholders with more accurate data on the sites identified, introducing the potential in grid-development computer models, adding economic parameters, and providing policy-makers (in particular spatial planning authorities), project developers and engineering companies with the knowledge on the potential sites.