Current Aguayo power plant

The Aguayo hydro power plant, located in San Miguel de Aguayo (Cantabria), has been operating since 1982. Today it accounts for 38% of Cantabria's installed generation capacity.

It is a reversible or pumped-storage power station. The main differentiating feature of this class of power station (relative to other hydro, fossil fuel, nuclear, wind facilities, etc.) is their ability to store electric energy. This unique advantage means they can be used within the power system for load balancing purposes, accumulating energy at times of surplus output and generating power at times of surplus demand. To this end, the electricity left over in the system is used during off-peak hours (mainly at night and on the weekend) to pump huge volumes of water into an upper reservoir. Then when extra electricity is needed to cater to surges in demand, the water is dropped to the lower reservoir (called Alsa) in order to move the turbines so that they start to generate electricity again.

The Aguayo plant uses the Alsa dam as its lower reservoir and the Mediajo dam as its upper reservoir.

Modernisation of this facility was completed in 2009. The upgrade work entailed capital expenditure of close to €11 million.

Key technical data

Current installed capacity (MW) 360
Generation flow rate (m3/s) 30
Upper reservoir capacity (hm3) 10
Lower reservoir capacity (hm3) 22,6
Average net head (m) 328,5