The Cortes-La Muela hydroelectric power complex located near Valencia, Spain, is the site for Europe’s biggest pumped storage power facility.

Owned and operated by Spanish electric utility Iberdrola, the 1.8GW hydropower complex comprises the 290MW Cortes II conventional hydroelectric plant, the 634MW La Muela I and the 878MW La Muela II pumped storage power plants.

With the commissioning of the La Muela II pumped storage hydroelectric facility expansion in October 2013, the power complex is capable of producing 1,625GWh of clean electricity a year, which is enough to meet the annual power demand of approximately 400,000 households.

Location and site details

The Cortes-La Muela hydroelectric power station is located on the right bank of the Jucar River, in the Cortes de Pallás municipality, approximately 85km away from Valencia.

The power complex utilizes the Jucar River as the lower reservoir and an artificial upper reservoir to store water for electricity generation during peak electricity demand.

The Cortes II conventional hydroelectric plant is located on the lower reservoir, and the altitude difference between the lower and upper reservoir is 524m.

La Muela I plant details

Construction of the La Muela I pumped storage power plant was started in 1983, while it started generating power along with the 290MW Cortes II conventional hydroelectric plant in 1989.

The La Muela I pumped storage facility is equipped with three reversible turbines of total installed generating capacity of 634MW and total pumping capacity of 540MW.

La Muela II pumped storage facility

The La Muela II pumped storage hydroelectric plant was built with an estimated investment of more than £296m ($390m).

Construction on the La Muela II expansion project was started in 2006, while commercial operations started in October 2013.

The La Muela II plant consists of four reversible Francis pump turbines housed within a 117m-long, 19.85m-wide and 50m-high underground cavern.

Each reversible unit with a 600rpm turbine can generate more than 218MW of electricity with a water flow rate of 48m3/s while operating in turbine mode during peak electricity demand.

The power rating of the hydraulic pump of each unit is more than 185MW. Operating in pump mode, each unit can lift water to the upper reservoir at a rate of 36m3/s utilising surplus renewable electricity in the grid.

Water flows between the two reservoirs via the underground power station, through an 840m-long, 5.45m-diameter and 45°-inclined penstock, and a conduction tunnel structure.

Power transmission

The electricity generated by the Cortes-La Muela hydroelectric power complex is stepped up from 14.5kV to 400kV, and is evacuated into the grid through a 400kV substation operated by public utility Red Eléctrica de España.

Flexible operations

The Cortes-La Muela hydroelectric power facility utilises excess renewable energy generation capacity from solar and wind sources to store water in the upper reservoirs during off-peak hours, especially during night time.

It functions as a conventional hydroelectric generation facility utilising the flow of water accumulated in the upper reservoir during peak daylight hours.

Apart from delivering low-cost electricity during peak consumption periods, the pumped-storage hydroelectric power complex also plays a key role in grid stabilization in eastern Spain.

Contractors involved with the La Muela II project

Fomento de Construcciones y Contratas (FCC) was engaged for civil construction works, including the erection of underground powerhouse structure as well as the transformer cavern for the La Muela II expansion project.

Obras Subterráneas (OSSA), a construction engineering company based in Spain, carried out tunnelling works for the project.

Voith Hydro won a €36m contract to supply four reversible Francis turbines and spherical valves in 2008, while French electrical equipment maker Alstom supplied four generators for the project.

A consortium of Cavosa, a subsidiary of Sacyr, and Alstom Hydro, was contracted to build the penstock, while Rowa Tunnelling Logistics was sub-contracted for the tunnelling work.

Sygma Technologies provided site management, construction supervision and quality management services during the penstock construction.

Alfran, a subsidiary of Grupo Aldomer, performed thermal welding treatment work for the penstock.

Tamoin was engaged for the assembly of electromechanical equipment, while Prysmian Group delivered power, instrumentation and control cables for the La Muela II expansion project.

Pine Equipos Eléctricos, a subsidiary of Zima Corporation, supplied 12 motor control centre (MCC) switchboards for the project.