Spain is facing many challenges trying to integrate a large amount of renewable energy (wind and solar) into real-time dispatch of its power generation to meet electricity demand. To meet sustainable criteria for grid stability and reliability, the major utilities in Spain are looking into alternative storage projects, and especially pumped storage projects. Spain has one of the most dynamic markets for pumped storage in southern Europe with a total installed capacity of 5, 350 MW in operation against a total estimated potential of 13,000 MW. Spain is slated to construct additional projects in the coming decades. One government report on renewable energy plans for 2011-2020 estimates a target installed capacity of about 6,300 MW by 2015 and 8,800 MW by 2020. Iberdrola, Gas Natural Fenosa (GNF), and Endesa are the three main utilities that are expected to undertake these developments to fulfill the government objective.

The difficulties in meeting government initiatives concerning renewable energy (RE) integration lie in its variability and unpredictability within the daily and hourly dispatch to match demand and generation. The challenge is to find a way to make energy created by RE resources available to meet changing demand. As the percentage of RE penetration grows, the risk of having a major system failure event from an unpredicted change of RE level will increase. Pumped storage offers the ability to store energy produced from RE resources when it is difficult to utilize these resources on the power grid or integrate them into the power system, and to release the energy at a time when it is most needed, most often during peak electrical demand, at a higher value.

To get a sense of the power generation mix in Spain, Table 1 shows the total installed capacity in 2012 was 108,296MW. Wind capacity in 2012 was 22,362MW or 20.6% of the total, as shown in Figure 1. Solar capacity was 6288MW or 5.8% of the total. Between 2011 and 2012, wind capacity increased by 1123MW and solar by 990MW. The share of renewable sources is expected to reach 38% in the future. Total generation was 287,251GWh, with wind producing 16.8% of the total generation and solar 4.1%.

Total peak demand in 2011 was 43,896 MW. For the period 2005-2011, electricity demand has remained between a low of 42,430MW in 2006 and a high of 45,450MW in 2007.

Looking more closely at pumped storage, in Spain, Pumped Storage Projects (PSPs) can operate in the following three markets:

– Primary Market: exploiting the energy price difference between peak and off-peak hours. Price difference between peak and off-peak energy is about 25 euros per MWh on average. Actual price range varies from 15 to 60 euros per MWh. A typical daily energy price fluctuation chart showed that only three to five hours of true off-peak energy is present in the system.
– Secondary Market: serving the spinning reserve. Current requirement for the spinning reserve in Spain is 5% of total load or 10% of wind generation whichever is greater. For the current conditions, 3,000 MW of spinning reserve is required, and the National Plan is to build an additional 4,000 MW of PSP to serve the future spinning reserve needs.
– Tertiary Market: the revenues from the tertiary market (voltage regulation and reactive power) are not clearly defined and established yet.

PSPs can also assist integrated utilities in better optimizing the operation and dispatch of other thermal power plants. This decreases operation and maintenance costs associated with reduced numbers of starts and stops or operation at lower output and efficiency levels.

In Spain, a day-ahead bidding exists for the various markets. A 100-second response time is currently required to serve the secondary market, and a response time of five minutes is deemed enough for tertiary market. Optimization of the cost of fast start-up of machinery is key. To be able to satisfy future market conditions involving the use of new pumped storage projects to integrate the renewable energy sources, specifically the wind power generation will require, a startup time of 100 seconds as a minimum standard. A shorter time, down to 60 seconds, could provide additional benefits in the future.

Below is a summary of several projects under planning, design or construction by the major utilities of Spain. The use of existing reservoirs is in part because the environmental constraints dictate that utilities are making maximum use of existing dams and reservoirs to develop new pumped storage projects.

Belesar III (Gas Natural Fenosa)
The proposed 210-MW Belesar III PSP will use the existing Belesar and Peares reservoirs on the Miño River, as lower and upper reservoirs. The project area is located near the city of Lugo in northwestern Spain. The main features of the waterways consist of an upper intake/outlet structure, upper level headrace tunnel, pressure shaft, lower level pressure tunnel and penstocks, draft tube tunnels, surge tunnel, a tailrace tunnel, and a lower intake/outlet structure. The powerhouse complex and waterways will all be underground, with limited environmental and visual impacts.
The original license for the development of the Belesar and Los Peares dams and reservoir on the Minos River in order to harness hydro-electricity was issued in 1948. GNF submitted a permit application to the Mino River Basin – Sil in December 2006 for the current PSP effort. The existing Belesar reservoir, which entered in service in 1963, will serve as the upper reservoir. The existing Peares reservoir, which entered in service in 1955, will serve as the lower reservoir.

Edrada (Gas Natural Fenosa)
Gas Natural Fenosa (GNF) is planning the design and construction of the proposed 760-MW Edrada pumped storage project to be located between the existing Edrada and San Estaban reservoirs in Orense in northwestern Spain. The permitting process started in 2008, and a basic engineering for various components were complete in 2011. The powerhouse complex and waterways would be underground.

Salas-Conchas (Gas Natural Fenosa)
The proposed 375-MW Salas Conchas pumped storage project will be located between the Salas reservoir and Las Conchas reservoir in Orense in northwestern Spain. GNF started the preliminary engineering and permitting process in 2008. As currently designed, this project would have an underground powerhouse complex and waterways.

Santa Cristina (Iberdrola)
The Santa Cristina project is a 728-MW planned pumped storage project to be located in northwestern Spain using the existing San Estaban reservoir as the lower reservoir and an artificial upper reservoir is to be constructed. The construction is expected to start in 2013 and to be completed in 2018. The project, with a gross head 820 m, will have an underground powerhouse and waterways. The transmission interconnection will be via a newly constructed 10-km long, 400-kV transmission line.

La Muela II (Iberdrola)
La Muela, with an installed capacity of 635-MW, is the largest pumped storage plant in operation in Spain. It has been in operation since 1989. This project, located near Valencia in southeastern Spain, utilizes the Jucar River as the lower reservoir and an artificial upper reservoir as shown in the picture at right. Expansion of this project by an addition of 852 MW, named La Muela II, is currently underway. La Muela II construction is nearing completion, and is expected to operate at a full installed capacity by the end of 2013.Iberdrola is reportedly investigating the development of three additional pumped storage schemes with a total capacity of 1,640 MW. In addition to these projects, Iberdrola is developing the 1200-MW Alto Tâmega pumped storage project in Portugal, the largest project of its kind in the Iberian Peninsula. This project will be interconnected to the Spanish grid and intended to serve both the Portuguese and Spanish power markets.

Moralets II (Endesa)
The Moralets II project is a 400-MW expansion of the existing Moralets pumped storage project. The existing plant has been in operation since 1985 and is located on Noguera Ribagorzana River in the northeastern part of Spain. The Moralets II expansion is under construction and is expected to come online in 2014. Similar to the existing Moralets plant, the Moralets II will have an underground powerhouse and waterways, largely paralleling the existing powerhouse and waterways.

In addition, Endesa is planning the development of the 550-MW Jabalcón pumped storage project in Zújar, Granada in southeastern Spain. This project would be expected to come online before 2020.

[Author Information]Javier Baztan Moreno graduated in Civil Engineering from the Universidad Politécnica de Madrid, Spain. He also has an Executive MBA from the Instituto de Empresa, Madrid, Spain. He is a member of SPANCOLD, Spanish Commission on Large Dams. He is the Hydraulic Director at Gas Natural Fenosa (GNF) Engineering.Email:

GNF is the biggest integrated gas and electricity company in Spain and the third biggest distributor of gas and electricity on the Iberian market, with 8,8 million connection points. The company ended 2011 with 15,392 MW of installed power, which generated 56,354 MWh. The combined cycle plants form the basis of the company’s mix, as they account for approximately 60.3% of its electricity generation capacity. The rest of the installed power is distributed as follows: coal power plants (13,3%), hydroelectric plants (12,5%), renewable energy (7%), fuel-oil-gas and fuel (3%) and nuclear (3,8%).

Manoj Bhattarai graduated with an MS in Civil Engineering from Southern Illinois University Carbondale, USA. He is a Senior Hydropower Engineer at MWH. Email:

Bruno Trouille graduated with an MS in Engineering from the Institut Catholique des Arts et Metiers of Lille, France. He also has an MS in Industrial Relations from Loyola University, Chicago, USA. He is a Vice President at MWH. Email:

MWH is a global engineering and management consultant with more than 50 years of experience in pumped storage, having been involved with the design and rehabilitation of more than 7,800MW of pumped storage capacity in the US and 8,200MW internationally. The projects range from 40 to 2,100 MW in installed capacity. Along with several thousand megawatts in Europe, Africa and China, MWH has recently looked at more than 10,000 MW of new pumped storage capacity in the United States. MWH has been assisting GNF in its review and analysis of potential PS projects in Spain.