That is the beginning - Tâmega - of the route to the 10,000 megawatts of pumping that Iberdrola estimates there is, potentially, in Spain. The company sees pumping as a "country project". Because Spain is an extraordinarily rich territory in sun and wind, which is good news for the energy transition, but it has a certain problem, and the problem is that neither the one (the sun) nor the other (the wind) can be easily stored. Because batteries are still too expensive and/or too small and hydrogen is still certainly far away. So if one night the wind blows "too much" and it turns out that the demand is low (because the truth is that at night many factories stop and domestic demand is also tamed), then either we look for a place to "store" that wind or the grid operator is forced to stop the machines so that there are no imbalances in the system and we have an upset. The problem did not exist in the past when there were only four wind turbines on the peninsula, but times are moving forward and Spain now has almost 30,000 megawatts of wind power (more than 21,000 wind turbines beating the wind), 30,000 megawatts to which Portugal adds another 6,000 MW more.
Well, the solution could lie in pumping, which could become the key accelerator of the energy transition. Iberdrola already has experience in this area. Ten years ago, in 2013, it inaugurated the Cortes-La Muela hydroelectric complex, in Cortes de Pallás (Valencia), with a turbination capacity of 1,762 MW and 1,293 MW of pumping. A formidable work that, ten years later, continues to be - the company boasts - "the largest hydroelectric power complex in Europe". Since then and until today Iberdrola has been involved in the surroundings of the Alto Tâmega, where geology has wanted something similar to what is happening in Cortes de Pallás. Because in the Alto Tâmega there is also a natural step that the engineers have taken advantage of to set up the company's second large pumping station on the peninsula: the so-called Sistema Electroproductor do Tâmega: three dams and three hydroelectric power plants; two of the dams (Daivões and Alto Tâmega) are located on the Tâmega River (which is a tributary of the Douro); the third (Gouvães), on the Torno River, all of them - the entire complex - in northern Portugal, near Oporto.
The three plants will have an installed capacity of 1,158 MW (more powerful the waters of the Tâmega and the Torno than the most powerful nuclear reactor of the entire Iberian Peninsula, Cofrentes, 1,092 MW). The 1,158 megawatts of hydro represents an increase of 6% of the total electrical power installed in Portugal.
Iberdrola estimates that the complex will be capable of producing 1,766 gigawatt hours per year, enough electricity to meet the demand of neighboring municipalities and the cities of Braga and Guimarães (440,000 homes).
But it is undoubtedly its status as a storage facility that distinguishes this hydraulic infrastructure from the vast majority. Because the Tâmega Electroproducer System, in addition to generating electricity, can store it. Its storage capacity is 40 million kilowatt hours (40 gigawatt hours), "the equivalent," according to Iberdrola, "of the energy consumed by 11 million people during 24 hours in their homes. According to the company's estimates, the entire system will avoid the emission of 1.2 million tons of CO2 per year and/or the import of more than 160,000 tons of oil each year.
The story, step by step
In March 2021, the first filling of the Daivões reservoir was completed. It is a concrete dam of the "gravity arch" type, 77.5 meters high, in which 240,000 cubic meters of concrete have been used. The reservoir has a surface area of 340 hectares and a volume of 56.2 cubic hectometers.
The Daivões project has not only involved the reservoir. It has also entailed more than 5 kilometers of power lines, more than 7 kilometers of roads, the construction of a 200-meter-long, 35-meter-high bridge and the commissioning of two wastewater treatment plants.
Daivões is the lower reservoir of the 880 MW Gouvães Pumping Hydroelectric Power Plant. This second plant is reversible, i.e. it generates electricity when it drops water from the upper reservoir, taking advantage of the more than 650 meters difference in elevation between the two, and pumps water from the lower reservoir.
Iberdrola commissioned the first power unit of the Daivões hydroelectric plant (a 220 MW capacity turbine) in January 2022. Gouvães came next. Portuguese Prime Minister António Costa and power company chairman José Ignacio Sánchez Galán inaugurated the Tâmega Gigabattery (the 880 megawatts of pumping) in July.
Right now, Daivões (conventional power plant) and Gouvães (pumped-storage power plant) are already in operation, while the construction of the Alto Tâmega dam and hydroelectric power plant is expected to be operational in the spring of 2024.
"Construction work [on the Alto Tâmega dam] is continuing - Iberdrola says - according to schedule". The dam will be 104.5 meters high: its concreting was completed last year and the reservoir is scheduled to be filled from the autumn of this year, while the two groups of the power plant, with an installed capacity of 160 MW, will come into operation in the first half of 2024.
The project also includes, in its Environmental Impact Statement (EIS), several measures to compensate ecological systems, such as the reforestation of more than 1,000 hectares, the planting of 17,000 cork oak trees or actions to improve the populations of protected fauna in the area. [Below, the Gouvães dam.]
But there is still more. Because Iberdrola wants to link two wind farms to the Tâmega Electroproduction System, "which will turn the complex into a hybrid generation plant". The parks will total 300 MW, so that, according to the company, this will become one of the largest wind power projects in Portugal.
The idea is - as we pointed out at the beginning - not to waste a single blade of wind. If there is demand, all of it will be met as a priority by the wind turbines that are producing; if there is no demand, the wind electricity generated will be used to pump water from the reservoir below to the reservoir above.
The company will thus be able to manage supply and demand between hydro and wind depending on the availability of both resources, but also on the dynamics of market prices, i.e. it will be able to pump water upstream when electricity is cheap, and it will be able to release that water (and generate) when the price per kilowatt hour is higher.
The pumping horizon
The Tâmega Gigabattery already contributes almost 900 MW of pumping capacity to the Portuguese electricity system, an increase of more than 30% over the megawatts of pumping currently available in the country.
Iberdrola is the undisputed leader in energy storage on the Iberian Peninsula, with 4,000 MW of power installed using pumped storage technology, a solution that it considers "the most efficient large-scale energy storage method available today (...) as it has a performance far superior to the best batteries on the market". According to Iberdrola, pumped storage is not only "more profitable", but also "provides stability, security and sustainability to the electricity system, as it generates a large amount of energy with a very fast response time".
The company expects to reach 90 million kilowatt hours (kWh) of storage capacity right now, which will represent an increase over 2018 of almost 30%: 20 million kWh more, "equivalent to 400,000 electric car batteries or 1.4 million batteries for residential use."
For all these reasons, Iberdrola considers pumping "a country solution for the energy transition". According to the company, pumped storage is called to play a fundamental role in this, "since it makes renewable energy production more flexible, guarantees its efficient integration into the electricity system and provides firmness to renewable production. In addition," the company adds, "pumping makes it possible to manage load ramps and diversions.
The government seems to think the same, at least according to its National Integrated Energy and Climate Plan, a document that establishes the national energy and climate objectives to be achieved by 2030. According to this Plan, Spain must add 3,500 MW of new pumping (between now and 2030) to the approximately 5,000 MW installed today (some 2,000 MW of mixed pumping and 3,000 MW of pure pumping, according to Iberdrola's data).
This ambition seems logical, since the National Plan itself proposes to obtain 74% of electricity demand from renewable sources by 2030. And it seems logical to propose that in order to manage a lot of wind and solar energy, storage systems are necessary (because the sun and wind are not always available when we need them). Thus, we need the support of manageable technologies (the sun and wind cannot be turned on and off ipso facto at our whim, as we can do with natural gas combined cycles or solar thermal) and we need to develop storage. Both solutions are essential to ensure security of supply.
Pumping is a mature solution, but there are new technological developments that improve the flexibility and efficiency of plants, increase the viability of sites or reduce costs.
There are different options for constructing a pumping facility, either by building new facilities, creating an upper reservoir in the vicinity of an existing one, linking existing reservoirs or retrofitting existing plants with variable speed reversible turbines. This last option has important advantages as it reduces costs, development time and environmental impact.
Well, Iberdrola assures that in Spain there is potential to build 10,000 MW of pumping "at a cost of less than 1,000 E/kW by making existing turbine plants reversible (with a cost between 150 and 500 E/kW) or by connecting two existing reservoirs by means of reversible groups (with a cost between 500 and 1,000 E/kW)". [Below, the Alto Tâmega dam, which Iberdrola estimates will be completed in 2024. The wall is more than 106 meters high, i.e. higher than the Statue of Liberty, which rises - including the pedestal - up to 93 meters from the ground].
The company estimates that the construction of "the 10,000 MW of viable pumped storage in Spain" would involve an investment of 8,000 million euros and calculates the creation of 112,000 jobs/year (direct effect) and "investments in renewables of 10,000 million euros and 140,000 jobs/year (induced effect)".
Even more: 85% of the investment in pumping - the company assures - would benefit construction companies and capital goods manufacturing companies, with a high percentage of national participation and with qualified employment and there would be a special impact in the emptied Spain.
The advantages are numerous. But the investments are not small and the return is perhaps not sufficiently attractive. Iberdrola sees it this way: "the benefits that pumping brings to the system are not reflected in the profitability of the projects, due to the insufficient remuneration they receive in a market like the current one, which only pays for energy".
So what does the company want?
Well, what the company, chaired by José Ignacio Sánchez Galán, wants is to go beyond the "product" offered by pumping (the kilowatt hour) and assert its status as a "service". Pumping offers a service: storage. And that is not offered by all technologies, nor by all solutions on the market.
"The solution to attract investment is to enable a capacity market, as other European countries have done, where all technologies can compete on the basis of the firm capacity they offer, including storage".
Iberdrola explains how it understands capacity mechanisms. A capacity mechanism -they explain- is a "remuneration mechanism additional to the energy market whose purpose is to promote energy storage and those plants that guarantee security of supply". As simple as that.
Iberdrola argues that capacity mechanisms are an essential element in a future with a high penetration of renewables.
And what does Iberdrola propose?
Well, the company's proposal is very specific: the capacity market should include long-term contracts for new investments that enable the participation of pumping (contracts of more than 25 years awarded more than 5 years in advance).
And it also proposes the involvement of the Administration in the processing of these projects, which should be treated - according to the company - as "projects of strategic interest to achieve the energy transition". Involvement of the Administration because pumping is facing - Iberdrola warns - obstacles such as "long periods to obtain authorizations, insufficient period of validity of the access and connection permit, inclusion in compulsory planning in some projects and concession problems".
In short: 10,000 megawatts, or the pumping route.