A physicist's dream come true: the largest industrial solar thermal plant in Europe | Technology


The industry is a devourer of resources, some as scarce as water and fossil fuels, and a polluter. However, converting a factory into an energy-independent center, without CO₂ emissions and that returns the equivalent of the supply used to the watercourses, is possible and profitable. It was the proposal of the doctor in physics and professor of thermodynamics at the University of Seville Valeriano Ruiz five years ago. Today, the dream of this benchmark in the clean energy sector, which did not survive (he died in 2021), is a reality and a technological model: the largest industrial solar thermal plant in Europe, installed by the company Engie in the beer from the multinational Heineken in Seville.

The solar thermal installations, which occupy eight hectares of the factory land, have just begun to operate and have reduced by more than half the consumption of fossil gas for the thermal energy necessary in the production process (cooking and pasteurization), which represents 65% of its demand. They hope to exceed 85% after this year. The other 35% of energy required is electrical, mainly for bottling and cleaning, and they already generate it through their own means: a solar plant in Huelva and another biomass plant in Jaén.

The brewing company's global investment in sustainability is 30 million euros in the last two years. The equivalent of two thirds of this amount (20,476,668 euros, of which 13,369,356 come from European Feder funds) has been the cost of the plant built by Engie in Seville, “Compensa. The numbers come out,” says Tomás Madueño, an engineer at the multinational that commissioned the project.

The strategy differs from that of other companies that limit themselves to purchasing additional energy from renewable sources to offset their emissions balances without reducing the use of polluting sources. “An offset strategy based on short-term operational emissions impacts says nothing about the long-term effect,” warns Jesse Jenkinsprofessor at the Andlinger Center for Energy and the Environment and co-author of a Princeton University study published in Joule.

Wilson Ricks, a researcher at this US university, adds: “There are solar projects that do not compete with energy based on fossil fuels, but with other solar projects that could have been built in their place.” In his opinion, “the most cost-effective approach for a company to declare net zero emissions is based almost entirely on acquiring enough solar or wind energy to meet its annual consumption.”

Sagrario Sáez, sustainability director of Heineken, match. “If the plan is to compensate, but you continue producing with non-renewable energy, production and emissions increase.”

With this premise of zero emissions from renewable sources sufficient for the entire production process, the Seville plant was born. The eight hectares of parabolic mirrors concentrate sunlight in a central tube (collector) that, unlike the facilities to generate electricity through this system, instead of synthetic oil, contains only water.

This liquid, as explained by Francisco Corral, engineer of Engie, reaches 210 degrees and is pressurized. From there it goes to a secondary circuit that, through exchangers, reduces the temperature to 160 degrees, which the plant needs to cook the cereal and pausterize the product. The power of this direct process is 30 thermal megawatts (MWt) per hour.

But this system would only allow its use in optimal conditions. To take advantage of all the solar thermal energy generated during the hours of solar radiation and keep the plant at full capacity at night or on days without sun, a warehouse was created to conserve 1,115 cubic meters of hot water. There are eight giant tanks insulated with 200 millimeters of carbon steel capable of providing 68 MWt.

In the tanks, the water is distributed in layers of different temperatures, permanently monitored to release only the lower one when, cooled by mechanical means, it reaches the required degrees. A complex system of tortuous pipes, designed to withstand the expansion produced by heat, directly connects the water from the collectors and the stored water to the plant.

The principle is similar to that of the well-known domestic solar water heaters, so it seems easy to think that its industrial application was obvious. However, the entire plant, unique in Europe, had to be generated from scratch. “The technology existed, but not on this scale,” explains Corral while pointing with his hand to the facilities equivalent to eight football fields.

Nor was it done before because it was necessary for the accounts to balance, for the investment, regardless of environmental and social compensation, to be profitable, something that the rise in energy costs has accelerated. The plant was built in two years, almost twice ahead of schedule, in a process hampered by deadlines to access Feder funds and which involved 150,000 hours of work.

Engie is now the builder, owner and operator of the plant. In 20 years it will transfer it to its client, Heineken, five years before the end of the theoretical useful life of the current installation. “There could be more,” Corral clarifies. “That is the duration for electricity generation plants, which withstand temperatures of up to 350 degrees.”

That useful life is key to the profitability of these facilities. In this sense, Stefaan De Wolf researcher at the KAUST Solar Center and lead author of a work published in Science, warns: “Deployed solar panels must have a useful life that lasts decades. Understanding degradation rates is crucial to establishing competitive pricing and warranties.”

View of some of the panels of the largest industrial solar thermal plant in Europe, this Tuesday. PEPO HERRERA

And, in addition to the economic reason, there is the environmental issue due to the generation of waste when plants become obsolete. Sagrario Sáez assures that the zero waste and complete recycling policy agreed for the entire production process will also apply to the new facility. The panels used are essentially mirrors and do not use the toxic and scarce materials of other systems, such as perovskite.

This project will be replicated, with different technology and scale, at the Heineken plant in Valencia, which opens this February 28, according to forecasts. But the creators of the entire system believe that it is applicable to any industrial process that requires heat for manufacturing and has land next to the factory, since distance is the main degrader of the power achieved.


Although the chosen system (concentrated solar power or CSP) consumes much less water than central tower plants, Valeriano Ruiz's dream was still incomplete. A brewery, by pure logic, is a water guzzler. In traditional systems, more than three liters of this resource are required for each one of the final product.

The Seville factory, where water is oil, has managed to reduce this proportion to 2.6 liters for each liter of beer. Of this total, most of it is part of the product that is consumed (95% of a beer is water), half a liter evaporates in the process and part of the rest is reused for uses other than consumption. “Every drop counts,” highlights Sagrario Sáez. But the objective was more ambitious: recover 1.9 billion liters.

The strategy in this case was to focus on nature's water reservoirs that have been deteriorated and made unusable by human action. A channel, naturally, creates the equivalent of artificial storm tanks, spaces where water from precipitation is stored.

On the Jarama River in Madrid, a former cement factory had nullified a natural wetland by creating a dam to prevent flooding in the plant. The factory abandoned the enclave and left the plug. The recovery of the natural space has revived the lagoon and animal tracks once again mark its shores. The same strategy has been used in several enclaves around Doñana. In the Valencian Albufera, the objective was to eliminate kilometers of reeds, an invasive grass introduced in the 16th century that alters the environment and dries it out.

The intervention in half a dozen natural spaces has allowed the return to the basins of the millions of liters of water planned with an investment of one million euros.

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