It has been linked to Abengoa for almost fifteen years, the Top 1 company in the world in solar thermal solutions (there is no company on the face of the Earth that has installed more thermoelectric solar power). Cristina Prieto arrived there, from Cepsa: “I always say that I saw the light, when, in 2006, I started to run the demonstration and R&D plants at the Solúcar Platform. I come from the refining area, and this was a challenge that I could not miss ”. Prieto is today, fifteen years after her arrival at Abengoa, one of the women who knows the best about solar thermal in the world. Energías Renovables has interviewed her: the role of solar thermal in the energy transition - she has told us - is "indisputable".

A general view of the Cerro Dominador Solar Power Plant is pictured in the commune of Maria Elena in the Antofagasta Region, Chile, July 1, 2019. Cerro Dominador Solar Power Plant/Handout via REUTERS – RC189C506020

Cerro Dominador is a solar complex that combines solar thermal and photovoltaic technologies, a formidable installation (110 megawatts of tower technology and 100 photovoltaic) whose start-up is led by two Spanish companies: Acciona and Abengoa. I ponder out loud: without fossil fuels, is hybridization the key to the transition to a 100% renewable model? Or why hybridize?

At Cerro Dominador, which is owned by EIG Global Energy Partners, and where we participate as designers, as a turnkey construction company, we combine photovoltaic production with solar thermal to provide a base supply: supply 24 hours 7 days a week. In fact, Abengoa was already a leader in hybridization of combined cycle plants with solar fields, plants in which gas is at best 80% and solar, 20%. Cerro Dominador is in a desert area of Chile, and there the main consumer is the mining industry, which consumes equally 24 hours a day. So their initial goal was to guarantee this supply.

It is not in any case the only plant where various technologies coexist in which we are working. Right now we are doing many studies on what it would be like to replace generators in coal-fired power plants so that the energy supply is provided by a photovoltaic, or wind, or thermosolar installation, a renewable installation in any case that feeds directly to the molten salts that produce the heat that goes to said generator. The idea is that the same power block can be used and therefore all the coal-fired power plants that have to be dismantled can be reused. We are in the pre-engineering phase. We are requesting these studies, feasibility analysis, in Australia, in the United States, in Chile, in some of the facilities in Spain. [These are projects linked to confidentiality agreements that Abengoa cannot disclose].

To summarize: would this be to replace coal with solar thermal and that everything continue to work?

Replace coal with renewable fuels. It does not have to be solar thermal. What happens is that thermal storage, which is the key product of solar thermal power, does play a fundamental role in these solutions. Thermal storage can be fed with solar thermal or other renewables. And the advantage is that: that you use existing facilities, existing power cycles, and you minimize the impact on local development: you can keep staff, direct and indirect positions ...

Abengoa is working on the analysis and development of "molten salt electric heaters to reduce dumping in the solar field". Heaters ... Dumping ... What is that exactly?

The salts can be heated with solar thermal energy: you charge the warehouse with the solar concentration, but you can also charge the salt tank with thermal energy with an electric heater that you feed from a wind installation, or from a photovoltaic one. Dumping is what you reject, the excess field that you have and that you cannot use because you have a limitation at your point of discharge. That excess field, whether it comes from solar thermal power, or even photovoltaic, you store it. Until now the reject was not used or used with batteries. Well, you also have the option of thermal storage. That is obviously inefficient from a thermodynamic point of view (we are talking about 40% efficiency), but at the same time it is economically profitable. Because when you apply these solutions on existing cycles, the economic reality gives.

Let's see if I understand. The idea is the following: we do not “unplug” the photovoltaic when production is very high and there is not enough demand; or we do not blur the mirrors and that they do not look at the tower when we cannot pour into the network for that reason –there is too much production and low demand–… but, in those cases, we accumulate electricity in the salt tanks in the form of heat And when the price of electricity is high, for example at ten o'clock at night on a Saturday in February, we use that solar energy stored in thermal salts to produce electricity and pour it into the grid.

So is.

And all this thanks to an electric heater.

Yes, through an electric heater that you have to specially design, because it is a complex element in terms of use and durability. And yes, what this equipment allows you to do is heat, with the excess electricity from the network or field, the salts. And when you need to produce, all you have to do is discharge the salts onto the generator and produce electricity on demand.

Okay, let's stop producing electricity for a moment, and let's move on to producing heat. Abengoa is working on the development of new applications for solar thermal technology in the field of process heat production. To what end?

Yes, we work in two main fields. One: electricity generation, and there we have gone to hybrid solutions, because the combination gives us better costs, better manageability and a better capacity factor of the solution. And two: the production of heat, which is actually the natural market for solar thermal power, a technology that concentrates the heat in a fluid (heat carrier), whether it is a thermal oil or salts. In short, that solar thermal technology produces heat: thermal energy with which we can then produce electrical energy, or thermal energy that we can put directly into an industrial process. And here I go. The solar thermal can be perfectly adapted to the heat demand of a refinery, or a petrochemical, or a pharmaceutical, or a food company, or a mining company. We are talking about process heats that demand between 150ºC and 400ºC, [for drying applications in the paper industry, fruit dehydration processes, etc.]. The solar thermal is capable of supplying process heat in that temperature range by heating transfer fluids in the parabolic trough collectors and you can integrate this solution without having to greatly modify the existing installation. In other words, you can change the existing oven, the one that the company now uses, for a solar oven with parabolic trough collectors.

Does that already exist?

Yes. We have facilities already built for the supply of process heat in a mining plant in Chile and for the supply of steam in power plants and supply of domestic hot water in public buildings in the United States. And in Spain we are working with different companies in order to replace the conventional fuel oil, diesel or diesel furnaces with which these companies are now working with solar thermal solutions.

Cristina Prieto directs the demonstration and R&D plants of the Solúcar Platform, where Abengoa has been testing its prototypes since the beginning of the century, 2005-2006. Is that (R&D) the key to Abengoa's success?

Well, all developments in innovation are raised with a commercial approach. And yes, from demonstration plants that allow scalability of results, our products end up reaching the market. We have countless examples of products that have been validated in our demonstration plants at the Solucar Platform, demo facilities that can be five megawatts, which is quite a relevant size. In Solúcar we work everything. On the one hand, parabolic trough technology. We develop new collectors, with different openings; We optimize the hydraulic mechanisms to improve solar tracking and reduce costs, but always maintaining the optical performance of the collector. Then, on the other hand, in a second location, inside Solúcar, we do exactly the same but on heliostats. We work on optimized designs for central receiver technology, we optimize the design, monitoring systems and pointing techniques of the different components of the solar field. And, finally, we have a third location where we do all the optical and quality validation of the equipment with different photogrammetry and deflectometry systems, so that we can see the optical quality of the systems we are designing. And, as I said, there are many examples of validation and jump to the commercial phase.

For example?

Solutions that we have implemented in the parabolic trough plants that we have in Spain, or also in the parabolic trough plants in the United States, or in the tower plant that we have in South Africa, in the facilities with a molten salt tower that we have brought to Luneng Haixi, in China, and that we have now also taken to Cerro Dominador, in Chile. Every time a solution developed and validated by us reaches a commercial phase, it is an example of the success of innovation at Abengoa.

Well, in any case, beyond Solúcar, Abengoa also exists. Because there are several and ambitious R&D projects (multipart and multinational) in which it participates. What is, for example, Solpart?

Yes, it is true, just as we do internal developments, we also participate a lot in European consortia, to continue maintaining this role of technological leadership. The natural evolution of solar thermal technology is process heat. There are already solutions for industrial processes that demand up to 400ºC, solutions that are mature at the component level. But the demand goes even further. There is a demand for solutions for industries that are highly energy-intensive, such as the alumina industry, those that operate with high-consumption minerals, cement plants, or kerosene production. And there we are, in the development of solar thermal solutions capable of producing that heat. We are talking about temperatures that are around a thousand degrees Celsius. This is a technological challenge for us, because to produce that heat in a tower, you have to design components, you have to tackle many challenges… and you have to set up consortia that guarantee each and every part of that technological solution. And an example of this is indeed Solpart, a European project that is in the final phase and that was looking for a tower receiver solution, on a demonstration scale, that would allow the reduction of consumption by cement companies. There we have developed, in collaboration with other R&D centers and with companies such as Cemex, for example, different configurations of receivers that allow working at these extremely high temperatures. And we have worked on the integration of this process heat in the cement industry.

And with what result?

The results have been quite positive. The receptor is still at a relatively low TRL, and that is why we are considering a second phase, a more relevant scale, to evolve the receptor. [The Technology Readiness Level criterion, which comes from the aerospace world, tries to define the different levels in which a technological development is found to try to know its degree of maturity; there are 9 levels; TRL 1 would become the base concept; and TRL 9, the product ready to enter the market].

I hear "solar thermal solutions for the electrointensive industry." Can CSP be a solution for Alcoa?

It is obviously a solution in terms of reducing costs and emissions. What I don't know is if it will arrive on time. We are working to make these processes much more competitive. But it is true that there is still a technological development that implies a series of years working on these solutions to make it a mature and reliable product.

I understand that this is so because temperatures of 1,000ºC are very high. But I have also understood that the solar thermal solutions to produce the other temperatures we have talked about, from 150 to 400, are imminent. Is that so?

Those are imminent. That can already be offered. At the component level you have it. And at the integration software level we have it practically closed. What remains of these solutions of innovation will come more by way of reaching operational maturity in the commercial phase. But at the development level the process is complete, and at the product reliability level on our part it is also completed. These solutions are ready for the market. We have verified them, as I said, in facilities in Chile and the United States. But it is also true that high temperature has not yet reached the relevant scale design closure and that therefore it will need some additional development before reaching its commercialization. We believe that it will be a technological solution, and that it will be a way of applying solar thermal, clearly, but it is not something that you can offer today.

Where is the Spanish innovation in terms of solar thermal compared to the rest of the world?

Well, we are the undisputed leaders, with 35% of the global solar thermal market. There is no other company at the international level that can have a higher development than we have, with a capacity in so many areas, in so many components. Abengoa, in this sense, and in general Spain, with its technology and research centers… We are leaders in solar thermal power. And this is something that must be guaranteed and maintained. Right now we have not outsourced anything. We have the entire value chain of the sector within the country. And I think few technologies can say this. And our commercial products (and I'm not just talking about Abengoa now, but also about other Spanish companies) are all over the world, which supports that leadership.

With whom does the Spanish CSP compete?

As a technologist, China has identified solar thermal as a potential product. And in the last five years she has made an investment that I would describe as… huge. Well, I do not have the word that can define the amount of millions that has been allocated to bring Chinese technology centers to the same level as other technology centers in the world. And it is true that they are catching up with us. I cannot deny that this is there, that it is a clear competition in terms of technological development, and that it has been fostered by an investment by the Chinese Government of an amount unimaginable right now anywhere else. So… At the level of who is going to be our main competition in terms of technological development… China.

What companies compete with Abengoa?

In the thermosolar world there are companies involved in the main projects under construction and development, such as ACWA or Masdar. And there are also other companies from solar belt countries, the Maghreb area, the Emirates, and Chinese companies. Large technology companies such as Google are also working on solar thermal and promoting solutions for both thermal storage and electrical storage with solar thermal fields. In summary, all the countries that are within the solar belt identify solar thermal power as the technology that will allow flexible electricity grids with high penetration of renewables, wind and photovoltaic, which are non-manageable renewable. They need solutions of these characteristics, thermosolar, so that the electrical systems that come are flexible.

What is missing from the solar thermal to re-install power in Spain? Because not a single plant has been opened here since 2013.

We are all thinking about the Integrated National Energy and Climate Plan [which sets as a 2030 Goal the installation of 5,000 megawatts of solar thermal power in Spain between now and then]. There is a need to reconvert the energy market at European level. And worldwide. And it is happening. It is actually being implemented. What we have to be clear about is that solar thermal cannot compete in cost today with other technologies, such as photovoltaics. It cannot compete if what we are looking for is a cheap generation and we only meet that criteria. What I am saying is that we must also attend to others. The additional point of solar thermal must be valued, which is a manageable technology, a technology capable of producing on demand in peak plant conditions or in base supply plant conditions. The Spanish and American markets, those of the entire solar belt area, are going to experience –and they are already doing it– a high integration of photovoltaics, and they will need solar thermal to counteract the curves and make the systems flexible. And that has to be valued, and that has to be reflected in the auction systems.

So I must understand that the key to 100% renewable is solar thermal?

Exactly. Manageability is the key factor that we are going to have in all markets with penetration of renewables. Without this manageability, we will not reach that 100%. And that is the role of solar thermal, an indisputable role, and that we have to put in value. In addition, we have to maintain this technology, as far as possible, as a key product of Spanish technology.

The last one, are there many women in the solar thermal sector?

In the field of research, in which I usually work a lot with research centers, there is a relevant representation. However, at the construction level of commercial plants, no. Our work begins in the conceptual development and ends in the construction and operation phase of the commercial solution. Therefore, we could say that in the earliest stages there is an important female component, but that, in the more commercial stages, in the construction sector, this presence is more minority.

http://helionoticias.es/sin-la-gestionabilidad-de-la-termosolar-no-alcanzaremos-el-100-renovable/

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