DirectIndustry: Where did the idea of using molten salts come from?
Santiago Arias: The idea comes from the United States. The initial project was called Solar 1 and was developed in 1978, after the oil crisis. However, this American experience was not very positive because of problems of salt solidification. So, the first solar plant with a storage system based on molten salts was developed by SENER 30 years later. SENER has been working for many years on prototypes of solar farms, exploring what did not work with Solar 1. Once the issues understood, we were able to conceive and construct Gemasolar, without any serious problems related to the use of molten salts.
DirectIndustry: What did not work with Solar 1? What were the major problems with molten salts?
Santiago Arias: According to the different reports and analyses that were made by the Americans and that we read, it seems that they had problems with pumping the salts, with using the right filter basket and with finding the right materials capable of handling high temperatures. We studied all this to avoid the same problems. And we developed a technology to facilitate molten-salt handling, to choose the most flexible materials and to solve the potential problems of solidification. We studied these questions before doing anything. And we never had a single problem.
My impression is that the first experience was handled mainly, not by industrial people, but by people coming from university, I think the Berkeley was involved. We, instead, seriously tested things before doing something that was commercial.
DirectIndustry: Gemasolar is unique compared to other solar plants but also compared to other renewable energy plants.
Santiago Arias: Gemasolar is the first plant in the world having this technology. The difference with the rest of the solar plants is that the thermal energy delivered to the grid is not related to the sun’s radiation. If you have a cloud, the process of producing electricity is not immediately affected. We can continue to generate electricity at the same rate. It’s very different than any other renewable energy, like wind energy for example, that produces energy according to environmental conditions. The thermal energy we produce can be stored and converted into electricity according to our wish, according to the demand, not according to the moment of the day when the sun is hot and powerful.
DirectIndustry: But Gemasolar needs tons of molten salts to work. Don’t you think this could prevent this technology from becoming widespread?
Santiago Arias: I don’t think the suppliers of sodium and potassium are going to create any limit to the technology. Gemasolar uses 8 thousand metric tons of molten salt. Molten salts are not common salts but they are available in various locations, in South America, in Europe and in China. And those salts are not to be replaced every year. They remain. The salt is just the medium, the material used to transfer the energy from a low temperature to a high temperature and vice versa. It is not consumed. It remains in a closed cycle, getting cooler and hotter everyday. We have been operating for 4 years now and the salts have never been replaced. Salts are ionic materials, so there are very stable. We don’t expect any problems with the molten salts. I dont’ see any reason preventing the plant from remaining operational during 60, 90 or even 100 years.
DirectIndustry: So, this is THE solution that will replace fossil energy?
Santiago Arias: I would say that the southern parts of countries like Spain, Italy or Morocco are going to be literally covered with solar plants in the future. The solar energy is going to be intensively used as well as the wind electricity. My impression is that the oil price is going to continue to increase in the following 50 years. Sooner or later, the renewable energy will replace the fossil energies because the oil price will not be affordable.
DirectIndustry: But do you think solar energy produced by plants like Gemasolar could cover the world’s demand?
Santiago Arias: If you fly over Spain and Andalusia, you will notice that just in the province of Seville there is room for thousands of Gemasolars. Spain has 50 plants in operation producing 2300 megawatts. They contribute to the electricity demand of Spain for 4.2%.
We are not talking about something marginal. And these figures are going to increase in the future. But I don’t think solar energy and concentrated solar plants will be able to cover the energy need of the planet. My idea is that it is going to be a combination of solar, wind, biomass and maybe new renewable energy sources.
DirectIndustry: But the investment is enormous. European funds were involved as well as Abu Dhabi’s capital.
Santiago Arias: The investment is pretty high, indeed. For Gemasolar it was about 220 millions euros.
But take into account that this plant was a first-of-a-kind, SENER is already involved in other tower plants with the same technology and the investment for those new ones will be lower, thanks to what we call ‘the learning curve’ that allows to cut down the construction and maintenance expenses. Anyway, we are speaking about big figures. But considering what Gemasolar is able to produce, from a free natural resource as it is the Sun, I think it is a good investment.
Also, something that is important with this type of technology is that most of the materials, most of the services to produce a plant need to be local. Reinforced concrete, metallic structures, steel have to be local and should not be imported from China. So it is also a way to activate the local economy. For Gemasolar, most of the investment was made on Andalusian resources. This is going to be very important for countries like Morocco and South Africa where SENER is building new solar plants.