Torresol: Towering over the CSP landscape

CSP Today talks to Alvaro Lorente, Torresol Energy’s CEO about molten salt technology and the future of solar towers.

By Rikki Stancich

Torresol Energy, a joint venture between Sener Aeronáutica (60%) and the Masdar initiative (40%), is the first commercial scale solar tower under development consisting of a central tower receiver, heliostats, and a molten salts storage system capable of reaching temperatures above 500 degrees Celsius.

CSP Today: Currently Gemasolar is the only commercial-scale plant to use molten salts in its thermal receiver system. Can you provide a quick overview of the benefits and drawbacks of using molten salts?

Alvaro Lorente: As the first commercial central tower-heliostat plant in the world, Gemasolar will be fitted with a heat storage system where the hot molten salts are stored in special tanks at temperatures exceeding 500 °C. This system will allow Gemasolar to operate up to 15 hours without solar radiation. Thanks to this system, Gemasolar will feature extraordinary energy efficiency, almost three more times than with conventional solar power technology, accomplishing this with only two-thirds of the investment required for others technologies. This new concept has been developed by SENER, the largest Spanish private  engineering and technology group and a 60-percent shareholder of Torresol Energy.

CSP Today: In view of the commercial viability that molten salts lends solar towers, are solar towers likely to dominate the CSP landscape in the future?

Alvaro Lorente: We think so, and in fact the name Torresol already stands for this commitment to tower receiver technology. Today, all the analyses that have been carried out either by us, SENER and Torresol Energy, or by major international institutions show that tower technology is the type of technology that will be capable of generating energy with the lowest costs.

CSP Today: Is Torresol looking at using molten salt as a heat transfer fluid for its parabolic trough plants? What other alternative heat transfer fluids is Torresol considering for its trough plants?

Alvaro Lorente: The molten salt storage system  has  already been installed in Torresol Energy's trough plants,  which  are currently under construction: Valle 1 and Valle 2, in Cadiz (South of Spain).  Oil is used as the heat transfer fluid, but this hot oil also warms up the molten salts that are storaged in tanks, allowing the plants to operate for periods of 7 hours without solar radiation. SENER, our technology provider for these plants, has successfully used this technology in a large number of projects for several clients. Three of these plants are already under operation, including Andasol 1, Andasol 2 and Extresol 1.

CSP Today: Now that the Gemasolar project is under construction, has Torresol run up against any hurdles (unforeseen costs, engineering challenges etc)? Can you share any lessons from this project so far?

Alvaro Lorente: You always learn while you are developing a project, in the process of putting the theory into reality. Gemasolar is the 'first of a kind', the first commercial plant with tower and molten salt technology. SENER and Torresol have come a long way to make this project a reality. It has taken more than four years of conceptual design and testing of critical devices and equipment. From our perspective, the only way to develop a new technology and to scale-up to industrial size is a deep conceptual stage, a rigorous trial run process and a detailed engineering project.

CSP Today: Does Torresol Energy have any other solar tower projects in the pipeline? If so, which ones?  If not, why not? 

Alvaro Lorente: Yes, we have other projects in the pipeline. In Spain we are constructing three CSP plants. Gemasolar plant, our central tower project, and two parabolic trough plants with thermal storage. In addition we are developing the conceptual engineering of a central tower plant in the MENA region and we are launching the development of several plants in the US.