600,000 mirrors under the Sun of Granada

On a plain near Sierra Nevada has emerged in recent years a spectacular complex of parabolic mirrors that follow the Sun from East to West, every day. The focus of each group of mirrors, or collector, through a special glass tube, it circulates an oil which increases of 300 to 400 degrees temperature along the circuit to concentrate on him the Sun's rays, to then transfer its heat to water, in the form of steam, moving one it turbine. Thus transforms the solar energy into electricity, as in a conventional thermal central, but on the basis of the Sun, source clean and free of charge and not coal or gas. Part of this energy collected throughout the day through the collectors has stored in the form of heat in huge vats of molten salts to be able to continue to generate electricity eight hours after sunset. Andasol is already, with the launching this month of the third stage, the largest park solar thermal in Europe; but it is, above all, a remarkable piece of engineering that future installations of this type will be based in southern Europe and in North Africa.

Its promoters are five German companies who recognize that they are doing in Spain what what they are especially strong, but they cannot do in Germany due to lack of Sun: the development and application of technology. There is no Spanish electric company in the Consortium, called Solar marquisate by the region in which the central, the Marquis of Zenete, near Guadix is located. It participates in the construction, operation and maintenance of the central, with most, the Spanish company Duro Felguera.

Andasol figures are striking, as it is the vast area covering the municipalities of Aldeire and La Calahorra, in which there was no industrial activity after the closure of some mines in an area.

Only the third stage consists of more than 200,000 mirrors installed in an area of two square kilometers. The solar field it travel 21.888 tubes of four meters long each and the storage capacity is 30,000 tons of salts for eight hours at full load. These are figures very similar to the of the other two earlier phases, totaling more than 600,000 mirrors, from 2 to 2.8 meters of side. Occupy much space, equal to about 210 football stadiums, to produce a relatively modest total power - 150 megawatts- but which is enough to serve half a million inhabitants and that - a very important fact - save 450,000 tonnes of CO2 per year.

"I know best the South from Spain to Germany", commented the German Rainer Kistner, director of Andasol 3, which has nearly two decades in Spain, on the occasion of the inauguration of this third phase. This is due to that Kistner, who worked at the Almeria Solar platform (germ of these and other plants), and now in Ferrostaal (member of the Consortium), has kicked throughout the territory to find the best areas to capture the Sun, which have greater direct solar irradiation. Interestingly, not only are those that have more days of sunshine a year, because it also has the height, among other factors.

It captures more energy from the Sun in Guadix, more than 1,000 meters above the sea level, than in the desert of the Arabian Peninsula to less height and with a more turbulent atmosphere. However, in this area of Granada, the climate is more extreme and in winter the plant will have to occasionally use gas to keep up production. In southern Europe there are other areas with slightly more irradiation, as the island of Crete, and Kistner believes that we must take advantage of them before make the leap to Africa, as he claimed the Desertec project. In any case, notable as factors of choice for a project of this type supported by regional and local authorities, legislation and public incentives and - something essential - the proximity of a high voltage line to dump the generated electricity. At the end and after is concentrated electricity generation different from the spread of photovoltaic.

The construction of several Central solar in Andalusia, with this technology or the concentration (of the rays of the Sun in a central tower, as the recently opened together, promoted by Arab countries and the Group Sener), make this autonomy leader in solar energy. Kistner says they opted for the parabolic collectors for being an already proven technology. However, technological innovation is continuous, and Andasol 3 has been technical improvements over the first two phases that make that less catchment area, and therefore fewer elements, are producing more electricity. The storage capacity has been increased and improvements as the hoses that circulates oil at the entrance of each battery of collectors.

The flat area of Andasol generates enough dust and that is bad for solar capture, so a special, very expensive machine with telescopic arms and revolving brushes continuously runs the collectors cleaning them. When he finishes his work at one end and it is time to start over in the other.

Andasol 3, which has built in only two years, represents an investment of more than 350 million euros and expected to have about 50 permanent jobs. The next project is Extremasol, very similar, in Villanueva de la Serena (Extremadura). It will end up building within two years.