From the road to the Solúcar solar plant outside Seville, drivers can see what appear to be glowing white rays emanating from a tower, piercing the dry air, and alighting upon the upturned faces of the tilted mirror panels below. Appearances, though, are deceiving: those upturned mirrors are actually tracking the sun and radiating its power onto a blindingly white square at the top of the tower, creating the equivalent of the power of 600 suns, which is used to vaporize water into steam to power a turbine.
This tower plant uses concentrated solar technology – otherwise known as solar thermal power – with a central receiver. It’s the first commercial central receiver system in the world.
Spanish companies and research centers are taking the lead in the recent revival of concentrated solar power, as expanses of mirrors are being assembled around the country for concentrated solar plants. At the same time, Spanish companies are also investing in huge photovoltaic fields, as companies dramatically increase production of PV panels and investigate the next generation of PV. Spain is already fourth in the world in its use of solar power, and second in Europe behind Germany, with more than 120 MW in about 8300 installations of PV. Within only the past ten years, the number of companies working in solar energy has leapt from a couple dozen to a few hundred.
Power from the Sun’s Heat
Southern Spain, a region known the world over for its abundant sun and scarce rain, provides an ideal landscape for solar thermal power. The tower outside Seville, built and operated by Solúcar, an Abengoa company, is the first of a number of solar thermal plants and will provide about 10 MW of power. The company SENER is completing Andasol 1, the first parabolic trough plant in Europe, a 50 MW system outside Granada that will begin operation in the summer of 2008.
Solar thermal power, also known as concentrating solar, works by utilizing the heat of the sun (unlike PV panels, which work on the principle of the movement of electrons between layers when the sun strikes the materials).
Concentrated solar has until recently cost nearly double that of traditional natural gas or coal power plants, and it only works effectively on a large power-plant scale. “You need a very large budget to set up a concentrated solar power system,†says Eduardo Zarza, solar research director at the concentrated solar research center in AlmerÃa. “You need a great deal of land, a steam turbine, an electricity generator, power equipment, people in the control room, staff to run the system.†The costs are also front-loaded, unlike traditional plants: the fuel is free, unlike oil, gas or coal, but the upfront development costs are significantly higher.
During and immediately following the energy crisis of the 1970s, nine solar thermal plants were built in California to produce a total of 350 MW, but until this year no new commercial plant had been built, anywhere in the world, for fifteen years.
PV costs run nearly double that of solar thermal for a power plant of a similar size, but PV has the advantage of modularity; individual homes, companies, and buildings can incorporate PV panels into the building or install solar panels in small spaces. This micro-power approach has helped the market for PV explode in the past five years, while solar thermal remained moribund.
With gas costs rising and the world sharpening its focus on global warming, and governments around the world making a concerted attempt to invest in alternative energy sources on a larger scale, solar thermal is attracting new attention. In Spain in particular, the technology has been assisted by Royal Decree 436, implemented in March 2004, which approved a feed-in tariff (a guaranteed price) for solar thermal power. The
feed-in tariff made building this type of power plant economically viable. The government also recognizes that, as with wind, the support is necessary at the beginning to enable the creation of new plants – which will most likely drive down prices, as has happened in Spain with wind power.
