Leading the solar energy blast-off

A technology to grow for decades to come

Power generated by CSP doubled in 2010 to 1,300 MW and could reach 17,000 MW in five years' time, according to estimates by consultancy Emerging Energy Research in its report, Concentrated Solar Power at a Crossroads (May 2010). For its part, the International Energy Agency estimated, in its New Policies Scenario (World Energy Outlook 2010), that concentrated solar power (CSP) would grow in the period between 2008 and 2035 at an annual rate (CAGR) of 19.3%, higher than any other renewable energy, to reach 91,000 MW operative.

In four years ACCIONA has become the world leader in installing Concentrating Solar Power - with three plants operating in Spain and one in the United States

Concentrating Solar Power (CSP), which produces electricity by heating a fluid to a super-high temperature by virtue of the Sun's irradiation, saw a rapid development in California at the end of the 1980s and start of the 1990s. Falls in petrol prices and other determining factors caused new developments in the technology to come to a standstill for more than a decade. But, in 2006, ACCIONA installed a small plant in Arizona and, the following year, brought on line a 64 MW station in the Nevada desert which marked a 'before and after' in the development of the technology.

After the construction and commissioning of its first plant in Spain in 2009 - at Alvarado in Badajoz (Extremadura region) - the Company last year connected another two CSP stations to the grid at Majadas (Caceres) and Palma del Río (Cordoba), respectively. This brought the total operational CSP capacity to 214 MW and investment in the technology to over one billion euros, turning the Company into a global benchmark. In summer 2011, ACCIONA will start up a further CSP station at Palma del Río and has started construction work on a sixth installation - fifth in Spain - at Orellana in Badajoz, which should be up and running by the end of 2012. By then, ACCIONA will have consolidated its position as a benchmark for this technology worldwide, with 314 MW operating. At the end of February this year, Mitsubishi Corporation took a 15% holding in the three Spanish plants ACCIONA already operates, and in Palma del Río II, within the accord signed by both companies to develop projects jointly.

Concentrating Solar Power is a technology with obvious development possibilities, although it is concentrated in the hottest regions on the planet. It differs from solar photovoltaic energy, whose development does not depend upon a high level of irradiation. In the case of CSP, the latter is essential since it consists of heating a fluid to a high enough temperature that, when passed through a heat exchanger, turns water into steam to turn a turbine connected to a generator that produces electricity.

Projects worldwide

Spain and the United States are the countries with the biggest installations in this technology to date. Others such as Australia and India, however, have projects underway. Some initiatives have a wide scope, such as the Desertec project, which will consist of using the potential of the Sahara desert to produce CSP to be consumed in Europe. Development of these and other initiatives will, however, depend upon the existence of regulatory frameworks and infrastructure guaranteeing feasibility of the projects.

Majadas

Second station for Extremadura
The Majadas plant has a capacity of 50 MW and produces around 100 million kWh a year, equivalent to electricity consumed by 30,000 homes. Its solar field occupies 121 hectares in this northern district of Caceres. The plant, which represents an investment of 237 million euros, started up in November 2010 and is ACCIONA's second CSP installation in Spain's Extremadura region. A third is already under construction in the region - at Orellana.

Palma del Río II

First plant for Andalusia
Palma del Río II is ACCIONA's first CSP plant in Andalusia (its twin, Palma del Río I, built by the Company on neighboring land in this district of Cordoba province, is at an advanced stage of construction). The 50 MW station will produce 116 million kWh a year, equivalent to electricity consumed by 35,000 households. Its solar field occupies 123 hectares. Palma del Río II was connected to the network in December 2010 and has meant an investment of 251 million euros.

Process to capture the Sun's heat and produce electricity

• Capturing the sun´s energy
  Solar collectors, lined along kilometers of rows of parabolic cylinder mirrors, rotate on an axis to follow the Sun's trajectory and optimize energy capture. The collector surface at the Majadas and Palma del Río II plants totals 372,240m2.
• Concentration of the sun´s light
  The form of the mirrors was designed to concentrate the Sun's irradiation on their focal line, where an absorbent stainless steel tube is placed, protected by a glass envelope containing a vacuum.
• Transferring the energy to a thermal fluid
  Due to the effect of the concentrated solar radiation, the thermal fluid (synthetic oil) circulating inside the absorbent tubes heats to close to 400° C.
• Steam production
  The fluid transfers its calorific energy to water circulating inside a heat exchanger and turns it into steam. Then the fluid returns to the collectors to heat up again and reinitiate the process.
• Electricity generation
  The steam under pressure drives a turbine which, connected to a generator, produces electricity. The electricity is conducted to a substation where the voltage is raised in order to incorporate it into the network.
• Cooling
  After transferring its energy to the turbine, the steam is converted back to water in a condenser. This is part of an open-circuit cooling system where the resulting water is used again to produce steam.