Solar Tower, Seville, Spain

A futuristic-looking 11MW solar tower has been completed near Seville, Spain as part of a 300MW solar power project.

Located in the Andalusian countryside in the municipality of Sanlucar la Mayor, the 40-storey concrete tower collects sunlight reflected by a field of 624 huge mirrors. The light is so intense that it lights up dust and water vapour in the air. The project has been widely described as looking like something out of a sci-fi movie.

The Solar Platform at Seville has been constructed by Solucar, using a range of solar technologies. The first two power plants to be brought into operation were the PS10, the world's first commercial thermoelectric solar tower, and Sevilla PV, the largest low concentration system photovoltaic plant. The world's second commercial solar power tower plant, PS20, located at the Solar Platform, started operations on 27 April 2009.

Costing around €1,200m, the whole plant will be completed by 2013, when it will produce around 300MW – energy for around 180,000 homes, equivalent to the needs of the city of Seville.

It will then prevent emissions of more than 600,000t of CO2 into the atmosphere per year over its 25-year life. The platform will create more than 1,000 jobs in the manufacturing and construction phase, and 300 service and maintenance jobs.

This project is the result of cooperation between institutions including Ciemat, the IDEA, and the University of Seville.

11MW Solar power plant

The 11MW PS10 solar power plant generates 24.3GW/hr per year of clean energy. It has 624 heliostats that track the sun, each with a 120m² surface area parabolic mirror. The mirrors are focused on a 115m tower, heating water pipes that provide 200m² of water-cooled energy exchange surface area. The thermal energy produces steam, which drives a turbine to generate electricity. During the day the power drives the air conditioners that cool buildings in Seville.

Heat is also stored as steam to allow generation at half load for an hour or longer after dark. This is a relatively short storage time, partially because the tower uses water rather than molten salt for heat storage. The water is held in thermally clad tanks and reaches temperatures of 250°C – 255°C (instead of around 600°C for systems using salt). Solucar has opted for water to reduce fatigue on the system components and to ensure simplicity and robustness for the project.

Second generation PS20

PS20 has twice the PS10 output (20MW), with 1,255 two-axis sun tracking heliostats driving 120m² mirrors. These mirrors concentrate solar radiation onto the receiver on top of a 165m tower. The tower follows the same technology as that of PS10 for electricity generation.

PS20 represents second generation technology with important improvements to receiver and other critical elements. Features include control and operational systems enhancements, improved thermal energy storage system and a higher efficiency receiver.

The tower can power about 10,000 homes and reduce 12,000t of CO2 emissions in comparison with conventional power plants. The plant has been designed by Abengoa Solar and Abener Energia was the contractor.

Sevilla PV

The 1.2MW Sevilla PV plant is composed of 154 silicon plate heliostats that produce electricity from solar radiation. Abengoa Solar, the research arm of Abengoa Solar, has developed the low-concentration photovoltaic (PV) technology. The plant can generate 2.1GWh of clean energy annually. The remaining power plants will be built over the next few years. They will include low- and high-concentration photovoltaic, tower thermoelectric, parabolic-trough collector and Stirling dish plants.

Abengoa Solar's parabolic trough plants, Solnova 1, 3 and 4, which can generate 150MW of power, are under construction at the Solar Platform. Although power from the plant will be more expensive than from conventional sources, prices will fall as the technologies develop. System costs are also more attractive if compared with the cost of generating power from coal or gas only at times of peak demand.

Solucar

Solucar is the parent company of Abengoa's solar business unit. Abengoa is a Spanish-based diversified energy company. Since having been founded in 1941, it has expanded its operations to include solar energy and bioenergy. The company has opened a new US subsidiary focused on generating electricity using CSP (Concentrating Solar Power).

Abengoa has five business units: Solar, bioenergy, environmental services, information technologies, and industrial engineering and construction.