In a patchwork of agricultural fields outside Seville, Spain, two giant 40-storey-high concrete towers rise. The obelisk-like structures are surrounded by an immense array of mirrors that reflect sunlight, bathing the top of the towers with a blinding white light. The rays of sunlight reflected by hundreds of huge mirrors are so intense that they illuminate the water vapor and dust hanging in the air creating visible beams. The otherworldly spectacle is the world’s first commercially operating power station using the Sun’s thermal energy to produce steam, which is used to power turbines to generate electricity.

The plant’s operator, Abengoa Solar, claims that it generates 11 Megawatts (MW) of electricity without emitting a single puff of greenhouse gas. The solar power plant, currently powers 60,000 homes, but when the project is completed sometime around this year, the plant should generate enough power to service 180,000 homes. The final project, which will be able to produce over 300MW, will include a series of towers, two more of which are being built, and standard photovoltaic power plants, as well as a mixture of newer parabolic solar collectors which will be installed at a later stage.

The power plant consist of two towers – PS10 and PS20. PS10 is surrounded by 624 heliostats – huge mirrors that track the sun throughout the year, reflecting the sun’s rays to the top of the tower where a solar receiver and a steam turbine are located. The PS20 plant is even larger with 1,255 heliostats and will produce up to 20 megawatts when fully operational in 2013. The towers together will prevent emissions of more than 600,000 tones of carbon dioxide into the atmosphere per year over its 25-year life.

The solar plant is supported by a 1.2 MW Sevilla PV plant composed of 154 silicon plate heliostats that produce electricity from solar radiation. The plant can generate 2.1GWh of clean energy annually. The remaining power plants, which will be built over the next few years, will include low- and high-concentration photovoltaic, tower thermoelectric, parabolic-trough collector and Stirling dish plants.

Although power from the plant will initially be more expensive than from conventional sources, prices will fall as the technologies develop.

Solar power plant producing electricity this way are being constructed elsewhere around the world. An even larger plant, Gemasolar Thermosolar Plant, also is Seville Spain operates with 2650 heliostats and produces 19.9 MW of electricity. Gemasolar is the worlds’ first solar power plant capable of delivering power round the clock.

The towers are 571 feet tall (174 m)

Two newer solar power tower facilities have come online in the United States that make the Seville power facility look small.

GWh Gigi Watt hours

The Ivanpah Solar Electric Generating System, is a solar thermal power project currently under construction in the California Mojave Desert, 40 miles (64 km) southwest of Las Vegas, with a planned capacity of 392 megawatts (MW). It will deploy 170,000 heliostat mirrors focusing solar energy on boilers located on centralized solar power towers.

Ivanpah Solar Power Facility Online

According to the State of California Energy Resources Conservation and Development Commission Opening Briefs regarding this project, “The project itself is visually imposing. It would cover roughly 4,000 acres (1,600 ha), most of which would be covered with mirror fields. The panoramic expanse of mirror arrays would present strong textural contrast with the intact, natural character of the desert floor [and] would rise to a height of roughly 459 feet [140 m]; an additional 10 to 15 feet [3–5 m] above that height would consist of lighting to meet Federal Aviation Administration (FAA) requirements.”

Each heliostat is roughly 1-2 square metres.