Discuss as:

Holiday calendar: Circle of power


A picture taken by the GeoEye 1 satellte on Nov. 4, 2010, shows the Gemasolar power-generating array in Seville, Spain. At the center of the array is a 40-story-high concrete tower, ringed by 2,650 mirrors. The mirrors focus sunlight on the tower, which stores the heat and converts it to energy.

Will future archaeologists assume this circular structure was some sort of 21st-century Stonehenge? They wouldn't be completely wrong if they did: This is Spain's Gemasolar power-generating array, as seen in a satellite image from the GeoEye commercial Earth-imaging venture.

Like Stonehenge, the array is laid out geometrically to track the position of the sun. But Gemasolar isn't meant to mark the year's astronomical milestones. Instead, it will concentrate sunlight to provide power for 25,000 homes around the city of Seville.

The light is focused by 2,650 large mirrors on a 450-foot-high concrete tower, with a central core that heats up to 1,650 degrees Fahrenheit (900 degrees Celsius). The energy is transferred to molten salt for storage, and the heat of the salt drives steam turbines that generate electricity even when the sun isn't shining. The $325 million plant had its official inauguration in October and is due to reach full operation in 2013. At its peak, the concentrated solar-power plant should be able to produce 19.9 megawatts of power.

Check out this previous PhotoBlog posting for ground-level pictures of the array, and watch this video to learn more about the Gemasolar project:

Learn how the Gemasolar power plant works.

Today's view of a solar power plant from space is the latest offering from the Cosmic Log Space Advent Calendar, which has been presenting images of Earth from space every day this month. It's also one of the pictures featured in GeoEye's 2012 calendar. You'll find more satellite views on the GeoEye High Resolution Imagery blog.

Only three more treats remain to be revealed on this year's Space Advent Calendar. Catch up on the pictures you may have missed:

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.