There is an estimated 175 petawatts of solar energy absorbed in the upper atmosphere at any time, around 8,000 times the worldwide energy usage in 2004.  This massive unharnessed power has motivated many to study solar power in its various forms as a promising source of alternative energy. 

While moderate adoption of solar power has occurred over the course of the last 40 years, with solar power currently accounting for 0.04% of the world's total energy consumption, there is still a long way to go to fully tap this massive energy source.  Currently, there are three main means of solar power production.  One method is the use of solar troughs or solar power towers which focus solar energy on water or another evaporant, turning it into steam.  This steam then drives turbines and is recondensed to liquid.  One disadvantage, however, is that most current trough plants cannot produce power at night.

Another method is photovoltaics, but these plants tend to be more expensive.  Photovoltaics can have the advantage of no moving parts, though some have motors to allow them to track the sun.  By featuring a smaller number of moving parts, photovoltaics have a slight advantage over troughs, as the extra mechanical components in troughs can easily break and require maintenance.  Troughs, towers, and non-concentrated solar voltaics have approximately the same efficiency -- around 15%.   More advanced solar cell designs promise even higher efficiencies, but are not yet commercially producible. Concentrated photovoltaics have a higher efficiency, but require more infrastructure and more mechanical components. 

Finally, a relatively new approach is to use concentrated solar energy, typically from a parabolic disk, to run a Stirling engine.  This type of production is more expensive and not as extensively researched, but it has efficiency unmatched by anything except concentrated photovoltaics.  

The current record for solar plants is held by a nine-plant 350 MW collective, named Solar Energy Generating Systems, located in the Mojave Desert.  The plant utilizes chiefly trough designs.  The U.S. also holds the record for the third largest plant, also implementing the trough design, the 64 MW Nevada Solar One plant.  The largest photovoltaic plant is far behind, the Beneixama photovoltaic power plant in Spain, at 20 MW.  The largest U.S. photovoltaic plant is the 14 MW Nellis Solar Plant.

Now a new 280 MW trough plant project looks to far surpass past capacities and maximize the potential of this type of solar power.  The new commercial endeavor, launched by Abengoa Solar aims to build what would today be the world's largest solar plant, operating in the Arizona desert.  Abegnoa Solar signed a contract with Arizona Public Service Co. (APS), one of Arizona’s leading energy utilities, to build and operate the plant.

The plant will cover a total of 1,900 acres, almost 3 square miles of desert.  The plant itself will consist of two 140-megawatt steam generators.  The plant will be capable of powering 70,000 homes, while saving 400,000 tons of greenhouse gases.  The plant also eliminates a host of other emissions typical with gas and coal plants.

The plant's name, Solana, was selected as it means "a sunny place" in Spanish.  The plant will implement tracking mirrors on its troughs to track the sun from east to west.  The troughs will concentrate the sun's rays, known as concentrated solar power (CSP) technology, as the sun travels from east to west.  The receiver pipes mounted in the center of the troughs will receive this energy and use it to heat water to over 700 degrees F.  The water is then sent to a heat exchanger to produce steam and generate power.  The troughs will be arrayed in long, massive rows, all feeding in to the two central generators.

As previously mentioned, one key disadvantage of many trough plants is that they cannot produce power at night.  Most current U.S. trough plants switch to burning fossil fuels to keep up with power needs at night.  As long as they only provide 27% of their output from fossil fuels, they are still entitled to alternative energy status.  The new Solana plant looks to do away with fossil fuels entirely, though.  Large tanks of molten salt will store solar energy by day, and by night the plant will maintain a steady production as this thermal energy is drained.  This storage will also help alleviate power problems on cloudy days.

The plant will come online in 2011.  It is located 70 miles southwest of Phoenix, near Gila Bend, Arizona.  APS plans to run the plant for thirty years or more, generating at least $4B USD in revenue, and making $1B USD in economic benefits for the state of Arizona.  The construction will bring in 1,500 jobs, which will help to counteract local effects of the national economic slump.  When the plant comes online, it will employ 85 skilled full-time workers.

Arizona Governor Janet Napolitano lauded both Abengoa Solar and APS.  She said of their efforts, "This is a major milestone for Arizona in our efforts to increase the amount of renewable energy available in the United States."

Santiago Seage, CEO of Abengoa Solar said, "This project not only shows leadership in Arizona and the southwest, but for America. This project will help usher in a new era of large clean and efficient solar power plants. Our commitment to solar energy is global and we will work with utilities, regulators and companies worldwide to make plants like this happen by leveraging the technologies we have been developing over two decades."

Abegnoa Solar is no newcomer to the solar industry.  It built large solar plants in Spain, Morocco, and Algeria.  With this new plant it seeks to expand in the American Midwest.  It hopes to develop gigawatts of capacity in the sun-rich southwest, powering millions.

The plant will receive a long term extension of the solar investment tax credit passed by the U.S. Congress.  For a video on the new plant, provided by Abegnoa Solar, please look here.  For more of the latest developments in solar technologies, please refer to additional stories found here at DailyTech.