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
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.
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,
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
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.