When thinking of solar power most people envision either photovoltaic cells that turn sunlight to electricity or they might think of solar thermal where mirrors reflect solar heat onto a water filled tower, boiling the water which turns a turbine which creates electricity. Enviromission uses hot air created by suns heat to turn turbines creating power.
Enviromission has signed a contract with Southern California Public Power Authority to provide 200MW of electricity from one of its two solar updraft towers slated to be built in Arizona. According to CNN that solar updraft tower will be 2,600 feet tall and will power 100,000 homes.
Both towers will be built of concrete in the Arizona desert. The first one is expected to be the second largest tower in the world. The second tower will presumably be as tall to generate as much energy. Both towers are expected to last 80 years which is much longer than other solar installations.
Around the base of the tower will be “a huge translucent sloping canopy” the width of a football field. The hot air that collects under the canopy is funneled to the solar tower. As the hot air rises through the solar tower it will turn 32 turbines which produce electricity. The taller the tower the faster the turbines spin.
Hot air continues to be released from the ground at night which will keep the solar tower producing energy. Unlike normal solar power, the solar updraft tower will continue producing electricity after dark. Although wind will contribute to the rising hot air in the tower, the production of energy won’t stop when the wind does.
This process also doesn’t require water like conventional forms of electricity production from coal and nuclear power plants. Which is good since Arizona only gets about 7.11 inches a year. Arizona is also in a drought which means it isn’t even getting the normal 7.11 inches of rain so any solar facility that added stress on the state’s water supply would not be welcome.
Other Enviromission solar towers have been built but they have not been as tall as this one. A small iron solar tower was built in Spain. It toppled after seven years because its support wires broke, hence the use of concrete in newer towers. Another small tower is being built in China. This tower will be “built in phases.” The first phase is already up and generating 200 kilowatts per day.
The company still has a few problems to overcome. While it has begun raising funds for the installation, it still has quite a bit more to raise. Then there are the “combination of political factors, environmental policies and the cheap cost of fossil fuels” that have to be overcome.
When these towers do begin operating there will be very little staff or maintenance required to keep the solar tower operational. Air is free unlike coal, nuclear fuel, or fossil fuel used in most power plants today.
The Enviromission’s solar tower will be one of the most environmentally friendly power installations built. It will only take two and a half years of hot air energy production to offset the carbon dioxide generated from shipping in supplies and building the installation. Overall the solar tower should offset 1 million tons of green house gases per year.
I wonder if an updraft tower could be built over Washington D.C.. It seems a shame to waste all that hot air.