The groundworks for the construction of the world’s first commercialsolar updraft tower may be little more than two years away. Solarupdraft towers use the power that lifts hot air balloons into the air to generate electricity.
The Australian company, EnviroMission has filed land applications inArizona for two 5,500 acre sites, suitable for development of two 200MWSolar Updraft power stations. The company has negotiated a powerpurchase agreement, approved by the Southern California Public PowerAuthority. EnviroMission has appointed ARUP as its design engineer. Thedetailed design of the towers is expected to take between 9 months and a year, when EnvironMission will move to the financing stage.
EnviroMission is planning to build two massive structures. Each tower will be roughly 750 metres in height and 130 metres in diameter. At the base of each tower will be enormous glasshouse structures, dedicated to heating air. The is funnelled into the towers. Hot air rises and theair rushing up the towers will turn a series of turbines – very similarto Kaplan water turbines.
“A key feature of solar updraft towers is that they are verysite-specific,” EnviroMission CEO Roger Davey recently told a reporterfrom CSP Today. “You need to take into account the geological landscapefor the foundations, and the meteorological conditions. The site inArizona is perfect, given that it is within close proximity to a majorgrid, it has flat land and a high insolation.”
The solar updraft does not use any water in the generation cycle andit does not need direct sunlight to generate electricity (unlikeconcentrated solar power and photovoltaics). Instead, the updraft towerrelies on radiant heat. Provided there is temperature variation betweenthe bottom and the top, the updraft tower can produce energy 24 hours aday, seven days a week. In good weather, the plant should operate at acapacity factor of 50% plus, according to EnviroMission.
A prototype tower was built in Spain in the early 1980s which provedthe concept. But the technology was not taken forward to commercialdevelopment. EnviroMission had planned to build its first updraft towerin North Eastern Australia, but the company struggled to get its visionoff the ground. It abandoned its Australian plans and moved to Phoenix,Arizona. They chose the US because they believe it provides the mostadvantageous environment to exploit their technology.
The towers have a lifespan of around 80 years and they do not require much maintenance. The turbines are pressure staged, with slow movingparts, so very low maintenance. They are more akin to jet engines andhydro turbines rather than traditional wind turbines. Duringconstruction, the project will employ 1,500 people. The Solar Tower isexpected to abate approximately 1 million tons of CO2; the equivalent of removing 220,000 motor vehicles from the road.