[The Vector] 200MW Solar Updraft Power Plant at Application Stage

The groundworks for the construction of the world’s first commercial solar updraft tower may be little more than two years away. Solar updraft towers use the power that lifts hot air balloons into the air to generate electricity.

The Australian company, EnviroMission has filed land applications in Arizona for two 5,500 acre sites, suitable for development of two 200MW Solar Updraft power stations. The company has negotiated a power purchase agreement, approved by the Southern California Public Power Authority. EnviroMission has appointed ARUP as its design engineer. The detailed 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 the air rushing up the towers will turn a series of turbines – very similar to Kaplan water turbines.

“A key feature of solar updraft towers is that they are very site-specific,” EnviroMission CEO Roger Davey recently told a reporter from CSP Today. “You need to take into account the geological landscape for the foundations, and the meteorological conditions. The site in Arizona is perfect, given that it is within close proximity to a major grid, it has flat land and a high insolation.”

The solar updraft does not use any water in the generation cycle and it does not need direct sunlight to generate electricity (unlike concentrated solar power and photovoltaics). Instead, the updraft tower relies on radiant heat. Provided there is temperature variation between the bottom and the top, the updraft tower can produce energy 24 hours a day, seven days a week. In good weather, the plant should operate at a capacity factor of 50% plus, according to EnviroMission.

A prototype tower was built in Spain in the early 1980s which proved the concept. But the technology was not taken forward to commercial development. EnviroMission had planned to build its first updraft tower in North Eastern Australia, but the company struggled to get its vision off the ground. It abandoned its Australian plans and moved to Phoenix, Arizona. They chose the US because they believe it provides the most advantageous 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 moving parts, so very low maintenance. They are more akin to jet engines and hydro turbines rather than traditional wind turbines. During construction, the project will employ 1,500 people. The Solar Tower is expected to abate approximately 1 million tons of CO₂; the equivalent of removing 220,000 motor vehicles from the road.