The Australian company Enviromission has come a long way with their massive solar updraft tower project in Arizona. This structure is planned to be even taller than the current highest building in the world, Burj Khalifa (828 m), and is estimated to generate 200MW, powering about 150.000 typical U.S households.
How does a solar updraft tower work?
Solar updraft towers are often confused with the towers that are used in solar thermal power stations. These use large solar mirrors called heliostats to focus the sun’s rays onto the tower. Water is heated to steam and drives around turbines that generate electricity.
There are in fact three different physical phenomena that contribute to the electricity that is generated from solar updraft towers: Kinetic energy in the wind, the green house and the chimney effect. Lets look at these in greater depth:
The sun’s radiation heats the 7 km diameter “green house” that surrounds the massive tower. The key is the difference in temperature from the base of the green house to the top of the tower.
We know that warm air rises up. This is what’s called the chimney effect. The movement of the air soon becomes wind, in other words, the potential energy that lies in the temperature difference, is converted into kinetic energy.
A gigantic suction will develop in the tower, and by strategically placing 32 large turbines at the base of the tower; some of the kinetic energy is converted to electricity, much like how wind turbines produce power (and why some call it a solar wind tower).
Enviromission initially tried to build the power plant in Australia, but due to no government incentives, moved the entire project to Arizona in the United States.
What are the benefits and issues with solar updraft towers?
The solar power tower has all the obvious benefits such as renewable and green, but what are the other ones? One of the major benefits of this power plant is that once it is built it costs nothing to run, other than maintenance and security.
The cost of the plant is calculated to be around $750 million and should be paid back within eleven years by selling the power that is being generated.
The power plant is due to begin delivery of power in the first quarter of 2015. We will be paying close attention to any future updates on this project.
For more details on this project, check out the interview below of Enviromission’s CEO Roger Davy: