Solar Tower Technology

The solar updraft tower uses a German design that dates back to 1982. From a design perspective, the tower, the design centerpiece, is encircled by a glass greenhouse that serves as a collection area.

The particulars of electricity generation with a solar tower starts with the sun heating the air in the greenhouse. As air warms, it naturally gets channeled up the tower.

As the air moves through the tower it passes through an electricity generating turbine.

The design plan is relatively simple and currently an Australian company, EnviroMission, has a license to the technology.

The project's dual construction needs, a large tower and a large glass enclosed greenhouse area, provide some building challenges, including getting a working project through the development and planning stage.

After close to a decade's worth of planning, the beginning of 2001 sees the state of Arizona in the final stages of approving the construction of a 200 MW solar updraft tower.

Mirror tower designs, the second type of solar power tower technology, build on solar thermal principles, or the idea of collecting the sun's heat to drive electricity generating turbines.

One of the better documented projects, went through three phases called Solar One, Solar Two and Solar Tres.

The first two phases of the project were designed to compare different heat storage and transfer processes. Solar One used water tanks as the steam conductor driving the electricity turbines. Solar II switched to a molten-salt conductor.

Storage tanks of molten salt were heated and then that heat was used to generate steam for the turbines. The advantage molten salt designs is that they retain heat longer than water and thus provide for more flexible electricity generation planning.

In 2002, a National Academy of Science Committee reviewed both the Solar One, Solar Two project. As to the cost effectiveness of the plant they say,

"The committee notes... and S&L concludes in the executive summary section that to achieve the cost reductions of scale-up, a total redesign and optimization of the field, the tower, and receiver are required. This implies considerable engineering development by commercial developers with commensurate risk to investors."

In the years following those early solar thermal tower designs, the basic idea underlying the design has been modified, and used as the design basis for contemporary solar thermal power plants.

© 2006-2011 Patricia A. Michaels.