Solar Thermal Tower

     A Solar Thermal Tower runs on the thermal law that hot air rises. Basically the way a thermal tower works is very similar to what would happen if you combined a convection oven with a chimney.

A solar thermal tower has three main parts. The tower, the collector, and the turbine. The more prominent is the tower itself. The tower is almost like an exhaust. Around the tower is a huge collection area. The collection area is usually a covering of very thin film polymer sheeting, glass, plexiglass or lexan. The sun hits the collection material, heating the area underneath. As this air gets warmed up to around 100 deg, the air looks for an escape route. The heated air can reach speeds of up to 35 mph when exiting out of the thermal tower. If you put wind turbines inside the tower so that the heated, escaping air is making them spin, the heated air can be used to generate electricity.

This type of power plant also works at night. With no modification, the sun not only heats up the air in the collector area, but it also heats up the ground, so at night when the sun goes down, the ground releases its heat which still produces the air current to make the turbines generate electricity. Because of the obvious absence of heat, the power output won’t be quite as much as during daylight hours. However if water is piped through the collection area, it will hold and transfer more heat with greater efficiency when the sun goes down.

One of the main drawbacks to this type of power generation is the need for size. The more area for collection, the greater the amount of heated air, the more power is generated. The same adjustments in output are made with the change in tower height and diameter. The more air you can heat and push through the chimney, the faster you can spin turbines and the more power the can generate. This means more land will be needed and taller stacks. The best types of land for these power centers seem to be desert or otherwise lower valued land

Prototype in Spain

In 1982, a medium-scale working model of a solar chimney power plant was built under the direction of German engineer Jörg Schlaich in Manzanares, Ciudad Real, 150 km south of Madrid, Spain; the project was funded by the German government. The chimney had a height of 195 metres and a diameter of 10 metres, with a collection area (greenhouse) of 46,000 m² (about 11 acres, or 244 m diameter) obtaining a maximum power output of about 50 kW. During operation, optimisation data was collected on a second-by-second basis. This pilot power plant operated for approximately eight years, but “encountered severe structural instability close to the tower due to induced vortices“, and was decommissioned in 1989.

Australian proposal

EnviroMission has since 2001 proposed to build a solar updraft tower power generating station known as Solar Tower Buronga at a location near Buronga, New South Wales. Technical details of the project are difficult to obtain and the present status of the project is uncertain.

On 18 March 2007, the company board announced a merger with the US-based SolarMission Technologies, Inc. SolarMission is now the official Solar Tower developer.

November 1, 2007- Mutual termination of the merger between EnviroMission and SolarMission. They will evaluate the possibility of future alliances when they serve the interests of both parties.

Ciudad Real Torre Solar

There is a proposal to construct a solar updraft tower in Ciudad Real, Spain entitled Ciudad Real Torre Solar. If built, it would be the first of its kind in the European Union and would stand 750 metres tall – nearly twice as tall as the current tallest structure in the EU, the Belmont TV Mast – covering an area of 350 hectares. It is expected to output 40 MW of electricity.