Solar Tower

The solar updraft tower is a renewable-energy power plant. It combines three old and proven technologies: the chimney effect, the greenhouse effect and the wind turbine. Air is heated by sunshine and contained in a very large greenhouse-like structure around the base of a tall chimney, and the resulting convection causes air to rise up the updraft tower. This airflow drives turbines, which produce electricity.




The generating ability of a solar updraft power plant depends primarily on two factors: the collector area and the chimney height. With a larger collector area, a greater volume of air is warmed to flow up the chimney; collector areas as large as 7 kilometres (4.3 mi) in diameter have been considered. With a larger chimney height, the pressure difference increases the stack effect; chimneys as tall as 1,000 metres (3,281 ft) have been considered. A tall solar draft tower looks like the KVLY-TV mast.

Heat can be stored inside the collector area greenhouse to be used to warm the air later on. Water, with its relatively high specific heat capacity, can be filled in tubes placed under the collector, increasing the energy storage as needed.1

Turbines can be installed in a ring around the base of the tower, with a horizontal axis, as planned for the Australian project and seen in the diagram above; or—as in the prototype in Spain—a single vertical axis turbine can be installed inside the chimney.

Carbon dioxide is emitted only negligiblycitation needed while operating, but is emitted more significantly during manufacture of its construction materials, particularly cement. Net energy payback is estimated to be 2–3 years.1

A solar updraft tower power station would consume a significant area of land if it were designed to generate as much electricity as is produced by modern power stations using conventional technology. Construction would be most likely in hot areas with large amounts of very low-value land, such as deserts, or otherwise degraded land.

A small-scale solar updraft tower may be an attractive option for remote regions in developing countries.23 The relatively low-tech approach could allow local resources and labour to be used for its construction and maintenance.

Wikipedia: Solar updraft tower(external link)