Solar updraft tower

The solar updraft tower (SUT) is a renewable-energy power plant for generating electricity from low temperature solar heat. Sunshine heats the air beneath a very wide greenhouse-like roofed collector structure surrounding the central base of a very tall chimney tower. The resulting convection causes a hot air updraft in the tower by the chimney effect. This airflow drives wind turbines placed in the chimney updraft or around the chimney base to produce electricity. Plans for scaled-up versions of demonstration models will allow significant power generation, and may allow development of other applications, such as water extraction or distillation, and agriculture or horticulture.

Commercial investment may have been discouraged by the high initial cost of building a very large novel structure, the large land area required and by the risk of investment, however, there appears to be a renewed interest in solar updraft towers especially in sunny remote areas. A few prototypes have recently been constructed and projects are being proposed for parts of Africa, USA and Australia. An important fact to consider is that solar updraft towers appear to be the only renewable energy technology that can generate electricity from low temperature heat. Functional or mechanical feasibility is not so much an issue now as capitalisation.

A comprehensive review of theoretical and experimental aspects of the solar updraft tower power plant (SUTPP) development is available, with a recommendation for commercial development. A popular update with interview of an informed engineering proponent has been published in National Geographic in 2014.

Power output depends primarily on two factors: collector area and chimney height. A larger area collects and warms a greater volume of air to flow up the chimney; collector areas as large as 7 kilometres (4.3 mi) in diameter have been discussed. A larger chimney height increases the pressure difference via the stack effect; chimneys as tall as 1,000 metres (3,281 ft) have been discussed.

Heat is stored inside the collector area allowing SUTs to operate 24 hours a day. The ground beneath the solar collector, water in bags or tubes, or a saltwater thermal sink in the collector could add thermal capacity and inertia to the collector. Humidity of the updraft and condensation in the chimney could increase the energy flux of the system.

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Wikipedia