"The idea for solar updraft towers…[originated in 1903]…In 1982 a German engineer…[trapped hot air] under a wide expanse of heat-absorbing material and then forced [it] up a central ventilation shaft, powering a turbine in the process…[but] only two fully-functioning solar updraft towers have ever been built: a 22-metre-high chimney in Botswana in 2005, and the 1982 prototype constructed by Jörg Schlaich of Schlaich Bergermann and Partners in Manzanares, Spain…
"Schlaich admits his pilot tower—a small-scale construction which produced up to 50 kW, had a height of 195 metres and a heat-collecting canopy measuring 46,000 sq meters…[was not optimal but] impressed with the results… In the Manzanares pilot, daytime heating of the ground under the canopy meant air continued to be heated into the night, driving the turbine around the clock. Researchers were also surprised to find that condensation allowed plants to blossom in the erstwhile dry earth…"
"…[A solar chimney] requires no water, has virtually no running costs and can be built from low-tech materials…Professor Christos Papageorgiou, whose company FSC Technologies aims to commercialise air-filled, fabric-based ‘floating solar chimneys’ in place of rigid solar updraft towers, estimates a 5 MW plant could be built for around €10 million, producing some 20 GWh per year….[FSC argues that 3% of Earth’s desert] and 1%-efficient solar aero-electric power plants…can produce 50% of [world electricity in 2050]…
"But first the concept will have to win over sceptics, including many in the investor and analyst communities…[They say solar updraft towers] are inefficient, take up a lot of land..[are] not cost-effective…[have investor-detering] long lead times…[and] might lose out to more conventional projects, such as photovoltaic arrays…"
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