A WHOLE NEW APPROACH TO SUN

Solar updraft tower technology: Not all hot air; Could 2011 be the year that solar updraft towers finally make their debut on the commercial renewable energy landscape?
Rikki Stancich, 15 November 2010 (CSP Today)

"Like many other solar technologies, the concept behind solar updraft towers, or solar chimneys, has been around for more than one hundred years. Based on the principle that heat rises, the idea is that heat, captured in an enormous greenhouse, funnels upward into a tall, hollow tower. As the hot air moves through the greenhouse and upward into the tower, it propels a series of turbines (similar to Kaplan hydro turbines) positioned around the base of the tower.

"…[T]he height of the tower creates the temperature differentiation to create the airflow that drives the turbines…The technology relies on radiant heat, rather than direct sunshine, to heat the air inside the greenhouse. This means that, unlike concentrating solar power (CSP) and photovoltaics (PV), the technology can operate in diffused sunlight – including cloudy or wet weather. In good weather, the plant should operate at a capacity factor of 50% plus, according to Australian solar updraft tower technology developer, EnviroMission."

The concept (click to enlarge)

"Despite the first prototype, (built in 1982 by Schlaich Bergermann in Manzanares, Spain), having been hailed a success, the technology has yet to be commercially developed. But 2011 may well be the year that the technology proves it weight in gold.

"EnviroMission, listed on the Australian securities exchange in 2001, has since been dedicated to refining the technology…[but] has struggled to get [a] project off the ground in the absence of adequate policy support frameworks and incentives…In [2009] the company set up its US headquarters in Phoenix, Arizona…[and its] solar updraft tower project was selected out of hundreds of others from the Southern Californian Public Power Authority’s RFP response for renewable energy projects."

The prototype at Manzanares (click to enlarge)

"EnviroMission has since filed land applications in Arizona for two 5,500 acre (2225.85 hectare) sites, suitable in size for development of two 200MW Solar Tower power stations, has negotiated an SCPPA approved PPA for the off-take of energy generated by the first of two planned solar updraft towers, and has appointed international engineering, design and consulting firm, ARUP, as its design engineer…"

[Roger Davey, CEO, solar updraft tower technology developer EnviroMission:] "The major [advantages are] that…solar updraft towers can produce more power per megawatt installed…it does not use any water in the generation cycle…[and] we can guarantee the output, unlike PV and wind…Nuclear is probably more expensive…While coal has a capacity factor in the 80% region, when you start costing in water, [solar updraft technology] is competitive…But all new technology needs incentives…The first solar updraft tower will be roughly 750 metres tall and 130 metres in diameter. Its visibility is unlikely to cause concern …The towers have a lifespan of around 80 years…"