Per Lindstrand plans inflatable 1km solar chimney By Dave Lee

Technology reporter, BBC News Published duration 20 November 2013

image caption Similar towers have been built - such as this effort in Spain that was shut down after it began to rust

Plans for a 1km (3,280ft) inflatable solar chimney have been outlined by a leading balloon specialist.

Per Lindstrand, who crossed the Pacific in a balloon with Sir Richard Branson in 1991, said the technology could offer more efficient green power generation in remote areas.

It could help in areas with high seismic activity, where maintenance of solid structures is difficult.

He told The Engineer magazine the project could cost about $20m (£12m).

Several companies are experimenting with "solar updraft" technology, which is seen as preferable to flat solar panels. And Lindstrand Tech specialises in developing "lighter than air" technology.

Mr Lindstrand told the magazine there was a need, particularly from research centres based in deserts, to have a cleaner alternative to diesel and gas power, but without the fallibility associated with existing solar technology.

"The problem in this part of the world is the sand is very fine and would very quickly clog up solar panels, so you have a very big cleaning job in a place that has no water," he said.

Making the tower an inflatable structure would bring the cost of the project down dramatically, Mr Lindstrand said, saving hundreds of millions of dollars compared with similar towers made of concrete.

Floating

Research into the technology is being carried out at the Urban Sustainability and Resilience centre at University College London.

While one application is in desert conditions, the team also said it believed building the chimney on water was another option - one which would allow it to support its own weight.

Engineer Patrick Cottam told the BBC that the idea was in its early stages - but work had begun on building a lab-based test model, measuring 3.5m.

"We're getting the first prototype of the floating chimney made by the end of the year," Mr Cottam said.

"I also have some additional funding that will allow me to build another one in the region of 20m tall."

Race to the sky

Using large, thin towers to harvest energy using solar updraft is an idea that is over a century old - a concept first mooted in 1903.

At the base of the tower, a large area of solar panelling collects energy from the Sun's rays. The resulting hot air is sucked up through the chimney, driving wind turbines that generate electricity.

However, the technology has been slow to be develop, thanks in part to the high financial risks in backing a technology that, at scale, might not work.

Past experiences with solar updraft have faced mishaps - one experimental chimney erected in 1982 was decommissioned after cables supporting it were weakened by rust, putting it at risk of falling over.

Ongoing projects include efforts by Australian firm Enviromission, which said it planned to build a tower in Arizona, US.

Mr Cottam said the increasing necessity of developing more efficient renewable energy - coupled with recent super-tall structure success like the Burj Khalifa hotel in Dubai - meant projects such as this could now quite literally get off the ground.

"We are daring to think big," he said. "The financial landscape is changing."

For now, the research is being funded in part by the UK's Engineering and Physical Sciences Research Council.

Mr Cottam has also been awarded money from the 1851 Royal Commission - a body that gives grants to researchers and engineers.