A solar chimney prototype in Manzanares, Spain. (Wikimedia Commons)

Towering chimneys have long been thought of as a potential alternative to traditional solar panels, but so far the concept has failed to become a viable reality. But aeronaut Per Lindstrand thinks he has the solution — making the chimneys inflatable. Lindstrand — who is best known for his record-breaking hot air balloon flights with Sir Richard Branson — is working to potentially develop the concept as a source of power for the ALMA Observatory in Chile. Known as a solar updraft tower, the concept was proposed as far back as 1903, and involves using the sun to create an updraft of hot air in the chimney, which is then used to drive turbines and produce power.

However, construction issues have so far held the idea back. In 1982 an experimental tower was erected in Spain, but after eight years it succumbed to the wear and tear of the weather and was decommissioned. An inflatable version, however, could remove issues like rust and wind erosion. "You do need to choose the right materials," Lindstrand tells The Engineer. "I suspect some kind of treatment might be necessary as well. It's the sort of thing that eventually becomes an economic question."

The proposed chimney would be 1 kilometer (3,280 feet) tall, and as big as 7 kilometers (22.960 feet) wide at its base. The inflatable nature would not only make the design potentially more weather resistant, but also cheaper — Lindstrand estimates that it would cost $20 million to build, while a concrete version could cost upwards of $750 million. There are possible issues with the proposal — like finding a material that won't tear and can stand up to UV radiation — but Lindstrand is optimistic those problems can be solved. "A lot of it can be dealt with by good design," he says.