A lick of solar-power paint could see the roofs and walls of warehouses and other buildings generate electricity from the sun, if research by UK researchers pays off. The scientists are developing a way to paint solar cells onto the steel sheets commonly used to clad large buildings.

Steel sheets are painted rapidly in steel mills by passing them through rollers. A consortium led by Swansea University, UK, hopes to use that process to cover steel sheets with a photovoltaic paint at up to 40 square metres per minute.

The paint will be based on dye-sensitised solar cells. Instead of absorbing sunlight using silicon like conventional solar panels, they use dye molecules attached to particles of the titanium dioxide pigment used in paints.

That gives an energy boost to electrons, which hop from the dye into a layer of electrolyte. This then transfers the extra energy into a collecting circuit, before the electrons cycle back to the dye.

While less efficient than conventional cells, dye-based cells do not require expensive silicon, and can be applied as a liquid paste.

The Swansea team's leader, David Worsley says the idea to paint the cells onto architectural steel grew out of previous research by his group into the ways steel on buildings is degraded by the elements.

They knew that paint fades in sunlight because the titanium dioxide pigment used is sensitive to sunlight. Worsely and doctoral student, Maarten Wijdekop realised they could exploit this by creating a paint that functions as a dye sensitised cell.

Wijdekop now works for steel manufacturer Corus, which is helping develop the technology.

Worsley describes the current research as "a collision between two existing technologies – one for generating electricity and one for applying paint to steel." "We should see a commercial cell in two-and-a-half years," he says.

The solar cells are built up in several layers. Firstly, a barrier of normal paint is laid directly on the steel, then the electrolyte and dye layers, and finally a clear protective film to guard against the elements.

The team have successfully painted small demonstration cells onto steel, and they and colleagues at various UK universities are working to improve the performance of the different layers.

Michael Grätzel [isic2.epfl.ch], at the Swiss Federal Institute of Technology, Lausanne, was one of the original developers of dye-sensitised solar cells, and says the project is "a fantastic idea."

He is confident that the cells will be able to survive on buildings for long periods, pointing out that cells tested outside in Japan were still at full efficiency after 4 years. "These are very rugged systems," he told New Scientist.

Mark Ratner [www.chem.northwestern.edu] of Northwestern University in Chicago is impressed but cautious. He points out that tackling some of the basic inefficiencies of dye-sensitised cells is still a priority – for example, by overcoming the problem of getting sunlight-boosted electrons back into the dye.

Energy and Fuels - Learn more about the looming energy crisis in our comprehensive special report [www.newscientist.com].