Spray-on solar may be future for green energy

As Japan seeks to optimize its use of environment-friendly energy sources in the wake of the nuclear crisis triggered by the March 11 earthquake and tsunami, a company here may just have come up with a major breakthrough: spray-on solar cells.

Mitsubishi Chemical Corp. has developed technology that enables solar cells to be applied to buildings, vehicles and even clothing in the same way that paint is applied. The breakthrough means that the places where energy from the sun can be harvested are almost limitless.

The new solar cells utilize carbon compounds which, when dried and solidified, act as semiconductors and generate electricity in reaction to being exposed to light. Most existing solar cell technology requires crystalline silicon to be sandwiched between glass sheets and positioned on the roofs of homes and office buildings, or in space-consuming "solar parks."

Scientists have been attempting to increase both the energy-gathering efficiency of solar panels and make them easier to install and use.

Mitsubishi Chemical is the first company to create prototype spray-on solar cells, which at present have a practical conversion level of 10.1 percent of light energy into electricity.

That figure is still some way behind the 20 percent that is standard in traditional crystalline silicon solar cells, but the firm expects to be able to improve the efficiency ratio to 15 percent by 2015 and is aiming to eventually reach 20 percent.

The company said the new painted-on solar cells would be particularly effective when applied to round or curved structures, such as chimneys or the noise-reduction barriers that line many highways in built-up areas of Japan.
It could also be applied to the exteriors of cars and theoretically used to help power the vehicle and even to such flexible surfaces as clothing.

The sprayed-on solar cells are less than 1 millimeter thick - far thinner than existing solar cell technology - and weigh less than one-tenth of crystalline solar panels of the same size, the company said.

Mitsubishi Chemical said it plans to work with domestic carmakers to build a car coated with the new solar cells with the aim of giving the vehicle sufficient power to travel 10 km after being exposed to sunlight for two hours.

The spray-on solar cells are a breakthrough concept, but other organizations are working on similar research to get the most out of energy from the sun. Scientists from The Australian Commonwealth Scientific and Research Organization, the University of Melbourne and the University of Padua in Italy are collaborating on 'printable laser' technology which could impose nano-particles onto wafer-thin panels which could then eventually be developed into into paper-thin solar panels.

JR