US scientists develop self-cleaning solar panels

Scientists in the US have developed self-cleaning solar panels based on technology developed for space missions to Mars.

In a report at the 240th National Meeting of the American Chemical Society (ACS), they described how a self-cleaning coating on the surface of solar cells could increase the efficiency of producing electricity from sunlight and reduce maintenance costs for large-scale solar installations.

‘We think our self-cleaning panels used in areas of high dust and particulate pollutant concentrations will highly benefit the systems’ solar energy output,’ said study leader Malay K Mazumder, Ph.D. ‘Our technology can be used in both small- and large-scale photovoltaic systems. To our knowledge, this is the only technology for automatic dust cleaning that doesn’t require water or mechanical movement.’

Mazumder, who is with Boston University, said that the need for this technology is growing with the popularity of solar energy. The use of solar, or photovoltaic, panels is said to have increased by 50 per cent from 2003 to 2008 and forecasts suggest a growth rate of at least 25 per cent annually.

Large-scale solar installations already exist around the world and are often located in desert areas where dry weather and winds sweep dust into the air and deposit it onto the surface of a solar panel.

This dust reduces the amount of light that can enter the solar panel, decreasing the amount of electricity produced. Clean water tends to be scarce in these areas, making it expensive to clean the solar panels.

‘A dust layer of one seventh of an ounce per square yard decreases solar power conversion by 40 per cent,’ said Mazumder. ‘In Arizona, dust is deposited each month at about four times that amount. Deposition rates are even higher in the Middle East, Australia and India.’

Working with NASA, Mazumder and colleagues initially developed the self-cleaning solar panel technology for use in lunar and Mars missions.

‘Mars is, of course, a dusty and dry environment, and solar panels powering rovers and future manned and robotic missions must not succumb to dust deposition,’ continued Mazumder. ’But neither should the solar panels here on Earth.’

The self-cleaning technology involves the deposition of a transparent, electrically sensitive material deposited on glass or a transparent plastic sheet covering the panels.

Sensors monitor dust levels on the surface of the panel and energise the material when dust concentration reaches a critical level. The electric charge sends a dust-repelling wave cascading over the surface of the material, lifting away the dust and transporting it off of the screen’s edges.

Mazumder said that, within two minutes, the process removes about 90 per cent of the dust deposited on a solar panel and requires only a small amount of the electricity generated by the panel for cleaning operations.

The current market size for solar panels is about $24bn (£15bn), according to Mazumder. ‘Less than 0.04 per cent of global energy production is derived from solar panels, but if only four per cent of the world’s deserts were dedicated to solar power harvesting, our energy needs could be completely met worldwide. This self-cleaning technology can play an important role.’