Researchers in Abu Dhabi have created a low-cost device that can make solar cells panels more efficient by splitting sunlight into its constituent colours.
The plastic device both concentrates and separates sunlight into its key spectral components: all the visible colours of the rainbow and invisible infrared. This allows for the layering of solar cells so each coloured ray is directed onto a solar panel designed to convert this colour at maximum efficiency, the researchers say.
“The new device is a combination between a prism, which separates the different wavelengths of sunlight, and a lens, which concentrates the light that can be used to help harness a greater amount of energy from the sun,” explains Carlo Maragliano, the lead author of the research and a PhD student in engineering at the Masdar Institute, a government-funded research organisation in Masdar City.
Traditional photovoltaic cells use silicon to transform light energy into electricity, but this can only absorb some of the sun’s wavelengths from the visible light spectrum, the researchers explain in a paper published in the Journal of Optics. Such cells are poor at absorbing the shorter blue and green wavelengths, converting only 15 to 18 per cent of this light into electricity, the paper says. And no light from the infrared spectrum is absorbed.
By splitting the light and layering the solar cells, around 40 per cent of the energy from the shorter wavelength colours can be turned into electricity, Maragliano tells SciDev.Net. Furthermore, making the device from plastic means it is cheap and can be mass produced, he explains.
“Layering solar cells improves the efficiency of the cells, and concentrating sunlight produces more electricity,” says Matteo Chiesa, a mechanical and materials scientist at the Masdar Institute and another author of the paper.
The Gulf states have huge potential to generate solar power: around 150 billion megawatt hours in a year or 400 times the regional demand.
All states are ramping up solar power production to loosen their dependency on oil, as stated in the national action plans of Gulf countries submitted to the UN Framework Convention on Climate Change setting out their emission reduction strategies. According to the United Arab Emirates’ submission, Abu Dhabi aims to generate seven per cent of its energy needs from solar power by 2020.
However, the new device needs further testing to ensure it can cope with the hot and dusty conditions in the Gulf, says Zeineb Abdmouleh, an engineer at Qatar University. She points out that the type of plastic used in the device is reported to warp under prolonged sunlight exposure.
“Weather conditions, like humidity and dust, could cause divergence of the light” that may weaken the device’s ability to improve solar cell efficiency, she says.
Nonetheless, the researchers want to stick with plastic because the low price would make the device a more attractive tool to improve solar power systems in developing countries. “The next step will be fabricating custom-made solar cells, and testing them with our optical element,” says Maragliano.
He says the team needs to collect more data to determine the best combination of materials for a prototype for mass production. “This process will require from three to five years,” Maragliano explains.