The Sun is about 150 million kilometres from Earth but the energy it generates is fundamental to life on our planet.
Light from this enormous star – it is more than 100 times the diameter of Earth – could provide vast quantities of electricity if only we were better able to harvest solar energy.
Instead, we remain beholden to other, often less environmentally-friendly, methods of generating power.
More than 40 per cent of the world’s electricity is produced using coal, according to the International Energy Agency, and it was only in 2014 that solar power exceeded the 1 per cent threshold in terms of global electricity production.
Investments in the sector are continuing apace, though, especially in the UAE. Facilities such as the Shams 1 solar power facility at Madinat Zayed reflect a pledge from the authorities that by 2021 clean energy will generate 24 per cent of the country’s electricity.
In Dubai, officials would like to see all buildings fitted with solar panels, and the Mohammed bin Rashid Al Maktoum Solar Park should, by 2030, be capable of producing 5,000 megawatts of electricity.
Aside from investing in solar power capacity, the UAE is improving the technology behind it. At Abu Dhabi’s Masdar Institute of Science and Technology, scientists are developing ways of turning the Sun’s rays into power that are inexpensive and efficient. First reported in The National last October, work by Carlo Maragliano, a doctoral candidate, and Matteo Chiesa, associate professor of mechanical engineering and materials science engineering, involves separating out the various wavelengths in light, and concentrating them. They hope a device that they are developing could be used in the UAE’s solar farms.
“I definitely believe that this technology is potentially useful for the UAE’s solar power industry, as it holds the promise to convert sunlight into electricity at a greater capacity compared to current commercial panels,” said Mr Maragliano.
If all of Abu Dhabi emirate was powered by standard solar farms, solar panels would have to cover about 9 per cent of the land, according to the researchers. With their technology, they say that number could be reduced by half – and the cost would be about the same.
How does it achieve such an improvement? A key factor is the technology’s ability to use a greater range of light wavelengths.
Solar power typically involves a semiconductor, such as silicon, attached to an electrical circuit. When light hits the semiconductor it causes electrons, which are negatively charged particles, to flow, creating electricity in the circuit.
At a commercial scale, this process only harnesses 15 to 18 per cent of the Sun’s energy when using standard silicon-based photovoltaic (PV) cells. The efficiency is poor because the cells do not absorb infra-red light, which has a longer wavelength than visible light, and is inefficient at absorbing blue and green light, which occupies the shorter-wavelength end of the visible spectrum.
Mr Maragliano and Prof Chiesa have developed a device known as a dispersive prismatic lens. As its name suggests, this combines the functions of a prism, which separates or disperses white light into the various colour wavelengths, and a lens, which concentrates light. Also included are different solar cells that each absorb the light of a particular wavelength.
It makes what Mr Maragliano calls a “spectral splitter photovoltaic system”, a reflection of the way that it splits up the light spectrum and, through this, generates electricity.
The researchers have calculated that their method could be about 30 per cent efficient when optimised, a significant improvement on current methods.
“We obtained an increase in efficiency of 15 per cent relative to flat PV panels like those used to power Masdar City,” said Mr Maragliano.
In another plus, this improvement in efficiency is not accompanied by high costs. In fact, the scientists indicate that affordability is one of the key advantages of their method. The device is made from polycarbonate, a cheap transparent plastic, and can be fabricated using injection moulding, which involves heated material being injected into a mould. This allows for inexpensive, large-scale manufacturing and is a process that could be optimised to achieve further savings, the researchers say.
They think that within the spectral splitter improvements can be made by using low-cost solar cells and by fine-tuning which sections of the solar spectrum are absorbed and converted into electricity.
One advantage of the spectrum-splitting technology is said to be that the solar cells used are cheaper than those needed for alternative methods that use lenses and mirrors to focus sunlight on to solar cells. “Lowering the cost of solar cells has a cascade effect on other requirements, making our technology potentially capable of producing electricity at a lower cost compared to conventional solar panels,” said Dr Chiesa.
In only a few years from now, the device could be being used in a commercial setting, the researchers say.
Currently, the spectrum-splitting PV system is “not optimised” and a first step would be for the fabrication of custom-made solar cells and field testing, potentially within the solar test field at Masdar City.
This field testing would allow the researchers to determine the best combination of solar cells, produce final prototypes and test them.
“This would build trust within the solar energy market, which is currently dominated by flat silicon PV. In our opinion, this process will require from three to five years,” said Dr Chiesa.
Although the Masdar Institute offers “continued support” to renewable energy research, the researchers are hoping to also generate interest from the private sector to hasten the commercialisation of their technology.
“External funding from the private sector or individuals is welcomed. We are currently looking for the best ways to promote our technology,” said Dr Chiesa.
The recent paper describing the technology, Point-focus spectral splitting solar concentrator for multiple cells concentrating photovoltaic system, was co-authored with Marco Stefancich, a researcher in Italy.
newsdesk@thenational.ae
Daniel Bardsley is a freelance journalist based in Britain
