The UAE’s seemingly never-ending sunshine makes it an ideal place to set up solar power plants.
However, as is the case elsewhere on the Arabian peninsula, the country also faces challenges when it comes to generating energy from the sun.
As anyone who has left their car parked for just a few weeks will know, dust builds up quickly on surfaces in the Emirates.
While the effects on vehicles are cosmetic, the accumulation of dust on solar panels creates a much bigger headache, as it cuts their ability to generate energy. With the UAE making multi-billion dollar investments in solar power, this is no trivial matter.
The issue is now being acted upon locally with, for example, Dubai Municipality having recently installed machinery to automatically clean solar panels at Al Khazan Park.
Like many other panel-cleaning devices developed in recent years, this machinery is powered by the sun and uses rotating brushes to sweep away dust.
Such sophisticated kit does not come cheap, and cleaning panels can also sometimes lead to damage.
It is therefore useful to be able to quantify how much of a loss of generating capacity that dust on panels causes, so that the costs and benefits of cleaning can be more precisely understood.
A recent study by scientists in the United States and India provides detail that could prove useful.
“With our method, you could start to quantify the downside — not just the damage [from cleaning], but the lost power when you don’t clean. That’s one of the most useful things for industry,” said one of the study’s authors, Drew Shindell, a professor of climate sciences at Duke University’s Nicholas School of the Environment.
Published in the journal Environmental Science and Technology Letters, the research focused on three areas of the world that are ramping up their solar-power capacity: the Arabian peninsula, northern India, and eastern and central China.
As well as looking at the consequences of particles building up on panels, the research also estimated the extent to which ambient particles, which are those floating in the air, block out solar energy. The researchers say theirs is the first work to measure the impact of both ambient and deposited particulate matter, or PM.
Using a computer simulation based on a global climate model developed by the space agency Nasa, the researchers found that the reduction in solar energy generation due to all types of PM in a central eastern section of the Arabian peninsula that includes the UAE is about 25 per cent.
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Perhaps surprisingly, particles deposited on panels accounted for only about two-fifths of this loss in energy, with most being the result, instead, of ambient particles.
The figures on the effects of PM in the study are based on the assumption that panels are cleaned once a month, so that at the beginning of each month, the amount of energy lost as a result of deposited PM goes down to zero, before building up again.
If panels are cleaned only once every two months, then the losses because of deposited and ambient PM jump to 35 per cent when averaged across central eastern Arabia.
However, the situation is potentially much more serious than the figures might suggest, since these numbers are averages for this area. In certain locations, as much as 40 per cent of the energy that solar panels could generate could be being lost, even with a monthly cleaning regime.
“Localised influences are much higher than the average values at some points within the regional [areas] we chose,” said Michael Bergin, a professor in the Department of Civil and Environmental Engineering at Duke University in the United States, and the study’s first author.
Work in other parts of the world has indicated smaller reductions because of dust on panels. A 2013 study in California, for example, found just a 7.4 per cent loss in efficiency if panels are not cleaned for an extended period, a modest enough reduction that, for small-scale installations, regular cleaning may not be worth the cost.
Prof Shindell said he was “a little surprised” at the size of the losses he and his co-researchers identified in Arabia, China and India.
“Other local data we had was typically from the US or Europe. These are generally cleaner areas. We expected the losses to be a bit greater in dirty or heavily polluted [areas]. But I was surprised how big,” he said.
In the Arabian peninsula, about 84 per cent of the loss of energy identified was due to dust. The rest was caused by non-dust PM, which is mostly smaller particles linked to pollution.
In northern India the effects are roughly equally split between dust and non-dust PM, whereas in eastern and central China, it is human-created PM that causes the greatest losses to solar power.
This means that in these other parts of the world, improvements in air quality, likely to happen in the long term as cleaner forms of transport and power generation are adopted, should benefit solar power plants, not to mention human health. In the Arabian peninsula, however, with most of the effects of PM the result of naturally occurring dust, reduced pollution may have less of a beneficial impact on the solar industry. Therefore plant operators will always have to face significant problems because of dust.
“One of the [other] things you could explore is coatings that could make the dust less likely to stick and coatings that would prevent them from being damaged when people wipe them,” said Prof Shindell.
With the recent research mostly based upon computer simulation, the scientists are now keen to carry out field work in this region to “ground truth” their findings.
“We would like to set up experiments across the Arabian peninsula and other locations in China and India to determine the overall impact of dust and air pollution on solar energy production. This is a new field and we are just beginning to understand the overall impacts,” said Prof Bergin.