Author: Jason Deign, Solarplaza
Chilean solar asset managers are gradually increasing the sophistication of operations and maintenance (O&M) procedures to deal the difficult operating conditions of the market. Although until now “O&M hasn’t been optimised,” according to one local developer consulted by Solarplaza, there is a growing trend towards adapting maintenance to the extreme conditions prevalent in Chile’s desert areas.
“Operating assets in these demanding environments is a daily challenge,” said Xavier Real, director of O&M for Solarpack, a Spanish developer with 37 MW of solar power spread across three projects in Chile.
“The presence of sand storms, corrosive environments and distant or logistically difficult work sites are significant factors in the ability to meet production and availability targets.”
The north Chilean Atacama Desert, which is favoured for solar development because it has the highest solar incidence in the world, presents a number of major O&M challenges for PV plant operators. It is the driest place on earth outside the polar regions, with average rainfall of just 15 mm a year.
While this results in little need for vegetation control around solar plants, it also means dust is a massive problem and water for panel cleaning must usually be transported from elsewhere.
In the few places where water can be extracted from wells, its use for panel cleaning can pit plant owners against local communities that also want access. Where it is freely available, the water still needs to be demineralised before use.
For this reason, said Mauricio Charles, technical adviser to the Chilean Solar Energy Association (Asociación Chilena de Energía Solar), “some companies have opted to clean without water, using mops.”
The Chilean solar industry has yet to employ cleaning robots such as those seen in Israel and other advanced PV markets, Charles said. However, a number of specialist companies are starting to introduce advanced cleaning techniques. VerticalClean, for example, is commercialising panel-cleaning technology from Europe and the US that can be used in locations without access to water or mains electricity.
Another firm, Serva, uses water for cleaning but puts it through a purification first to remove minerals that may cause scale or bleaching with long-term use. Based on their experience and on field studies, they usually opt for a special brushing system with a polyester material that has a particular bristle density and width, able to avoid any kind of scratch on the glass of the panel.
Despite these precautions, Charles said that even using purified water can be challenging in the high desert regions in the north of Chile. “There is a lot of wind, which means dust rapidly adheres again to the PV modules,” he said. “Even though they may be dry, microscopically there is still a thin film of water after cleaning which immediately traps or captures small particles of dust, once again forming a film on the solar panel.”
An alternative technology approach to avoid dust on panels is to employ panel coatings that reduce the microscopic irregularities on the surface of cells, making it harder for particles to stick to them.
Using these coatings means the panels “can be cleaned with just compressed air and without the need for water,” Charles said.
Solarpack is considering yet another method to reduce the impact of dust on PV panels, which is to erect wind barriers that help prevent airborne particles from being carried across the solar field. “We would like to evaluate environmental panels that could give us a reduction in wind erosion and fine-particle transport,” said Real.
For now, the use of barriers is more of an ambition than a reality. However, the developer is already using simpler, lower-cost measures to avoid dust deposition on its plants, which include the 25 MW Pozo Almonte and 10.5 MW Pozo Almonte I projects, both in the Tarapacá Region in Northern Chile.
“There are things you can do during the design and engineering phase and that come with experience, such as playing with the position of the trackers so you cut the amount of dust that falls on the PV when they’re not following the sun,” Real said.
Another challenge facing O&M teams tending PV plants in the Atacama Desert is the remoteness of locations. PV plants serving Chile’s mining sector, such as the Pozo Almonte project, can be far from human habitation, which means getting materials, engineers and technicians on site may be expensive and time-consuming.
This is expected to be less of an issue for sub-9 MW Chilean plants being planned under the Pequeños Medios de Generación Distribuidos or PMGD programme, since these smaller projects can be sited closer to urban centres. “For us, it’s a lot easier,” said Thomas Stetter, managing director of Soventix Chile, which is setting up a fund to finance 100 MW of PMGD projects. The Fund’s plants, he said, “are all located close to cities or big villages, and further south, closer to Santiago, not in the desert region, so we can optimise our O&M.”
One of the reasons for caring about O&M under the PMGD scheme is that it provides a guarantee of income similar to a feed-in tariff.
The lack of such a guarantee for plants selling power into the spot market has served as a disincentive for O&M investment in recent times, according to some observers.
This is because an abundance of solar power on the grid in some locations and at some points in time has led to near to zero energy prices and has even seen plants being curtailed. Thus, while many plant owners may be aware of ways to improve output, they may not have much revenue to invest in improvements in the short term.