Sand and dust can be some of the worst enemies of photovoltaic energy. This problem, known as soiling impact, is one that Enel Green Power is working to resolve by innovating and developing new technologies.
It’s called soiling impact and it’s one of the most frequent problems in solar technology: in happens when sand, debris or simply dust accumulates on photovoltaic panels.
Because of the dirt, the module cannot capture solar irradiation optimally. Besides not being able to generate the right amount of energy, it could malfunction or break.
The problem of soiling power losses exists in all photovoltaic plants, but it’s a variable phenomenon, and mostly depends on the environment where the site is located: it ranges from 5% a year in temperate climates with moderate rainfall up to 40% a year in particularly arid and desert-like climates.
In some areas, furthermore, where there is night frost or dust in the early hours of the morning, further sedimentation of debris can be caused on the panels’ surface. This further inconvenience is not easy to remove with conventional cleaning tools.
To date, the traditional method of fighting soiling impact has been the periodic manual washing of the panels: a particularly expensive process in terms of economic resources, labour and water, a resource that, in desert areas, leads to an additional sustainability problem, especially for large plants.
Think of our Villanueva plant in Mexico, for example, located in the stifling climate of the semi-desert, with over 2.5 million photovoltaic panels.
Whether by measuring, using new technologies or studying robotic solutions to mitigate the soiling impact at its plants, Enel Green Power is working on a series of initiatives to improve current cleaning systems, with innovation as their strong point.
Measuring the of solar panels Dirt
The first approach in the battle against Soiling impact is the ability to accurately measure the production loss it causes at each location.
To do this, devices are used that automatically calculate the level of energy loss due to the dirt on each panel. The calculation of the Soiling factor is based on the comparison between the measurement of a reference cell or module and a photovoltaic module. All the data collected are analyzed by a software developed entirely by O&M Chile, using algorithms that indicate the best working strategy and the appropriate number of annual cleanings. Currently, Chile has 16 measurement devices installed, in addition to the software implemented in its 8 solar plants.
The tool developed in Chile is called the Optimal Soiling Management Tool, and it allows for the definition of the optimal cleaning strategy for each photovoltaic plant. This model, added to the use of efficient technologies to carry out the cleanings, has been fundamental for the O&M team in Chile, considering the high costs associated with carrying out cleanings and the scarcity of water in the Atacama Desert. In one year, OPEX expenses have been reduced from what was budgeted, higher revenues were obtained thanks to a more efficient cleaning strategy that takes advantage of moments of increased resource, and water consumption at all the solar plants was considerably reduced.
The Solar Panels Cleaning of the Future
EGP’s second front in the fight against soiling impact is the possibility of using ASCs, nanomaterials dispersed in generally alcohol-based solutions.
Once nebulized on the surface of the panels, ASCs create a thin film that, in addition to having hydrophobic properties, is also able to break up the dirt and keep plants clean.
In recent years, at our Innovation Hub&Lab in Catania, we’ve tested seven different ASC solutions, which have shown conflicting characteristics: some showed a real advantage in terms of energy produced/recovered, while others either did not produce any benefits or actually worsened performance.
EGP is now evaluating the feasibility of investment in ASCs in light of the technical problems that are still involved, like application methods.
Robot 2.0 at the Service of Renewable Energy
The use of robotic solutions to automate photovoltaic panel cleaning systems is a particularly stimulating working area for Enel Green Power, which has one of the world’s centres of excellence in its Innovation Hub&Lab di Catania.
In Catania, we tested commercial robots, which we put to the test based on our needs, simulating conditions in the Atacama Desert in Chile.
The results were not especially encouraging, given the specific nature of our needs, the design limitations of the robot and the exact features of the land.
At the same time, our E&C division has been working for years on completely automatic robotised solutions, aiming for dry solutions, that is, without water consumption, and thus responding to the needs of our South American plants.
In collaboration with a start-up in the industry, we developed a completely innovative robotised solution, which is able to deal with uneven ground and clean very efficiently without the use of water, even in unfavourable situations.
The first 3 prototypes of the Italian start-up were tested in Adrano, in the province of Catania, while at the Innovation Hub&Lab, in addition to the commercial solution, we tested the second version of the “Italian” robot.
The robot’s 2.0 version was then brought to Brazil, to the Ituverava plant, where it was put to the test in real dirt conditions, where the modules are mounted on trackers, allowing them to “follow” the position of the sun throughout the day.
The tests at Ituverava confirmed what we had already seen in Catania and led us to work on a lighter version of the robot, to be able to move around with greater ease and lower costs.
Once the current limitations are overcome, we’ll have a solution that is usable on a large scale, to be used for other purposes as well, like the inspection of modules or checks on trackers.
In the last few days, a beauty contest within the E&C Revolution project for “Robot for Module Cleaning” also came to an end, which we hope will help us identify a solution suitable to our needs that can be quickly integrated into plants.
The goal is to bring out the experience we’ve gained over these years and continue to follow the path of innovation in renewable energy.
