The objective is clear. In its commitment to renewables, Brussels wants to double the capacity of solar energy installed in the EU to reach 300 GW in 2028. It is not alone in the effort. In China and the US, among other countries, they have also moved to give more weight to photovoltaics and the sector itself has been innovating for years to achieve more efficient installations and gain new spaces.
The point is that more solar panels also means more higher maintenance requirement. And that, in turn, has its own consequences, such as a high demand for water. After all, the most common method for cleaning hobs is pressure jets and sprays.
In 2022, researchers from the Massachusetts Institute of Technology (MIT) collected the available studies, used the calculator and concluded that both photovoltaic plants and concentrated solar thermal energy (CSP) plants consume more or less each year during their cleaning tasks. , between 3.7 and 18.9 million liters of water per 100 MW.
A lot of water… and a considerable expense
That translates into a lot, a lot of water, when taken to a global scale.
At the time of the study, with global photovoltaic capacity exceeding 500 gigawatts (GW), it translated into annual consumption across the planet of up to 10 billion gallons of water, the equivalent of 37.8 billion liters. We are talking about a sufficient contribution to cover the annual needs of up to two million people in developing countries.
The alternative uses that could be given to such a supply – a similar approach can be done with other uses of water, from washing streets to watering gardens – is not, however, the only data that encourages reflection. Sprinklers and washers also cost money, especially in desert regions where the liquid must be transported. It is estimated that cleaning with water can account for up to 10% of the maintenance cost of a photovoltaic park.
With these data on the table, the question is obvious: Is there other forms to clean the solar panels? The option of relaxing maintenance is not on the table. It is estimated that the accumulation of dust on the plates and mirrors can reduce their productivity by about 30% per month.
At MIT there is a team convinced that there is an alternative that would allow us to save enormous amounts of water. Which? Electrostatic repulsion, a method that dispenses with liquid, brushes or other mechanisms that could scratch the delicate surface of the panels.
Cleaning #solar panels currently is estimated to use about 38 billion liters (10 billion gallons) of water per year — enough to supply drinking water for up to 2 million people
— Prof. Michael Tanchum (@michaeltanchum) September 18, 2022
The system consists of passing an electrode—it comes with a simple metal bar—over the plate to generate an electric field that imparts a charge to the dust particles while another is applied through a very thin conductive layer on the surface of the panel. The result is that dirt fragments “jump out”are repelled… and the panels end up clean.
For the system to work, ambient humidity plays a key role.
“We carry out experiments with variable humidity, from 5% to 95%. As long as it is greater than 30%you can eliminate almost all the particles from the surface, but as it decreases it becomes more difficult,” says Sreedath Panat, an MIT student who has described his work with engineering professor Kripa Varanasi in an article published in Science Advance.
The percentage may seem excessive, especially if the system is proposed for photovoltaic installations in the desert, where water is scarcer and cleaning with sprinklers is higher, but the team insists that even in the majority of these environments it could apply its solution.
“It works when the 30% humidity and most deserts fall into that regime.” It would be a matter, they explain, of scheduling tasks well to take advantage of the dew.
Cover image: Mariana Proença (Unsplash)
In Xataka: If solar panels want to be massive, they first have to solve an unexpected problem: dust