Much is said about the need to periodic cleaning two photovoltaic modules as a measure of preventive maintenance, whose objective is not to reduce the efficiency of capturing solar energy from a photovoltaic plant, but at the same time there is a lot of doubt about the Frequency this cleaning.
In mid 2017, 2018, there was still a lot of talk in the market that the rain would be enough for cleaning photovoltaic modules – Hoje if you are convinced that it helps, but it is not enough for the vast majority of cases.
But what the manufacturers say? What is the real impact whether or not to carry out preventive cleaning of photovoltaic modules? It's a little bit of what we will discuss next article, bringing a practical case about the impact of dirt on photovoltaic modules in an operating system.
When we deal with the topic of cleaning photovoltaic modules, the main objective, obviously, is the maximum use na capture da solar irradiance by the photovoltaic energy system installed on site. However, this maintenance is also necessary so that we do not have problems regarding equipment warranty and damage to photovoltaic modules.
The so-called hotspots (hot spots) are caused mainly by pre-existing microcracks and also due to dirt concentrated at some point in the module, which can damage the equipment in more serious cases.
Cases of failures caused by hotspots with this cause are not covered by the manufacturers' warranty, resulting in a great loss protocols for Final client, simply because there was no adequate preventive maintenance, that is, there was a loss of generation and loss of material. Not to mention the risk de extreme situations, where this hotspot can even be the starting point for a fire in a photovoltaic system. In the article available on our blog we discuss this effect in more detail – https://amaranzero.es/academia/blog/enemigos-de-la-fotovoltaica-el-hotspot
But what about cleaning? which is a Frequency that manufacturers recommend and which is o type de cleaning which must be applied? Below is a print of the installation manual from a photovoltaic module manufacturer for example:
Figure 2 – Excerpt from the manual from the manufacturer Trina Solar regarding cleaning photovoltaic modules
The system we will present as an example has a 3 kWp inverter and 10 370 W modules, installed in July 2021 in the state of Paraná. Since then, it had not undergone any preventive cleaning maintenance, after 2 and a half years of operation.
Beforehand, we can already say that this is not appropriate and that it certainly ended up impacting the efficiency of the photovoltaic system, not to mention the possible risk of a hot spot occurring that could damage the module.
To have a reference to the impact of dirt on the equipment, we will take three time references from the system monitoring history:
- First months of operation, in August 2021;
- Days before cleaning;
- Days after cleaning, carried out on 10/01/2024.
This is so that we have a reference of how much the system initially produced and how much cleaning may have actually contributed, as comparing the power of the modules with 2 and a half years of operation with the first moments of operation in 2021 would not be 100% correct, due to the natural degradation that all PV modules suffer throughout their useful life.
In figure 3 (Dec-21), the system routinely exceeds 20 kWh, reaching 23, 24 kWh generated on the day. In figure 4 (Dec-23), a few days before the cleaning carried out, we see that it was difficult to even reach 20 kWh in the day's generation. But in addition to the direct impact on daily energy generation as we saw above, we can see the impact also in the power curve of the installed photovoltaic system, exemplified in the illustrations below:
In the first, we have the power curve of the system on a day in the first months of the plant, where it can be seen that the system reached its power limit at around 09:30 am and remained there until around 14 pm, the so-called clipping – when the inverter limits the system power when it reaches its nominal power (in this case, 3 kW).
In the second, we see a day of generation with very little impact of shadows or oscillations, the day before cleaning and we see that at no point was there clipping, as the module power did not even reach the inverter's 3 kW at some point during the day. This demonstrates a limitation in the power of the modules, in this case impacted mainly by dirt on them.
Finally, in the curve below, we see a clean day in January with the system a few days after cleaning the modules, with power clipping occurring again due to the limitation of the inverter's maximum output power, which gives evidence that the dirt on photovoltaic modules was severely limiting the daily production of the photovoltaic system on site.
Looking at the month of January 2024 (when the cleaning took place) completely, after a few days of cloudy/rainy weather, we see that we have already had something around a 10% increase in the system's daily generation, as can be seen below by the inverter manufacturer monitoring platform:
Last point and not least, it is essential that companies specialized in this type of service are hired or that the integrator, who seeks to expand their portfolio of activities and wants to generate value for their client, is trained to offer this type of service.
It may seem basic, but even today we see many situations of companies providing cleaning services that, among other things: step on photovoltaic modules, are not careful with the time of carrying out this service (which can generate thermal shock due to the difference in water temperature) and that use abrasive products not recommended by the manufacturers in their operation and maintenance manuals.
In other words, in order to improve the customer's production, it ends up causing losses to the customer, who may no longer benefit from the photovoltaic module manufacturer's standard warranty. This is linked to the importance of using all individual and collective safety equipment that work at height (on a roof, for example) and with electricity requires.
To conclude the article, extremely relevant information: considering a system that was designed to generate around 450 kWh/average per month, 10% impact means 540 kWh less generated during a year. In other words, the impact of dirt was the same as the system being turned off for more than an entire month during the year. And if cleaning was not carried out, this percentage of loss would normally increase with the accumulation of dirt in the PV module.
References:
manual – Trina solar. Available in https://www.trinasolar.com/pt/resources/s
/como-deve-ser-realizada-a-limpeza-dos-paineis-solares/
The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.
An answer
I read the article and did not find the information I was looking for about CLEANING FREQUENCY, even in the excerpt or printout of one of the manufacturers' manuals. Although each manufacturer can indicate its own interval, it would be good to have a recommendation in the article or citation of what these intervals are on average... annual, semi-annual... or based on URBAN and RURAL, or even some point of observation by the Consumer for this purpose...
Sergio Arestides
Aracaju/SE
29/06/2024