How to Clean Solar Panels on Roof: Best Practices
Cleaning solar panels is not that hard. But, before you do anything, check the solar panels thoroughly for any damage- check the undersides for any exposed wires, as small animals might have gotten into them. Check the solar panel glass for any cracks, even minor cracks, and postpone your cleaning until they are fixed.
First, use a soft brush to wipe off some of the loose dust and debris from the surface of your solar panels. This will make cleaning the solar panel much more effortless.
Do not use rough scrubbers or anything sharp or metallic as they can scratch the solar panel’s glass. The glass you will be cleaning is just the outer covering of the solar panel – the photovoltaic cells that generate electricity from sunlight are present underneath this glass.
Scratches on the surface of the glass will permanently cast a shadow onto the PV cells and lead to reduced electricity production. A few scratches might seem like a small problem, but this can greatly reduce their efficiency over the years and successive cleanings.
After brushing, use a garden hose, or a bucket, to wash the solar panels with water. Do not use a power wash to clean your solar panels, as water with a pressure of more than 35 bar can damage power cells.
This will be enough to get rid of dust most of the time. However, if grime persists, or to clean the edges of your panels, use a soft brush, sponge, or microfiber cloth and water to clean thoroughly.
You can also use soft detergent, soap, or window cleaning solutions. We will discuss what chemicals to use and what to avoid in a later section.
After cleaning with water, use a squeegee or wiper to remove any water from the surface of the solar panels. Water that remains on the glass surface will attract dirt and then dry off, leaving a residue, making all your hard work vain.
So you see, cleaning solar panels is not that difficult. Still, sometimes it may be better to forgo doing it yourself and get the services of a professional solar panel cleaning company. Why? Read on to find out.
Safety measures while cleaning solar panels
Most domestic solar panels are installed on rooftops.
That means you need to get on a roof to clean solar panels most of the time. If it is a flat roof, then it is not that much of a problem, but things get a little more dangerous if it is a sloping roof.
Since you will be working up on the roof with brushes and hoses, you will need a proper safety harness and safety gear. That is the best option if you can clean your rooftop solar panels from the ground.
If you cannot ensure proper safety for yourself, do not go on the roof to clean your solar panels. Hire professionals.
Also,
- Do not clean rooftop solar panels in stormy, windy, or rainy conditions.
- Do not meddle with electrical wiring – if you see an exposed wire, do not wash your solar panels; get it repaired first.
- Use a sturdy ladder or scaffolding to get on and off the roof safely.
What should I use to clean solar panels?
Many manufacturers are selling solar panels in the market, and their products have small but significant differences. Always read the manufacturer’s recommendation for cleaning a solar panel, and follow those steps.
Wipe dirt off with soft material.
You can use normal tap water, but deionized water is best suited for cleaning solar panels.
Deionized water is water that is passed through a series of filters to remove all impurities. Since it has almost zero impurities, deionized water leaves no residue when it dries and helps keep your solar panels clear.
You should also avoid using very hot or very cold water. Especially avoid using cold water on hot days or hot water to clean your solar panels on cold days. Such temperature differences can lead to thermal stress in the solar panel glass and even cause it to crack.
Use water that is at ambient temperature.
You can also use window cleaning solutions or soap to clean your solar panels. Just make sure that you wipe them off properly- soap is likely to leave behind a film that attracts dirt.
The cleaning solution or soap that you use has to be mild, non-abrasive, and non-caustic. Use soft, natural cleaning materials without strong acids or alkalis.
Avoid detergents.
You can also use isopropyl alcohol to clean tough stains, as it does not leave any spots on the glass.
Can I clean my solar panels using vinegar?
Yes, you can use vinegar to clean your solar panels.
Vinegar contains acetic acid that breaks up the dirt, grime, and other deposits. It can be a safe, natural alternative to acid-containing soaps and cleaning liquids that can damage your solar cells.
Use domestic vinegar (the kind you have in your kitchen) and not the commercial ones. Their acid content is too high to use to clean solar panels safely, and domestic vinegar has only 5-8% acetic acid by volume.
Can I use a blower to clean my solar panels?
Debris like twigs and leaves can cover up your solar panels’ surface. And unlike dust or sand, which let some light through unless deposited in a thick layer, leaves can cast a complete shadow.
Blowers can be very helpful in removing loose and large debris from the surface of your solar panels.
If you live in a forested area, you may need to frequently blow such debris away to keep your solar panels working efficiently.
Even if you don’t have the time to clean, using a blower to blow debris away can help.
How often should I clean solar panels?
It would be best to clean your solar panels at least one to two times per year.
But that’s the bare minimum.
The real number of times you need to clean your solar panels to maintain optimum efficiency depends on where you live.
If you live in a pollution-free rural area, you can probably get away with the bare minimum.
But if you live in a polluted region, close to industrial areas, highways or construction sites, you will need to clean your solar panels more often.
The same goes for dry and dusty areas, where the wind can blow sand and dust onto your solar panels.
Forested areas will see a lot of bird droppings, which are enemy number one of the solar panels, along with pollen and dry leaves.
Solar panels installed on homes near the sea will see a build-up of salt or marine residue that can affect energy production and require frequent cleaning.
Depending on the level of dust and pollution affecting your solar panels, you may need to clean them as frequently as twice a month.
Panels getting a lot of pollen on their surface will need more cleaning during certain seasons, such as spring.
Rainfall does a very good job of cleaning solar panels for you. In fact, in many cases, in areas that receive frequent rainfall, homeowners can get away with cleaning their solar panels only once a year.
Dry seasons will require more frequent cleaning than wet seasons. But bird poop- bird poop is evergreen- you will need to clean bird poop all year round.
You can probably guess by now that there aren’t any hard and fast rules on how frequently you need to clean your solar panels, and it’s more a matter of realizing when your solar panels need cleaning.
How do I know when my solar panels need cleaning?
You can find out whether your solar panels need cleaning by looking at two things:
- The power output of your solar system
- The solar panels themselves
If the power output of your solar system drops by more than 10 percent, it is usually a good time to clean your solar panels.
Calculating your daily solar panel output is simple:
The wattage of your solar panels × average hours of sunlight your area gets × 75%
Let’s say you have a 150 W solar setup and get around 5 hours of peak sunlight a day. Your average daily output should be
150×5×75/100= 562.5 watts
In this case, if you see the power output from your solar panels dipping to around 500 watts, it’s time to clean them.
Next, you can observe the solar panels themselves. Photovoltaic cells have a deep blue color. While the color varies depending on whether your cells are mono-crystalline or poly-crystalline, you will have an idea of their color when you install them.
Keeping this color in mind, look at the surface of your solar panels.
If you can see a visible brown layer, it’s time for a cleaning.
Also, if the edges have dirt accumulation, or there is a lot of bird poop, or salt encrustation if you are close to the sea, it’s time for cleaning.
Looking at your solar panels is better to determine if they need cleaning than looking at some numbers. Sometimes there might not be much of a drop in energy production, but dust accumulation on the edges and the lower side of a slanted solar panel can cause problems.
Why should I clean solar panels?
Research has found that the energy production by a solar panel can fall by as much as 46% due to the accumulation of dirt and dust on its surface.
This was in the Middle East.
If you live in a dusty desert area, you might see drops in the efficiency of that degree. You can see your solar panels’ energy production decreases by 5-20% when they get dirty in less dusty areas.
Solar panels are awesome because they just sit there and help you by reducing electricity bills. But the accumulation of dust and dirt on them can make your bills go through the roof again, and a little periodic cleaning can prevent that.
Not only bills, less energy produced by solar cells means more non-renewable energy used.
Apart from a fall in energy production and efficiency, dust and grime on the surface of a solar panel can actually damage your solar panels and reduce their lifespan.
You see, a PV cell’s conductivity, or its ability to transmit electricity through it, depends on how much energy the PV cell is producing. So if a PV cell, for some reason, like dust accumulation on its surface, produces less electricity than its neighbors, it also conducts less electricity than the surrounding cells.
In other words, the photovoltaic cell becomes a resistor. And since it acts as a resistor, it gets heated up due to the flow of electricity through it.
Such a heated region on the solar panel is called a hotspot, and the phenomenon is called hot-spotting.
Hotspotting can severely damage PV cells. Such PV cells turn brown and lose their ability to generate electricity, needing to be replaced. Hotspotting thus decreases the durability of your solar panels, and you lose money.
Hotspotting is especially likely if only a part of the solar panel is occluded by dirt- the edges, dust accumulation on the lower side of a slanted solar panel, or grime that sticks to the glass, like bird poop.
These regions constantly get heated, which is intensified by the fact they are exposed to sunlight all day long and break down earlier than the other parts of the solar panel.
When should I clean solar panels during the day?
Check your manufacturer’s recommendation to see if they recommend any time for cleaning their solar panels.
Otherwise, you can choose a time to clean the solar panels on your roof based on two things:
- To prevent hampering energy production
- To keep it safe and comfortable for the person cleaning
Generally, solar panels produce most of their power between 7 AM in the morning and 5 PM in the evening. If you clean your solar panel during this time, you are casting shadows and reducing energy production.
Similarly, trying to clean solar panels on your roof at high noon with the sun beating down is not going to be comfortable. If you live in a warmer climate, working on the roof in such conditions, especially during the summer months, can cause you to actually get sick.
Heat and discomfort can also make you less cautious and more likely to hurry, leading to accidents when working on the roof.
Thus, the recommended times for cleaning solar panels on the roof are early morning and evening, when the temperatures are cool and comfortable and your solar panels aren’t at their peak production. Conversely, you can choose a cloudy day to clean your solar panels.
If you happen to be cleaning solar panels in the evening, remember that the panel might still be hot after being in the sun all day long. Do not use cold water as it can make the glass crack.
However, it all really depends on when you can make time to clean your solar panels. If you have to clean them in the middle of the day, be sure to wear light clothing, have protection such as goggles and a cap, and drink fluids throughout the process.
New Methods of cleaning solar panels
As solar energy is becoming increasingly common and new domestic and commercial installations are coming up, researchers are trying to come up with new methods of cleaning solar panels that do not require so much effort as the traditional method described here.
Here are some of the new methods for cleaning solar panels:
Bots
While using robots may not be feasible at the moment for small domestic installations, some commercial installations are using autonomous and semi-autonomous bots for cleaning their solar panels.
This requires little or no human effort and interference, and some bots can be programmed to automatically clean the panels at night and charge and refill water during the day.
These bots can range in size from tractors or cranes to small portable ones.
Maybe they will soon be available for homeowners to use.
Vibrations
Researchers at some universities, such as MIT, are trying to develop a method to make your solar panels self-cleaning.
That’s right. Solar panels will clean themselves, no bots, no humans. They are trying to achieve this by making solar panels vibrate at set frequencies to “shake off” any dust accumulated on their surface.
While this still doesn’t solve the problem of grime like bird poop – yes, I hate bird poop – or the dust that collects at the edges and corners, using vibrations to keep solar panels clean will help maintain higher energy production while requiring far less cleaning.
Nanoparticle coatings
What if, instead of cleaning or shaking the dust off, you didn’t allow dust to settle on your panels in the first place?
Seems like a no-brainer, doesn’t it.
That is popularizing the use of nanocoatings- like the ceramic coatings that you get to protect your car paint- to cover the glass of solar panels.
Such nanoparticle coatings have been used extensively on glass used in windows and facades to keep them spick and span. Now they are being tried on solar panels to prevent dust and grime from sticking to them.
Less dust sticking to your solar panels means less frequent cleanings. Also, nanoparticle coatings are hydrophobic, which means they repel water. So water flows off instead of drying on the panel, as happens in non-coated glass, thus leaving little to no residue.
As such, you could get away with splashing some water on your solar panels from the ground, further reducing the effort or money spent on cleaning them.
Conclusion
Solar panels do not need much maintenance in their lifetime of twenty-five or so years. But they need to be cleaned at least once or twice a year.
Or more, depending on where you live and how easily they collect dust.
Solar panel cleaning can be done using professional help, which costs money, or DIY, where you get to work.
If you think it is unsafe to clean solar panels on your own, always get professional help. In fact, you should get your panels cleaned by professionals at least once a year.
If you decide to go DIY, here are a few Do’s and Don’ts.
Do’s of cleaning solar panels:
- Inspect thoroughly before cleaning
- Use unionized water, if possible
- Use organic/neutral soap
- Get the dust collected at the edges
- Use a soft brush or microfibre cloth to clean solar panels
- Use a safety harness on a tilted roof
Don’ts of cleaning solar panels:
- Do not clean solar panels while they are turned on
- Do not clean the area if the glass is broken, even if there is a small crack
- Do not stand on the solar panels
- Do not use sharp objects to get the grime off your solar panels
- Do not use abrasive/ harsh soap or detergents
- Do not use high-pressure water
- Do not let the water dry off on the surface of the solar panels
