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Cleaning Solar PV Panels

Updated February 2020. If the recent awful weather including storms, driving rain and powerful winds haven't cleaned your solar panels yet, then it's time to face some hard facts ... we suspect, having found this article, as you might already know, these so called 'self cleaning' solar panels are sometimes nothing of the sort! We regularly find solar panels covered in bird droppings, moss, algae, lichen, dust ... Needless to say, there are a lot of very dirty 'self cleaning' solar panels out there... So what do you do about it? If anything?

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Cleaning Solar Panels: Lichen & Algae

Lichen can be a real pain to shift once it's taken a hold of the glass on the top of the solar panel. If you scrub lichen off a solar panel when you are up close, you can see that the lichen is constructed in layers. The top layer (the flower) is relatively easy to dislodge. As this is sometimes coloured, from the ground it might look like once the flower has been removed that the panel is clean. However, it is when you look closely that you can see that the bulk of the underside of the lichen, which has the look and consistency of sticky mud, remains, and that your day of scrubbing has only just begun.

The thing to know about lichen is that it can take many forms and comes in different colours. From the ground lichen can easily be mistaken for bird droppings. Lichen is however much harder to clean. The only way we have ever succesfuly completely cleaned lichen off a solar panel is up close by hand, scrubbing quite hard, using just water.

In researching this topic we did find chemical solutions that claimed to be endorsed by solar panel manufacturers but we haven't yet tried or verified any of these.

Lichen finds the conditions it needs to grow, in wet, warm environments where algae is present, solar panels fit this bill quite nicely. If you can see a luminous green liquid or seaweed looking stuff on your solar panels, then this is likely algae.

Algae will feed the lichen, if you keep the panels free from algae then you will reduce the risk of a lichen problem.

What to do? - Lichen is just horrible for solar panels, the less lichen you have on them the better. Lichens will reduce power outputs and potentially create hot spots on the panels, neither good for power production or the life of your panels. Eventually, if the situation isn't changed and warm, wet conditions and algae remain, then there is nothing stopping the lichen eventually completely covering the solar panels.

A little bit of lichen If there's only a small amount of lichen on your solar panels, then it might be the case that managing the algae with a semi-regular cleaning schedule might keep the situation under control. The best solutions for this (that we know of) are long fibre glass window cleaning poles, no chemicals, cleaned using 'pure water'.

A lot of lichen If there's a lot of lichen, then we would advise that you either hire a scaffold and clean them by hand, pay to get them cleaned, or if you're comfortable, by using chemical methods. Either way, be aware that although cleaning lichen off solar panels is long, hard work by hand. We do not believe that the amount of pressure needed to clean the panels completely free of lichen could be carried out from ground level or even from a scaffold using pure water and poles.

It will be worth it, cleaning off the lichen; as well as likely seeing an increase in power production straight away, your panels will thank you for it. Once cleaned, if the algae problem can be kept in check, than so will the lichen problem. A good window cleaner with a pure water solution could then help keep them clean.

Cleaning Solar Panels: Dust, Dirt & Droppings

Although we have heard of some epic battles involving seagulls, rubbish tips and solar panels; in less extreme cases, a reasonable amount of dirt and soiling can be cleaned off solar panels relatively easily from either ground level or from a scaffold tower with the aid of a fibre glass pole and a 'pure water' system.

The question of when, or whether or not to clean the panels will come down to power production, the cost of cleaning and your personal preference. If you like your panels looking sparkling clean at all times, then your system will not complain if treated this way. If the decision comes down to power production Vs the cost to clean the panels then in our experience, although panels will always perform better when sparkling clean, they can also get pretty dirty before any noticable reduction in power production is experienced.

When looking at the panels, it's the cells that generate the electricity. Quite a bit of dirt could build up on the frames and the non cell parts without neccessarily affecting power production. However if the cells or circuitry is covered with dirt than power will likely be affected.

Most solar panels can also deal quite well with random dirt such as bird droppings but should there come a time where the cells are starting to get covered in dirt and dust and the rain isn't washing it off, and or you notice a decrease in power production then this would be a good time to clean them. Every location and system is different, so the regularity of cleaning could be from every couple of months, to once every few years.

How to clean Solar Panels Safely

Not too hot! Don't clean solar panels when the weather is too hot.

Never clean a damaged system Even when isolated from the mains and with the inverter off, the DC connections will remain live.

Isolate Whenever anyone is working on or near the solar PV system the system should always be isolated and shut down. Isolate the solar PV system by 1) Turning off the AC Isolator (either at the inverter or meter point) 2) Turning off the DC isolators either near or within the inverter. The system will then shutdown.

Watch out for cables Don't touch them or get them wet.

Be on a Safe Footing Ideally cleaning should be carried out from ground level using a long fibre glass pole and a 'pure water' system. If this isn't practicle, then cleaning from a scaffold tower would be far more preferable to using ladders, we would advise against cleaning solar panels from a ladder.

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Solar PV System Repairs

Problems with your solar power system? Solar panels not working? Established in 2007, we are one of the longest serving renewable energy companies around and experts at fixing all things Solar. Solar installers have had a rough few years and many have closed down leaving customers in limbo when things start to fail and systems start to weather and age.

Solar Panel System Repairs

If you do have an issue, any issue with your solar PV system and are currently without an installer then we can help. This includes repairs to roofs, mountings, cables, isolators, meters, inverters, batteries and connectors; anything involved with the day to day maintenance and repair of existing residential and commercial solar PV systems of any size.

You will find us very straightforward and easy to deal with, everything is agreed at the outset and delivered as instructed, at the agreed price. If all you would like, is to have your solar PV system professionally tested and or something needs to be replaced or fixed, then we hope and will do our best to ensure that you will find us to be a good choice of installer to carry out this work.

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Solar PV Installation & Commissioning

Need experienced hands and heads on-site? Our engineers and electricians are some of the best and most experienced in the business. We can add real value to any project through our flexibility, efficiency and the quality of our work.

Solar Panel Installers

Our solar PV installers, roofers and electricians have carried out installations of all shapes and sizes; building solar PV arrays onto most types of roof including commercial roofs and flat roofs. We have built ground mounted frames and installed solar panel mounting structures such as carports and canopies; we have safely installed solar panels on top of barns, in open fields, on factories, houses, workshops, stables, garages and sheds.

Solar PV Installation & Commissioning



Further reading and calculators related to designing, installing, repairing and maintaining solar photovoltaic and electrical systems:

Mains Power Supplies & Earthing Systems

Mains Supply and Earthing Systems: Location & accessability, supply systems, earthing, bonding, labelling, installing RCDs.

Types of Solar Photovoltaic (PV) System

Introduction to the different types of Photovoltaic (PV) System available including Grid Tied, Off-Grid, Hybrid and Batteryless solar PV systems.

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

Solar PV System Components

Overview of the basic components needed to install a complete solar PV system. Introduction to solar PV panels. power inverters, AC & DC isolators and mounting systems.

Free Solar PV Calculators

A list of free solar PV calculators, solar design tools and software, Use to calculate solar yields and the Return on Investment (ROI) for solar PV systems.

Evaluating Solar PV Panels - Which panels to buy?

What to look for when evaluating and selecting solar PV panels for UK installations. Electrical characteristics of solar PV arrays and the safety factors used for selecting BoS equipment, also mounting options.

Solar Panels - PV Array Calculator

Solar Panels: Solar PV System sizing and power yield calculator. Use to work out roof layouts, PV array sizes, No. of panels and power yields. Based on SAP 2009.

Flat Roof Solar PV Array Spacing / Shade Calculator

The minimum required space between parallel rows to avoid shading is decided by the height of the array immediately in front, the slope of the roof and the lattitude of the installation site. This table illustrates the different row spacings required for optimum positioning in different locations.

Solar Electricity - Frequently Asked Questions (FAQs)

How to size a system?, What is kWp?, What is the difference between a kilowatt (kW) and a kilowatt hour ( kWh)?, How does a solar PV system work? Can I add more solar panels to my system? How do I know if my solar panels are working?

Preparing for a Solar Panel Installation

As with any construction project the success and efficiency of a solar PV panel installation comes down to good planning. Some advice for potential system owners preparing for a new solar panel installation.

Planning Permission for Solar Photovoltaic (PV) Systems

A solar PV installation can be classed as 'permitted development' subject to conditions and when not located within a conservation area, AONB or world heritage site.

Solar PV, Safety & The Building Regulations

Residential PV systems notifiable under Part P. Special consideration needed for Part A. A combination of serious risks for solar PV installers.

Safely Retrofitting Solar PV Roof Mounts

The things to consider before installing a retrofited solar PV system on a roof and an introduction to the type of equipment used to secure an on-roof solar PV system.

Smart Switching / Solar PV Power Switching

Available as an addition to existing solar PV systems or installed as a package alongside a new system, Smart switching puts full control of a solar PV system's power output firmly in the hands of the system owner.

Solar Photovoltaic (PV) & Electrical Glossary of Terms

An alphabetical list of many of the industry and technical terms you are likely to come across when installing a solar PV system. The glossary also defines terms that are used in roofing and electrical work as well as in solar PV installation and solar manufacturing.

Electrical Warning Signs & Labelling

A quick overview of some common electrical warning signs and labels that you might find attached to electrical equipment.

ABB / Power One Aurora Inverter Faults and Repairs

Power One, at one point were the second ranked inverter manufacturer in the world and there are many Power One Aurora Inverters installed in the UK. The most popular models being the Uno PVI-3.0-TL-OUTD and the Uno PVI-3.6-TL-OUTD.

Fronius IG / IG Plus Inverter Faults and Repairs

Fronius IG and IG Plus series inverters have LCD displays on the front of the chassis that providing it's working, will highlight any errors with the inverter or the solar PV system that it runs.

Mastervolt Inverter Faults and Repairs

Mastervolt Sunmaster and the smaller Soladin ranges of inverters were widely installed in the UK between 2011 and 2014. Popular Sunmaster models being the Sunmaster XS2000, Sunmaster XS3200 and the Sunmaster XS4300.

SMA Sunnyboy Inverter Faults and Repairs

SMA Sunnyboy Inverters have been widely installed in the UK, some of the most popular being the SB1200, SB2000 and SB3000. High frequency models include the SB2000HF, SB2500HF, and SB3000HF. Transformerless models include the SB3000TL and the SB3600TL.

SolarEdge Inverter and Optimser Faults and Repairs

The SolarEdge system is unique and in our opinion unrivalled in terms of it's ability to monitor system performance down to panel level. This is achieved through the installation of a small unit called an optimiser.

Sonnen Macht Inverter Faults and Repairs

The problem we often find with these inverters are damaged relays, the tell tale sign of a relay failure is an Error 19: Relay or Error 19: Relay Fault warning displayed on the inverter's display.

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