On the roof, access is a safety problem first and a cleaning task only second – and the array remains a live system throughout the work.
Photovoltaic cleaning is first a question of roof access: modules are not load-bearing surfaces, and skylights or continuous rooflights are typical fall-through points. During the work the array stays energised, because a module cannot be switched off. Cleaning agents and water must suit the coated glass surface and the manufacturer's instructions. A statement about the expected yield is not part of this service.
The triggers are very different observations, and not all of them lead to the right measure: the yield is below what the monitoring leads you to expect, and nobody knows whether it is the dirt. On the roof lies a layer of dust and soot that wet weather does not wash off. Moss sits under the lower frame edge. Bird droppings make individual areas stand out visibly. After the grain harvest the whole array is coated. Or it was cleaned with a mains water hose, and now limescale marks stand on the glass. The expectation is often that cleaning will solve a yield problem. But yields can also fall for other reasons: shading by vegetation, soiling on part of the strings, ageing, a defect in one string or an inverter issue. A serious answer therefore begins with the question of which cause applies – not with a quotation for an area clean.
At the start stands the review of the trigger: is this visible, area-wide soiling or a drop in yield with an unclear cause? In the second case the first step is to narrow it down, not to clean. Then follows the survey, covering roof shape, pitch, row spacing, accessibility, fall protection, roof structures, skylights, gutters, vegetation and access routes. Manufacturer documents on cleaning are consulted, as are the roof manufacturer's specifications on roof use and the conditions of the insurance contract. From this an access and safety concept is produced: how the modules are reached without stepping on them and without damaging the roof. Only then are water quality, agents, brush type and pressure matched to the module surface, frame and surroundings, and the cleaning carried out. At the end comes the visual check of the module array with a completion report and photographic documentation.
Tailored to this service – aligned with site and industry.
Modules are not load-bearing surfaces, and skylights or continuous rooflights are typical fall-through points. The access concept therefore stands at the beginning of the planning.
Module glass is coated. Abrasive removal, strongly alkaline or acidic agents and hard water are problematic – the manufacturer's instructions are the decisive reference.
What is usual is trigger-based deployment, for example after the pollen and dust season, after the harvest, or when observations give grounds. There is no fixed interval.
Process
First it is clarified whether there is visible, area-wide soiling or a drop in yield with an unclear cause. In the second case, narrowing it down comes before cleaning.
Roof shape, pitch, row spacing, accessibility, fall protection, roof structures, skylights, gutters, vegetation and access routes are recorded.
How are the modules reached without stepping on them and without damaging the roof? Fall protection, walkways and rescue belong to this step.
Water quality, agents, brush type and pressure are matched to the module surface, frame and surroundings; work is carried out under suitable conditions with regard for weather and solar radiation.
The module array is checked; the completion report and photographic documentation record the scope and any irregularities found on the modules and the mounting structure.
This service sits within a framework of statutory duties, technical rulebooks and operational practice. The distinction matters because it determines who is responsible for what.
The rulebooks named here describe requirements for how the work is carried out – they are not a certification held by BREREI. VDI and DIN normative texts are chargeable and were not available in full; where a statement touches the normative detail, this is noted in place.
These references describe the requirements the work is performed against. They are not a certification, inspection or approval held by BREREI.
Short answers to help you assess whether this service fits your site.
Partly. With sufficient pitch and a smooth surface, rain removes loose dust. Sticky deposits such as soot and grease films, bird droppings, pollen and agricultural dusts however adhere firmly, and areas near the edge remain dry and dirty. Whether rain is enough in your case depends on roof pitch, exposure, row spacing and the type of deposition – that is a question for the site survey, not a general statement.
No. Point loading from stepping on them or from equipment set down can damage cells and laminate, often without any immediately visible consequence. Work is therefore carried out from the roof edge, along walkways, with telescopic or leaning equipment, or from an aerial work platform. This decision is part of the access concept and depends on the roof shape, the roof structures and the structural analysis.
Those that suit the surface – and that the module manufacturer permits. Module glass is coated; abrasive removal, strongly alkaline or acidic agents and hard water are problematic. Working with soft water and soft brushes is usual, because no residues then remain on the glass. The manufacturer's instructions are not a legal norm, but they take effect through the purchase contract and the warranty terms: anyone who deviates from them risks warranty claims.
A module cannot be switched off. As long as light falls on the cells, voltage is present. Some inverters have an isolation facility that disconnects the AC side; the DC side of the strings remains an energised system. For cleaning this means: distance from plug connectors, junction boxes and inverter areas, no water in electrical components, and a safety concept that treats the array as an active system.
No, and we deliberately do not give such a commitment. Monitoring shows that a deviation exists, but not where it comes from: vegetation, soiling, ageing, shading and technical causes produce similar patterns. What makes sense is to narrow down the cause first – through a visual check and, if you commission a thermographic survey, through its result – and only then to decide on the scope and frequency of a cleaning.
It makes sense to know the conditions. System and building insurance policies often contain requirements on maintenance, documentation and the handling of the array; these requirements are not a legal norm, but they take effect through the insurance contract. If the array has to be in a particular state during the work, or records are required, that belongs in the discussion before the assignment.
Send us the system layout, the module type, the inverter, the access routes to the roof, and your observations and monitoring data. A site survey is then arranged; the quotation names the access concept, the method, the water quality, the preparation on your side, the boundary to electrical and maintenance work, and the scope of documentation. Statements about the expected yield are not part of the quotation.
Service, property and contact details – that is all we need.
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