1. Cleaning
Cleaning solar panels from the outside seems like a simple task, but it is not from a technical perspective. The goal is not to make them "sparkle beautifully", but to ensure that dirt does not cause disproportionate production loss or local overheating. Using the wrong method can do more harm than good: micro-scratches, sealing problems, water ingress, and even long-term optical degradation can result.
The correct approach is always the same: first understand what type of contamination is present, and only then intervene.
When is cleaning necessary?
The necessity of cleaning should be decided based on condition and production data, not a calendar. Many residential systems in Hungary operate for years without significant intervention, as rain naturally washes away fine dust.
Problems arise when deposits appear on the surface that:
- significantly reduce light transmission,
- cause permanent shading on a particular cell area,
- or accumulate along the bottom edge of the panel, impairing drainage.
Bird droppings, for example, can have a significant impact even on a small area. This is not because they cover a large area, but because shading a cell area affects the behavior of the entire string, and in extreme cases, can cause local overheating.
Another important indicator comes from the monitoring system. If daily production noticeably decreases under identical weather conditions, or a particular string performs disproportionately weaker, a physical inspection is warranted.
What tools should be used for cleaning?
The glass surface of a solar panel is tempered but not indestructible. The coating and the optical quality of the glass matter in the long run.
Basic rule: the less scrubbing, the better.
The safest solution generally involves:
- a soft-bristled brush specifically designed for solar panels,
- a microfiber mop or head,
- a low-pressure water jet (not "cutting" type).
Water quality also matters. Softened or deionized water does not leave limescale stains, so no cloudy layer remains on the panel after drying. With hard water, thorough rinsing is particularly important, and ensure not to let the water dry on the hot glass.
Cleaning agents are rarely needed, for example, in case of strongly adhering, greasy deposits. In such cases, only mild, pH-neutral, PV-compatible agents should be considered.
What should not be used?
It is important to be firm here, as damage is often not immediately visible.
Avoid:
- scouring pads, abrasive surfaces,
- powdered or abrasive cleaning agents,
- strong acidic or alkaline chemicals,
- solvents (e.g., acetone),
- and high-pressure, concentrated water jets.
High-pressure washers can be particularly risky because water can penetrate the interface between the frame and the glass, and around the connectors. This does not necessarily cause an immediate fault, but can lead to problems in the long run.
It is also important to avoid thermal shock: do not suddenly spray cold water on a hot panel. The ideal time is early morning or late afternoon when the panel temperature is lower.
Impact of cleaning on production
The impact of cleaning on production is site-dependent. In a clean, rainy environment, minimal difference is expected. In dusty, agricultural, or industrial environments, however, measurable improvement can be observed.
The realistic professional goal is not to "increase by x percent," but to:
- eliminate disproportionate losses,
- equalize differences between strings,
- and avoid local overloading.
To accurately assess the impact, it is advisable to rely on monitoring data. Under similar weather conditions, daily production can be compared before and after cleaning, but more importantly, whether unjustified fluctuations or string discrepancies disappear.
Practical, safe approach
When cleaning on a roof, safety at work is the most important consideration. If fall protection is not provided, cleaning becomes a safety issue, not a technical one.
A reasonable, professionally sound sequence:
- Choose a cool panel and an appropriate time.
- Pre-rinse to prevent rubbing loose dust into the glass.
- Gentle cleaning with a soft tool, using minimal pressure.
- For dried-on stains, soak rather than forcefully scrub.
- Thorough rinsing, followed by a quick visual inspection (cables, fastenings).
The essence: cleaning should not be more aggressive than the contamination itself.
A well-maintained system does not necessarily require frequent intervention, but when necessary, it should be done consciously, gently, and with a technical mindset.
2. Periodic Inspections
Periodic inspection is not about "taking a look to see if everything is in place." It's more about noticing small changes that slowly develop into problems over months or years. A solar panel system typically works silently, providing no loud warnings, so faults often don't appear suddenly but build up gradually.
Most serious malfunctions start with a seemingly insignificant deviation. A slightly loosened connection, a minor insulation damage, a slowly deteriorating contact. The purpose of periodic inspection is precisely to stop this process at its beginning.
Mechanical Inspections
The mechanical parts of the system are under continuous stress. Wind load, snow pressure, thermal expansion, and minimal building movements all affect the support structure and panel mounting.
During inspection, it's not enough to see that "everything is on the roof." The question is rather: has anything changed compared to the original state?
It is worth checking:
- the panel mounting points – for displacement, gaps at the clamps,
- the rails and hooks – for visible corrosion or deformation,
- the area around roof penetrations – for signs of moisture,
- the cable routing – to ensure they are not hanging or rubbing against sharp edges.
Mechanical problems are often precursors to electrical faults. A slightly moving panel undergoes micro-movements, which can lead to connector overheating or even micro-cracks at the cell level in the long term.
Electrical Inspections
Electrical inspection does not mean a complete re-measurement, but a targeted condition assessment. The emphasis is on the connections and the condition of the protective devices. Special attention should be paid to DC side connectors. An MC4 connector rarely "breaks apart" dramatically. Instead, slowly increasing contact resistance develops, causing heating. The first signs of this can be slight discolorations, plastic deformation, or hardening of the insulation.
During periodic inspection, it is advisable to check:
- the functionality of DC and AC disconnectors,
- the status indicators of surge protection devices,
- the inverter's grounding point and connections.
The goal here is not to disassemble everything, but to detect abnormal signs in time.
Analysis of Production Data
The greatest advantage of modern systems is that they continuously provide data. Periodic inspection is now unimaginable without analyzing monitoring data. It's not the daily kWh value that's interesting, but the trend. A well-functioning system's production is weather-dependent but follows a logical pattern. Strings with the same orientation move together and do not show persistent, unjustified deviations.
If a string performs weaker for an extended period, the cause could be, for example:
- partial shading,
- soiling,
- connection problem,
- or accelerated degradation.
Data analysis often indicates a problem even before a physical fault is seen on site. This "invisible diagnostic" is one of the most effective tools for prevention.
Early Fault Detection
The greatest value of periodic inspections is prevention. A fault detected in time can usually be repaired quickly and cost-effectively. However, if it remains hidden for months, it can easily trigger a chain reaction.
These are not necessarily serious faults, but rather warnings. The essence of periodic inspection is not to downplay them, but to investigate them. In the long run, it's not whether the system works today that matters, but whether it will continue to produce with the same safety and efficiency ten years from now. Periodic inspection is one of the most important tools for this.
3. Monitoring Systems
A monitoring system is the "nervous system" of a solar power system. It doesn't just draw graphs, but continuously provides feedback on whether the system is truly doing what it was designed for.
Anyone who does not monitor the data is practically operating blind.
For modern PV systems, monitoring is the primary tool for checking performance, early fault detection, and fine-tuning operation. Often, it's not spectacular faults that cause the biggest losses, but rather imperceptibly deteriorating operation.
Inverter Monitoring
The inverter is the central measurement point. All energy passes through it, so it provides the basic data.
A typical inverter shows:
- instantaneous DC and AC power,
- voltage and current per MPPT or per string,
- grid voltage and frequency,
- its own temperature,
- current operating status.
This level is primarily for technical status checks. It quickly reveals if the inverter is not operating within the correct range, limiting due to temperature, or shutting down due to grid problems.
However, it is important to understand: the inverter only "sees" what passes through it. For example, it does not indicate a slowly degrading panel as a separate fault, but only senses that the performance has decreased.
Cloud-based Systems
Cloud-based monitoring not only shows current performance but also stores and organizes data over time. This is where the real analysis begins.
It's not about the moment, but the context.
Longer-term graphs reveal:
- how daily, monthly, and annual production develops,
- whether there is a slow decrease in performance,
- whether a certain deviation recurs at a specific time.
A slight but continuous deterioration is not noticeable on a daily basis. However, it becomes evident on a six-month graph. This is particularly important, for example, with increasing shading, soiling, or for cycle monitoring in battery systems.
Monitoring thus becomes a real decision-making tool.
Interpreting Production Graphs
The daily curve of a healthy system is relatively predictable: it rises in the morning, peaks around noon, and then gradually decreases. If it deviates from this, there is a reason.
For example:
Flat peak: power limitation or clipping due to DC/AC ratio.
Sawtooth pattern: grid voltage fluctuation or thermal derating.
Asymmetrical curve: orientation difference, shade, or soiling.
Recurring, identical-time dip: typically fixed shading.
Comparison by string or MPPT is particularly telling. Parts with the same orientation should behave very similarly. If one consistently lags, there is almost certainly a technical reason.
The graph is not merely decorative
Error codes – not every red signal is a tragedy
Inverter error codes often sound alarming, but not every error indicates a true malfunction.
It could be, for example:
- excessive grid voltage (external cause),
- temporary temperature limitation,
- communication error,
- or DC insulation warning.
The key is repetition and duration. A short, one-time warning often does not require intervention. A recurring signal, however, always needs investigation, even if the system is producing in the meantime.
Monitoring is important here because it records the event with a timestamp, reveals patterns, and helps determine whether it is a one-off phenomenon or a systemic problem.
Remote Monitoring
Remote monitoring allows tracking the system's status without physical presence. This is not just a convenience feature. From an operational perspective, it means that faults can be detected quickly, downtime can be reduced, and maintenance becomes more predictable.
For larger systems, it is practically indispensable. But even for residential systems, it offers significant advantages: we don't hope it works, we see it working.
Ultimately, monitoring provides confidence. Confidence that the system is not just installed, but actually working – and if it deviates from normal, it will signal it in time.
