Dirty Solar Panels
By far the most common issue with lower generation is that dirt has built up over time and is stopping light from reaching the surface of the PV modules. Regular panel cleaning will ensure that the maximum amount of light reaches the active surface of the panel. If left for too long, dirt builds up and lichen can become established – making the panel cleaning more time consuming and expensive.
Inverters are the hardest-working component in PV installations, having to deal with variable loads every day of every month of every year. Over time this will eventually lead to inverter failure and the inverter will need to be replaced.
Many of the major manufacturers supply inverters with 5-year warranty terms. Increasingly we are encountering sites where inverters had broken before this period had elapsed, but the problem was not noticed until after the 5-year cut off – costing the owners thousands, when the unit could have been replaced under warranty.
NWT’s electrical testing & inspection report will identify any causes for concern with your system and provide you with a ‘traffic light’ classification for how urgently these require attention.
Blocked Air Vents
It is important for the inverter units to be able to dissipate heat effectively. If left unattended for too long, dust and dirt can build up to the point where vents become blocked. If the inverter is unable to cool then eventually the overheating is ultimately likely to cause some form of internal failure.
If plants are allowed to grow in and around the installation this can cause problems for the electrical components. Where trees or higher surrounding foliage reaches the point where it can cast shade over the panels this will also have a significant impact on the amount of electricity being generated. If you have a standard string inverter, even if only one panel is in the shade this will have an impact on a whole string – meaning that anything up to thirty or forty panels may have their output reduced.
Loose AC Connections
This burnt out switch meant that one of the three inverters on site was inactive. The most likely cause was that the connection was not made securely, reducing the surface area of contact and leading to overheating, which is why NWT’s testing & inspection programme checks all system connections. Simply replacing the switch fixed the issue and allowed the inverter to operate properly again.
We have seen many cases of this issue, where the connecting cables have not been secured fast to the mounting system, or have become loose at a later stage. Where the connections between panels fall into a valley in roof corrugations they can become wet, increasing the insulation resistance in the circuit and causing inverters to stop functioning. A detailed inspection will identify this and we recommend ensuring that any connectors are not able to sit where they can come into contact with pools of water.
Incorrect terminations leading to overheating
Where connections are not terminated properly, electricity arcing can occur. These arcs are at very high temperatures and can lead casings to melt, breaking the connection.
Over time the seals around cabinets can become worn out, allowing water to enter. This can cause various issues in terms of the earthing and other connections.
Ingress of water into an enclosure can also cause protective devices to trip, potentially leading to a partial or total system shut down.
Particularly in farm setting, rodent infestation is an issue. In this example our engineers discovered a family of mice that had eaten their way into, and nested in, the trunking that housed connection cables. One of the mice subsequently chewed through the insulation around the cables, electrocuting itself and causing a system shutdown. This issue can be avoided by improving the ingress-protection at cable entry points.
Monitoring System Faults
Monitoring systems are an integral part of a solar installation and make it possible to check whether there are any system faults remotely. In many cases, monitoring systems are no longer active, or the contract for data transmission has expired. We strongly recommend keeping up any associated web portal and SIM card subscriptions to ensure that you are alerted to any faults at the earliest possible opportunity.
DC Cable Bunching
DC cables in a PV system typically operate at around 750 Volts. This high voltage cannot be switched off and is always present when the panels are in daylight. When cables are bunched together they are unable to dissipate heat effectively because they are surrounded by other warm cables on all sides. This can cause the insulation to smoulder and if not rectified, this could eventually lead to total breakdown of cable insulation which can lead to electrical arcing and eventually fire.
Accidental or Malicious Damage
This is not particularly common, although we have experienced a handful of situations where panels have been broken by an impact, either by something being dropped accidentally or by some other means. As part of NWT’s initial inspection we use a drone to photograph the installation because often these issues are not visible from the ground.