How do I know if my Solar Panels are working? is a frequent question. Here is a list of 10 common reasons why you may experience poor yield from a Solar Panel system.

1. Solar Panel Failure

Name: C Gascoigne Ltd.
Address: 56 Pitsford Drive, Loughborough, Leicestershire, LE11 4NY
Telephone: 01509 341971

If you have a solar panel failure it will routinely show itself up in one of two ways:

– physical damage – This can usually be seen through a visual inspection of the array such as broken glass, water ingress and mould growth.

– electrical failures – These can range from a bypass diode failure in the back of a panel, cell failure or damaged cables and connectors. These faults will usually show up as a low voltage or open circuit.

C Gascoigne Ltd will visit your site, undertake a visual inspection of your solar system and provide you with a summary of our findings and recommendations. In most cases system faults are identified during this visit with minor faults corrected.

2. Solar PV Inverter Failure

Almost all inverters have some sort of on board diagnostics and show a fault code or illuminate a series LED lights to indicate there is a problem with the system. You should consult your inverter manufacturer’s literature to find out what the fault code means, as this will vary between different manufacturers. As I am sure you can appreciate, there are far too numerous reasons for inverter failure to discuss in this article.

3. Solar PV Inverter Mismatch

Inverter mismatch can result in very poor performance and yields. Inverters have a minimum/maximum voltage/current window that they will operate in efficiently and constantly track the voltage and current received from the solar array.

Matching the inverter to the array is one of the fundamental design requirements in a solar PV system and if mis-matched it will show up as poor performance, an oversized inverter would be late to start up in a morning due to low voltage and early to shut down in an evening. In extreme cases it may also close down unnecessarily in the day under cloudy conditions and thus miss large parts of the solar day.

If an undersized inverter is used then the unit may shut down at the highest yielding times of the solar calendar due to overheating and over voltage to protect itself from harm.

4. Solar Panel Shading Problems

Shading of an array can be disastrous. However the effects can be reduced by good design and the use of inverters with multiple tracking points or micro inverters. Significant differences in shading losses can be made by simple panel orientation changes. Shading is an obvious problem and can be seen very easily by monitoring shade on the array throughout the year at different times of the day.

Ideally the array should remain un-shaded between 10am and 14pm April to September to yield good returns in the UK without the need to employ secondary measures to counter the effects. This will however vary between system layouts and can only be accurately monitored through a site survey.

By employing shading tools or some good site-specific information from a survey, the site can be quickly mapped out on a 3D model using design software. In turn the whole of the solar year can be simulated and the effects compared against an un-shaded array with the same characteristics. By employing this approach it will quickly tell the assessor if the shading is the issue, if the site is unsuitable or the system wiring is not optimised for the layout/shade.

5. Solar Panel External Influences

Weather – External influences such as bad/freak weather events; in particular a bad summer with exceptional cloud cover can skew figures and look like a faulty system.

Dirt – Dirty panels will yield poorly; make sure the panels are kept clean and free from leaves, bird droppings, dust and the like. If leafs are allowed to collect on the panels, we have found pine needles to be a particular problem as they can gather in the corners of a panel around the raised edges and if not removed can allow the growth of an algae like fauna which left to its own devices could spread across the panel. In these situations it is good practice to use panels with extra deep boarders between the cells and panel edges. Low-pitched panels exaggerate collection of debris where the natural cleaning of panels by rainfall is not so good due to the low mounting angles. In these situations regular cleaning will be required to maintain yields.

6. Solar Panel Installation Problems

The quality of the installation can play a part in the yielding of a system although these problems quite often take time to show up e.g. water ingress, loose connections, under voltage, over voltage etc…..

7. Solar Panel Temperature Related Problems

High panel temperatures in sunny conditions will result in lower performance due to the panel heat coefficients that reduce the efficiency of a panel the hotter it gets. These losses should not be excessive and can easily be calculated using the panel data sheets and the panel temperatures. I would not expect these losses to start a chase for answers to a poor yielding system, particularly in UK conditions. So for the purposes of seeking a problem of poor yielding can largely be disregarded.

8. Solar PV Inverter Overheating Problems

An inverter’s temperature, like almost all electronic devices, can be critical to its life expectancy and efficiency. The cooler the conditions they operate in general mean they will operate closer to their maximum life expectancy and more efficiently. Some inverters have a reduced power mode when high ambient temperatures are reached.

9. Electrical Supply Fault to Solar PV Inverter

An electrical supply fault to the inverter could cause significant losses. If the supply is regularly tripping out then like over and under voltage the system will experience serious losses. This problem may not be related to the Solar PV system but some issue pre-installation which causes a supply to temporary fail such as nuisance tripping of RCD’s and the like. It may be that a faulty fridge is to blame for the consistent tripping of an electrical supply and later on in the same year it is noted that the Solar PV system has recorded poor yields, yet the fridge problem has been long forgotten. These problems can be easily overlooked leaving the contractor no real chance of finding the fault as it no longer exists.

10. Solar Panel Cell Degradation

This is not something you should be experiencing in the early years of a system but may play out in years to come. A typical solar panels output will degrade at approximately 1% year on year. This can be easily calculated using the age of the system and rate of degradation from the panel manufacturers data sheet.

By writing this article I am not encouraging anybody to go reaching for the toolbox as these systems can be extremely dangerous. Look, but don’t touch! Under NO circumstances should an untrained person attempt to access the electrical components of such a system as they can be highly dangerous.

If by reading this article you still believe there is something wrong with your system that you don’t understand or cannot resolve then please feel free to contact us either by phone 01509 341971 , by email info@cgascoigne.co.uk or by using the “contact us” tab on our web site. We are here to help.

Please note the above guide has been formed through my own experiences within the industry and should be read with errors and omissions accepted.

How do I know if my Solar Panels are working?