When installing solar panels for the first time, it is not always easy to check that your photovoltaic system is working properly. Similarly, over time, small anomalies or drops in performance can go unnoticed and cause lasting damage to the condition of your modules.
In either case, you can take a few simple steps yo ensure that your panels are correctly connected and produce electricity optimally. Here is our advice for carrying out an adequate diagnosis.
Basics of how a solar panel works
To diagnose your solar installation properly, you must understand its essential operation. A power plant consists of several photovoltaic panels that transform sunlight into electricity before injecting it into an electrical network (public or private). This system has various elements.
The different elements that make up a solar panel
A photovoltaic installation consists of four main elements: the photovoltaic cells, the connection box, the cables, and the inverter.
The photovoltaic cells and the connection box are located on each side of the solar panel. The photovoltaic cells, made from silicon, cover the panel’s entire surface. They are placed under a glass pane on the front to be exposed to the sun. They are the ones that react to contact with light and produce electric current.
On the back, the connection box allows the transfer of the current, which is thus generated to the inverter via a series of cables. The inverter converts the direct current produced by the panels into alternating current so that it can be injected into the public distribution network (in the event of resale) or into the circuit of your home if you wish to power your devices with your electricity production (self-consumption).
Why check the operation of your installation?
Once connected and regularly throughout its useful life, it is necessary to check the operation of your photovoltaic installation. Indeed, a solar panel that works optimally guarantees that your power plant’s performance will meet your expectations today and for all the years that you will use it. It also ensures the longevity of your installation and, therefore,its profitability in the short term.
The stages of diagnosis
Contrary to what the technological complexity of a photovoltaic panel system might suggest, carrying out a diagnosis is a simple operation within the reach of many people, as long as you have some basic knowledge of electricity. However, if you do not feel comfortable with these concepts or with the tools necessary for these checks, call on a professional who can guide you.
Prerequisites before a diagnosis
Before starting your diagnosis, it is necessary to remember that this intervention must be well-prepared. Indeed, your photovoltaic installation is connected to the electrical network; a handling error can permanently damage the panels.
However, when you carry out maintenance operations yourself, the damage that you may cause will not be covered by the legal guarantees. So follow each step carefully. In order to protect yourself and operate safely, also equip yourself with the basic equipment: gloves, safety glasses, cable stripping pliers, set of screwdrivers and wrenches.
To perform a diagnosis, you will also need specific tools: a voltmeter and an ammeter or a multimeter. These boxes allow you to measure the intensity (ampere) of an electric current and the voltage (volt) that flows through it.
The two measurements can be carried out separately (voltmeter and ammeter), but most of the time we use a single device, the multimeter, which combines these two functions with that of an ohmmeter (measuring the resistance of a circuit or a component). In stores, its price varies between $15 and $150 .
Finally, get the technical specifications provided by the manufacturer of your panels. This may be the user manual or a sheet placed on the back of the photovoltaic modules. You will find the reference values for voltage and intensity to compare with the measurements you are going to take.
Inspection of both sides of the panel
First, a first visual check is required. Indeed, if one of the elements of the installation is damaged, soiled or hindered by any external element (leaves, branches, infiltration, etc.), production will automatically be impacted. Therefore, check that each side of the panel does not show any signs of deterioration.
On the front side, you should pay particular attention to these signs:
- cracks;
- grooves;
- brown spots (traces of oxidation also called “hot spots”) at the welds.
If you notice any of these signs on your panels, it is imperative to call in a professional to replace the faulty module. If you have bifacial solar panels (photovoltaic cells on both sides of the module), you should also check for these signs on the back.
On a conventional solar panel, the back side does not contain any cells. However, it is necessary to check that the coating (polyvinyl fluoride) is free of scratches or holes. Such deterioration can create infiltration and therefore, oxidation (hot spot). Also, pay attention to possible traces of corrosion or potential cable tears.
Inspection of the connection box
On the back of your solar panels, you will notice the presence of a small black box. This is the connection box, an essential element that makes the link between the production of your cells and the transfer to the inverter. This is also where you can safely carry out the various electrical voltage and intensity measurements.
First, perform a visual inspection of the case, then open it using a screwdriver to check the condition of the cables and electrical connections. If you notice the slightest trace of oxidation, if the case is damaged, broken or if a component has melted, have the case replaced by an RGE professional.
Check that the panel is delivering voltage
You can take the measurements once you have carried out these various checks. First, it is essential to turn off the panel’s disconnector or circuit breaker.
Some modules do not have a disconnection device. In this case, the panel cells should be temporarily covered before disconnecting cables from the regulator terminals. You can then expose the photovoltaic cells again.
Choose a day with maximum sunshine for your voltage measurements to be relevant. Take your multimeter and proceed as follows:
- Place the cursor on the “V” values (for Voltmeter);
- set the cursor to 200 Volts because a solar panel provides a voltage beyond 20 Volts;
- Connect the negative end of your cable to the COM port (black) and the positive end to the V port (red);
- Note the value that appears on the digital display.
Remember that this is a measurement of open-circuit voltage (Uoc or Voc) that varies depending on the sunlight. It should be close to the voltage mentioned on the technical sheet of your photovoltaic panel but do not worry if it does not reach it. These reference data are maximum measurements and were obtained in the laboratory, so your panel will never get them in real outdoor conditions.
Check that the panel is producing current
As with voltage measurement, precautions must be taken: turn off the disconnector or cover the panel before disconnecting the cables. At this step, you will be using the ammeter function of your multimeter, so simply switch your cursor to the “A” values and plug the positive (red) side into port A. Since the current is usually below 20 Amps, the cursor should be placed at this value.
The data you get is the short-circuit current value, also called no-load current. It should be as close as possible to that specified on the data sheet of your module.
What to do if your panel is faulty?
Suppose you notice a problem at one of these steps, and your voltage and current measurements are very far from the values displayed by the manufacturer. In that case, it is best to call a professional or the technician who carried out your installation. Write down precisely the problems you have noticed and the measurements taken because all this data will facilitate their intervention.
Indeed, a malfunction does not automatically mean that your installation must be replaced or even repaired. Thanks to this diagnosis, the technician will have concrete elements that will allow him to refine his point of view on your problem and provide you with an appropriate solution: maintenance, minor repair, replacement of parts, etc. It also ensures that you benefit from all the two-year and ten-year guarantees linked to your photovoltaic installation.
