The importance of the correct installation in photovoltaic

When we request a job in our home, we usually look for the cheapest. Whether for an air conditioner, for the boiler and even for photovoltaic installations. Nevertheless, it is a mistake to look only at the price of the installation. In most occasions is a factor that we should compare when all other factors are equal.

In this article we want Analyze those installation errors that are made due to lack of experience or professionalism in the photovoltaic installations. Remember, cheap is not always the best and, on many occasions, cheap is expensive.

Calculation and installation errors in photovoltaics

In all sectors there are great professionals, however, there are also people who declare themselves installers without proper knowledge nor the necessary experience. They derive from it serious errors in all the steps or processes of an installation of photovoltaic solar modulesboth in the calculations and in the generation study, in the choice of components and materials and, of course, during installation.

As usual, many of the errors can be detected thanks to the monitoring of the installation. Something that most, if not all investors can already do. Thus, a monitoring system must provide us with some minimum data, which are:

• Production: generation and historical data; daily, weekly, monthly and yearly.
• Instant Power: power peaks delivered at each moment.
• DC voltage: voltage on the DC side. Depending on the monitoring we can see this data for each inverter or on inputs of an inverter (MPPT or string). Some inverters have several inputs, which allow the solar panels to be separated into two independent installations. The inverter works internally as two inverters, so what happens in one part of the installation does not affect the other.
• Current in DC: Current on the DC side. Depending on the monitoring, you will be able to see this data for each inverter, or on inverter inputs (MPPT or string).
• AC voltage: is the voltage to which it is connected to the injection network.
• Current in AC: is the current you are injecting into the supply network.

PV calculation errors

Many people believe that a photovoltaic installation consists of placing a series of solar panels on the roofan inverter inside the house and connect everything, lowest possible price. Nevertheless, each element that is chosen conditions the rest of the components. For example, the electrical cables that must be used to connect all the elements of the installation and this with the electrical distribution network.

To illustrate this typical error we rely on two graphs of the same installation, extracted from the monitoring system several days apart. It is a self-consumption installation with discharge to the network, something that is most common in Spain.

On the left, marked with ① we see the monitoring image of an installation. The interesting thing is the green graph, in which the part of the image that shows us the problem has been indicated. East problem was caused by an inadequate connection cable between the inverter and the electrical panel general housing protection, to be able to pour surplus electricity into the grid.

At certain times of the day, when production was important, the inverter was unable to feed that electricity into the grid. In other words, our facility was producing a surplus that could not be compensated for, because the cable did not allow the passage of so many kW. The resistance of the cable to the passage of so much electricity was too high.

Upon detecting the problem, se called a professional to study the problem and find a solution. The connection cables were changed and only a few days later a production and discharge graph was obtained, which shown in the picture ②. As we see, the inverter could already pour all the electricity generatedeven being greater the power that was achieved.

Errors in the choice of components

We have already commented that when a certain component is chosen it can affect the rest, or simply by the arrangement of solar panels on a roof. To illustrate it, we see another example of an installation in which the roof conditioned the placement of the photovoltaic collectors. And for this reason, the decision had to be made to install 2 inverters.

To cover the self-consumption of this house, more panels were needed than would fit on the south side of the roof. For this reason, the solution of the image was studied, placing 7 panels to the east and 7 to the west. A big mistake would have been to carry out the installation with a single invertersince the production of the entire set would have been affected by the panel with the lowest production.

The following image shows the monitoring of the three sets of solar panels. 2 inverters were installed, one of them with two inputs, so that each group of plates was totally independent. Thus, first thing in the morning, the group that faces east (purple color) enters into full production, while the one facing south (dark green color) has low production and the one to the west (blue color) almost zero. .

Also included in the image the generation graph of the inverter with two inputs (in light green), which corresponds to the sum of the production of the two sets that the inverter manages.

It is observed that during the morning that this image collects, some groups of clouds passed by, damaging the electrical production, however, the rest of the day was very sunny.

At noon, the group facing south (dark green) was in full production. Already at sunset it was the set facing west that produced the most.

In the case of having connected all the solar panels to a single inverterand that this would have been a single entry, production would have been significantly reduced, barely surpassing the dark green graph. However, when performing the installation correctly, the total production of our installation is the sum of the two green graphs.

Errors during photovoltaic installation

A typical mistake that happens is not giving importance to the photovoltaic structure, among others, so that the appropriate one is not chosen, or the blacksmith we know is used, without taking into account that photovoltaic collectors are relatively fragile. Although the supporting structure does not generate the electricity, it is vitally important.

The photovoltaic structure has different missions. The one that everyone knows is to act as a bridge between the plates and the roof, a mission that is very important, but that, however, not just any structure will do. The appropriate structure must be specifically designed for the type of panels that we are going to use and adapted to the characteristics of the roof..

A sloping roof is not the same as a flat one, with Arabic tiles than with sheet metal, and a simple sheet metal roof is not the same as a sandwich panel roof. It is because of that it is advisable to go to an expert in photovoltaic structures to choose the most appropriate. We will win in price and in security and service.

A photovoltaic structure must ensure that the solar panels will be in the chosen location the 25 or 30 years they have of life. If we do not choose it well, things can happen such as the panels blowing away with a strong wind, the structure rusting or the anchors not being well sealed and causing leaks.

These are some of the problems that can arise when someone without the proper knowledge, the wrong choice of materials or poor execution of work can damage the photovoltaic installation, although there are many more errors that cause serious problems in photovoltaic systems. Our recommendation is to always talk to real professionals and have them explain everything to us properly..