Inverters are essential in any photovoltaic solar energy system. In fact, we could go as far as calling them the real “brain behind the system”.
Why do we say this? Because this element is responsible for converting direct current (DC) into alternating current (AC), which is suitable for our use. When the photovoltaic panels receive sunlight, the photons activate the electrons, which begin to move inside the solar cells, producing “direct current electricity”. This energy is not usable by itself, so the circuits inside the photovoltaic cells are responsible for collecting it and sending it to the inverter, which will then transform it into alternating energy that will have the same voltage as the power sockets in our house or at work.
This is why any PV installation, regardless of its size, needs to have at least one inverter.
What do PV inverters do?
The inverters synchronise the electrical current generated by the panels and the electrical current of the grid to ensure they are compatible.
These elements also have built-in protective functions to guarantee the quality of the electricity fed into the grid and the safety of the installation itself and of the people who will use it.
Another of the tasks of photovoltaic inverters is to monitor the system’s energy performance, as well as its electrical activity, and any potential problems or faults that may arise in the installation.
How to choose a PV inverter
Choosing the right inverter will maximise the solar panels’ energy production in a photovoltaic installation, which, in turn, will improve the installation’s overall performance.
Power capacity, the key to choosing the best photovoltaic inverter
The first thing to bear in mind is the power of the inverter (in watts). You will need to ensure that it is able to control the total output of the solar panels without causing problems for the rest of the installation.
For example, if we have a 5 KW inverter, the sum total of the energy produced by the panels connected to it must not exceed this figure. If it does, we would have to look for a more powerful inverter.
The importance of good design
Another important factor is the design of the installation itself, as electricity is not distributed in the same way in grid-connected installations as in off-grid self-consumption installations, where it is vitally important to store part of the energy produced.
In the latter case, inverters must be chosen according to the system’s battery capacity.
This basically means that, before buying an inverter, its power must be taken into account and compared to the battery’s power in order to improve its efficiency.
Ideally, the inverter should have twice the power of the electrical device it is connected to (in this case, a battery). Exceeding this can be counterproductive because, if the system works at low power, its efficiency will be reduced.
Furthermore, we must bear in mind that if a photovoltaic inverter has an efficiency of 90%, and is connected to a 200 W battery, then there will be a 10% loss of energy.
One final aspect to be taken into account when choosing a PV inverter is the input voltage, which will limit the output voltage (12, 24 and 48 V in order to convert it into 110, 220 or 230 V).
If you have any questions, then please do get in touch with our experts. They will be able to tell you about the most suitable inverter for you.
Types of PV inverters
These are the most common option in domestic PV installations. In this case, all solar panels are connected to the same “centralised” inverter.
String inverters are more affordable and easier to maintain, as they are usually located in visible areas (the terrace, rooftop, garage, etc.).
Their only drawback is that they only produce as much usable electricity as the solar panel with the lowest performance, which can reduce the yield if panels are not working or are located in the shade.
For this reason, they are recommended for houses with obstacle-free roofs that receive radiation throughout the day.
Unlike string or centralised inverters, microinverters are “distributed”. This means that each solar panel has its own microinverter.
Microinverters are very efficient and can monitor each panel’s performance to identify production problems.
However, they are rather more expensive and, because they are always installed on the roof, they can be more difficult to repair.
Power optimizers combine the strengths of both string inverters and microinverters.
Like string inverters, they are mounted on roofs, individually for each solar panel. However, optimizers do not convert direct current to alternating current, but, rather, they “stabilise” the voltage and send the electricity to a centralised PV inverter for conversion.
After reading this article, maybe you still have some more questions about PV inverters. Get in touch with us and we will be more than happy to help you.