In addition to the panels themselves, the inverter is a key component of a PV system. This device is responsible for converting direct current (DC) from the solar panels into alternating current (AC), compatible with the electricity grid and also for yield maximization (MPPT’s). But what are the characteristics of an inverter? An overview.
The lifetime of inverters in household installations is about 10 years. On average, during the lifetime of solar panels, the inverter should be replaced once. The life expectancy of an inverter depends on its environment. For example, a high temperature has an adverse effect on lifetime. Preferably install the inverter in a rather cool and well-ventilated area.
Manufacturers of micro-inverters pretend that these devices have an average lifetime of 25 years, but this has not been proven to date. Micro-inverters are designed to be mounted directly in front of a solar panel to the frame. These devices are normally connected to one or two panels. Therefore, conversion to alternating current occurs close to the solar panel. Micro-inverters are located on the roof, which is obviously detrimental if any defects occur.
NUMBER OF INVERTERS
For househould PV-systems, basically one central inverter is sufficient. In large-scale projects or projects where solar panels are remote, it is advisable to install multiple inverters.
When purchasing a PV-system, it is important that the solar panels and the inverter are properly dimensioned. With a view to a maximum technical output, the best dimensioning of the inverter is between 90% to 110% with respect to power of the solar panels. In a PV-system of 3 kWp, this for example means an inverter with a capacity between 2.7 and 3.3 kWp.
Typically, one opts for an ‘underdimensioning’ of the inverter with respect to the solar panels. This is because in Belgium, the solar panels virtually never reach their peak efficiency because of non-optimal weather conditions.
Factors that one should definitely bring into account when dimensioning are the possible presence of shade and the slope of the solar panels on the roof. Shadow on solar panels must in any case be avoided. In case of shadow objects, one should connect the solar panels on a separate MPPT to reduce the loss by shade.If unsuccessful, the installation will pay less.
WITH OR WITHOUT TRANSFORMER?
When purchasing an inverter, the efficiency is an important factor to consider. Inverters without transformer have a higher efficiency than inverters without transformer. Especially inverters without transformer with an efficiency of at least 97% seem to be a good choice.