Several factors influence the productive life of solar inverters for residential buildings. In the second part of our new series on the subject of resilience, we deal with PV inverters.
September 20, 2021
From the PV magazine International
In the first part of this series, PV magazine checked the Productive life of solar panelsthat are quite resilient. In this part we examine residential solar inverters in their various forms and consider their resilience and lifespan.
The inverter, a device that converts the direct current generated by solar panels into usable alternating current, can come in a variety of configurations.
String inverters vs. microinverters Image: Solar Reviews
The two main types of inverters in residential applications are string inverters and microinverters. In some applications, string inverters are equipped with power electronics at module level (MLPE) or DC optimizers. Microinverters and DC optimizers are generally used for roofs with shading conditions or sub-optimal orientation (not facing south).
String inverters with DC optimizers
Image: Solar Reviews
The technology ensures that each panel produces its maximum output in real time and is not limited to the weakest link in the chain or "string". String inverters are subject to the “Christmas light” effect, in which if a panel does not work or is shaded, the remaining panels connected in series are limited to the production volume of that panel.
Some string inverters are equipped with a bypass diode, a technology that completely prevents the “Christmas light” effect shown here by Fronius.
In applications where the roof has a preferred azimuth (orientation to the sun) and little or no shading problems, a string inverter can be a good solution.
In a string inverter, there are fewer moving parts to break, less complicated wiring, and a central location for simple repairs for solar technicians. Usually they are less expensive, said solar reviews. It is said that inverters can typically cost 10 to 20% of the total solar panel installation, so choosing the right one is important.
How long do they take?
While solar modules can last 25 to 30 years or more, inverters generally have a shorter lifespan due to faster aging of components. A frequent source of errors in inverters is wear and weather conditions on the capacitors in the inverter. The electrolytic capacitors have a shorter lifespan and age faster than dry components, Solar Harmonics said.
Energy saga called that a typical centralized string inverter for private households will last about 10 to 15 years and must therefore be replaced at some point during the life of the modules. String inverters in general have Standard warranties range from five to 10 years, and many have the option to extend to 20 years. Some solar contracts include free maintenance and monitoring throughout the contract period, so it is advisable to take this into account when choosing inverters.
Microinverters installed at panel level Image: Enphase
Microinverters have a longer lifespan. EnergySage said they can often last 25 years – almost as long as their panel counterparts. As a rule, these inverters come with a standard guarantee of 20 to 25 years. It should be noted that while microinverters come with a long warranty, they are still a relatively new technology from the last decade, and it remains to be seen if the devices deliver on their 20+ year promise.
The same applies to DC optimizers, which are typically paired with a central string inverter. These components last 20 to 25 years and are guaranteed for this period.
A study by kWh Analytics has shown that 80% of the failures of solar systems occur at the inverter level. There are numerous reasons for this.
Corresponding Fallon solutions, one cause is network disturbances. A high or low voltage due to a grid failure can cause the inverter to stop working, and circuit breakers or fuses can be activated to protect the inverter from high voltage failure.
Sometimes failures can occur at the MLPE level where the components of power optimizers on the roof are exposed to higher temperatures. If reduced production is found, it could be a bug in the MLPE.
The installation must also be carried out correctly. As a rule of thumb, Fallon recommended that the solar panel capacity should be up to 133% of the inverter capacity. If the panels are not properly matched to an inverter of the correct size, they will not function efficiently.
Maintenance is important
So that an inverter runs more efficiently over a longer period of time, these Solar Guys have recommend to choose a cool, dry place with plenty of fresh air circulating. It was also recommended that you avoid installing in areas with direct sunlight, although certain brands of outdoor inverters are designed to withstand more sunlight than others. In installations with multiple inverters, it is important to ensure that there is the correct spacing between each inverter so that there is no heat transfer between the inverters.
These Solar Guys said the best practice is to inspect the outside of the inverter (if accessible) quarterly to make sure there are no physical signs of damage and all vents and cooling fins are free of dirt and dust.
It is also recommended that you schedule an inspection by a licensed solar installer every five years. These standups typically cost $ 200 to $ 300, although some solar contracts include free maintenance and monitoring for 20 to 25 years. During the inspection, the inspector should check the inside of the inverter for signs of corrosion, damage, or pests.
In the next part of the series, PV magazine will investigate the lifespan of energy storage applications for residential batteries.
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