Several factors affect the productive life of a residential solar inverter. In part 2 of our series we deal with solar inverters.
September 15, 2021
In the first part of this series, PV magazine checked the productive life of solar panelsthat are quite resilient. In this part we examine solar inverters for residential buildings in their various forms, how long they last and how resilient they are.
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 inverter vs. microinverter
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), which are referred to as DC optimizers. Microinverters and DC optimizers are usually used on roofs with shading or less than optimal orientation (not south-facing).
String inverters equipped with DC optimizers.
Image: Solar Reviews
The technology ensures that each panel produces its maximum performance 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.
While this doesn't seem to have a reason for a string inverter, it isn't always the case. In applications where the roof has a preferred azimuth (orientation to the sun) and few 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 10-20% of the total solar panel installation, so choosing the right one is important.
How long do they take?
While solar panels can last 25 to 30 years or more, inverters generally have a shorter lifespan due to more complex moving components.
EnergySage said that a typical centralized string inverter for residential buildings will last about 10-15 years and will therefore need to be replaced at some point during the life of the modules.
String inverter generally have Standard warranties of 5-10 years, many with the option to extend to 20 years. Some solar contracts include free maintenance and monitoring during the contract period, so it is advisable to take this into account when choosing inverters.
A micro-inverter is installed at panel level. Image: Enphase
Micro-inverters have a longer lifespan; according to EnergySage, they can often last 25 years, almost as long as their panel counterparts. As a rule, these inverters have a standard warranty of 20-25 years.
The same applies to DC optimizers, which are typically paired with a central string inverter. These components last for 20-25 years and are guaranteed for this period.
failure
A study by kWh Analytics showed that 80% of the failures of solar systems occur at the inverter level. There are numerous reasons for this.
According to 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 modules are not properly matched to an inverter of the correct size, they will not work efficiently.
maintenance
So that an inverter runs more efficiently over a longer period of time, these solar guys have recommended selection a cool, dry place with plenty of fresh air circulating. It has also been suggested to avoid installing in areas with direct sunlight, although certain brands of outdoor inverters are designed to withstand more sunlight than others. And 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.
Regular maintenance checks for inverters are recommended.
Image: Wikimedia Commons
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 20-25 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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