Solar inverters are a smaller, less obvious part of your solar photovoltaic (PV) system, so people tend not to think of them as much as the solar panels.
But solar inverters are a critical part of your PV system as they do the work of converting the direct current from your PV panels into the alternating current that your business uses.
But how do solar inverters work and what types are there?
How do solar inverters work?
Direct current is the type of electricity used by batteries and portable electronics, like phone and laptop. It is electricity that flows in one direction. This is what your solar panels produce.
But your business cannot use DC power directly. In Australia, our domestic household and business power supply is 240 volts alternating current (AC), 50 hertz (Hz). This means that it switches direction 50 times a second.
It’s the job of the solar inverter to convert the DC power into the AC power that you can use.
Are there different types of solar inverters?
The simple answer is yes. Several major types of inverters exist, each with their own pros and cons. And because your choice of inverter is critical to the efficiency and output of your PV system, it is good to consider your options carefully.
Regardless of where your solar panels are located, they are wired together in one or more “strings.” A string inverter has connections from each one of these strings and handles the power output from all of them.
String inverters are the least expensive option. But they are also the least efficient.
This is because a power drop in one panel, causes the power to drop across the entire string. (Remember that old analogy of one rotten apple spoils the barrel?) Power drops can happen if a panel is faulty. With a string inverter, if you lose power in the array, you won’t know if there you have a single faulty panel or a more system-wide issue.
Shading and over-shadowing on the panels, birds, falling leaves and dirt can also affect power collection.
Because most solar arrays will experience shading for at least some parts of the day, a string inverter is likely to deliver reduced power collection compared with other inverter types.
String inverters with two or more Maximum Power Point Tracker (MPPT) units can be a partial solution. Each MPPT unit handles the output from a string of panels and can individually optimize the power output of a string. So, your solar array can be wired in a way that means if one of your strings gets some shade during the day, the other string won’t be affected.
Finally, a string inverter limits your options for future expansion. For example, if you want to add more panels, you will be limited by the capacity of the inverter. To go above this capacity, you would need to look at upgrading or adding another inverter.
A power optimizer-based inverter system is a string inverter that attaches an MPPT unit to the back of each solar panel. This mitigates the major flaw of string inverters. Each panel has its own power optimizer, so a power drop at one panel will only affect that panel, not the rest of the system.
With power optimisers you can monitor the output of each panel and track or identify problems with each one.
These systems cost more than a string inverter but are generally not as expensive as microinverters.
Microinverters are small, self-contained inverters that attach to the back of each solar panel and manage the power output for that panel.
Microinverters are the most expensive of all the different types of inverter systems but also have the most advantages.
Because panel failures or shading will affect only individual panels, not the entire system, they let you harvest the maximum amount of power from your system.
You have flexibility to expand your system in the future, by simply adding as many panels as you want.
If one microinverter fails, you only must replace one, not the entire system.
And you get individual panel monitoring.
Solar panels factory-integrated with microinverters
It is also possible to purchase solar panels that ship from the factory with integrated microinverters which provide all the benefits of microinverters with potentially lower installation costs.
Your solar installer will be able to provide you with detailed options on which inverter offer the best and most cost-effective solution for you and your business.