Inverters are a critical component of your solar energy system. Their primary role is to convert the DC power generated by your panels into AC power, which most domestic appliances use. Other functions include system monitoring and providing diagnostic information.
In addition, you can assess your system’s efficiency using the inverter. Modern units also have integrated battery management features.
Solar Inverter Types
The three most common inverter types are string, micro-inverters, and power optimisers.
String inverters, also called central inverters, are the oldest, most common, and least expensive inverter type. As the name suggests, they convert DC energy from a ‘string’ of solar modules into usable AC power.
Besides affordability, string inverters are popular for their reliability. This is because they’ve existed for many years, allowing engineers to make tweaks to increase their dependability.
String inverters are usually placed centrally, making them easy to troubleshoot.
Despite reliability, string inverters have low efficiency. During overcast or cloudy days, your panels will generate little power because these panels lack optimisation features.
Also, blocking one panel from the sun interrupts the entire system. This is because the panel is connected in series.
Another shortcoming of the series connection is that you can’t monitor each panel independently. Instead, you scan the entire system.
Micro-inverters are small units attached to solar panels. They convert the DC to AC before transmitting it to your appliances over cables. As such, you don’t need a central inverter.
Shading or damaging one of your solar panels doesn’t affect the entire system if your modules have micro-inverters. Instead, it’s one panel that will generate less energy.
It’s easy to expand a system with micro-inverters. Since each panel works independently, you don’t have to purchase a higher-rated central inverter whenever you add more panels to your system. This is often the case with string inverters.
Also, microinverters allow for panel-level system monitoring. As a result, you can troubleshoot panels independently instead of wasting time looking for defects across the entire system.
On the downside, microinverters are expensive. For example, a panel with a microinverter can be up to five times costlier than a standard solar panel.
Microinverters are challenging to repair because of their positioning. Opening them risks damaging the entire panel.
Like microinverters, power optimisers are small units attached to solar panels. However, they work with string inverters.
The power optimisers receive and condition DC energy from solar panels before transmitting it to a string inverter from conversion into AC. Therefore, optimisers are a blend of microinverters and string inverters.
Power optimisers make it easy to monitor your solar energy system. For example, you can assess the efficiency of each module to see how much it contributes to the system. Similarly, you can evaluate the entire array of solar panels.
However, power optimisers are small and difficult to repair. Furthermore, unlike microinverters, they can’t work independently – you still need a string inverter.
A newer inverter type called hybrid inverters is gaining popularity. Hybrid inverters have inbuilt batteries that allow you to run appliances for short periods during outages. They have small batteries that get charged as the sun shines and a built-in automatic switch that starts drawing energy from the battery when there’s no other power source.
What is MPPT?
Modern inverters have a maximum power point tracking feature. An MPPT works like a power optimiser, increasing your panels’ efficiency and output. However, MPPTs optimise the entire array rather than conditioning a single solar panel.
Solar panels are good, but you need inverters to enjoy their benefits. Remember, panels generate DC power which is only valuable for a few appliances. You need an inverter to convert into AC to use it to power your TV, music system, refrigerator, and other appliances.
String inverters are suitable for small-scale domestic use because of their affordability and reliability. On the other hand, microinverters are ideal for commercial premises due to their high output and efficiency, even on cloudy days.