Inverters – what do they do?

Inverters have 2 jobs

The first job of an inverter system is to maximise the available energy being generated from the panels.  We call this Maximum Power Point Tracking (MPPT).

The second job is to change the DC current from the panels in to AC current acceptable for your appliances and the grid.

As you’ll see from the information below, there’s different ways these two jobs can be completed with different advantages for each system.

Inverters are often fitted in people’s lofts.  This make installation easy but we strongly recommend they are sited in a cooler place.  The extreme heat in a loft, especially on a day that you’re asking the inverter to work it’s hardest, further raising it’s operating temperature will both reduce the life of the inverter and reduce the amount of energy it can generate.  They also have a display on the front which will let you know if the system is working ok.  If it’s hidden away in the loft you might not realise there’s a problem until you go and get the Christmas decorations out.

Most inverters now have internet connection capability, so you can keep an eye on your system using apps or web browsers, even when you’re not at home.  Most Solar PV users find that these apps also raise their awareness of their energy usage, allowing them to make more savings too.

String inverters

A string is a chain of panels connected together in series.  This is the most basic inverter system.  All the panels in a string must be at the same pitch and orientation, otherwise there will be inefficiencies in the system.  Many string inverters have 2 or even 3 MPPTs, which means that you can have a different string of panels on each MPPT.  This could work well for an east/west set up.

Microinverters

One of the disadvantages of string inverters is that if there is a fault or shading on one panel in the string, it will affect the performance of all the panels on the same string.  In a microinverter system each panel is isolated by having an inverter all of it’s own.  Each panels is therefore isolated so any faults or shading will be isolated.  As microinverters are often hooked up to the internet, this means that if there are any problems with any panels, the microinverter an easily identify which panel has the problem, saving a huge amount of investigation time in identifying the problem.

Optimised inverter system

A hybrid of the previous two systems which separates the two jobs of the inverter , system.  There are optimisers behind each panel which carry out the role of MPPT, therefore isolating any shading or fault issues.  These optimisers are connected to a central inverter which can work more efficiently as it is always presented with the same voltage from the panels (string inverters have to deal with variable voltages).  These systems are also internet connected which allows pro-active maintenance.  This means that if there is a problem your installer will get an email alert and will be able to respond quickly and accurately to the fault.