Q. I had a domestic solar system installed ($24,000) Now we recently had a grid outage due to high winds on a very sunny day.
To my surprise our solar panels shut down for the duration of the outage. Upon enquiring of our installers they quoted AS4777.2 'anti islanding'. So the consequences of AS4777.2 is that we don't receive any solar generation except what ever is left in the battery at the time of a grid failure? Not what I expected!
I would have expected the system would be able to (a) isolate the grid in accordance with AS4777.2 and keep our dwelling supplied with solar energy with any excess charging the battery, and so on the next day assuming that as it turned out was a perfect solar day. The outage lasted only 3.5 hours but we have had outages for a week on several occasions in the past decade. I researched the subject as well as I could but I am stunned to find my system inoperative as a result of AS4777.2. Surely a switching circuit can be designed to comply and at the same time continue to supply the property + charge the battery?
A. Great question. More and more people are going to find this out the hard way.
Before quoting, the solar company absolutely should have:
1. Asked you about your backup requirements
2. Quoted you for adding backup functionality to the system - it is possible to do but usually costs extra.
Further They are not correct about AS4777.2 - it does allow for disconnection from the grid without shutting down - if the inverter and system are designed for it. The kind of inverter that can disconnect from the grid and stay active is known as a 'Multiple Mode Inverter' in the standard
Under Australian Consumer Law - the system should be fit for purpose - and if any reasonable person would have assumed that it would work in a backup situation - then I would say you have a case to have it rectified for free.
Also note, even when specifying that you require backup / blackout protection from your hybrid solar/battery system you have 2 choices:
1. Backup mode provides power only from batteries (solar panels are shut down when grid is down - this is what you got whether you wanted it or not!)
2. Backup mode provides power form batteries and solar panels stay active even without the grid.
Both are possible - option 2 is more complicated than option 1. Option 2 can be achieved with any inverter using a technique called frequency shifting where it changes the frequency of the 240V AC slightly to control the solar inverter output. The Powerwall 2 does this well as described here.