The last 12 months have seen unprecedented issues with both the cost, and reliability of our electricity supply. A question we get asked more and more frequently is – “If we install solar PV and battery storage, will be be able to keep the power on through a blackout?” The answer isn’t quite as simple as you think.
Almost all the Solar PV installed in the UK is a “grid-tied” system. This means in simple terms, that the electricity generated by the solar panels, is converted from DC electricty to AC electricity, and then “synced” with the grid’s frequency. From the perspective of your appliances, it doesn’t know if its using solar-generated power, or power received from the grid. This makes solar power totally automatic from the perspective of the end user, and also allows for power export for any excess power produced.
However, there is an issue with this configuration. If there was some sort of fault with the grid, and power is cut for safety reasons – either to the public, or for grid operators to work on the lines, there is the risk that energy produced from the solar panel array or your batteries could flow up the “dead” powerlines and potentially harm someone. As a result, all inverters detect power flow from the grid – if it detects a cut in grid power, it will automatically shut off the flow of power from the solar array, to ensure that the power lines leaving your home are safe.
So in the standard configuration, the answer is no, a solar system will not work in a blackout. However there are ways it is possible.
Emergency Power Supply (EPS)
An EPS system is one in where there would be either some or all of the electricity available if there was no supply from the grid. The inverter would detect the loss of power from the grid, and automatically switch over to your solar/battery storage, while also isolating the system from the main grid. This is achieved either with a manual or automatic switch. In theory this seems ideal, but there are some caveats you need to be aware of. The most simple of which is just the cost. Setting up an EPS does have some complexity to it, and is not a simple thing to install and setup. The other issue is that most battery systems cannot supply the peak loads and demands of a typical house. Something as simple as a hairdryer can demand up to 3kW of power – and this could easily overwhelm a battery storage system alone. As a result, normally only certain circuits are energised under the emergency conditions – typically things like your fridge, lights, wifi router, etc. Also a consideration must be given to how much of the battery can be used at any one time – there must always be sufficient charge in the battery system to ensure the EPS works as intended. We only use the top battery and inverter manufacturers, and they allow to battery to be kept a certain level of charge – which guarantees you will always have some capacity for your EPS backup.
The other consideration depending on your homes construction is earthing. Most houses depend on the grid for an earth connection – in the event of a power cut, this can no longer be relied upon to protect you in the event of a short. As a result, an additional earth rod is installed and linked to your inverter – this earthing method (known as TT earthing), gives you protection from shock without relying on the grid.
Summary
In short – being safe from blackouts is possible, but not without challenges. We don’t offer it as a standard product, but are more than happy to discuss the possiblity with you if you are looking at installing Solar PV and batteries in your home. Get in Touch if you wish to learn more.
