Why does a grid-tied system-without battery backup-shut down durning a power outage?
Grid-tie solar systems are appearing in more and more neighborhoods as homeowners seek to reduce their rising electricity bills, charge electric vehicles, or just “green up” their energy footprint. However, many people are surprised to learn that the grid-tie solar panels on their roofs don’t supply power to the home when there is a utility blackout. This is due to the ani-islanding safety requirements of a grid tie solar power system.
When the grid is down, a grid tie solar power system must shut down its power output so that the electricity produced does not electrify the wires outside the home. When utility workers work on repairing electric lines after a storm, they count on the wires to be “dead” or not energized with electricity. If a grid-tie solar system was still passing power backward through their utility meter onto the electric lines, the utility worker could be killed or injured. Therefore, grid-tie solar systems do not automatically provide power to your home when the utility grid is in a blackout. Instead, they automatically shut down to keep the line workers safe.
But what if you want to have power when the grid is down?
Providing backup power to a home with an existing grid-tie solar system can be accomplished and can power the home safely in the event of a power outage event. In this case, you would need to add a battery bank to store collected energy and an inverter.
A portion of the home can be backed up with what is known as an “Essential Loads Panel.” This is an electrical breaker/distribution panel that would maintain power to only a few circuits in the home – for instance, your refrigerator and freezer appliances to keep food from spoiling, maybe a few lighting and electrical outlet circuits to enable phone and computer charging etc. This Essential Loads Panel is powered by a Grid Forming, Battery-Based Inverter that is wired between the Grid Tie Solar System and the home’s main utility panel (where the utility meter is). When a grid blackout occurs, the Grid Forming Inverter (or a Microgrid Interconnection Device, MID) can continue to receive and regulate power from the grid-tie solar system, supplying available power to the essential loads while also stopping power from exporting outside the home to the grid keeping line workers safe.
If you want to power your entire house when the grid is down, a Whole House Transfer Switch (MID) that disconnects the Utility Service Panel from the utility grid wires allows the backup battery system to supply power to all the circuits in the home without exporting to the wires outside the home.
Choosing the right solar power system for your needs is an important step in the process, and we are here to help you.
For more information on Transfer Switches, Grid Tie Solar Systems, and AC Coupled solar systems visit our learning center or speak with our application engineers directly. They can help you with system design and support you for the life of your purchased system.
Three items to consider if you are looking at going to a grid-tied system are the LG ESS, Outback Mojave, or the Sol-Ark 15K.