In short: We introduce you to the 9 components you’ll need for a grid tied solar plus battery backup system, and explain how they work together to provide more resilience for your home when the power is out in your area.
With all the recent power outages due to extreme weather, there’s been strong homeowner interest in learning how to be more resilient and self reliant when the grid is down. Because of our new partnership with Solar Energy International (SEI), the leader in solar energy job training, we are able to provide a more in depth view of how grid tied solar plus battery backup systems work. In this article, we show you 9 components you need for such a system and explain how they all work together to create the electricity you need to power crucial home appliances when the grid is down.
Our sun (1) and your solar panels (2)
First, we need sunlight and a solar panel array. Sunlight excites electrons within your panels, and creates direct current (DC) electricity. While DC electricity sure will be able to give you a zap if you touch a live wire, it isn’t all that useful in your home, since almost all our appliances use alternating current (AC). We’ll tackle this problem a little later, but it’s important to note that once that electricity gets created, we need to control where it goes and what form it takes.
Your charge controller (3) and your battery bank (4)
The first place DC electricity from your solar panel is gonna go is to a special little gadget called a charge controller. It’s aptly named, because it controls how much electricity (or charge) goes to the place where all your precious electrons get stored for use later – your battery. The charge controller is important, because you can run into serious mechanical problems if you overcharge your battery. A good charge controller will also ensure once your battery is full, the power gets rerouted efficiently to our next piece of equipment, your multimode inverter charger.
Check out our full article on solar battery banks.
Your multimode inverter charger (5)
One of the definitions of “invert”, outside of being a dated term for a homosexual person, is to “turn something around”. One important mission of the inverter for your home solar battery backup system is to turn the DC electricity which pumps out of your panels into AC electricity your appliances can use in your home.
There are a few types of inverters, and the one you’ll need for this type of system with a battery is called a “multimode charger” inverter. It’s called multimode, because it is smart enough to recognize when to pull electricity from your battery if it detects a power drop from the grid OR to pull electricity from your utility to charge your battery if it isn’t full and the sun isn’t doing a good job creating electricity through your panels.
The graphic shows how your multimode inverter charger can accept DC electricity from your charge controller AND also from your battery. As you’ll soon see, your multimode inverter charger can draw power from the grid through your AC service panel in your home as well.
Your AC service panel (6)
As mentioned, your multimode inverter charger also accepts AC electricity from the grid, and converts it to DC to charge your battery when it is low on charge and your panels aren’t doing a good job of creating power. The thicker squiggly bidirectional arrow between the multimode inverter charger and your AC service panel represents AC electricity. Your multimode inverter charger converts DC solar power and DC battery power to AC and sends it along to power your home through your AC service panel. It also accepts AC power from your grid through the service panel in your home to charge your battery during times the sun isn’t shining.
Connecting to the utility grid (7) through your electricity meter (8)
When the grid is up and the sun is shining, your panels will create DC electricity. That electricity gets sent along to your charge controller. The charge controller detects when your battery is full and routes the DC electricity from your panels either to the battery or along down the line to your multimode inverter charger.
Your multimode inverter charger converts the DC electricity from your solar panels into AC power and ships it off to your AC service panel to power stuff in your home. If there’s less draw from your home appliances than your solar panels produce, the extra AC electricity gets sent back through your meter and sold to your utility company. If you’re lucky enough to live in a state with strong net metering policy, you’ll be credited at the full retail rate for electricity. Next, let’s take a look at what happens when the grid is down!
Resilient solar electricity servicing your Backed-up AC Loads Panel (9) when the grid is down!
When the grid is down, your inverter charger is still powered by your battery and converts the electricity available from your battery and your solar panels into AC and routes it to the final piece of equipment in your system, your backed up AC loads panel. This is a separate electric panel usually sited right next to your regular AC service panel, and it has connections to crucial appliances in your home like medical mini-fridges, a few outlets and backup lighting. In this way, you’re still resilient and able to have electricity when the power is out in your area.
If you have any questions about how solar plus battery backup systems work, fill out our form to be connected to a local solar installer who can help answer all your questions.
Last modified: March 11, 2020