What is an off-grid solar power system?
Put simply, off-grid solar is a combination of electrical components that are used to create and supply power where a mains connection is not tenable.
An off-grid solar power system is usually made up of 4 components: solar panels, batteries, a charge controller, and an inverter.
Solar panels turn the sun’s rays into power that is then fed into the charge controller. The charge controller controls the amount of power going into the batteries to safely charge them up to 100%. The inverter then takes the energy stored in the batteries (48V DC) and turns it into power that is usable by everyday household appliances (240V AC).
So how does an off grid solar power system work?
It’s a pretty simple process!
The solar panels collect energy from the sun’s rays, which is stored in the batteries, so the energy will be available to use after the sun goes down. This is the key difference between grid-tied and off-grid solar - grid-tied solar doesn’t store any energy for later.
To make this system a little easier to understand, you can also visualise this as water collection.
The solar array is like the roof area that collects the rain, and the battery bank is like a water tank that stores the rain caught on the roof. When it rains, the water fills the tank at a rate proportional to how heavy it is raining. Having more roof area allows you to catch more rain, so you can catch more water even when it's raining lightly, than you would with a small roof. This is the same for solar panels - having more solar panels means you can catch more solar energy on a cloudy day than you would with fewer panels.
In the same way, increasing how many batteries you have in your solar system is the same as having a larger water tank. You can store more power, and will have more energy available for times when there is less sun. Just like a water tank, the down side to a large battery bank is that it takes much longer to charge if the solar array (or the water collection area) isn’t sized to match. However, while you can leave a tank half filled, leaving batteries in a partial state of charge and charging them up slowly will reduce the lifespan of the batteries.
Our off-grid solar kits include two more components to make them work - a charge controller and an inverter. The charge controller goes between the solar panels and the batteries, and regulates the charge to the batteries. It ensures that they are evenly charged at the current voltage and current, up to 100%. When they reach 100%, the charge controller cuts off power to the batteries, and when you use that energy, the charge controller will top them back up when the sun comes out again. In our water collection analogy, the solar charge controller would be a valve that regulates the water flow to the water tank to stop it from overflowing.
The batteries store energy as direct current so we need an inverter that takes that energy and turns it into alternating current at 230V to mimic the grid power in order to power your normal household appliances. Both the charge controller and inverter need to be sized to match the solar array and battery bank. The larger your solar array and battery bank, the bigger your charge controller needs to be to handle the extra energy that's going to be running through it.
The inverter affects how much of your stored energy you can use at once. It needs to be the same voltage as your battery bank, and the size is determined by what you will be powering with your solar kit. If you think you might need to run a high-power item like a microwave, or multiple things at once, you’ll need a larger inverter. It’s best to have an inverter that is just large enough to handle your power needs, otherwise you run the risk of accidentally using more
energy than you intended, just because you have it available.
Researching solar power can lead you down some incredibly technical and confusing rabbit holes, so feel free to get in touch with us if you’re not sure what the right solution is for you.
Want to learn more about how off-grid solar power systems work? Check out our Off-Grid Basics - Solar Power Systems 102 article.