Photo voltaic batteries are available in two flavors, DC and AC coupled, which differ in how environment friendly they’re and the way they connect with your photo voltaic panels and the grid. If you happen to’re including a battery to an current photo voltaic set up, it’s virtually all the time more cost effective to decide on an AC-coupled battery. If you happen to’re getting a brand new photo voltaic+battery set up, DC-coupled photo voltaic batteries are virtually all the time extra environment friendly and less complicated to function.
However what’s the distinction between AC and DC coupling, and which one is finest for you? Let’s discover out.
How photo voltaic houses use AC and DC electrical energy
Direct present (DC) electrical energy means electrons flowing in a single course to supply energy to a circuit. Alternating present (AC) electrical energy means electrons flowing in two instructions, switching quickly. The explanation we’ve AC electrical energy is it’s cheaper and safer to transmit over lengthy distances, and subsequently a lot of your house’s home equipment have been constructed to make use of it.
Photo voltaic panels create DC electrical energy, which in a house photo voltaic system flows right into a field referred to as a solar inverter, which changes the DC electricity to AC electricity your home’s wires carry to outlets and appliances. Batteries also store and transmit direct current (DC) electricity, and they also need to be connected to an inverter, too.
Solar battery banks can add flexibility and peace of mind for homeowners. You can use them to back up your whole home in the case of a power outage, or choose just enough batteries to keep critical loads up and running.
DC-coupled solar batteries
When a battery is installed alongside a home solar system, the solar installer can install special equipment that first connects the solar panels to a charge controller, then to a battery bank, then a solar inverter, and finally to the home’s main electrical panel. This is called DC-coupled battery backup, because the battery is charged and discharged using DC electricity.
Some batteries commonly used in DC-Coupled systems include the 400V LG Chem Resu Lithium ion battery, SimpliPhi’s Lithium Ferrous Phosphate batteries and Trojan’s Flooded Lead Acid batteries.
Right here’s a diagram of a DC-coupled photo voltaic battery system:
Benefits of DC-coupled batteries
- Extra environment friendly, as a result of there isn’t any conversion of DC to AC till after the batteries cost
- Makes it straightforward to cost the batteries from photo voltaic panels, even when the grid is down
- If the inverter goes offline, the photo voltaic panels can nonetheless cost the batteries as a result of the cost controller and inverter function independently
- Many widespread DC-coupled batteries may be put in as AC-coupled techniques by including a battery-based inverter between the principle panel and the battery
Disadvantages of DC-coupled batteries
- DC Coupling shouldn’t be obtainable for PV techniques that use microinverters
- DC-coupled batteries are tougher so as to add to an current photo voltaic set up
AC-coupled photo voltaic batteries
For a very long time, DC-coupled batteries have been the one variety obtainable, however extra just lately, individuals who have already got photo voltaic panels wanted a simple option to add battery backup in case of energy outages and obligatory shut-offs.
For individuals who have already got photo voltaic connected to a grid tie inverter or microinverters, a DC-coupled battery doesn’t normally make sense. Why set up costly new gear that replaces what’s already working? As an alternative, present photo voltaic house owners can add AC-coupled battery storage to an current photo voltaic system.
In contrast to a DC-Coupled system, an AC-coupled battery has its personal inverter, which suggests it produces AC output that goes on to your house’s essential panel. Particular wiring permits the battery to cost from the grid or your photo voltaic panels, and likewise keep backup energy if the grid goes down.
Fashionable AC Batteries embrace the Tesla Powerwall, Panasonic EverVolt AC, and the sonnen eco.
Here’s how an AC battery system all connects together:
Advantages of AC-coupled batteries
- Relatively easy to add to a home because they come with all the hardware necessary
- Can be added to a home with or without solar panels
- If something goes wrong with your solar panels or inverter, the batteries can keep working, and if something goes wrong with your batteries, the solar panels can keep working
Disadvantages of AC-coupled batteries
- Less efficient than DC systems, because the electricity needs to be converted from AC to DC for charging, then back to AC for use in the home
- Additional hardware means more parts that can fail and cause problems
There’s a lot more to learn, and if you want to see if a solar battery is right for your house, get the process started with our new solar panel calculator today!