How a Solar Energy Storage System Works
Adding solar batteries to a solar PV system can provide economic benefits including time-shifting energy use, energy arbitrage, and preserving the benefits of net metering. They can also help homeowners cut their utility ties completely or become more self-sufficient during grid outages.
Before adding storage, consult with local AHJs to make sure the battery installation meets their requirements. AHJs can require building permits for storage upgrades.
Solar panels convert energy from the sun into usable electricity. They are composed of multiple silicon solar cells surrounded by glass and a metal frame, all wired together into solar modules — the large sheets of panels you see on roofs. Solar energy is a clean, renewable resource that is inexhaustible and doesn’t require fossil fuels to produce. Unlike traditional energy sources, which create harmful emissions and waste products, such as acid rain, water pollution, air pollution, smog and rapidly-filling landfills, solar power doesn’t harm the environment in any way.
Solar energy can be stored in batteries for use during the night or during a power outage. It can also be used to avoid peak demand charges and lower your utility bills. Solar battery storage can be a smart addition to any residential or commercial solar system, even those connected to the grid.
A solar energy storage system combines the output of your solar panels with the capacity of a battery to generate enough electricity for your home or business to stay on all day, regardless of when the sun is out. This allows homeowners to Solar Lithium Battery be less dependent on the grid, protect themselves from future electric rate increases and know exactly where their power is coming from. Battery storage for solar systems is available in a range of sizes, allowing homeowners to choose the size that best fits their energy usage and budget.
Solar energy storage systems rely on an inverter to convert direct current (DC) from your solar panels into alternating current (AC) electricity for use at home. The inverter also controls how the solar system interacts with the battery, such as when to charge from the grid vs. the battery or when to send electricity back to the grid, which can earn homeowners rebates or credits.
Solar+battery inverters can also be designed to enable grid-forming, which allows homeowners with a large enough solar+storage system to form their own behind the meter microgrid. This capability can help to stabilize local power supplies during outages, reducing the need for expensive generators and keeping critical loads online until utility power returns.
Some inverters can be equipped with a battery charge control that monitors conditions and determines when to switch between charging from the solar system or the grid, how much to store in the battery, and when to return any excess electricity back to the grid. This technology enables homeowners to practice something called “peak shaving” during peak energy demand periods, when utility companies charge higher rates than at other times of the day.
Several of the manufacturers and installers we spoke with offer batteries designed to work well with their solar PV systems. These include LS Energy Solutions, a California-based company that offers a hybrid inverter Solar Lithium Battery Manufacturer and battery solution with StorEdge DC that can be used for both on-grid and off-grid installations.
The electricity that solar produces is in the form of direct currents (DC). To use it in your home, it needs to go through something called an inverter, which will convert it into alternating currents (AC) that are used by homes and businesses.
Batteries work by having a negative electrode, or anode, and a positive electrode, or cathode, with an electrolyte solution in between. A chemical reaction at the anode frees electrons from the battery, allowing them to gather on the cathode where they can be captured and turned into electricity. When paired with solar panels, a battery system is used to store this electricity during the day and then use it at night when the sun isn’t shining.
In addition to providing resiliency during grid outages, solar battery systems can also help lower your utility bills. Many utility companies offer Time-of-Use rates, charging higher electricity prices during peak demand times (usually from after work into the evening). Solar batteries can be used to reduce or even eliminate these high TOU charges.
There are multiple types of batteries that can be used for solar energy storage, including lead-acid, lithium-ion, and flow chemistry. Aurora Solar provides smart battery sizing modeling as part of our software platform, analyzing load off-set and forecasting pricing to provide our customers with a clear understanding of the financial benefits of solar + storage.
If you’re looking at a solar+storage system that can be used full-time or as a backup for off-grid use, a charge controller is essential. The charge controller ensures that the amount of energy being sent from the solar panels is not so high that the battery voltage will overcharge, which can be dangerous.
The charge controller also disconnects the battery from the solar panel when its voltage is too low, preventing the battery from being drained or damaged. It will reconnect the battery when the solar panel is able to put out more than the battery needs, allowing it to continue charging.
There are a few different types of charge controllers on the market, with varying degrees of efficiency and cost. Pulse Width Modulation (PWM) and Maximum Power Point Tracking are the two main options. PWM charge controllers use a transistor switch that rapidly opens and closes to regulate the power being fed into the batteries. They are simpler than MPPT controllers, and they typically operate at 75-80% efficiency.
MPPT charge controllers utilize a DC-DC converter to optimize the voltage of your solar array, matching it with the voltage required by the battery bank. They are more expensive than PWM controllers, but they can boost the efficiency of your system to 94-98%. Xantrex, Morningstar, Victron Energy and other brands produce MPPT solar controllers.