What Are the Key Ingredients in a Solar Battery System?
Solar batteries allow homeowners to store the energy their panels create, enabling round-the-clock clean power. They can also be used to provide backup power during grid outages.
When your home needs the power, a multi-mode inverter in the battery flips DC electricity to AC for use in your house. In backup mode, a battery system is configured to power only the systems in your critical load sub-panel during blackouts.
Solar Panels
Solar panels are grouped together into an array and mounted on rooftops or in outdoor spaces. They convert sunlight into electricity, and for homeowners who choose to install a battery, they can store energy for cloudy days or night usage.
Panels are made of semiconductor materials such as silicon, and they’re encased in glass for durability. When light hits a solar panel, it creates an electric field that knocks electrons loose from their pairs (electrons and holes). These free electrons flow through the module to produce electricity.
Solar modules are angled to match your latitude and sun exposure to capture the maximum amount battery solar panel of energy during daylight hours. They’re also oriented and positioned to prevent shading by nearby objects or trees, since if even a single panel is shaded it significantly reduces energy production. Blocking diodes may be used in series or parallel connections to allow current to bypass shaded modules and prevent short circuits.
Batteries are a critical component of any solar system, and they’re available in a variety of sizes to suit your energy needs and budget. The capacity of your batteries—measured in kilowatt-hours (kWh)—directly affects how much surplus energy can be stored for use when the sun isn’t shining. Traditionally, lead-acid batteries have been used, but their limited depth of discharge and shorter lifespans are contributing to an increase in popularity for lithium batteries.
Battery
The key ingredient in solar battery systems is a high-quality battery. Typically, this is a lithium-ion unit (although there are other types) and the specific model will depend on the application in question. Lithium batteries are well-understood and safe technology and many solar installers will be able to offer guidance on the best fit for your system.
Batteries are designed to store energy so that it can be used at the homeowner’s convenience when the sun isn’t shining. This functionality allows solar panels – which only produce electricity when the sun is out – to work efficiently round the clock.
Solar batteries come in a range of sizes and shapes. They also use different chemistries. The chemistry will determine how much power the battery can hold and the depth of discharge (DoD) that it can sustain before it needs to be recharged. Lead-acid batteries have a DoD of 50% and nickel-cadmium batteries are rated at 15%; exceeding this limit will decrease the lifespan of the battery.
Lithium iron phosphate (LFP) batteries, which are commonly seen as the best option for home solar systems, have a DoD of 80% and can be used up to 4,000 cycles. They also have a long service life and operate at high efficiency levels. Most solar battery models will include an inverter, which converts DC to AC electricity so that the stored energy can be used within the home if needed.
Inverter
Inverters convert DC power from your PV and battery into AC electricity. Most electrical devices operate on AC power, which comes from the grid and other sources. DC power is flat and only has voltage and current – it doesn’t have a frequency or waveform, and ideally would have a pure sine wave.
In addition to changing the voltage of the outgoing AC power, inverters have other functions. Most modern inverters will have some type of intelligent processing that helps regulate power. This is done via different circuit topologies and control strategies.
The inverter also acts as a safety device to protect the battery from overcurrent. Overcurrent is dangerous and can damage all-in-one-ess or even burn your solar panels and cables. An overcurrent protector is a fast-acting fuse or circuit breaker that will blow within milliseconds of a short circuit occurring.
Some inverters are also smart and can be programmed to start charging the batteries at a specific state of charge or sell power back to the grid at certain times of day, for example. Inverters can also be designed to handle partial shading of the panels. Some inverters have built-in internet connectivity, allowing you to remotely monitor system performance from your mobile phone or computer. Inverters that can do this are often referred to as “smart inverters”.
Controls
The solar charge controller is one of the most important parts of a solar energy system. It regulates current from the solar panels to the battery to avoid overcharging and over-discharging. It also prevents the batteries from draining back to the solar panel during low solar irradiance or night time. It achieves this by incorporating a blocking diode and other electronic components.
The most basic type of solar charge controller, a shunt charge controller uses a semiconductor to control the voltage passing through your battery. This allows for one- or two-step regulating. The first step is to hold the voltage at a safe maximum level for charging your batteries. The second step is to drop the voltage lower to sustain a trickle charge. This is the best way to maintain a full battery charge while minimizing water loss and cell stress.
For larger, more complex systems and locations with variable weather, a more advanced charge controller is needed. These are often referred to as MPPT controllers and work much like a standard charge controller but can deliver up to 30% efficiency gains over simple controls. They calculate and deliver the highest power point between the PV array and your battery, allowing you to maximize your solar energy harvest. They also provide additional features including protection against reverse polarity, short circuit, overcurrent and high temperatures.