Solar storage in batteries needs consideration. It is not just about being off-the-grid, but helps to resolve several problems with renewables. If you add solar batteries in your grid-connected residential solar panels, it will help to supply extra stored solar power to the grid during critical load situations.
Commercial consumers can decrease their peak hour demand charges with solar storage and thus lower their utility bills. Solar storage needs are growing as the state passes laws to encourage solar battery usage.
Solar batteries need to fulfill unstable grid energy demands, irregular full charging, and heavy cycling. There are different kinds of solar batteries available.
Lead-acid batteries
For decades the deep cycled lead-acid solar batteries have been used in residential and commercial off-grid applications. A lead-acid solar battery is less expensive than a lithium-ion.
Pros
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More storage capacity and recharged more often.
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Less costly.
Cons
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Lifespan is 5 years and needs multiple replacements over the solar panel system’s warranty life.
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Low energy efficiency and risk of depletion.
Lithium-ion batteries
These are widely applied in power tools, vehicles, and even laptops.
Pros
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They can operate consistently for 10 years without any concern of degradation in storage capacity.
Cons
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Cost is high but as technology advances the price may get better and cheaper.
Flow batteries
Flow batteries are of three types – Vanadium Redox, Zinc Bromide, and Polysulfide Bromide.
Pros
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Easy scalability.
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No detrimental effects of deep discharge
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The cost for a large system is low
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Long cycle life
Cons
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As the system is intricate along with low power and energy densities, there is a need for pumps and plumbing for electrolyte circulation across the membrane, so not suitable for residential application. It is fine for massive commercial applications needing large-scale storage.
Nickel Cadmium batteries
There are two kinds of Nickel-Cadmium batteries – vented and sealed.
Pros
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Delivers high energy output.
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Tolerates overcharging.
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Inexpensive than other battery technology.
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High cycling life.
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Good low-temperature performance.
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Fast recharging.
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Handles harsh environments.
Cons
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Cadmium is toxic and needs cautious recycling.
How to choose the correct PV system battery?
The most common batteries on the market today are the Tesla Powerwall, LG Chem, and Sonnen.
When you evaluate solar storage options, you will need to consider the following.
Capacity & power
Capacity defines the battery size and not the amount of power it supplies. For this, you will need to consider the power rating, which is measured in kW [KiloWatts]. You get an idea of how much total electricity the battery can deliver. Choose a battery with a low power rating and high capacity, to enjoy electricity for a lengthy time.
DoD or Depth of Discharge
There is a need for batteries to retain some charge every time because of their chemical compositions. If the battery gets completely drained, its lifespan gets shortened. DoD defines the capacity level for the usage of the battery.
Round-trip efficiency
It means the energy you can use is proportionate to the energy stored. If four kWh of electricity is stored in a battery then you can use the only 3kWh. It means the battery has a 75% round-trip efficiency. The higher the round-trip efficiency, the more economic value you get from the battery.
Cycle life
It is the number of charge/discharge cycles provided by the battery before dropping the specified percentage. The cycle life of a solar battery will depend on the materials, design, and quality.
