Primary Functions of Solar Battery:

As a Solar Developer/ Consumer, do we really know the primary functions of Solar Battery – the most important but poorly understood component next to the PV module.

Its time you learn about the primary functions of battery used in the Solar PV(Standalone) System. Note that the most important, but poorly understood component next to the PV module is battery.

Be aware that there is no one perfect type of battery available for all standalone PV power systems.

Batteries are classified into 2 major categories:

  • Primary Battery
  • Secondary Battery

Primary Battery :

Primary Battery can store and deliver electric energy, but cannot be recharged. Typical Carbon-zinc and lithium batteries commonly used primary batteries.Primary batteries are not used in PV systems because they cannot be recharged.

Secondary Battery :

Secondary battery can store and deliver electrical energy and can also be recharged. Therefore secondary battery is only option in Solar PV systems.

 

Look:

There are many factors that influence the choice and performance of a solar battery in the PV Systems.Also battery technology keeps changing with new constructional features and enhanced performance levels.

 

Primary Functions of Solar Battery:

  • Energy Storage Capacity and Autonomy.
  • Voltage and Current stabilization
  • Supply Surge Currents

 

Lets dive in :

Energy Storage capacity and Autonomy:

It is the capacity to store electrical energy when it is produced by the PV array and supply to the electrical loads as needed or on demand. The most important function of Solar batteries in stand-alone PV systems is to allow the loads to operate when the PV array by itself cannot supply enough power.

A stand-alone PV System can have autonomy if sufficient battery storage capacity is available to operate the electrical loads directly from the battery, without any energy input from the PV array.

Energy storage in batteries is required if electrical loads are required to operate at night time or during extended periods of cloudy or overcast weather.

During the stand-alone PV system sizing, the battery storage capacity is generally sized to meet the average daily electrical load for a specified number of days(Autonomy days) without the input from PV module or PV Array.

The more the number of Autonomy period, the larger the battery capacity required for a given load demand.

  • For Less critical PV applications : 2 to 6 days of Autonomy.
  • For Critical loads  such as public safety :  10 to 15 days of Autonomy.

 

Voltage and Current Stabilization:

It is the ability of storage system to supply  power to electrical loads at stable voltages and currents, by suppressing or ‘smoothing out’ transients that may occur in the Power System.

A PV array can theoretically operate at an infinite number of operating points between the short-circuit  current and open-circuit voltage.

When electrical loads are directly connected to a PV Array( for e.g : Solar Water Pump ), the load impedance decides the operational voltage of the PV array, which may not be suitable to operate the load at its prescribed conditions.

Batteries are present to ensure that PV array is operated near its maximum power voltage.

Batteries acts as a buffer between the PV array and electrical loads in which the load power oscillates or change with respect to time.

Supply Surge Currents:

Surge Currents is the ability to deliver high peak operating currents to electrical loads for a short duration of time.

While the PV array may be large enough to supply the total energy needed by a load over a day, it may not be large enough to meet the momentary surge power demand by a load at any particular time.

A battery is capable of delivering such large surge currents to the load for short duration. The discharged battery  will be charged again by the Solar PV array at lower currents during the day.

Examples of common loads that require momentary surge currents are electric motors . These motors can be found in Compressors, Power tools and other motor loads.

The Surge current may be 5 to 10 times the normal running or operating level of the load. A battery can supply hundreds of amperes for short duration of surge requirements.

Related reading:

References: GSES Standalone Photovoltaic Systems

I would be happy to hear  more about functions of solar battery. Do share your thoughts in the comment section below.

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