Certain mathematical verifications were required to
design a system in order to develop solar system. The first step was to
calculate the power requirements of the load. This was done by listing each
load and making an estimate for how much energy it would consume in a day. This
can be done with measurement made use by multimeter to calculate both voltage
and current in a range of time on the load with their conventional power supply.
Base from the measurement, we can calculate power and watt-hour (Wh) on that
time. The battery size calculated such as in equation (1), (2) and (3).
Eload (Wh)=∑ (
Vload x Iload x Time) (1)
Ebattery (V)=
(Eload x Autonomy) ÷ (nbattery x DoD) (2)
In the (2) formula, there are autonomy, nbattery,
and DoD (Maximum Depth of Discharge). Autonomy is the number of days that the
battery can support the system while the nbattery is the Battery
Efficiency Factor. Usually the Battery Efficiency Factor is set to 0.9. Lastly,
the Maximum Depth of Discharge is the percentage that percentage will use the
storage of the battery. The standard value of Maximum Depth of Discharge for
standalone PV system is 0.8.
AHbattery (AH)=
Ebattery ÷ Vbattery (3)
In order to choose the battery size, the battery must
have the AH value more than the calculated.
The type of battery that have been widely use is Sealed Rechargeable
Battery because of their characteristics. After that, the amount of the battery
needed must be count as in equation (4) and (5) to know how many numbers of
batteries that can be arrange in series and parallel base on earlier
calculation.
Nparallel (unit)
= AHbattery ÷ AH one battery (4)
Nseries (unit) =
Vsystem ÷ Vone battery (5)
The sizing of the battery can help to minimize cost and also to
count the ability of the system to get enough power from the battery. Then, the
storage of the battery will support the system tally with the time that has
been set.
Written by : Mohd Saiful Najib Bin Ismail @ Marzuki
: Ahmad Izzat Bin Mod Arifin
#technical article
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