Answer to Question #233263 in Mechanical Engineering for Molahlegi

Question

Design a standalone (off grid) Photovoltaic (PV) system with special reference to the village in South Africa with the following PV panel generation factor of 7

Answer 1

Calculations of power consumption demand 

(80W*4hours)+(60W*2hours)+(75W*12hours)

$=1340.0 watt hour/day$

Total pv panel energy needed= 1340.0*1.3

=1742 wh/day

Calculations of size of pv panel

The total watt peak rating needed by the pv panel = $1742/3.4=512.352$

total number of pv panel needed=$512.352/110=4.65$

actual number of pv panel=$5 modules$

Inverter sizing:

total watt of all appliances =$80+60+75$

for safety inverter size should be=$279.5$

(25-30%) higher

battery sizing:

total appliances use=$(18*4) +(60*2)+(75*12)$

Normal battery voltage =12V

battery capacity =$(1340*30)/(0.85*0.6*12)=656.86$

So the battery should be rated 12V, 700Ah for three days autonomy

solar charge controller sizing:

solar photovoltaic module specification 

P_m=100W_p

V_m=167V_dc

I_m=6.6A

B_dc=20.7 V

I_x=7.5A

solar charge controller =( 4_strings*7.5)*1.3

=39 Amp

Thus, the solar charge controller should be rated 40 Amp at 12V or greater.