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ADVANTAGES OF MPPT VS PWM TECHNOLOGY (CONTINUED)
GAINS OF A MPPT OVER PWM
The voltage of a photovoltaic solar panel varies according to its temperature: its voltage decreases as the
temperature increases and vice versa. This normative value, called the temperature coefficient, is given
with a cell temperature of 25°C.
Example: with a panel that di/-0.34%/°C, we must correct the Vmp voltage by -0.34% per cell
degree above 25°C.
As shown in the example below, which highlights voltage variations due to temperature and voltage drops
due to the cable, a UNIMPPT charge regulator allows an
APG (Average Production Gain)
of 20% in
summer and up to 40% in winter.
In addition, it is noted that the more the battery is discharged and/or the panel voltage is high, the greater
the advantage of an MPPT over a PWM is.
100 W solar panel with a UNIMPPT regulator
Solar radiation
during the winter
Solar
panel
temperature
Panel
Voltage
Vmp
-Voltage
drop due to
the cables
(5%)
Voltage
battery
charge
Theorical
Gain in
value
Theorical
gain in
%
Gain
rectified
MPPT *
Sunrise
9h
5°C
20,0
19,0
12,2
6,8
56%
53%
19,9
18,9
12,5
6,4
51%
49%
19,8
18,8
13,0
5,8
45%
42%
12h
19,7
18,7
13,5
5,2
39%
37%
19,6
18,6
14,0
4,6
33%
31%
End of charge
16h
15°C
19,5
18,5
14,6
3,9
27%
26%
GPM Moyen
+ 40%
Solar radiation
During the summer
Solar
panel
temperature
Panel
Voltage
Vmp
-Voltage
drop due ti
the cables
(5%)
Voltage
battery
charge
Theorical
Gain in
value
Theorical
gain in
%
Gain
rectified
MPPT *
Levé du jour
7h
30°C
18,4
17,5
12,2
5,3
43%
41%
17,2
16,3
12,5
3,8
31%
29%
17,2
16,3
13,0
3,3
26%
24%
10h
16,6
15,8
13,5
2,3
17%
16%
16,3
15,5
14,0
1,5
11%
10%
Fin de charge
14h
70°C
16,0
15,2
14,6
0,6
4%
4%
GPM Moyen
+ 20%
* Example MPPT efficiency 95%
