Lesson on Solar Panels
1. Solar Cell
1.1. Material
a) Monocrystalline silicon – used for outdoor solar panel (see figure 1)
b) Polycrystalline silicon – used for outdoor solar panel (see figure 2)
c) Amorphous Crystalline silicon– used for indoor solar panel (5-star does not make this
type)
1.2. Differences between Monocrystalline Silicon Solar Cell and Polycrystalline Silicon
Solar Cell
a) Polycrystalline silicon has right angle corners (figure 1) while monocrystalline silicon
has round or slanting corners (figure 2).
b) Polycrystalline silicon is light reflective while monocrystalline silicon is not. (If
polycrystalline silicon is specially processed, it is also non-reflective)
Figure 1
Figure 2
1.3. Anode and Cathode of Solar Cell
For a solar cell, the obverse is the cathode and the reverse is the anode.
1.4. Common Size of Solar Cell
a) 103 X 103MM
b) 125 X 125MM
c) 156 X 156MM
1.5. Optical and Electrical Characteristics
1.5.1. Conversion Efficiency
Temperature and light intensity affect directly the conversion efficiency of solar cell.
a) The higher the temperature, the lower the efficiency, and the lower the temperature,
the higher the efficiency.
b) The stronger the light intensity, the higher the efficiency.
Conversion efficiency also has something to do with the quality of the solar cell.
Theoretically, the conversion efficiency of monocrystalline is higher than polycrystalline
but actually, they are almost the same due to the quality.
1.5.2. Voltage and Current
a) Voltage – 0.5V per piece (for the whole solar cell and also when it is cut into small
pieces)
b) Current – for example, if the whole solar cell is 1A and when it is cut into 1000 pieces,
the current of the split piece will be 1mA.
1.5.3. Stringer/Current collector
Stringer/current collector
2. Solar Panel
Encapsulation
Epoxy Resin
PC Film
Structure
PCB + solar cell + epoxy resin
PCB+ EVA + solar cell + EVA +PC
film
Life
(0℃ - 80℃)
3 – 5 years
0.1 – 0.5W
5 – 6 years
0.6 – 2.0W
20 – 25 years
High
power
Wattage
PCB+ EVA + solar cell + PC film
Tempered Glass
glass + EVA + solar cell + EVA +
TPT
Note:
a) The encapsulation is to protect the solar cell from oxidation in the outdoor. (Once the
solar cell is oxidized, the conversion efficiency will decrease rapidly)
b) For PC film encapsulation, either one layer of EVA or two layers of EVA is OK and it
depends on the customer’s request. EVA is also used to protect the solar cell.
c) For the solar panel with glass encapsulation, there always has frame to support the
whole solar panel and protect it from damage. Also a junction box to connect the solar
panel and the load by a wire/cable.
d) Solar cell is very thin (about 0.18 - 0.35mm) and easily broken. Please avoid hit or
pressure to the obverse of the solar panel.
3. Solar Panel System
3.1. Solar Panel System for DC Load
Solar Panel
Controller
Rechargeable
Battery
DC Load
3.2. Solar Panel System for AC Load
Solar Panel
Controller
Inverter
AC Load
Rechargeable
Battery
4. Usage
a) Slanting angle of the solar panel = local latitude
b) Direction: Southward in the northern hemisphere
5. Information Needed for an Inquiry (** stands for the information is very important)
5.1. For Solar Panel
a) Size **
b) Operating voltage (Vm) and current (Im)**
c) Application **
d) Short circuit current (Isc)
e) Open circuit voltage (Uoc)
5.2. For Solar Panel System
a) Power consumption of the load per day **
b) Name and rated power, working time, operating voltage and current of the load **
c) How many days the solar system needs to work if it is cloudy or rainy?**
(The battery charging duration vs battery discharging duration)
d) Area the system is used (longitude and latitude is the best) **
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