RENEWABLE ENERGY LABORATORY

REPORT # 1

“Solar Panel Testing: Standard Test

Conditions”

NAME:
VALERIA TEJENA SOJOS

PROFESSOR:
ING JIMMY CORDOVA

LABORATORY ASSISTANT:
WALTER MARISCAL

COURSE:
1

YEAR: 2018 – 2T
1. Objectives (2.5%)

• Analyze the behavior of the solar panel when the sun does not hit some of
its cells (under shadow condition).

• Observe the behavior of a solar panel in different situations such as with an

open circuit or with a connected load.

2. Procedure (2.5%)

a. Connect the panel with the resistor in a series configuration with the voltmeter
and ammeter for measurements, as shown in figure 1.
b. Fill table 1 with the measurements of current, voltage and power, varying the
resistance.
c. Calculate the power from the values of table 1 and fill the table 1.
d. Cover the lower left corner, the upper right corner, the center and half the
panel. Comment on the results from the measurements and explain why the
curve change the shape.

Figure 1

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 Voltage and Current measurements with panel exposed to the sun
Voltage [V] Current [A] Power [W]
1 11.90 0.50 5.95
2 15.46 0.45 6.96
3 16.36 0.40 6.54
4 17.00 0.35 5.95
5 15.60 0.30 4.68
6 15.53 0.25 3.88
7 16.12 0.20 3.22
8 16.86 0.15 2.53
9 17.50 0.10 1.75
10 17.91 0.07 1.25
Table 1. Voltage and current measurements with panel exposed to the sun.

Measurements of voltage and current with panel in the shade

Voltage [V] Current [A] Power [W]
1 8.12 0.50 4.06
2 8.57 0.44 3.77
3 8.66 0.40 3.46
4 8.70 0.34 2.96
5 8.79 0.30 2.64
6 8.93 0.25 2.23
7 8.95 0.20 1.79
8 9.03 0.15 1.35
9 9.04 0.11 0.99
10 9.09 0.05 0.45

Table 2. Measurements of voltage and current with panel in the shade.

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3. BACKGROUND (10%)

Solar Panels
Photovoltaic solar panels absorb sunlight as a source of energy to
generate electricity. A photovoltaic (PV) module is a packaged, connected
assembly of typically 6x10 photovoltaic solar cells. Photovoltaic modules
constitute the photovoltaic array of a photovoltaic system that generates and
supplies solar electricity in commercial and residential applications.

The most common application of solar energy collection outside agriculture

is solar water heating systems.

Standard Test Conditions (STC)

STC stands for “Standard Test Conditions” and are the industry standard for the
conditions under which a solar panel are tested. By using a fixed set of conditions,
all solar panels can be more accurately compared and rated against each other.
There are three standard test conditions which are:

1. Temperature of the cell – 25°C. The temperature of the solar cell itself, not the
temperature of the surrounding.
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2. Solar Irradiance – 1000 Watts per square meter. This number refers to the
amount of light energy falling on a given area at a given time.

3. Mass of the air – 1.5. This number is somewhat misleading as it refers to the
amount of light that must pass through Earth’s atmosphere before it can hit

Earth’s surface and has to do mostly with the angle of the sun relative to a
reference point on the earth. This number is minimized when the sun is directly
above as the light has to travel a minimum distance straight down and increases
as the sun goes farther from the reference point and has to go at an angle to hit
the same spot.

Measurement problems

Although an industry-wide accepted standard of comparability between modules,

it often happens that in the manufacturing process STC requirements are not
diligently met by the manufacturers’ internal quality control,
with frequent deviations in lamp spectrum, cell temperature, environment
temperature, irradiation etc.

Purchasers of solar modules do therefore often request the inspection services of

3rd party solar PV module quality inspectors to ensure the manufacturer’s
stated performance claims.

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4. RESULTS ANALYSIS (40%)

No shadow condition

In this experiment, at the beginning, there is no load (R=0) and the voltage is the
lowest with the highest current. Then, the load starts to increase, and we can see
in the graph bellow that the voltage increases as well, but the current decreases.

V vs I
0,50
0,45
0,40
0,35
Current [I]

0,30
0,25
0,20
0,15
0,10
0,05
-
11,90 12,90 13,90 14,90 15,90 16,90 17,90 18,90
Voltage [V]

The behavior of the Power is similar to the Current, that’s because they are
proportional.

V vs P
8
7
6
Power [W]

5
4
3
2
1
0
11,00 12,00 13,00 14,00 15,00 16,00 17,00 18,00
Voltage [V]

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 Under shadow condition

We can observe a clear difference between under shadow and full exposure
condition. For example, the voltage is a lot lower with under shadow condition, as
well as the graph shape in general. It’s the same for the power cuve.

V vs I
0,60

0,50

0,40
Current [A]

0,30

0,20

0,10

0,00
8,00 8,20 8,40 8,60 8,80 9,00 9,20
Voltage [V]

V vs P
4,50
4,00
3,50
3,00
Power [W]

2,50
2,00
1,50
1,00
0,50
0,00
8,00 8,20 8,40 8,60 8,80 9,00 9,20
Voltage [V]

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5. QUESTIONS (40%)

a) Investigate about the Standard Test Conditions.

STC is an industry-wide standard to indicate the performance of PV modules and

specifies a cell temperature of 25°C and an irradiance of 1000 W/m2 with an air
mass 1.5 (AM1.5) spectrum. These correspond to the irradiance and spectrum of
sunlight incident on a clear day upon a sun-facing 37°-tilted surface with the sun
at an angle of 41.81° above the horizon.

b) What kind of cells does the PV panel? Write the principal characteristic of it.

Monocrystalline cells
The panels are manufactured with monocrystalline cells. Logically, they are also
usually the most expensive. Its cells are manufactured by a controlled
crystallization process at high temperatures, at about 1500 ºC, from a single germ
that achieves a cylindrical ingot forming a unique crystalline structure. This glass
bar is cut into thin sheets or wafers with thicknesses of around 0.3 mm.

Polycrystalline cells
Polycrystalline cells are manufactured from metallurgical silicon by less extensive
solidification processes. The growth of the silicon crystals is not controlled so that
different crystalline structures are formed. This allows the manufacture of
rectangular-shaped ingots that facilitate the subsequent formation of the
photovoltaic cells. Panels with polycrystalline cells have lower yields.

Amorphous cells
The third method of manufacturing consists of depositing in a controlled manner
the layers of photovoltaic material on all the materials that act as support. Silicon,
cadmium telluride, copper, selenium is fixed to plastics, glasses or fabrics to
manufacture flexible cells or integrated into the different building materials. The
thickness of the cells is reduced up to fifty times, which also allows considerable
savings in raw materials.

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 c) What happened when the panel was covered? Briefly explain.

A solar panel is composed of several solar cells and all act together to generate
electricity. If a part of the panel receives the shadow of a tree or any other surface
the energy is lost exponentially because each solar cell affects the others.

d) Write a swift summary about the Bypass Diodes.

The blocking diodes prevent the battery from being discharged through the
photovoltaic panels in the absence of sunlight. They also prevent the flow of
current from inverting between blocks of panels connected in parallel, when one
or more of them produces a shadow.

The bypass diodes individually protect each panel from possible damage caused
by partial shadows. They should be used in arrangements where the modules are
connected in series. They are generally not necessary in systems operating at 24
V or less.

While the blocking diodes prevent a group of panels in series from absorbing
current flow from another group connected to it in parallel, the bypass diodes
prevent each module from individually absorbing current from another of the
modules of the group, if one or more modules of it produces a shadow.

6. CONCLUSSIONS & ANEXXED (5%)

• It was observed how the shade affects a photovoltaic panel as the

decrease of its voltage and in the production of energy.

• it was possible to determine the importance of the bypass diode in the

photovoltaic panels, since they serve as protection for the cells, since if
there were no cells they could absorb electrical energy due to shadows,
causing damage to the panel.