Welcome to the first video of the third chapter. Let’s again take a look
at the PV system design overview. In week 2, you learnt about
the location-related aspects of PV system design, such as the meteorological data, surrounding landscape
and the plane of array irradiance. In this part of the course,
we will focus on the PV modules. This week you will learn
how modules are constructed from solar cells and how multiple modules form a PV array. We will discuss
the state of the art PV module structures and you will learn
how the interconnection of cells and modules affect their electrical properties. But first, let’s take a look at relevant
properties of PV modules, as found in a typical datasheet.

This is the datasheet of a PV module by Panasonic,
based on heterojunction technology. The enlarged area indicates
the dimensions and weight of the PV module. The dimensions of the PV module
are important for PV system design, in order to estimate
the total irradiance incident on the module and the space required for the installation. Starting from the left-hand side,
we have front, side and back views of the PV module, including the frame and the junction box.

The junction box is represented
by the little square on top of the back view with the connectors attached to it. The weight of the module
can be found underneath this figure. The weight can be an important property, if the area on which the modules are installed
has limited weight bearing capacity. Below the dimension and weight box,
the warranty strategy can be found. The warranty varies depending
on the module manufacturer. You can see for example that
this module has a standard tiered warranty, that guarantees a power output of 90%
of the minimum power output for the first 10 years. From year 10 to year 25,
80% of the minimum power output is guaranteed. Then, the various materials
of which the module is composed are listed. These materials include
the heterojunction with intrinsic thin layer solar cells, the anti-reflection coated glass, the black anodized
aluminum frame and the connectors.

Finally, the certificates are listed,
indicating that the module is up to standards. You will learn more about these certificates
later in the course. Another important module parameter is the
irradiance dependence of the module. These are the voltage-current characteristics
under different irradiance conditions and at a constant module temperature of 25 °C. Generally, a single light source is used
to simulate the different irradiance level. The irradiance level is reduced through the use of filters. At a fixed temperature,
the current increases with increasing irradiance, starting from more than 1 A at 200 W/m2
to a value 5 times higher at 1000 W/m2. Finally, let’s take a look at – perhaps –
the most important part of the datasheet: the electrical data. These are organized into four groups. The first table provides the properties
at Standard Test Conditions. Next, the temperature characteristics are shown, followed by the module properties
at normal operating conditions. Finally the module performance
under low irradiance conditions is shown. Let’s start with the properties
at standard test conditions. As you may recall,
the standard test conditions are 1 sun illumination, which is the AM1.5 spectrum at 1000W/m2, a constant module temperature of 25 °C,
and the absence of wind.

under outdoor conditions, the modules are typically at
higher temperatures than 25 °C and at lower irradiance conditions. Therefore, the Nominal Operating Cell Temperature,
or NOCT, of a PV module is provided in the datasheet. This NOCT is the temperature at which the module will
operate when it is under open circuited conditions, when the air temperature is 20 °C,
the AM1.5 solar irradiance is equal to 800W/m2 and the wind velocity is 1 m/s. In this example, the NOCT is 44 °C. Having defined both the STC and the NOCT,
let’s focus on the electrical data of the module.

The power, the voltage and the current
at the maximum power point, the open circuit voltage and the short circuit current. For the STC, also the maximum current and
system voltage are reported for safety reasons, as well as the production tolerance power. This last parameter specifies the range within
which the PV module will either over perform or underperform
with respect to its rated power at STC. The second table also provides temperature
coefficients for the short circuit current, open circuit voltage and maximum power. With these coefficients, the performance of the module
can be evaluated when the module operates at temperatures
other than the NOCT. In fact, as you can see, at higher temperatures
the short-circuit current is increased, but the voltage and maximum power are decreased. In summary, in this video we discussed how
to interpret a PV module datasheet.

In the next video, you will learn more about
the PV modules available in the market. That way, you will be able to select the best
PV module for YOUR PV system..

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