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Heat loss in PV modules

When it comes to  PV modules, there are several things one needs to consider. Here, we are going to focus on the category of heat loss which occurs in PV modules.

The mechanism of heat loss in PV modules

Heat loss in PV modules can occur as a result of three mechanisms. They are as follows.

  • Conduction
  • Convection
  • Radiation

Let us take a deeper look at each of the above methods to know more.

Heat conduction

Heat lost in PV modules due to conduction mainly occurs because of thermal gradients which are present between the PV module and other materials that the module tends to come in contact with. The temperature differential is the key reason which leads to loss of heat owing to conduction. This analogy can be compared to an electric circuit and the same power equation can be mapped to calculate heat loss.

Mathematically speaking,

 

 

In the above equation,

  • Pheat is actually the power which gets generated by the PV module
  • ΔT would be the temperature differential
  • Φ is a measure of the thermal resistance of the surface

The thermal resistance in turn depends on how thick the material is and also the kind of resistance which the conductor has. If the structure tends to be complicated, then the individual thermal resistance will have to be added. The additional will be done on the basis of series or parallel connection as it may be.

Convection

Coming to the convection form of heat loss, it occurs when one material moves across the surface of another. When it comes to a PV module, it is mainly seen when wind blows above the module surface.

Mathematically speaking,

 

 

In the above equation,

  • A denotes the area of contact which is present between the materials
  • ΔT refers to the temperature differential
  • h would actually be the heat transfer coefficient for convection mode of heat loss.

Radiation

The final way by which heat loss occurs in PV modules is radiation. Like the blackbody radiation law states, any object is likely to radiate heat and dissipate it to the other environment via radiation.

Once again, mathematically speaking, the equation would be:

 

 

In the above equation,

  • P refers to the net power generated on the PV module
  • T denotes the temperature which the solar cell reaches
  • σ refers to the Stefan Boltzmann constant

But this equation needs to be modified slightly because the PV module isn’t a perfect blackbody. This is why the equation is appended with the emissivity parameter. This parameter is governed by the absorption properties of the particular area.

The modified equation will be:

 

 

So, these are the different points which govern the heat loss which occurs in the PV modules. Knowing them can help  minimize the overall loss significantly.

 

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