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Thermal expansion and stresses

When designing a PV module,  several factors should be considered. It is important to take into consideration the different aspects which can lead to heat loss and even thermal expansion and stress   as well. By knowing these specifics, one can maximize output and minimize energy losses and thermal expansion errors.

What creates thermal expansion?

Just as the name implies, thermal expansion actually refers to the expansion of the module elements due to the change in temperature. This hampers the efficiency of the module. Mostly, due to the different thermal expansion coefficients which vary because of the change in the material of the modules, there is a change in temperature. This, in turn, creates thermal stress.

If we want to represent it mathematically, we can do so with the help of the following equation:

Thermal expansion

 

 

In the above equation,

  • αG and αC denote the expansion coefficient of the glass and the cell respectively
  • C is the cell center to the center distance
  • D is the width of the photovoltaic cell

This equation is actually calculating the amount which the cell spacing is trying to increase due to the difference in temperature.

This is the reason different cells are interconnected while keeping the stress relief arch in between. They are also looped, the main reason being the fact that it helps in curtailing the amount of cyclic stress which would be otherwise caused.

The thermal stress generated could be so whopping that it could also lead to fatigue failure of the PV module and this is why there are double interconnects which are used.

This is not the only kind of stress, as cyclic stress due to temperature fluctuation is likely to be one major factor as well. This necessitates the right detailing and offering the best provision during the designing of the PV module. Doing this can help in minimizing heat loss and thermal stress. It is this minute attention to details which end up helping in improving the energy efficiency and the net power output which the PV module would offer.

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