Thermal Losses - Default Options

[patrikbusta]

Hello everybody,

I would like to ask your opinión regarding thermal losses.

I am working on an offer for a Client, who is asking for guarantees related to production and PR.

Usually I choose the default option 'Free mounted modules with air circulation' because is the one which better fits my configuration. However, the resulting losses due to temperature are quite low (at around 7%) and so PR is higher than expected.

Do you recommend me to choose a less dissipative option ('semi-integrated' or 'fully back insulated') in order to be less agressive with the guarantees? Do you recommend me specific values for Uc and Uv instead of the three default options? Which is the most sensible option for an offer with which we do not want to be very agressive with the guarantess we provide?

Thanks in advance and regards.

Patrik.

[André Mermoud]

This depends of course on the geometrical positioning of your installation. You don't tell anything about this.

[patrikbusta]

Hello again!

Sorry that I did not explain correctly.

The default configuration which better fits my installation is the 'free mounted with air circulation on both sides'. What I was trying to say is that with this option losses due to temperatura seem to be too low.

Would it be a good option to choose one of the other default configurations, so that the resulting losses due to temperatura are not too low (so the PR I guarantee is not too agressive), despite the fact that the one which better fits my configuration is the 'free mounted' one?

This would be a strategy in order to be not too agressive with the guarantees of PR and production. Does it make sense?

[André Mermoud]

If you consider the thermal loss as your decision, and not the result of the simulation, you can of course put the parameter you want for getting this result.

[awills]

Hi,

For thermal loss factors at this point:

According to their own measurements, some users proposed, when using standard meteo values such those in the US TMY2 data (usually around 4-5 m/sec on an average in continental - not-coast places), the following U-values:

Uc = 25 W/m²·k, Uv = 1.2 W/m²·k / m/s

How are these values calculated?

Does PV Syst recommend a way this can be calculated?