how qloss is positive

Dear Paul,
I am working on SWHS. I have few confusions while simulat.
a) How come Qloss is +ve although Tamb is greater than Ttank?
b) Does -ve Qloss represent Qgain from atmosphere?
c) How Quseful is zero though there is temperature difference between Tout and Tmains?

I am attaching two images of my simulation result.

Hello,

Please see the "Results" Help topic under "Solar Water Heating" for details about what the solar water heating outputs mean. Also please see the "Solar Water Heating" topic for a description of the type of system the model represents.

a and b) I'm not sure what you mean by +ve and -ve. Qloss is calculated from the difference between the temperature of water delivered by the solar collector and the ambient temperature of the mechanical room where the tank is located (not the ambient temperature of outside air). By default it is set to 20 degrees C.

c) The model sets Q_useful to zero when the incident irradiance is zero. It is the heat delivered to the water tank by the solar collector, so you would expect it to be zero at night and when there is no solar energy.

Best regards,
Paul.

Hi Paul,

Sorry for bringing this issue up again.
But, is it possible to consider a variable temperature at the mechanical room?

Best regards

Hi Jose Miguel,

For the solar water heating model, the mechanical room temperature is a single value that applies throughout the year. It is not possible to consider a variable temperature.

Best regards,
Paul.