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Old 12-27-19, 11:07 AM   #6
MN Renovator
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In a solar air panel/module(whatever you want to call it), the exiting air temperature should be lower by increasing airflow so less of the heat is lost through the glazing, sides, and back of the panel as well as increasing the heat transferred through the solar capture media(such as metal window screen).

Regarding the position or angle of the screen, you want the air to pass through the screen and not around it. I imagine the airflow path is a bit turbulent in any case and difficult to control when it comes in through a small round duct into a large thin rectangular cavity. Ideally if you separated the air to prevent it from getting in contact with the glazing and the glazing was completely clear, you would probably be better off because most of your heat loss inside the panel will be through the glazing. I wonder how a double glazed panel would perform. The reality is that the faster the airflow, the lower the temperature of all of the surfaces that would transfer heat out of your solar module and the higher the transfer to the air. This is where the 2-4 cfm rule of thumb comes from. I don't remember the figures from the builditsolar site were but he tested different airflows there. Also keep in mind that you will lose heat from any ductwork between the module and the building, if it's not directly piped into the building effort to insulate the ductwork is a good idea.
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