Solar thermal collectors need to face the sun to obtain maximum sunlight exposure. The installation angle should be equal to or up to 15o higher than the latitude of the location. This angle ensures optimal heat output throughout the year. Depending on the application, higher or lower installation angles may be more suitable as determined by the solar professional designing and installing the system.
The diagram below shows the path of the sun throughout the sky, cycling from low in the sky in the winter, to high in the sky during the summer.
Solar collectors should face as close as possible to the equator, which is the direction of the midday sun. Based on needing to face the equator, this means that in the northern hemisphere the collector should face south, in the southern hemisphere the collector should face north.
It may not always be possible to mount the collector due north/south, and so 45o east or west is acceptable and will not reduce collector output too much. Facing the collector more easterly will increase morning sunlight exposure, westerly will increase afternoon sunlight exposure. Pointing further away from the equator direction will reduce daily output and so a larger solar system may be required. This should be considered by the system designer or installer when sizing the system.
The diagram above shows the approximate losses in output for solar collectors when installed at angles off equator pointing.
To understand more about collector efficiency, click here.