The effect of off-south orientation on the performance of flat-plate solar collectors

There are many instances in which an off-south installation of a flat-plate solar collector is more compatible with a building's orientation than a due-south installation. In these cases it is important to determine the magnitude of the performance sacrificed by conforming to the building architecture. This study investigates the collector performance and optimum tilt as functions of the off-south angle, collection temperature, number of glass covers and the relative amounts of direct and diffuse radiation. It was found that the yearly energy collection for a given collector tilt is insensitive to the off-south angle and that in some cases it actually improves with increasing azimuthal angle. It was also found that for a given azimuthal angle an optimum collector tilt exists which is between 3 and 10° less than the latitude. Calculations were based on New York City weather.