Efficiency comparison between tracking and optimally fixed flat solar collectors.

We investigate the optimal orientation for a fixed flat plate solar collector using the clear sky model. The ground reflection component of irradiation that hits the collector's surface is ignored due to its relatively small magnitude when compared to the direct beam and sky diffusive components. Analytical calculations demonstrate that regardless of the collector's latitude, the most effective azimuthal angle, [Formula: see text], is 0, which generally corresponds to a North-South direction. However, the optimal tilt angle, [Formula: see text], is dependent on both the Day of  Year (DoY) and the collector's local latitude. For latitudes typical of mid-altitude climate zones, we can calculate the optimal tilt angle and the maximum energy that the collector can harvest during each DoY. We compare the maximum daily received energy-which is the sum of the direct beam and sky diffusive energies-associated with this optimal orientation to their corresponding values when the flat plate tracks the Sun. The relative increase in total energy due to Sun tracking depends critically on the DoY, with a minimum value of about [Formula: see text] in early winter and a maximum value of [Formula: see text] over a large interval.