The load factor can also be adjusted to simulate nonideal solar conditions or reach the desired solar collector efficiency
 found that by using CuO-water nanofluid, the flat-plate solar collector efficiency was enhanced by 16.7% than that of water for 0.4 wt%.
Thus, the flat-plate solar collector efficiency depends on solar radiation, surface geometry of the collector and mass flow rate of the working fluid.
Solar collector efficiency
(delivered heat to incident solar radiation) depends on the type of the collector, the hot water storage and back-up systems, averaging on an annual basis 40 to 55% for SHW, while annual average solar utilisation (accounting for storage heat losses and waste heat) of 20 to 25% have been obtained in combi systems (Philibert 2006).
(1996) reported that the [COP.sub.sr] of the solar ejector cycle working with R-142b for the refrigeration application was estimated to be 0.34 at a generating temperature of 105[degrees]C, an evaporating temperature of -10[degrees]C, a condensing temperature of 30[degrees]C, and a solar collector efficiency