Solar energy is the most abundant renewable energy source on the planet. The energy influx from solar radiation striking land surfaces is sufficient to meet the present primary commercial energy needs of the world thousands of times over. Usable solar influx is affected by diurnal and geographic variation and weather. Worldwide, the yearly average values of effective solar irradiance reaching Earth's land surface vary from a low of 0.06 kW/m2 (kilowatt per square meter; ∼500 kWh m-2 yr.-1 [kilowatt hours per square meter per year]) at the highest latitudes to a high of 0.25 kW/m2 (∼2,200 kWh m-2/yr.-1) in some desert areas of Africa and Australia. Conversion of this potential energy into secondary forms, such as electricity or process heat, depends on technical factors (e.g., ...