Your knowledge about the hotness or coldness of your environment and the available rainfall or sunshine in your locality may be thought of as similar to solar radiation resources but they vary in many respect. They are similar because both are related to a common source, which is the Sun. However, their difference lies in the ability of human senses to perceive the former, whereas the later goes beyond what we see and touch. Fortunately, the latter is what fuels and determines the performance of our solar PV system. For this reason, the performance of every Solar PV system depends on the local climatic conditions, specifically the global horizontal irradiance (GHI), direct normal irradiance (DNI) and ambient temperature.

Just as it is often difficult to take something out of nothing, solar module hardly can perform to its optimum capacity if the local weather radiations are not sufficient or properly estimated to correspond with your energy demand and the capacity of your selected Solar PV system. Thus, one important but often overlooked decision is whether to consult an expert to compute the necessary figures as related to local climatic conditions or to use a general rule of thumb.

The solar radiation graphs, developed from the historical weather records of NASA’s MERRA-2, clearly shows that no two regions in Nigeria have the same total annual value of solar radiation resource. Similarly, average monthly solar radiation varies among states in the same region as well as local governments in a given state. Therefore, it is necessary for a potential owner to consult a PV system designer for effective planning of a solar electric system.