Going Solar Chapter 5 : Know Your Sun Hours

It is commonly known that, when there is sunlight, you can generate power from the solar PV systems. However not every time when it is day time it have a full sun (solar insolation). In the morning and evening there will be sun shining but it won’t be in its maximum intensity (less power being generated from solar PV). The solar PV will gain in power generation momentum when the sun is slowly raising till mid day where it is in its maximum intensity.

Since the solar radiation fluctuates allot in a day due to weather conditions, however it still generally follows a normal distribution curve. To ease understanding and calculation, an average daily solar insolation is used – The peak Sun Hours.

“Peak Sun Hours” refers to the solar insolation which a particular location would receive if the sun were shining at its maximum value (1 kW/m2) for a certain number of hours. The longer the Sun Hours, the more potential for solar PV power generation.

The “peak sun hours” is the solar insolation that a particular area can received if the sun is shining at its maximum value for certain number of hours.  Since the peak solar radiation at the sea level is 1 kW/m(when the sun is directly above without clouds) , the number of peak sun hours is numerically identical to the average daily solar insolation.

For example, a location that receives 8 kWh/m2 per day can be said to have received 8 hours of sun per day at 1 kW/m2. In Malaysia we have average 4-4.5 kWh/m2 per day, and hence we can translate it into average of 4-4.5 hours of sun per day in related to 1 kW/m2. In areas around the tropics (Tropics of Cancer and Capricorn) will have 5 -7 kW/mduring summer solstice where the duration of the day is longer than the night, it will have 1.5 -3 kW/mduring winter solstice.

This is important because the solar PV modules are often rated at an input of standard 1kW/m2. The higher the Sun Hours, the more energy can be harvested from the sun light.

NEXT CHAPTER >> Know Your Solar PV System