What is solar
insolation?
The amount of electromagnetic energy (solar radiation)
incident on the surface of the earth. Basically that means
how much sunlight is shining down on us.
Why is knowing the insolation level useful?
By knowing the insolation levels of a particular region we
can determine the size of solar collector that is required.
An area with poor insolation levels will need a larger
collector than an area with high insolation levels. Once you
know your region's insolation level you can more accurately
calculate collector size and energy output.
What units are used to express Insolation levels?
The values are generally expressed in kWh/m2/day.
This is the amount of solar energy that strikes a square
meter of the earth's surface in a single day. Of course this
value is averaged to account for differences in the days'
length. There are several units that are used throughout the
world.
The conversions based on surface area as follows:
1 kWh/m2/day
= 317.1 btu/ft2/day
= 3.6MJ/m2/day
The raw energy conversions are:
1kWh = 3412 Btu = 3.6MJ = 859.8kcal
Is my region's insolation level low, moderate or high?
The following scale is a basic guide for insolation levels.
Although a value of 5 is not considered very high during the
summer months, as an average annual value this is very high.
You will see that in central Australia, which is a hot,
sunny place, the annual average insolation is 5.89.
You may compare
you location to the following two extreme locations.
Average annual insolation levels:
Central Australia = 5.89 kWh/m2/day - Very High
Helsinki, Finland = 2.41 kWh/m2/day - Very Low
Now I know my
insolation level, how do I calculate my collector's size?
Please
click here to visit the collector sizing page.
Click on the links below
to view insolation levels for Canada.
Nasa Surface meteorology and Solar Energy Data Set