Insolation is the measure of Solar Radiation as it falls on the earth,
this varies depending on where you live in the world. It is a measure
of a how much energy falls on a given surface area in a given period of
time. It is generally measured in "Watts per Square Meter" or W/m2 at
any moment in time, or averaged over a period of time such as Kilowatt
hours per square meter KWh/m2.
Outside the earths atmosphere the solar radiation is approx 1367 W/m2.
the solar radiation passes through the atmosphere it absorbs some of
the radiation, by the time it hits the earth surface it has reduced to
approximately 800 to 1000 W/m2.
This reduction is due to a number of factors such as
- Absorption by molecules in the atmosphere.
- Scattering of the radiation by dust and pollutants in the air.
- Reflection back into space.
- Scattering of the solar radiation by interaction with the air molecules known as Rayleigh Scattering.
This chart shows the Insolation for Calgary.
From this table you can see that between May and August the Insolation averages about 5 kWh/m2/day.
this to Brisbane Australia, the summer months shows calgary gets almost
as much sun as Brisbane does, however come the winter months and the
numbers for Brisbane are much better.
In Canada, in the winter the
sun is very low on the horizon and this means the sunlight hours are
shorter and being at such a low angle the solar collectors can only
collect smaller amounts of heat.Heating Your Home
It is also for this reason that using Solar Collectors to heat your house is so difficult in Canada, especially in very cold areas. You have the double problem of needing so much heat due to the cold temperatures, but also our winter Solar Insolation is so low.
You can still get the heat you need, it just means more Solar Collectors. Increasing the number of collectors for more winter heat is great in the winter, but in the summer you end up with far too much heat produced as you now do not need the heating. One way some people achieve year round heating is using huge amounts of storage. This is usually only practical for people with lots of space. A water tank holding several thousand gallons of water can absorb a lot of heat and be released slowly in the form of heating your house.
This article describes one families solution to home heating. Please note although it talks about "Victoria" it is Victoria in Australia! Also, as it is in Australia, they face their panels North, in Canada they have to point South.
Click here for Home Heating Article
Normally for Domestic Hot Water, the System is sized to provide 100% of
your hot water need in July/August and this drops to 20% in winter.
Over the year it averages out about 50% over the year.
You either live with not enough panels in the winter, or if you want more winter hot water, you need to find a way to dump the extra heat during the summer months. If you have a swimming pool the extra heat can extend your pool season earlier in the spring or later in the autumn.
Not everyone has a swimming pool, so it is usually a balance of winter/summer sunshine that is installed but Pool heating is one of the most efficient and cost effective ways of using Evacuated Tube Solar Panels.Find the Solar Insolation for your Area.
This website is great for looking at how much Solar Insolation YOU get. Gaisma
Just click away and find your town.
Comparing Calgary data with Vancouver data, the numbers show, Calgary will produce more heat from the Collectors than Vancouver will, even though it is much colder in Alberta. The amount of cloud cover in Vancouver reduces the Solar Insolation.