When choosing a solar collector, selecting the
correct size is important. To find out what size collector you need
. Once you have
determined what size collector suits your needs, the next question
is where to install it.
Deciding the Direction and Angle of Installation
The angle and direction of installation is also
of great importance as it will effect the efficiency of the solar
collector. Naturally you want the collector to receive the maximum
amount of sunlight each day and throughout the year. As a general
rule if you are in the Northern Hemisphere then the collector should
face South and if you are in the Southern Hemisphere then the collector
should face North. See diagram below.
The angle at which you mount the collector should roughly correspond
to the latitude of your location. For example:
- Melbourne, Australia has a latitude of 37o South - the collector should therefore face north at a 37o angle.
- London, UK has a latitude of 51o North - the collector should therefore face south at a 51o angle.
You do not have to be too careful about mounting
the collector at the exact angle suggested. If your roof angle is
within 10o+/- of your desired angle
you can just mount the solar collector flush against the roof surface.
The added trouble of adjusting the collector to a precise angle
is not warranted as it will not result in a great improvement in
Seasonal Changes in Heat Output
How to prevent excessive summer heat output
If you are using the solar collector for space
heating as well as hot water production, or if you just want a larger
solar contribution, you will need a system that will greatly surpass
heat requirements in the summer. Generally in the summer heating
will not be required, in contrast cooling is. Unfortunately, at
present solar cooling for domestic applications is not yet economically
viable, so what to do with the additional heat? If you have a swimming
pool or spa, the excess heat can be used to supplement heating.
Turning off the pump and letting the collector stagnate is not ideal
as high pressure and temps, and large volumes of vented steam may
result (wasted water).
If you do not have an additional means of using the excess heat,
then adjusting the angle of the collector can help to reduce summer
heat output. As can be seen by the diagram above, the sun is low
in the sky during the winter and high in the summer. Solar smart
house designs will take advantage of this by having big North or
South (depending on your location) facing windows allowing maximum
absorption of winter sun, with large eves or veranda to block out
the summer sun.
By increasing the vertical angle of the collector by about 20o more the location's latitude (ie. 60o instead of 40o), greater winter
performance will be experienced. This is because the collector is
"facing" the sun (perpendicular - longitudinal angle).
Due to the higher location of the sun in the sky during the summer,
the collector will be around 40o from perpendicular and as such heat output will be reduced as the
collector is not fully "facing" the sun. This simple solution
alone can reduce peak summer output considerably, thus reducing
problems associated with excessive summer heat production.
The above photo shows an ideal example of an
installation angle that optimises winter, spring and autumn heat
output, while minimising summer output. The high angle not only
maximises expose to the direct winter sun, but also allows the sunlight
reflected off the snow to be absorbed. In the summer when the sun
is high overhead the exposed surface area is small, especially with
the overhanging roof which would partially shade the collector.
In areas without snow fall (and a latitude range of 30-40o)
an angle lower than that shown above would be suitable.
Please note: For the Sunrain solar water heater,
optimal heat pipe performance is achieved in the angle range of
20-70o. Although your locations
may have a latitude of less than 20o,
this basic installation guideline should be adhered to. Horizontal
angles of +/- 5o are acceptable
and may be appropriate if the manifold needs to be drainable (end
port models only).