When choosing a solar collector, selecting the correct size
is important. To find out what size collector you need
please
click here. 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 efficiency.
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 optimizes winter, spring and autumn heat output,
while minimizing summer output. The high angle not only
maximizes 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 AP 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).
