21
Sizing the Solar Cylinder
Domestic Sizing
The storage cylinder sizes for domestic solar
thermal installations should be sized
according to the following minimum
guidelines :
20 Tubes = 200 Liter cylinder
30 Tubes = 300 Liter cylinder
40 Tubes = 400 Liter cylinder
60 Tubes = 600 Liter cylinder
The storage capacity can be a single tank or
multiple tanks plumbed in parallel.
Using a smaller capacity tank will lead to the
system reaching maximum temperature
sooner, which will often result in wasted
and/or uncollected energy.
If the installed collector area exceeds the
storage capacity of the cylinder there will be
wasted energy and excess heat in sunny
weather. Letting the collector stagnate is an
acceptable means of preventing excessive
tank temperatures during summer, but
stagnation periods should be minimised in
frequency and duration for the sake of
overall system efficiency. Otherwise, the
longevity of the evacuated tubes may be
compromised by more rapidly reducing the
vacuum level.
Commercial Cylinder Sizing
Sizing storage for commercial applications is
more complex than residential sizing and
requires a detailed evaluation of hot water
usage patterns.
Commercial applications are too varied in
demand, peak demand, required output
temp, etc. for set, rules to apply. Hot water
usage patterns and the total hot water
demand should both be considered. Use of
modeling software is strongly advised when
designing Commercial Systems and this is an
area where CoolSky can provide system
designs expertise to our customers.
Pipe Type and Size
Pipe Material
The solar collector loop can get very hot (i.e.
200°C under stagnation conditions) and
therefore the only recommended material
choices are copper (hard or soft coiled) or
corrugated flexible stainless steel pipe.
Cool Tip
Rule of Thumb to Size the
Storage Cylinder :
10 litres per Solar Tube
