Collector Gaskets and Sealants
Gaskets and sealants must be carefully
selected if a collector is to have a long life.
Generally, the housing and the glazing have
different rates of thermal expansion. Gaskets and
sealants form a flexible interface between the two
components and seal out moisture and other
contaminants. If they fail, moisture fogs the
glazing and may damage the absorber coating and
the insulation. These problems can drastically
reduce the thermal performance of the collector.
Two suitable sealing methods are shown in
figure 15-3. The gaskets provide flexible support
and the primary weather sealant ensures against
,oisture leakage. Desiccants are sometimes
placed between the two glazings to absorb any
moisture that may remain after cover installation.
When you are selecting collector gaskets and
sealants, certain material requirements must be
kept in mind. The gaskets and seals must do the
1. Withstand significant expansion and
contraction without destruction
2. Adhere effectively to all surfaces
3. Resist ultraviolet degradation
4. Resist outdoor weathering
5. Not harden or become brittle
6. Withstand temperature cycling from -30°F
Silicone sealants have been found adequate
for use as gasket material. Silicone sealants have
exceptional weathering resistance and have
received widespread use for many years.
Collector FluidCorrosion and Freeze
The choice of collector fluid is important
because this is the lifeblood of the system. The
cheapest, most readily obtainable, and thermally
efficient fluid to use is ordinary water. However,
water suffers from two serious drawbacks:
freezing and corrosion. Therefore, the choice of
collector fluid depends on the type of solar system
the choice of components, future maintenance, and
several other factors.
Implicit in this discussion is the use of fluid in
the collector. As explained in table 15-1, an air
solar system does not suffer from corrosion or
freezing. The low density and heat capacity of an
air solar system requires the use of fans, large
Figure 15-3.Typical sealing methods for single or
ducts, large storage volumes, and it is not suitable
for domestic water heating.