Solar water heating
Practical Action
Evacuated Tube These tend to be more efficient but more expensive
A series of pipes are connected at the top by a manifold. The tubes consist
of a vacuum with a pipe running through the middle containing the working
fluid. The water moves up and down and along through the series of pipes
to exit the system at a significantly higher temperature.
Manifold casing
Manifold
Manifold
insulation
Fluid moves along manifold
by passing up and down
each tube
End of outer tube sealed
Evacuated tube
Figure 4: Sections through an evacuated tube solar collector (Illustration by Author with
reference made to CIBSE Solar Heating Design and Installation Guide, 2007 & Capturing
Solar Energy, 2009)
An important feature of both of the above is the medium through which the solar radiation is
absorbed, i.e. the ‘absorber’. It is well known that dark surfaces with a matt finish absorb
radiation more effectively than light and polished, therefore the absorbers incorporated into
the design of these collectors are often painted/coated in a dark, matt finish.
(Capturing Solar Energy, 2009)
There are four main types of flat plate collectors:
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