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A novel design of solar heat collector
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The Solartherm PanelWhyChooseSolartherm.doc 
The Solartherm Slimline ™ Panel.
Why choose Solartherm?
Solartherm Slimline ™ heat collector panels are deceptively simple yet have a great deal of physics in the design.
1                     The materials are almost wholly UPVC and polypropylene (from which most double glazing frames are made), covered with twinwall polycarbonate (with which most conservatories are glazed).  The panels are so strong that they will survive intact from impact by hailstones large enough to smash glass (either windows or evacuated tube solar collectors). 
2                     They weigh 10kg, much less than any other design available and so are very easy to place on a roof (except in a high wind!).  Thus they put much lower stresses on to a supporting structure, moreover, they are only 25mm thick, so are less obtrusive than other designs (there will usually be no need to apply for planning permission.)  Panels are simply lifted into place lengthways up with the protruding tubes at the top and these pushed through any convenient gap in the tiling – or two 8.5mm holes drilled through.  There is no need for making pipe connections out on the roof!
3                     They are resistant to extremes of temperature.  The panels should never reach boiling point, however strong the solar insolation because the static temperature, whether full or empty is around 90oC.  This is because the panel is a Black Body Radiator and the surface radiation is proportional to the fourth power of the absolute temperature,  meaning that it is a very efficient heat collector at temperatures up to 50oC above ambient  (60% ‘in the tank’ based on the solar insolation value) but drops to zero efficiency at around 90oC.  As a precaution, panels should never be left empty in bright sunshine and therefore should preferably be installed with the long axis in the vertical plane and with the supply and return connections at the top.  As an additional precaution during installation, they should be covered until filled with water.
Polypropylene tubing is freeze resistant and can safely be allowed to remain full of water in winter conditions.
4                     They do not leak.  The serpentine array is one continuous length of tubing with a high burst pressure, even when hot.  Additionally, the system runs on low water pressure so that dangerous overpressures cannot arise.