Sunday, June 26, 2011

Idea for sloping front panel

26 June 2011: Comparing the Winter, Equinox and Summer performance, I can see that the vertical orientation of the boxes becomes a subject for discussion.
  My earlier motivations were six-fold:
  • You get automatic Planning Permission if you keep renewable technology devices down to equal or less than 200mm projection. As a wall-based system is highly visible, this would be a consideration in other installations in the future.
  • I only had a south facing wall, I don't have a south facing roof, so the wall was the only place.
  • Construction and maintenance are easier to a panel that is wall mounted as I can get access to every part of it from a scaffold or ladder.
  • I can improvise as I go along (while building it) making design decisions as they become needed, while the scaffolding was up.
  • They look neat and architecturally minimal, being compact rectangular structures, like rather unusual windows.
  • I thought that temperatures would get dangerously high in summer, and the vertical orientation would protect them from overheating.
Now that they have had a year and a quarter of operation, I have seen them working through two summers. They never overheat, and if there is good heat, then it is dumped underground. The top and bottom mirrors give the existing boxes a distinctive appearance, and they increase the capture of sunshine at low sun angles by increasing the apparent surface area. However, if the entire front face can be tilted like these illustrated, the angle incident to the sun is far more effective, and mirrors would not be needed. A 60º angle face will be better for Equinox and Summer sun angles. Also, when the sun does shine and the air temperature builds up, the volume of air in the boxes is greater, so that the chilling effect of the black panels is reduced. The volume of air is presently 1.2 m3 and it would be 2.48 m3 if enlarged in this way.
  This idea illustrated would project more than 200mm, but hey! this is research and we are trying to discover the best form - Rushcliffe BC have given me planning permission to project more than 200mm, so let's consider it further. 
  The slope can be accomplished with the existing (and expensive) sunbox fronts simply taken off and refitted with new structural polycarbonate side panels. The sloping underpanel will be insulated, to reduce heat loss downwards in winter, and the upper surface of the underpanel will be brightly reflective to add more heat to the black panels in summer. There will still be a polycarbonate soffit next to the wall (re-using the existing). The top rail can be of aluminium, and can probably support the existing top mirrors, repositioned at their present angle of 60º to enhance winter performance.
  I would like to make one long super box to enclose all four of the black panels but that would require me to waste the existing fronts, and to have too many modifications to the aluminium fixing rails. I am thinking about it though, because the existing fronts might be big enough to be cut into the structural side panels. They are of PalSun polycarbonate which is sun filtering and if I can get completely clear polycarbonate, then I might get a completely new long front panel, in 6mm or 4mm polycarbonate... and might consider two skinned PC, if that admits heat, but doesn't let it leave.

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