The easiest method is to use wood screws which can pierce the aluminium and screw into the wooden foundation board. These can be manually applied or an automatic screwing machine can be used.

7. Example of MEGASOL installation.

A traditional Scottish cottage with a slated roof was chosen to install a MEGASOL solar water heating collector. Firstly the slates were removed from the area devoted to the collector to leave the bare wooden boards covered with thin roofing felt. Then a layer of reflective bubble polythene sheet was fixed over the roofing felt. Then a grid of thermally enhanced EPDM pipes (1mm wall thickness, 15mm outside diameter) was fixed to the insulation, with spacing between pipes of 150mm. The pipes were formed into U loops with both flow and return manifolds at the same end. The pipes were temporarily fixed in place with adhesive tape. Then standard size aluminium sheets of 1mm thickness were laid on top of the pipes and screwed through the aluminium to the wooden substrate with wood screws. Then the aluminium sheets were painted with matt-black paint (non-selective). Finally, sheets of twin — wall polycarbonate were located over the absorber plate, with a 25mm air gap, and fixed by standard glazing bars. Air gaps at the top and bottom of the sheets were sealed up. The EPDM pipes were connected to 22mm diameter flow and return manifolds by 15mm stubs. These pipes were then connected into the building’s central heating system. Pictures of the collector in construction and finished are shown in figs 2 and 3 below.

The whole collector was constructed by a two workmen who had no previous solar experience. The collector area was 25m2 and the total cost of materials and construction was approx EU2,500, giving a cost per unit area of approx EU100/m2. This is believed to be unusually low.

8. Collector efficiency

Thermal analysis of the above described collector has been undertaken and gives Fr tau. alpha= 0.64 and Fr U= 4W/m2K.

9. Pressure resistance

Burst tests indicate that the collector should be able to handle pressures of up to 4bar.