Method of making static solar heat collectors

A load-bearing building panel capable of forming an external wall cladding or roof component has a solar heat collecting capacity in the form of channels for heat exchange fluid incorporated in the fabric of the panel. The panel is made of a structural plastics material, such as G.R.P. laminate, successive layers being moulded to simulate tiles. On the back or underside, longitudinal reinforcing beams are built in during laying up of the panel. Between the beams cores or formers defining a matrix or channels are encapsulated in layers of the G.R.P. Wax cores are melted or dissolved out after curing of the panel; metal formers remain embedded in the fabric of the panel. The matrix is connected by flow and return pipes to a heat exchange system within the building. Panels intended for roofing have ridge flanges and wall plates moulded into the substrate at the appropriate pitch angle, and a split capping tube embraces the ridge flanges. A pitched roof formed by oppositely sloping panels is self-supporting. An integral box girder can also be formed across the underside of the panel at the eaves to rest on the top of the external wall to be loaded with concrete in situ so as to anchor the roof on the walls.

FIELD OF THE INVENTION 
This invention relates to static solar energy collectors which consist of 
panels for exposure to solar and other cosmic radiation combined with heat 
exchange means such as a fluid circulatory system in heat-conducting 
contact with the exposed surface. 
Most static heat collector panels as hitherto constructed have been 
designed to be either free-standing or to be mounted on an existing 
structural surface such as a wall or roof as an extra layer thereon. The 
heat exchange fluid system must then be plumbed to the point of use of the 
heated fluid, and if this is within the building the walls or roof skin 
thereof must be pierced by flow and return pipes, which involves sealing 
problems at the points of penetration, and sometimes extended or 
circuitous piping. There are also problems of maintenance and repair of 
the overlaid zone of the roof or wall. 
PURPOSE OF THE INVENTION 
It is an object of the present invention to provide a construction of panel 
which combines a facility for solar heat exchange with the requisite 
physical and mechanical properties of a structural building components, 
thus providing a dual-purpose building panel which can be used as the 
exterior cladding or skin of a wall or single span roof unit. As a 
building panel, the unit must be sufficiently rigid to be at least 
self-supporting between adjacent fixing points which, in the case of a 
roof panel of a domestic dwelling, may be at the eaves and the ridge. 
Another object of the present invention is to provide a simple and 
efficient design of panel which requires a minimum of mechanical support, 
especially when used as a roofing element, and which can be assembled into 
larger units, such as complete roofs, with relative ease by semi-skilled 
labour before being mounted as a complete unit in position on a building. 
With particular reference to roofing panels, it is an object of the 
invention to enable a complete roof to be assembled from prefabricated 
panels at ground level and then be lifted into place on the tops of the 
walls of a building. 
A further object of the invention is to form a panel of a structural 
plastics material with an integral channel or matrix of interconnected 
channels for the flow of heat exchange fluid. 
A still further object is to provide a method of forming the integral 
channel or channels within the fabric of the panel. 
SUMMARY OF THE INVENTION 
With these and other objects in view the present invention provides a solar 
energy collector panel consisting of a longitudinally corrugated building 
panel of a structural plastics material having a series of preferably 
uniformly spaced transverse ridges or steps at least on its front or upper 
side to simulate rows of overlapping tiles, and an internally formed 
longitudinal stiffener on the back or under side. This panel is built up 
from laminae of the structural plastics material bonded together and 
moulded to the required shape, two successive laminae being separated over 
a specific zone to form the channel or channels through which heat 
exchange fluid is to be circulated, while inlet and outlet fluid circuit 
connections are embedded in the outer lamina or laminae for connecting the 
channel or channels to an external flow circuit. 
A structural plastics material is defined, for the purposes of this 
specification, as one which withstands the normal changes in temperature, 
humidity, wind and other external loadings without permanent sag or 
dimensional distortion; resists degradation from exposure to ultraviolet 
light; is suitably fire-resistant in accordance with fire regulations; and 
is substantially non-toxic when subjected in situ to abnormal 
temperatures. 
A convenient material for the building panel is a glass-fibre reinforced 
plastics material (G.R.P.); and this may be "doped" or loaded with one or 
more substances for promoting heat transmission across the thickness of 
the panel. Such substances include, for example, a powdered or granular 
metal such as aluminium; glass beads of a size between about 4 and 40 
microns, or other additives. Only the zone of the or each channel or duct 
need be so doped or loaded, and the glass beads can if desired replace 
some of the conventional glass fibres in the material. 
The fluid circulated through the channels and ducts in the building panel 
is preferably passed through a heat-exchanger within the building, the 
heat exchanger being adapted to heat, say, a reservoir of water. The heat 
exchange fluid preferably has a high heat absorption characteristic. The 
complete solar heat storage system comprises a solar panel according to 
the present invention; a reservoir for a fluid to be heated; and a heat 
exchanger. 
The invention also includes a self-supporting roof panel designed to span a 
roof pitch from eaves to ridge, the ridge end of the panel having an 
upturned flange angled to the general plane of the panel so as to be 
secured to the corresponding flange on a similar panel on the opposite 
roof pitch, while an integral depending flange near the eaves end of the 
panel is designed to be fixed to an external wall of the building.

Referring first to FIGS. 1-7, a roof is made up of a plurality of basically 
similar panels 10 each having longitudinal corrugations 12 of roughly 
semi-circular shape divided into equal frusto-conical sections which meet 
end-to-end at regularly spaced transverse walls or steps 14. The substrate 
of the panel, as represented by the valleys 18 between adjacent 
corrugations 12, is planar. Each transverse row of corrugation sections 12 
between successive steps 14 simulates a row of roof tiles, and each step 
14 simulates the overlap between rows. As shown in FIG. 4, each panel 10 
is reinforced longitudinally on its underside by three integral beams 16, 
one central and one each along each longer side. Each side beam 16 is 
mounted at the crest of a marginal corrugation 12, one of which, marked A 
in FIG. 4, is a full corrugation while the other, marked B in FIG. 4, is a 
half-corrugation. This pattern allows the half-corrugation B to nest under 
a counterpart full corrugation A on a laterally adjacent panel and thus 
allow the respective side beams 16 to abut and be bolted or otherwise 
secured together. The free edge of each beam 16 may be straight while the 
main substrate 18 in which the longitudinal corrugations 12 and transverse 
steps 14 are formed is hogged or outwardly convex (FIG. 7). This 
configuration of a building panel affords a high load-bearing capacity, 
but is not esssential, and a flat substrate 18 can be reinforced by beams 
16 each having its free edge convex to the substrate 18. 
The panel 10 is first formed by laying up a number of laminae of G.R.P. on 
a mould contoured to form the pattern shown in FIG. 1. When the 
appropriate thickness of substrate has has been laid up in the mould, and 
the resin has set to a soft gel ("green" stage) the core of a 
heat-exchange fluid matrix is assembled on the substrate. The matrix 
conveniently consists of five channel and two header strips or fillets of 
a hard-setting wax such as Okerin 4140 made and sold by Astor Chemical Co. 
Ltd. or like substance which can readily be softened and melted under 
heat. In FIG. 1, two matrices are indicated by channel and header 
center-lines 20, 22. First, longitudinal fillets 20, measuring 
approximately 21/2 inch by 5/32 inch in cross-section, are placed where 
channels are to be formed in the thickness of the eventual panel. A fillet 
20 is laid along the (inverted) bottom of each of two corrugations 12 and 
along the flat zones between corrugations 12 for the greater part of the 
distance between eaves and roof ridge. In order to ensure that each fillet 
20 snugly conforms to the contour of the exposed surface of the substrate 
18 and excludes all air pockets, the fillets are first softened to a 
plastic state (at 50.degree. for Okerin 4140) so that they can be pressed 
into contact with the substrate throughout their lengths. When each fillet 
20 has thus been laid in position all their top ends are checked for 
transverse alignment, and similarly all their bottom ends--"top" and 
"bottom" being related to the attitude of the panel when erected on a wall 
surface or roof pitch. 
After the accurate transverse alignment of the top and bottom ends of the 
longitudinal fillets 20, shorter and usually thicker core components 22 of 
the same hard wax or like material are moulded transversely onto the 
substrate to bridge the ends of the longitudinal fillets 20 and are firmly 
united with each other. These transverse fillets 22 define cross-ducts in 
the finished panel which will form top and bottom headers of the heat 
exchange fluid matrix. While the wax or other material of the complete 
core 20, 22 is still soft, inlet and outlet pipe connectors 24, 26 
respectively (FIG. 3) are pressed at their correct final positions into 
the respective headers 22. The core is now allowed to harden. If Okerin 
4140 is used, this will be 10 min. at 22.degree. C. 
Referring particularly to FIG. 5, after the core has hardened, a "gel coat" 
28 of a thixotropic resin is applied over the surface immediately 
surrounding and embraced by the core assembly, special attention being 
paid to the filling in of sharp corners or pockets (such as at 29) where 
parts of the core meet the substrate 18 or each other so as both to 
exclude air from these pockets and to present a smooth surface to the next 
layer. When the gel coat 28 has gelled (i.e. reached a soft rubbery 
consistency) a coat 30 of lamination resin is applied over it and covered 
with a glass fibre tissue 32, or layer of similar reinforcement cloth, 
which is pressed into the wet resin. The resin coat 30 is in turn allowed 
to gel. At that stage, another lamina 34, identical to those laid up to 
form the substrate 18, is laid over the entire exposed under-surface of 
the panel 10, and care is exercised to ensure that the external circuit 
connectors 24, 26 are thoroughly and firmly embraced by laminate. The 
latter is allowed to gel. 
When the laminate 34 has gelled it can either be allowed to cure or a 
further coat (not shown in FIG. 5) of pure resin can be applied so as to 
add a further safeguard against "pinholing" of the composite coating 
overlying the core. 
Whichever option is exercised, the completed panel is stripped from the 
mould when the last coat or layer has gelled and is allowed to cure at a 
temperature of 65.degree.-70.degree. for 24 hours. At the end of the 
curing period, the external circuit connectors 24, 26 are cleared of all 
embedded wax and the panel is placed in a dewaxing chamber at an angle of 
20.degree.-30.degree. to the horizontal. A drip tray or trough is placed 
beneath the outlet connector 26 and the core 20, 22 is either melted out 
or dissolved out, recovered and recycled. Finally, the heat exchange fluid 
matrix is scoured by a dewaxing agent at about 90.degree. C. The panel is 
now ready for use both as a structural component and as a solar heat 
collector with heat exchange fluid channels incorporated in its fabric. 
In FIG. 4, the several layers 28 . . . 34 are shown encapsulating the 
matrix core 20, 22. The final glass-fibre lamina 34 is extended beyond the 
zone occupied by the matrix core and is laid up over the adjacent faces of 
the central and edge beams 16 to bond each more firmly to the substrate 
18. Each of the beams 16 is conveniently formed by cutting one or more 
sheets of hardboard, plywood, metal or the like to a segment of a circle 
and placing it or them upright on one or other edge along a corrugation 12 
to form a web as shown at 36 in FIG. 6. If the hardboard or other sheets 
are placed with the straight edge down, then the substrate 18 of the panel 
10 lies flat when erected, and the free edges of the beams 16 are convex. 
Assuming that the beams 16 are arranged so that the panel 10 is hogged, a 
tension strap 38 is stretched over the web 36 of the beam 16 and "tacked" 
in place by a coating of resin. A straight rigid rule or bolster 40 is 
pressed on top of the strap 38 until this coating has set to hold it 
symmetrically to the web 16 while tension is applied and the ends of the 
strap are locked into the underface of the substrate 18. A layer of 
laminate can be laid over the strap 38 to bond to the laminate layer 34 
and make the entire undersurface of the panel homogeneous. 
The underside of the panel 10 is thus divided by the beams 16 into two 
longitudinal zones of roughly equal area, and it is preferred to apply a 
heat exchange matrix 20, 22 to each zone in order to equalise as far as 
possible the temperature distribution over the whole area of the panel, 
thus tending to minimise local temperature stresses in the panel. 
In an alternative method of forming integral heat-exchange fluid channels 
in a panel 10, as illustrated in FIGS. 8 and 9 each channel 20 is defined 
by a former 42 of light alloy or like fluid-impervious material, and each 
header 22 is defined by former 44 of similar material, the formers 42, 44 
being shaped and dimensioned so as to fit snugly together. The whole 
matrix of channel and header formers is then overlaid by a composite layer 
46 of gel coats and laminae similar to those described above with 
reference to FIG. 5. The layer 46 serves both to lock the matrix of 
formers 42, 44 together and to the panel 10, and to seal the fluid circuit 
against leakage. 
A further alternative method (not illustrated) of forming a matrix of heat 
exchange fluid channels utilises the vacuum forming process. Uncontoured 
G.R.P. sheet is bonded to a conventional vacuum forming plastics 
sheet--such as A.B.S.--and is vacuum formed to the required profile 
without the matrix. A second sheet of vacuum forming plastics sheet--such 
as A.B.S.--is vacuum formed to the required contour including the matrix. 
The two vacuum formed products are then bonded together so as to present 
the matrix as a precisely contoured gap or clearance between layers or 
plies of the fabric of the panel. The process can be substantially 
continuous and automated so that the composite G.R.P. and plastics (A.B.S. 
or the like) sheet is continuously delivered to its vacuum forming dies at 
the same time as the second sheet of vacuum forming plastics is also being 
continuously delivered to the matrix-forming die. The completed panel thus 
constitutes a laminated product in which a precisely controlled separation 
between adjacent laminae provides a matrix of channels for the flow of 
heat exchange fluid within the fabric of the panel. 
FIG. 10 illustrates a typical heat exchange fluid circuit. A group of five 
ducts 20 are shown connected in parallel by headers 22, and these latter 
may be extended from one panel 10 to the next, or from one side of a 
reinforcing beam 16 to the other, to inter-connect a plurality of groups 
of channels 20, as indicated in dotted lines. A heat exchanger coil 48 
immersed in a tank 50 connected by flow and return pipes 52, 54 
respectively to the headers 22, the flow pipe 52 including a circulating 
pump 56 to feed heat exchange fluid up into the bottom header 22. 
FIGS. 11 and 12 show a preferred method of securing together the ridge 
flanges 80 of meeting panels on opposite roof flanks or pitches. Each 
flange 80 is in two parts 81, 83 of equal length. The part 81 is a plain 
flat rib but the part 83 has a short lateral lip or "nose" 85 of a width 
to overlie the complementary plain part 81 of a mating panel on the other 
roof flank or pitch. The two flanges 80 are bolted or riveted together at 
87 (FIG. 12) and a G.R.P. split-tube capping 89 is introduced over the 
joint to seal it. The threaded ends of the bolts 87 preferably project 
alternately from opposite faces of the united flanges to engage the split 
tube 89. Not only does the capping tube 89 provide an aesthetically 
acceptable finish to the ridge of a roof but also it performs both a 
primary sealing function to resist ingress of water past the joined 
flanges 80 and a mechanical function as an abutment for engagement by a 
clamp on a hoist cable. Tests were carried out on a full-size pitched roof 
measuring 11 ft. 9 in. eaves to ridge.times.17 ft. 10 in. span between 
wall plates and a ridge length of 32 ft. It weighed approximately 91/2 
cwt. Lightweight battens kept the panels spread at the proper span. The 
roof was hoist clear of the ground by means of four clamps on the capping 
tube 89 and was held suspended. Consequently, it becomes eminently 
feasible to construct the entire roof of a dwelling at ground level from 
prefabricated panels 10 and then hoist it in position on the tops of the 
walls, leaving only the operations of securing it to the walls and 
completing the heat exchange fluid circuit connections to be carried out 
in situ on the building. This means that any tests for strength of joints, 
effectiveness of seals, freedom of flow through the heat exchange 
matrices, and so on can be carried out, and faults rectified, at ground 
level. 
The invention thus provides a dual-purpose building panel which can be used 
as the sole load-bearing component of a building at its designed location 
whilst at the same time providing within its fabric an effective solar 
heat exchange facility. For example, a panel made in accordance with the 
process described above can be used by itself to span the pitch of a roof 
between eaves and ridge on a conventional surburban house without 
additional support from below other than the walls of the building. At the 
same time, the panel 10 has the in-built facility of collecting heat from 
the rays of the sun and transferring it to a hot water storage cylinder or 
tank without significantly increasing the weight of the roof panel as such 
or necessitating the extra complication of making fixings and passing flow 
and return pipes through the external skin of the roof. Similar advantages 
apply if the situation concerned is a wall instead of a roof. 
In use as a solar heat collector, it is preferred to use an oil in the 
matrix for absorbing the radiant heat and to circulate this round a closed 
circuit which includes a heat-exchanger coil or equivalent in a tank or 
cylinder of a hot water system. Oil has a higher heat capacity than water 
and can attain a higher temperature in the matrix for a given radiation 
dosage. It will, however, be understood that the precise mode of 
application of the invention is optional according to local conditions and 
requirements. 
A building panel constructed according to the present invention can have 
the area or areas to be exposed to absorption of solar heat "doped" or 
loaded by the addition to the mix for the substrate laminae of one or more 
substances for promoting heat transmission across the thickness of a 
lamina, such substances including powdered or granular metal such as 
aluminium, or glass beads of between 4 and 40 microns. The approximate 
thickness of the substrate 18 in which such "doping" or additive is used 
is of the order of 1/8 inch. 
THERMAL PERFORMANCE TESTS 
A building panel according to FIGS. 1-7, but having two Vee-section 
reinforcing beams as illustrated at 60 in FIGS. 11 and 12 in place of the 
three flat beams 16 of FIGS. 1-7 and made from chopped strand glass fibre 
mat and a resin/glass ratio of 21/2:1, was tested under practical 
conditions of very low wind speeds over several days in August in Swansea, 
W. Glamorgan, Wales. The test panel was set at an angle of 35.degree. 
throughout the tests, and water was used as the heat exchange fluid. The 
underside of the panel between the reinforcing beams 60 was insulated by a 
mat of glass fibre wool 7.5 cm. thick to prevent heat loss from the water. 
Table I records the results of tests to establish optimum flow conditions, 
and table II records the results of tests to establish the heat 
accumulation performance under different panel orientations and with 
different masses of water in the storage tank. 
From table I it will be seen that the heat collection efficiency is 
dependent on water flow rate, and is a maximum at a flow rate of 0.125 
Kg/s. This is the rate adopted for the constant flow rate tests. The time 
of day recorded in all cases is British Summer Time, and the sun reached 
its zenith in Swansea in August at approximately 1:15 p.m. 
Table II records the heat absorbed by the water in terms of megaJoules 
accumulated over periods of 1 hour. It should be noted that although the 
flow rate of the water through the storage tank--0.12 Kg/s--is low, it is 
relevant to a practical domestic installation in which several panels 
would normally be connected in parallel. It will be noted that with the 
smaller volume of storage water there is an energy loss from the water 
after about 2:30 p.m. This is due to the increase of the storage water 
temperature over that of the panel surface when the sun's elevation 
declines. However, when the volume of storage water is doubled, the rate 
of its temperature rise is lower, and energy loss from the water does not 
begin until later in the day. Thus, energy collection can continue over a 
longer period. Furthermore, the surface temperature of the panel is lower 
due to the cooling effect of the circulating water, so that convection and 
radiation losses by the panel are reduced. 
The tests indicate that a panel according to the present invention operates 
as an efficient collector of solar radiant energy so long as its surface 
temperature is kept as low as possible by the circulating heat exchange 
fluid. 
Heat conduction tests carried out on samples of the structural plastics 
material (G.R.P.) from which the test panels were made showed that the 
addition of aluminium granules to the mix improves the thermal 
conductivity by up to 35%, the improvement being greater the larger the 
size of granule. Such an increase in thermal conductivity is beneficial to 
the energy collection performance of the panel both by reducing the 
thermal resistance of the structural plastics material and probably by 
increasing the collection area. 
TABLE I 
______________________________________ 
Effective Absorption Area = 1.553 m.sup.2 
Panel Orientation South 25.degree. East 
Energy 
Solar 
Flow Col- Radia- 
Panel 
Type Rate Temp. lected 
tion Collec- 
of Kg/s Rise KW/ KW/ tion 
Test Time .times. 10.sup.-2 
.degree.C. 
m.sup.2 
m.sup.2 
Eff. % 
______________________________________ 
Vary 10:30 am .272 31.5 .232 .7 33.2 
Flow to .48 23.5 .306 .735 41.6 
Rate 2:30 pm .715 18 .348 .725 48 
.78 12.8 .272 .594 45.9 
.86 15.3 .358 .601 59.5 
1.22 13 .429 .692 62 
1.46 9.4 .37 .615 60.1 
2.08 7.8 .436 .74 59 
3.45 .7 .438 .734 59.6 
Const. 
9:00 am .uparw. 6.4 .168 .43 39.2 
Flow 10:00 am .uparw. 10 .288 .484 59.5 
Rate 10:30 am .uparw. 13.4 .448 .578 77.5 
11:30 am .uparw. 15.1 .499 .76 65.6 
12:30 pm .uparw. 18.8 .58 .893 65 
1:00 pm 1.25 18.9 .569 .893 63.8 
1:30 pm .dwnarw. 19.8 .589 .91 64.8 
2:00 pm .dwnarw. 18.9 .562 .834 67.5 
3:00 pm .dwnarw. 14.4 .415 .745 55.8 
3:50 pm .dwnarw. 10.2 .301 .625 45.2 
4:30 pm .dwnarw. 10.3 .301 .625 48.2 
______________________________________ 
E.sub.c = Energy collected by water KJ/s or kW = .m C.sub.P (T.sub.2 - 
T.sub.1) 
.m = Mass flow rate of water Kg/s 
C.sub.P = Specific heat of water KJ/kg deg. C. 
T.sub.2 = Mean outlet water temperature .degree.C. 
T.sub.1 = Mean inlet water temperature .degree.C. 
I = Solar radiation KW/m.sup.2 
A = Effective absorption area of panel m.sup.2 
##STR1## 
TABLE II 
__________________________________________________________________________ 
Temp. 
Energy 
Panel 
Solar Radiation 
Temp. 
Rise 
Accumul. 
Accumul. 
Orien- 
Mass M 
Time KWh/m.sup.2 
MJ/m.sup.2 
.degree.C. 
.degree.C. 
MJ Eff. % 
tation 
__________________________________________________________________________ 
40 10:00 
am .532 1.916 
25.6 
6.7 1.13 38 South 
11:00 
am .595 2.14 
33.5 
6.3 1.06 31 25.degree. East 
12:00 .745 2.68 
38 5.2 .875 21.1 
1:00 
pm .835 3.01 
43.2 
3.5 .59 12.6 
2:00 
pm .79 2.84 
45.7 
1.8 .303 6.9 
3:00 
pm .704 2.53 
46.3 
-1.3 
-.22 
3:30 
pm .274 .985 
42.3 
-2.7 
-.45 
40 10:00 
am .522 1.88 
25.4 
7.7 1.29 40 Due 
11:00 
am .665 2.39 
34.25 
7.5 1.26 34 South 
12:00 .767 2.76 
40.75 
6.75 
1.13 26.4 
1:00 
pm .806 2.9 46.3 
4.75 
.8 17.8 
2:00 
pm .704 2.53 
49.4 
1.5 .252 6.45 
3:00 
pm. 
.63 2.27 
50 -1 -.168 
80 10:00 
am .533 1.92 
24 5.2 1.75 58.5 Due 
11:00 
am .642 2.51 
28.5 
5.0 1.68 47 South 
12:00 .682 2.46 
34 5.0 1.68 44.2 
1:00 
pm .691 2.49 
37.6 
3.3 1.11 28.7 
2:00 
pm .705 2.54 
40 .7 .236 6 
3:00 
pm .619 2.23 
41 1.2 .405 11.7 
4:00 
pm .247 .89 42 -.4 -.134 
__________________________________________________________________________ 
E.sub.A = Energy accumulated in 1 hour KJ 
M = Mass of water in collecting tank Kg 
C.sub.P = Specific heat of water KJ/kg deg C 
.DELTA.T = Temperature rise of water in collecting tank in 1 hour 
.degree.C. 
E.sub.A = M C.sub.P .DELTA.T 
I.sub.A = Average solar radiation in 1 hour KJ/m.sup.2 
A = Effective absorption area of panel m.sup.2 
.eta..sub.A = Panel accumulation efficiency measured over 1 hour 
##STR2## 
MECHANICAL PERFORMANCE TESTS 
The panels used to obtain the solar energy collection data were also 
subjected to mechanical loading tests in order to establish their 
performance under wind, snow and personnel loadings. The specimens used in 
these tests were assembled ridge to ridge at pitch angles of 30.degree. 
and 40.degree., and were supported at their wall plates (19, FIG. 7). Each 
specimen panel measured 11 ft. 9 in. long overall by 3 ft. wide, and the 
length between ridge and wall plate was 10 ft. 6 in. Measurements of 
deflection were made at three symmetrically located points between ridge 
and wall plate. Each panel weighed 1.125 lb/ft.sup.2. 
1. WIND LOADING 
The imposed load due to wind was calculated in accordance with the British 
Standard Code of Practice No. 3 (B.S.C.P.3), Chap. V, part 2, 1972, 
assuming a building whose wall height (to the eaves) lies between one and 
a half times and one half the span between wall plates. Two extreme 
conditions were simulated: horizontal wind at right angles to the ridge 
and parallel to it. A wind speed of 62.6 miles/hr (Beaufort Scale 10=full 
gale) was assumed. Upward deflection is regarded as negative. The results 
are given in Table III. 
TABLE III 
______________________________________ 
(Values of deflection at each pressure relate to lower, middle, 
and upper gauge points, the latter appearing at the foot of each 
column). 
Pitch Angle 40.degree. 
Pitch Angle 30.degree. 
Pressure 
Pressure Deflection 
Deflection 
(N/m.sup.2) 
(mm) (N/m.sup.2) 
(mm) 
______________________________________ 
A. Wind at Right Angles 
Windward pitch 
-241 -10.1 125 4.9 
-17.4 8.2 
-11.1 3.2 
Leeward pitch -385 -14.8 -385 -14.2 
-25.6 -22.6 
-14.6 -11.0 
B Wind parallel 
Either pitch -529 -20.0 -529 -20.4 
-34.6 -33.8 
-22.4 -18.5 
______________________________________ 
2. SNOW LOADING 
The loading due to snow was simulated by a uniformly distributed vertical 
load of 750 N/m.sup.2 applied by sandbags on each pitch. The results are 
given in Table IV. 
TABLE IV 
______________________________________ 
Deflection (mm) 
Gauge point 30.degree. pitch 
40.degree. pitch 
______________________________________ 
lower 21.3 17.3 
middle 37.3 28.6 
upper 24.3 15.6 
______________________________________ 
3. PERSONNEL LOADING 
A load of 900 N was concentrated on a square area of side 125 mm. on one 
pitch. This loading was superimposed on the snow load and the additional 
deflections were measured at the same gauge points. The results are as 
follows: 
TABLE V 
______________________________________ 
Deflection (mm) 
(Additional to snow loading) 
Gauge point 30.degree. pitch 
40.degree. pitch 
______________________________________ 
lower 14.0 11.6 
middle 25.0 19.4 
upper 12.8 9.0 
______________________________________ 
4. IMT TESTS 
An official certification organisation for the building industry in Great 
Britain known as the Agrement Board, of Waterhouse Street, Hemel 
Hempstead, Hertfordshire, England, issued in January 1974 a "Common 
Directive for the Assessment of Products in Glass Reinforced Polyesters 
for use in Buildings" (January 1974). Two types of test are described--a 
hard body test and a soft body test. The hard body test involves the 
dropping of a steel ball weighing 1 Kg. from a height of 1 m. onto the 
panel, and this test caused no observable damage to the panel. 
Before pursuing the hard body test to the point where damage becomes 
observable, it was decided to carry out the soft body test. This involves 
the dropping of a bag weighing 50 Kg. from a height of 2 m. onto the 
panel, and this test caused slight local separation of laminae. The panel 
was then repaired by the use of 0.16 Kg of material, and it was decided to 
subject the repaired panel to renewed snow and personnel loading tests to 
determine what effects, if any, such repair might have had. These repeat 
loading tests were carried out on the single repaired panel in order to 
isolate its behaviour from the influence of the other panel to which it 
was originally joined at the ridge. In the repeat tests, the repaired 
panel was anchored at the wall plate at a pitch of 30.degree. and 
supported at the ridge with freedom of horizontal movement. The snow load 
was the same, at 750 N/m.sup.2 and the personnel load was of the same 
individual magnitude--900 N/m.sup.2 --but was applied separately from the 
snow loading. The difference in constraint at the ridge precludes a direct 
comparison with the original snow and personnel loading tests, but the 
repeat test values are a valid indication of the strength of the repaired 
panel, and hence have a significance in the overall evaluation of the 
performance of roofs according to the present invention under practical 
service conditions. The results are given in Table VI, deflections being 
measured, as before, normal to the plane of the panel. 
TABLE VI 
______________________________________ 
Deflection (mm) 
Gauge point Snow Personnel 
______________________________________ 
lower 10 4 
middle 12 6 
upper 7 5 
______________________________________ 
5. EARTHQUAKE LOADING 
In order to gauge the performance of a panel under earthquake conditions, a 
single test panel was rigidly supported at eaves and ridge at a pitch 
angle of 30.degree. and a horizontal load of 200 N/m.sup.2 --equivalent to 
a gravitational acceleration of 33.8 m/sec.sup.2 (i.e. about 31/2 times 
normal gravity), assuming that the specific gravity of the material is 
1.4--was applied. This value of acceleration is approximately 10 times 
that measured during the El Centro earthquake. The results are given in 
Table VII. 
TABLE VII 
______________________________________ 
Gauge point Deflection (mm) 
______________________________________ 
lower 2.3 
middle 2.7 
upper 2.0 
______________________________________ 
No damage was observable, indicating the ability of a roof according to the 
present invention to withstand severe earthquake conditions. 
6. WALL PLATE FLANGE 
Each panel had a wall plate flange (19, FIG. 7) extending across its full 
width at about 1 ft. 9 in. from the eaves edge of the panel. The panel was 
inverted and clamped by its wall plate flange, the ridge 80 being also 
supported. The eaves end of the panel was then uniformly loaded to a value 
of 250 N/m.sup.2 (50 lb/ft.sup.2) to represent an up-wind which can occur 
in practice. No detrimental effect on the structure was observable. 
7. CREEP TESTS 
Two panels were assembled ridge to ridge as in the wind, snow and personnel 
loading tests 1-3 above at pitch angles of 30.degree. and 40.degree.. At 
each pitch angle, both panels were loaded at 673 N/m.sup.2. The initial 
deflection was measured at each gauge point on each flank of the roof, and 
the load was left in situ for 24 hours. Each gauge on each flank was then 
read again, the load was removed, and the immediate recovery value noted. 
The latter was recorded in Table VIII as a mean value under "Unload--0 
hrs." The rate of recovery beyond that point was comparable with the creep 
rate. The creep values are given in Table VIII. 
TABLE VIII 
__________________________________________________________________________ 
Deflection (mm) 
Pitch Angle 
30.degree. 40.degree. 
Time: 
Unload Unload 
0 24 creep 
0 hrs 
0 24 creep 
0 hrs 
Gauge Point 
hrs hrs. 
(diff) 
(mean) 
hrs hrs. 
(diff) 
(mean) 
__________________________________________________________________________ 
Flank I 
lower 23.2 
34.1 
10.9 21.2 
28.1 
6.9 
middle 40 58 18 3.2 35.5 
47 11.5 
3.0 
upper 24.6 
36.1 
11.5 18 24.5 
6.5 
Flank II 
lower 20.5 
28.6 
8.1 19 23.5 
4.5 
middle 37.1 
50.5 
13.4 
3.2 30.5 
38.5 
8 3.0 
upper 25.2 
37.2 
12 19 23.5 
4.5 
__________________________________________________________________________ 
CONCLUSIONS 
A solar heat collecting panel according to the present invention behaves 
mechanically in a generally linear fashion under particular load 
conditions. The result of the soft body impact test shows both that 
failure under excess load tends to be progressive rather than sudden--as 
with brittle materials--and that original strength can usually be restored 
by repair in situ. With reference to the Earthquake test, it is noteworthy 
that if the roof falls as a result of collapse of one or more walls, the 
absence of the conventional timber roof support structure consisting of 
rafters and purlins greatly reduces the impact on the interior. In 
addition, there is no risk of fragmentation comparable with dislodged 
tiles, and removal during rescue operations is easier.