UFC 3-440-01
14 June 2002
Figure 3-5. Minimum Collector Row Spacing
3.4.1.6.1
Azimuth Orientations. The curves shown in Figure 3-5 are for collector
azimuth orientations of plus or minus 20 degrees. For the due south orientation (0
degrees), the deviation from these results is less than 10 percent. Use of Figure 3-5 for
due south orientations is thus slightly conservative. The effect of elevating the rear
collector row (larger C/L values) shows a marked decrease in the minimum spacing
(S/L). The flat roof, no elevation collector case is represented by the curves where C/L
= 0.
3.4.1.6.2
Roof Pitch. Collectors can also be mounted on pitched roofs. Often,
when a solar energy system is to be added to a building, the roof is pitched and
constructed such that the collectors could be mounted on the roof surface. This
practice does not necessarily impose unreasonable constraints in the roof design, since
there is some flexibility in the choice of collector tilt angle. If the roof cannot be pitched
to allow flush mounting of the collectors, or if the tilt angle must be fixed, then the
collectors can be raised at one end to give them the proper tilt. Figure 3-5 can be used
to determine the spacing by including the appropriate roof pitch with the height C.
3.4.1.6.3
Array Layouts and Estimated Roof Area Options. Collector array
layouts and estimated roof area requirements for the system can be determined by
using the estimated array size. For example, assume that 818 ft2 (76 m2) of collector
area is required for a project located at 40 degrees N latitude. The number of collectors
to install can be determined by dividing the calculated array area by the net aperture
area of the collector. If a 4 by 8 foot (1219 by 2438 mm) collector with 31 ft2 (2.9 m2) of
net aperture area is to be used, the calculation results in 26.4 collectors. Since 26
collectors cannot be divided evenly into banks of four, five, six, or seven, the designer
must deviate from the calculated value by rounding to the next highest possibility result
(i.e., 28 collectors). These units can be grouped into four banks of seven collectors or
3-8
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