3.4.1.6.1

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

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

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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