Page 328 - Handbook of Energy Engineering Calculations

2. Compute the energy insolation for the solar collector
To determine the insolation received by the collector, the orientation and tilt
angle of the collector must be known. Since the collector can be oriented and
tilted for maximum results, the collector will be oriented directly south for
maximum insolation. Further, the tilt will be that of the latitude of Grand

Forks, MN, or 48°, since this produces the maximum performance for any
solar collector.
Next, use tabulations of mean percentage of possible sunshine and solar

position and insolation for the latitude of the installation. Such tabulations are
available in ASHRAE publications and in similar reference works. List, for
each month of the year, the mean percentage of possible sunshine and the
2
2
insolation in Btu/(day · ft ) (W/m ), as in Table 4.
TABLE 4 Solar Energy Available for Heating

Using a heating season of September through May, we find total solar
energy available from the collector for these months is 103,627.6 Btu/ft 2
2
(326.9 kW/m ), found by taking the heat energy per month (= mean sunshine,
2
percent)[total insolation, Btu/(ft · day)](collector efficiency, percent) and
summing each month’s total. Heat available during the off season can be used
for heating water for use in the building hot-water system.

3. Find the annual heating season heat load