Page 329 - Handbook of Energy Engineering Calculations

Since the heat loss is 100,000 Btu/h (29.3 kW), the total heat load during the
9-month heating season from September through May, or 273 days, is H =
a
(24 hours)(273 days)(100,000) = 655,200,000 Btu (687.9 MJ).

4. Determine the collector area required

The calculation in step 2 shows that the total solar energy available during the
2
2
heating season is 103,627.6 Btu/ft (326.9 kW/m ). Then the collector area
2
2
required is A ft (m ) = H /S , where S = total solar energy available during
a
a
a
2
the heating season, Btu/ft . Or A = 655,200,000/103,627.6 = 6322.64 ft 2
2
(587.4 m ) if the solar panel is to supply all the heat for the building.
However, only 70 percent of the heat required by the building is to be
supplied by solar energy. Hence, the required solar panel area = 0.7(6322.6)
2
2
= 4425.8 ft (411.2 m ).
2
2
With the above data, a collector of 4500 ft (418 m ) would be chosen for
this installation. This choice agrees well with the precomputed collector sizes
published by the U.S. Department of Energy for various parts of the United
States.

Related Calculations. The procedure shown here is valid for any type of
solar collector—flat-plate, concentrating, or nonconcentrating. The two

variables which must be determined for any installation are the annual heat
loss for the structure and the annual heat flow available from the solar
collector. Once these are known, the collector area is easily determined.
The major difficulty in sizing solar collectors for either comfort heating or

water heating lies in determining the heat output of the collector. Factors such
as collector tilt angle, orientation, and efficiency must be carefully evaluated
before the collector final choice is made. And of these three factors, collector
efficiency is probably the most important in the final choice of a collector.

COMPUTING USEFUL ENERGY DELIVERY IN SOLAR
HEATING USING THE F-CHART METHOD

Determine the annual heating energy delivery of a solar space-heating system
using a double-glazed flat-plate collector if the building is located in