Page 327 - Handbook of Energy Engineering Calculations

reduces the amount of insolation, requiring a larger collector area to produce
the required heating or cooling. ASHRAE also publishes tables of the
average percentage of sunshine for use in the relation for determining the
actual solar insolation for a given location.

TABLE 3 Solar Position and insolation Values for 48°N latitude*

COLLECTOR SIZING FOR SOLAR-ENERGY HEATING

SYSTEMS FOR BUILDINGS

Select the required collector area for a solar-energy heating system which is
to supply 70 percent of the heat for a commercial building situated in Grand

Forks, MN, if the computed heat loss is 100,000 Btu/h (29.3 kW), the design
indoor temperature is 70°F (21.1°C), the collector efficiency is given as 38
percent by the manufacturer, and collector tilt and orientation are adjustable
for maximum solar-energy receipt.

Calculation Procedure:

1. Determine the heating load for the structure
The first step in sizing a solar collector is to compute the heating load for the
structure. This is done by using the methods given for other procedures in
this handbook in Sec. 13 under Heating, Ventilating and Air Conditioning,

and in Sec. 13 under Electric Comfort Heating. Use of these procedures
would give the hourly heating load—in this instance, it is 100,000 Btu/h
(29.3 kW).