Page 357 - Handbook of Energy Engineering Calculations

Computer models of the earth’s atmosphere and the warming that might be
caused by excessive accumulation of carbon dioxide show that steps must be
taken to control pollution. Although there is some disagreement about the
true effect of carbon dioxide on global warming, most scientists believe that
efforts to reduce carbon dioxide emissions are worthwhile. Both a United

Nations scientific panel and research groups associated with the National
Academy of Sciences recommend careful study and tracking of the
possibility of global warming.

For these reasons solar heating will receive more attention from designers.
With more attention being paid to the environment, solar heating offers a
nonpolluting alternative that can easily be incorporated in the design of most
buildings.

SOLAR WATER HEATER ENERGY SAVINGS
COMPUTATION

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An engineer for a small office building of 2000 ft (186 m ) area housing 12
people 250 days a year believes the building can more economically heat its
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required domestic hot water with a 6-ft (0.56-m ) solar collector water
heater. Is this true?

Calculation Procedure:

1. Assemble the data needed to analyze the water heating needs
Data needed for this procedure: (a) daily hot-water consumption in gallons

(L) per person; (b) total solar insolation incident on a vertical surface in the
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area of the building in Btu/(yr · ft ) [kJ/(yr · m )]; (c) percent annual sunshine
for the building location; (d) difference between incoming city water
temperature and the hot-water service temperature e (= 100°F [180°C]) for

this building. For the typical office building, you can use data from the
ASHRAE Guide. Assembling the data gives: (a) = 1 gal (3.79 L) per person
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per day; (b) 732,000 Btu/(yr · ft ) [8345 MJ/(yr · m )]; (c) 59 percent; (d)
100°F (180°C).

2. Determine if a solar water heater will save energy