Page 254 - Alternative Energy Systems in Building Design

230 PASSIVE SOLAR HEATING TECHNOLOGIES

3 Will there be a backup heating system? What kind?
4 Does the pool have a screen enclosure?
5 Will the owners use a blanket?
6 Do the owners have a solar window?
7 Is the wind going to be a problem?
8 Is shading going to be a problem? How many hours a day?
9 In what direction and at what angle will the collectors be mounted?
10 What is the surface area of the pool?

Some of these questions will be answered as part of your pool-heating survey. The rest
will be determined by measurement and inspection.
The following guidelines will provide a factor that represents how many square feet
of solar collector area is needed in relation to the pool’s surface area. Once deter-
mined, this factor is multiplied by the pool’s surface area. The resulting answer is
divided by the selected collector area to determine the number of collectors required.
To begin, you will want to determine a sizing factor for optimal conditions in your
geographic location. To obtain this information, you need to consult with a sales rep-
resentative of a solar pool-heating system. You also can contact the local weather
bureau and ask for the mean daily solar radiation (Langley’s) for the coldest month of
the desired swimming season. Using the following table, determine the starting sizing
factor by the corresponding Langley reading:

LANGLEY READING SIZING FACTOR

200 1.05
250 0.96
300 0.85
350 0.75
400 0.67
450 0.60
500 0.55
550 0.51
600 0.48

For optimal efficiency, solar collectors should face south. If you are unable to face
your system south, multiply the sizing factor by the applicable following figure:
East facing 1.25

West facing 1.15
This figure should be increased if the roof pitches are equal to or greater than 6/12.
Decrease this figure if you have a roof with a pitch equal to or less than 4/12.