Solar Collector Orientation

Table 15-1.—Advantages and Disadvantages of Air and Liquid Heating Systems A I R ADVANTAGES DISADVANTAGES Moderate cost. Can only be used to heat homes; can not presently be economically adapted to cooling. No freezing problems. Large air ducts needed. Minor leaks of little consequence. Larger storage space needed for rocks. As air is used to heat the house, no temperature losses due to heat exchangers (devices which transfix heat from one fluid Heat exchanger needed if system is to be used to heat water. to another), when the system is used for space heat. No boiling or pressure problems. WATER OR LIQUID ADVANTAGES DISADVANTAGES Holds and transfers heat well. Leaking, freezing, and corrosion can be problems. Water can be used as storage. Corrosion inhibitors needed with water when using steel or aluminum. There are liquids which are noncorrosive and Can be used to heat and cool homes. nonelectrolytic; however, they are toxic and some of them are flammable. Compact storage and small conduits. A separate collector loop using a nonfreezing fluid and a heat exchanger or, alternatively, a draining water or inhibited water system is required to prevent freezing. In warm regions, where freezing is infrequent, electric warmers or recirculation can be used. The amount of solar energy collected by a In addition to choosing the best collector tilt solar collector depends on its efficiency. The angle, take into consideration the direction that construction, configuration, and the choice of the collector faces. Normally, true south is the material determines the efficiency of a solar best and most frequent choice, However, 10 collector. degrees west of south maybe preferable in some locations if early morning haze or fog is a regular SOLAR COLLECTOR ORIENTATION occurrence. Although solar collectors can collect heat Equally important as collector location is from the diffuse component of solar radiation, keeping the collectors out of the shade, especially solar systems are designed to use radiation. Direct between 0900 and 1500 hours, when most of the radiation is in the form of parallel rays coming useful energy collection occurs. In summary straight from the sun. To capture this energy, tilt although many buildings do not have a “perfect” the solar collector, as shown in figure 15-1, so it is solar orientation, there are still many places with nearly perpendicular to the solar rays. good solar energy potential. 15-2