As we saw earlier, active solar systems differ from passive solar systems in that mechanical devices such as pumps and fans are used to transport heat from collection to storage, or from storage to use.
Because active heating systems use mechanical components, they are generally somewhat more complicated than passive systems in their operation; and they are therefore more expensive to purchase, install, and maintain. On the other hand, they are generally adaptable and automatic, capable of achieving higher temperatures in shorter times over more extended periods than are passive systems. and because they can be controlled by a thermostat, which is not possible with a passive system, they do not require the close regulation of heat intake necessary with a passive system. Finally, active equipment is, on the whole, more compact and more readily adaptable to a variety of heating tasks than the cumbersome pieces of the passive package.
For all their evident differences, how ever, passive and active solar heating systems work on the same basic principles; and the success of any specific system reflects its ability to collect, store, and distribute the heat from solar energy in an efficient manner.
Air and Liquid Systems Flat-plate collectors use either air or liquid (water, water-antifreeze solutions, or — rarely — oil solutions) to transport heat from the collection point to the storage unit, and then from storage unit to the de sired points of distribution in the house. If a liquid system (also called a water system or hydronic system) is used, the solar-heated water itself is transported to a hot-water storage tank, and carried from the tank through a pipe system to the space to be heated. A pump pipes the hot water from collector to storage and /or from storage to distribution. If an air system is used, the solar- heated air is transported to a bin of rocks, which absorb and retain the heat. Air blown across the rocks picks up the heat and carries it through a system of ducts to the desired distribution point. A fan or blower is used to duct the solar-heated air from the collector to storage and /or from storage to the distribution point.
Air System: Warm-air duct to house; Corrugated or finned absorber plate; Air space above and below plate; Cool-air duct into collector at lower corner opposite warm-air duct; Housing; Insulation. |
Next: Solar Collectors and Placing the Collector