What is Passive Solar Heating?
Passive solar heating is one of the most efficient ways to heat any building. Usually the amount of solar power reaching your building is greater than the energy being used inside, which means that you have the potential to use this energy effectively.
The building itself acts as the solar collector, unlike a mechanical system, which is a completely separate system. In this way, the passive solar heating system actually adds little to the initial cost of the construction. The home or office increases in value, the system requires very little maintenance, and is generally trouble free. For a minimum of extra work, passive solar heat can help reduce your energy costs. Yet you sacrifice nothing in terms of comfort and convenience.
An alternate heating source is still necessary, but you will notice a dramatic decrease in your heating bills. Because the structure is the solar panel, as well as the distribution system, it is extremely efficient. During the daytime, the windows allow the heat to be absorbed by the walls and floors, or other heat sinks. Then, during the cool of the night, the heat is released into the living area.
Requirements for passive solar heating
Engineers and builders have learned the best way to orient the house to the sun, which angle of the roof is most advantageous, etc. You need to have a clear, unobstructed exposure to the sun, which in the Southern Hemisphere is obviously the north. Even partial shade can drastically reduce the efficiency of the system.
Another important prerequisite is that the construction materials must be able to absorb the heat of the sun and later release it. The building can be the collector, or you can use other structures to absorb the sunlight.
Designing a passive solar heating system
You must consider the climate where you live, and the lay of the land where your building sits.
Gaining heat directly
Direct gain is the simplest type of passive solar heating. The heat of the sun is soaked up by the building, right to the core of the structure. Later, this heat is naturally released into the living area. You should be able to heat your home for several days this way, provided you do not have much heat loss from windows, poor insulation, etc.
Gaining heat indirectly
This is one step above the direct gain system. You place structures or objects between the sun and your living area. These absorb the heat of the sun and use a natural convection system to distribute the heat throughout the house. These areas are closed off and can reach very high temperatures. The airs flows naturally from top to bottom because of the temperature difference at the floor and ceiling.
During the night the air vents can be sealed off the stop heat loss. By closing the vents the convection process is not allow to reverse and steal your precious heat by taking it back to the area with the collectors. The heated wall also radiates warmth into the living area, much like a heated fireplace wall.
Gaining heat by isolation
Isolated gain of solar heat means that an external solar panel is used to collect heat. Natural convection causes the fluids in the solar panel to flow into a storage area. Later, the heat is transferred from the storage to the living area. It is necessary that the solar panel is lower than the storage area, and the storage area must be below the living area. If not, there will be not natural convection and a pump will be required. You would then not have a true passive solar heating system.