PASSIVE AND ACTIVE SOLAR POWER

Passive solar energy converts sunlight directly into useful energy. It involves designing architecture in a way which may capture and store heat radiated from the sun. The architectural innovations that are conducive to solar power are typically incorporated into the initial design.
In other words, a house is typically built for solar energy via overall orientation and the construction of large skylights and other south-facing windows, enhanced by efficient insulation (this is not always the case, though, and passive solar features can be added onto a building).

Active solar power, on the other hand, utilizes solar electric technologies such as photovoltaic cells to convert sunlight into energy. These are typically "add-on" features. The means of conversion are actively mechanical, versus the receptive nature of passive energy provided via design.

Features
• Passive solar energy is largely used for space conditioning (heating and cooling areas), in addition to providing light.
• Houses are constructed, in the northern hemisphere, with their long axis in an East-West direction. This orientation maximizes solar gain and minimizes the losses. It also allows for cool summer afternoon to stay cool (for the sun is in the western part of the sky). and warm winters when the sun is to the south.
• A common design feature of solar houses is a greenhouse-like addition which is attached to the outside of the building. These "sunspaces" facilitate heat transfer into the house during the day. They cool down rapidly during the night (for the windows allow warm air out just as they allowed it in). For these reasons, they are often used as storage houses for heat exchanges, but are not normally used as a living space.
• Passive solar energy has almost no negative impact on the environment, giving off no air or water emissions at all.

Thermal masses are used to store the heat radiation. Common objects used as thermal masses are brick, slate, rock, concrete and water. Optimal thermal storage can take place by increasing the mass of these materials on the inside of a building.
Every building has some of its heating requirements met by windows, the primary tool in passive solar heating. Window glass is virtually transparent to solar radiation. Placing windows facing south maximizes this effect.