ECOShift

There are basically two key types of solar heating systems; solar passive and solar active.  Solar passive systems are typically less complex as they make use of solar energy without the need for additional electrical components and technology.  This typically makes them less costly but in many cases passive solar heating may not be effective for existing buildings if the current orientation of the building cannot take advantage of solar energy.  Solar active systems are a little more complex, although still relatively simple in comparison to some other environmental technologies, and are effective in both new and existing buildings.  Buildings don't have to use only one or the other.  It is certainly possible for a building to make use of both solar passive and solar active systems.  Let's take a quick look at the basics of both passive and active solar heating systems (even though you might not be thinking about heat today since it has been scorching hot outside this week).

Passive Solar Space Heating

Passive solar space heating takes advantage of the suns energy and warmth through features like large south facing windows and materials within the building that can absorb the suns energy in the form of heat during the day and release it at a later time.  These surfaces that collect this heat are often referred to as thermal mass, but we won't get into a big discussion on thermal mass right now other than to say they are a mass of some material that can effectively collect, and later release, thermal energy.

There are generally 3 design approaches used in Passive solar systems:

Direct gain - This is the simplest system.  It involves the collection of the suns energy in the form of heat by allowing the sun to shine directly on surfaces such as tile or concrete, directly within the room to be heated.  The surface absorbs the heat energy from the sun and later releases the heat into the room to help maintain the temperature.

Indirect gain - Indirect Gain is very similar to direct gain.  The difference is pretty slight so you might need to read this twice.  Indirect gain also uses a thermal surface to absorb the sun's heat energy and later release it but the surface is not located directly in the room to be heated.  The thermal surface is usually a wall which absorbs heat from one room during the day and later transfers that that heat to another room.  Therefore, the heat energy released into the room came indirectly through energy collected via the suns energy from another room.

Isolated gain is the 3^rd type of passive heating.  In an isolated gain system the solar energy is collected in a remote location off the primary living area and the warm air then flows naturally to other areas of the home.  A good example of this would be a sunroom that heats up during the day and the natural airflow distributes that heat into other areas of the home.

Active Solar Space Heating

Active solar space heating systems are very similar to passive systems in that they collect the suns energy in the form of heat, but, they also contain active components that are used to distribute that heat.  In a passive system the heat is either naturally released from a surface that has absorbed the heat, or it flows due to natural air flow.  An active system may use electric fans or pumps to transfer and distribute the collected solar heat to other areas of a building or home.  Typically active solar heating systems use either liquid (i.e. water) or air as the heat-transfer medium in their solar energy collectors.

A liquid based system heats water or an antifreeze solution and then later transfers that heat to some other medium or end use. Air based systems heat air in an air collector which then delivers that heated air to some other area that makes use of the heat within that air.  To take advantage of solar energy collected during warm summers many air based solar heating systems will use an air-to-water heat exchanger.  This allows the heat energy from the air to be supplied to heat the domestic hot water and thus makes the system useful in the summertime when you wouldn't necessarily be trying to heat the building but that heated air would be wasted.  In the winter the hot air can be used directly to heat the building.  It takes much less energy in the winter to heat incoming fresh air that has already been pre-heated with a solar air heater.  Both liquid and air based systems collect and absorb solar radiation and then transfer the solar heat directly to the interior space or to a storage system for later distribution.  As there may not be sufficient solar energy during parts of the year a system needs to be installed to ensure sufficient heating is possible during times when the solar radiation is to low to handle all the heating needs.