Components of Passive Solar Systems

Passive solar energy is a concept that is incorporated into housing design so that the energy requirements of heating the house are minimal or nil.  Passive solar heating is widely used and well-known, but passive solar energy can also be used for cooling a house in hotter climates.

Passive solar energy is a concept that has to be built into the house design from the beginning; it cannot be retrofitted very easily into an existing building, although one or two things may be adapted.  The most significant use of passive solar energy that can be retrofitted to a home is a solar water heating system, but conservatories as an extension are other examples.

Have you ever noticed how lizards, snakes and other cold-blooded animals like to sit on rocks and on road surfaces once the sun goes down?  This is because the stones absorb the heat energy of the sun during the day, then emit it during the night.  This is the basic idea behind passive solar energy.

Common Features of a Passive Solar System

This illustrates some of the fundamental features which reinforce Passive solar system design for the house

As you can see in the picture, there are a number of attributes which make a site suitable for passive solar heating. For those of you who prefer easier to understand components of this design principal here are some features of buildings designed with passive solar energy in mind:

• Plenty of windows facing towards where the sun is at midday (in Australia, this means northwards);
• Living areas (dining room, kitchen, lounge, etc.) placed in the north-facing rooms;
• The building is elongated along the east-west axis (this increases the area of the building facing north).
• Small windows on the south (sunless) side of the building (this is where the toilet, laundry and bedrooms go);
• Building materials with a high amount of thermal mass such as stone are used (Stone floors are also common);
• Verandahs and overhangs that are at the right angle for the latitude (you don’t want it to get too hot inside);
• Double-glazing on windows so heat and light are let in but not out.
• Staircases, which can act like “chimneys” that funnel heat away, are eliminated or blocked off.

Using Passive Solar Systems for Cooling

Passive solar energy is also used in hot climates to use convection created by solar heating as a cooling system.  These passive solar cooling systems were adapted from the cooling systems noticed by researchers in… termite mounds.  Once again, orientation and the amount of windows are taken into account – although in hot climates (e.g. the Australian Outback), many of the passive solar energy principles for heating are reversed:

• Buildings are spread along the north-south axis to minimize the area facing the midday sun;
• Shading is used appropriately to keep it cool and shady indoors
• Things with a lot of thermal mass are used to soak up the heat – roof ponds for example.
• Chimney-like constructions are used to catch convection and create air currents.

An example of a large building with passive solar energy for cooling is seen in Harare, the capital of Zimbabwe, where an entire mall has been built using a termite mound as the inspiration (not for the decor, though!).