In a physical sense, a passive system is one that uses only
locally available energy sources and utilises the natural flow
paths of that energy to produce work. In other words, no
auxiliary equipment (such as fans or pumps) are required to make
the system to function - the transmission media is directed by
induced convection currents or reflected/refracted to where it
is needed to do the work. In an architectural design sense, the
work that needs doing is usually the heating, cooling and
lighting of enclosed spaces. The kinds of low-grade ambient
energy systems available within most building sites are actually
well suited to these tasks, as is evident by our ability to
survive prior to the discovery of electricity. On-Site Energy
Sources There are many sources of energy available locally
within a building site. These include direct and diffuse
radiation from the Sun, air movement from winds and temperature
differences, biomass from vegetation, as well as geothermal and
hydro-kinetic sources. This does not mea