Utilisation of Passive Solar Energy - Renewable Energy: Technology, Economics and Environment - page 104

Heat losses
to ambient due to
thermal conductivity
(transmission losses)

June 21

Heat flow
within the building
(transmission,
ventilation)

Heat supplied
by space
heating system December 21

Heat losses
due to
ventilation and
infiltration
Internal heat
gains due to
persons and
equipment

Passive
solar gains
by windows

Heat storage
in thermal
mass

Heat losses to the ground
due to thermal conductivity
(transmission losses)

Fig. 3.1 Main energy flows within a building

Passive solar energy utilisation is based on the absorption of short wave solar
radiation, either by the building interior, as solar radiation penetrates through the
transparent external structural elements, or by the building envelope. The con-
cerned structural elements are warmed up by the absorbed solar energy. The en-
ergy is released back to the exterior by convection and long wave radiation. The
quantity of absorbed solar energy of surfaces, exposed to radiation, depends on
their orientation, shading equipment and the absorption coefficient of the con-
cerned absorber surface (see Fig. 2.20 and Fig. 2.21). The quantity and timing of
released energy are determined by thermal conductivity, density, and the specific
thermal capacity of the absorbing material itself and the material placed behind, as
well as by the difference to surrounding temperature. The seasonal effects of pas-
sive solar energy utilisation can be further intensified by an appropriate orienta-
tion of the concerned surfaces or shading devices (see Fig. 2.21 and Fig. 3.3).

3.2 Technical description

In the following chapters all system elements involved in the utilisation of passive
solar energy are described and illustrated. However, explanations are limited to a
selection of the current main aspects. First, a compilation of the fundamental tech-
nical terms is provided.