Utilisation of Passive Solar Energy - Renewable Energy: Technology, Economics and Environment - page 119

bearing façades ventilated at rear). If the internal temperature is very high even
energy savings of above 700 MJ/(m 2 a) can be achieved /3-8/.

Solar systems with convective heat flow. A further variant of indirect gain systems
are solar systems with convective heat flow (Fig. 3.11). These systems do not
require any shading, as, in summertime, the hot air between absorber and accumu-
lator is evacuated to the outside.

Air collector principle
outer flap closed
inner flap open

Winter:

Summer: outer flap open

inner flap closed

Solar wall principle

Winter: outer flap closed

inner flap open

Summer: outer flap open

inner flap closed

Principle of the simplified ISE System

Winter:
Summer:

outer flap closed

outer flap open

Fig. 3.11 Different types of solar wall systems with convective heat flows (see /3-8/)

Decoupled systems. Some components of decoupled solar systems (such as heat
transfer devices and fans) are not part of the building structure. Since they actually
belong to the energy provision system, it is not always possible to clearly distin-
guish them from active solar systems.
These decoupled systems convert the incident solar radiation on an absorbing
surface, thermally insulated from the internal space (Fig. 3.12). Subsequently,
solar heat is transferred to a heat accumulator via a channel system, using air as
heat carrier. The heat accumulator can either be incorporated into the building
structure or be itself an individual technical component (or a combination of
both). Hollow ceilings and double wall masonry are examples of accumulators
incorporated into the building structure, whereas rock and water storage tanks are
systems that are independent of the building structure.
If heat exchange is entirely convectional (thus excluding auxiliary units), and if
the accumulator is part of the building structure, the solar system is unambigu-
ously passive. However, if fans are used for air circulation, the respective system
is referred to as semi-passive. By means of accumulators equipped with thermal
insulation heat distribution throughout the room can be controlled independently
from absorber and storage temperatures.