Environmental Engineering Reference
In-Depth Information
6.3.3 Solar Communities
If many houses in a community have solar collectors, these can be integrated into
a solar district heat network. This can also involve setting up a large central collector
complex. At the heart of such a heat network is a central heat storage tank. Its size
helps to minimize heat losses, thus also enabling heat to be stored for longer periods.
However, the extensive tube systems involved can result in disadvantages, such as
higher costs and the possibility of major line losses. Some solar district heat com-
munities have already been successfully installed (Figure 6.15).
Figure 6.15
Solar district heat supply.
6.3.4 Cooling with the Sun
As paradoxical as it may sound, the heat from the sun can also be used to provide
excellent cooling for buildings. In the hot and sunny regions of the world large
numbers of energy-hungry air conditioning systems ensure that room temperatures
are pleasantly cool. The sunnier and hotter it is, the greater the need for cooling. As
the radiation from the sun increases, the output of a thermal collector also increases.
In contrast with the requirement for heat, cooling load demand coincides almost
perfectly with the supply of the sun.
Along with a large and effi cient collector, an absorption-refrigerating machine is an
essential element of a solar cooling system (Figure 6.16). In this context, the term
absorption does not refer to a solar absorber. An absorption-refrigerating machine
utilizes the chemical process of sorption. A chemist interprets sorption or absorption
as the absorption of a gas or a fl uid by another fl uid. A popular example is the dis-
solution of carbon dioxide gas in mineral water.
Absorption-refrigerating machines use a sorbable cooling agent with a low boiling
point, such as ammonia, which is later dissolved in water. Even aside from ammonia,
