Environmental Engineering Reference
In-Depth Information
Table 9.2
Variations of shallow energy utilisation
Depth
Heat carrier
Remarks
Closed systems
Brine
a
Ground coupled
collectors (horizontal)
1.2 - 2.0 m
Influence of the climate, large
surface
Direct evaporation
(horizontal)
1.2 - 2.0 m
Heat pump work-
ing medium
Material copper, sometimes
galvanised
Brine
a
Ground probes - pile-
driven (vertically
or diagonally)
5 - 30 m
Material steel, sometimes synthetic
material, only in lose rock
25 - 250 m
Brine
a
,
possibly water
Material HDPE
b
, ideal in solid rock
Drilled (vertically)
Heat transfer poles
("Energy poles";
horizontal or vertical)
5 - 30 m
Water, possibly
brine
a
static function most important, if
possible no frost temperature
Open systems
Groundwater wells
(Doublet)
4 - 100 m
Water
Minimum of 2 wells (production &
injection well), groundwater pump
Other systems
Coaxial wells
(vertical)
120 - 250 m
Water
High bore costs, overload not pos-
sible
Pit-/tunnel water
Water
Possibilities limited to certain areas
Air preheating/cooling
(horizontal)
1.2 - 2.0 m
Air
Tubes in the ground sucking air in
The depth values are typical mean values;
a
water-antifreeze mix (in the past salts, nowadays rather
types of alcohol or glycol);
b
high density polyethylene
Closed systems.
The ground-coupled heat exchanger for closed systems are dif-
ferentiated as horizontally and vertically installed heat exchanger. Additionally,
there are special forms that cannot be allocated unambiguously (i.e. soil-contact
components) and are generally not primarily used for energy generation (i.e. dou-
ble utilisation).
Horizontally installed ground-coupled heat exchangers.
Two forms of installation
of horizontal ground-coupled heat exchangers common in Europe in closed sys-
tems (also called ground-coupled heat collectors) in the form of tube registers are
shown in Fig. 9.8. The (galvanised) metal tubes in direct evaporation systems and
the mainly plastic tubes in systems with a brine intermediate circuit are sunk into
the ground at a depth of approximately 0.5 m below the frost level (normally be-
tween 1.0 and 1.5 m below the earth's surface). The distance between the individ-
ual tubes ought to be approximately between 0.5 and 1.0 m. In order to avoid
damage, they are embedded in a layer of sand.
According to current heat insulation regulations, the utilised surface for build-
ings should be approximately 1.5 to 2.0 times the space to be heated in order to be
able to withdraw enough heat from the ground even during longer cold periods.
Search WWH ::
Custom Search