Environmental Engineering Reference
In-Depth Information
standard feature in residential buildings (e.g. North America, Japan), such sys-
tems are widely spread. The "heat pump" often operates primarily as a refriger-
ating machine for space cooling and only secondly as the proper heat pump.
Given the climatic conditions in Central Europe with its comparatively low
need for refrigerating, space cooling can be achieved without running the heat
pump as a refrigerating aggregate. The heat exchanger that consists of ground
probes can deliver sufficient temperatures of 8 to 16 °C with a simple cooling
with cooling ceiling or blast convectors and between 9 and 10 °C for the
groundwater.
COP characteristics.
The quality of heat pump systems can e.g. be measured with
the COP, the SPF and the heating rate (Chapter 9.1). In the following dimensions
that can be achieved nowadays will be discussed.
−
Coefficient of performance (COP). The COPs given by the producer always
refer to certain operational conditions (heat source and sink temperature).
Given ideal conditions, between 40 and 65 % of the COPs generated by a loss-
free Carnot Process can be achieved /9-12/. However, this gives reason to as-
sume a certain level of energetic development potential for the current state of
technology. Fig. 9.19 shows an example for the use of the heat source ground
(brine circuit, no direct evaporation) and groundwater. Mean values of cur-
rently achievable COPs and those that can be expected in the future are given
as an example using a maximum flow temperature of 35 °C in this case.
7
Medium to long term
available HP
6
5
Currently available
heat pump (HP)
4
3
2
1
0
-15 -10 -5 0 5 10 15 20
Evaporator inlet temperature in °C
Fig. 9.19
Coefficients of Performance (COPs) of ground-coupled electric heat pumps
(flow temperature of heating system 35 °C; evaporator inlet temperature approximately -10
to +10 °C for brine and approximately +5 to +15 °C for water; see /9-19/)
−
Seasonal performance factor (SPF). For groundwater heat pumps the SPFs of
new systems are between around 4.0 to potentially slightly above 4.5. When
utilising ground as the heat source, currently SPFs of approximately 3.8 to 4.3
can be achieved. For direct evaporation, the SPF of the system is mostly around
10 to 15 % higher. The decisive factor for high SPFs of the heat pump systems
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