Environmental Engineering Reference
In-Depth Information
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For bivalent-parallel operation the heating demand is simultaneously covered
by the heat pump and an additional heating system from a certain tempera-
ture onwards.
In principle, if the return-flow temperatures are acknowledged and the heat stor-
age is suitably large, various further heat sources can be integrated into a heat
pump system, for example solar collectors or a fireplace.
The operation of ground-coupled heat pumps is normally monovalent. This is
possible as the ground as a heat source only shows low seasonal temperature fluc-
tuations and is thus available throughout the entire course of the year. Bivalent-
alternative operation is only useful for systems with a non-adjusted heating system
(high temperature). For bivalent-parallel operation, the flow of the heat pump is
fed into the return-flow of the heater, where the water of the heater is heated
further. Especially for larger systems with marked peaks in demand this mode of
operation can make sense from an economic point of view. If ambient air is util-
ised, a bivalent mode of operation can also ensure a corresponding security of
supply.
Areas of application.
Areas of application for heat pump systems are mainly in
space heating and domestic hot water supply. The generation of process heat for
commercial and industrial use - also in the low-temperature segment - has played
a minor role so far /9-18/.
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Space heating. For space heating almost exclusively electrically driven heat
pumps are used. In comparison, compression heat pumps with a combustion
engine drive and absorption heat pumps are not been very widely spread so far.
Ambient air as well as ground (including groundwater) and possibly surface
water can be used. In order to achieve high SPFs, a temperature difference be-
tween heat source and heat sink (space heating system inlet temperature) that is
as small as possible has to be aimed for. The dependency of the COP on the
inlet temperature of the heating system and the heat source temperature shown
in Fig. 9.18 clarifies that heat pump systems are preferable for low-temperature
heating systems. The use of heat pump systems in older heating systems with
flow temperatures of up to 70 °C is therefore uneconomic compared to low-
temperature systems due to their resulting low annual work rates. As a substi-
tute or an alternative for single heaters (e.g. storage or coal heaters) single-
space heat pumps using ambient air as the heat source can be utilised. These
compact appliances (depth around 20 cm) are fixed directly to the wall of the
space to be heated.
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Domestic hot water. Heat pumps for domestic hot water supply are offered as
compact appliances and generally use ambient air as their heat source. They are
normally installed in basement rooms, which act sometimes also the source of
the used air. However, it is better to also use ground or ambient air as heat
sources for domestic hot water supply pumps. At air temperatures below 7 °C,
the heat pump becomes non-operational and the electric heating that has to be
part of the domestic hot water storage takes over and heats the water up. Thus
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