Environmental Engineering Reference
In-Depth Information
One of the main disadvantages of cooling buildings in general, and in particular
with such systems, is the increasing electricity demand in hot summer climates
during the day (e.g. Southern Europe). This results in different price levels in
summer during day and nighttime in some European countries.
Fan(s) used in the condensing unit can be a relatively loud noise source that
may require special consideration depending on the application.
Air handling equipment near the centre of the building requires special provi-
sion to admit outdoor air. Units with economiser cycles must usually be located
near an outside wall.
An element of care is necessary to design refrigerant piping, especially for long
piping runs. Improperly designed piping can cause the system to lose capacity.
An improperly designed piping can even cause compressor failure.
Each installation has to be equipped with drainage for the water from dehu-
midification of indoor air (cooling mode) or outdoor air (heating mode).
Systems aspects. In the following selective systems aspects of heat pump systems
are discussed.
Types of operation. With regard to operating a heat pump system, the following
variations can be differentiated.
Monovalent operation. Only the heat pump supplies the required domestic heat.
Furthermore, the following operational modes can be distinguished
without interruption (i.e. the heat pump always supplies the required heat on
its own),
with interruption (i.e. operation of the heat pump can be stopped temporarily
by the Utility Company supplying the end energy (i.e. electrical energy) to
run the heat pump. If the heat distribution system does not have the required
heat storage capacity to bridge these operational interruptions, a buffer stor-
age has to be connected to the heat pump) and
with additional electrical resistance heating for electric heat pumps to cover
demand peaks. This so-called monoenergetic operation is not used for
ground-coupled heat pumps in Central Europe.
Bivalent operation. The heat pump supplies the required heat together with
other systems. Bivalent-alternative and bivalent-parallel operation are distin-
guished. In addition, there are bivalent mixed types. Bivalent operation is not
very significant for the utilisation of ground as the heat source. Only for larger
systems it might be of a certain interest.
For bivalent-alternative operation the heat pump covers the entire heat de-
mand up to a certain switch-over point (i.e. a certain ambient temperature).
Afterwards, an alternative additional heater takes over the entire heating sup-
ply (e.g. a gas-fired boiler). The heat pump system is only designed for cer-
tain percentage of the maximum heating demand. The additional heater,
however, has to be able to cover 100 % of the entire heating demand.
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