Development and exemplary application of methods for assessing the energy efficiency of refrigeration systems in operation

The energy efficiency of refrigeration and air conditioning systems depends on a variety of factors, which additionally can also affect one another.

The most important are:
  • Components (compressor, condenser, expansion valve, piping etc.),
  • Process control,
  • Working and ambient temperatures,
  • Coolant and
  • Control systems.
The energy efficient operation is by no means guaranteed just by using efficient components. Rather it results from a combination of optimal components and their interaction. The ratio of (electric) input to thermal output must be held at a minimum continuously.

While the measurement of the electric power consumption of a chiller is relatively easy, the supplied cooling capacity (the heat flow extracted from a material or room) cannot be readily determined. It is even more difficult to obtain the cumulative values, i. e. the total cooling energy generated over a period of time, because additional dynamic effects (such as switching on / off) must be considered.

Also not only the cooling generation must be efficient, but also the so-called "cooling distribution", e. g. in cold water pipe networks or cold air distribution systems. It is thus necessary, based on the respective system boundaries, to make energetic observations and to develop criteria for an overall assessment.

A standardised methodology for a systematic energy monitoring and energy benchmarking of refrigeration systems and cooling plants during operation is not known. It is only customary to operate more or less optimised components and systems of different manufacturers, although control strategies for achieving a system or building efficiency cannot be set readily.

Thus a standardised method shall be developed and tested in several pilot applications in practice to assess the energy and efficiency of refrigeration systems in operation. An essential aim is the assessment of efficiency and the comparison thereof at different working temperatures and in various application areas.

 

Project Management Agency:
Jülich (PtJ), Umwelt, Klimaschutz
(UMW 3)

 
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