green cooling initiative: Energy efficiency ratios

Energy efficiency ratios

There is relatively little data published on chiller efficiency trends or efficiency in different countries. The differences between countries are lower than those within countries, which can be very high. The highest efficiency in part-load efficiency lies at 9.4, which is reached by an oil-free centrifugal water cooled chiller.

This is made possible by magnetic bearings reducing friction losses, the lack of oil interfering with efficiency, extremely high efficiencies in the 25 to 60% load operating range and very good control of variable load (McQuay, DanfossTurbocor). In the US, more than 40% of centrifugal chillers use this technology already. Other significant markets are Europe and Australia and growth is expected in China, India, Russia, and Brazil.

Energy efficiency can be improved by replacing some components with high efficiency parts. The highest gains can be reached by optimising the heat exchanger and using an inverter compressor to allow for part-load operation. As most chillers only run at full-load for a short period of the year including an inverter or another means of controlling the capacity (e.g. installing two compressors and being able to switch one off if it is not needed) leads to higher overall energy efficiency. Hydrocarbons have particular advantages in high ambient temperature environments where energy efficiency improvements of about 15% compared to HCFC-22 chillers can be achieved thanks to the thermodynamic properties of hydrocarbons.

More information can be found in the following source:

GCI-study, chapter 6.1  (request PDF here)

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