Page 43 - Climate Control News September 2021

Variable Speed Compressors
refrigeration equipment’s cooling demand. This operational pattern requires abrupt power loads when starting; furthermore, as the compressor maintains the maximum speed for all the run- ning period independent from the thermal load, it leads to wasted energy.
As described previously, variable speed com-
“THERE IS NOW MORE INTELLIGENCE INSIDE THE INVERTER REMOVING THE NEED FOR AN ADDITIONAL CONTROL UNIT.”
pressors come with an embedded set of electronics that allow the compressor to control its working speed, decreasing it when reaching the target tem- perature and also increasing it when there is need for more heat removal, ideally without switching on and off (or with a consistent reduction of on-off cycles and with a limited starting torque power versus on-off compressors). This enables the com-
pressor to use only the amount of energy required at each moment and nothing more.
The energy saving from variable speed varies ac- cording to the application but is always very signifi- cant. We have made many case studies with Em- braco compressors, where the only change made was the switch from a fixed to a variable speed compressor, and the results were energy savings of at least 15 per cent up to around 40 per cent.
Just to give an example, in a horizontal island freezer with optimized performance, for using an on-off high efficiency R290 compressor, the energy consumption reduction was 38 per cent, in an ambient temperature of 25°C, when using an Embraco variable speed compressor with Smart Drop In (SDI) control logic, without any other system optimization (see graphic).
Quicker recovery of the heat load. VCCs recov- er from door openings much faster. By overdriv- ing to higher RPMS these compressors are able to quickly regulate the delta between product and ambient temperatures.
It has a quicker average pull down time, which is the time required to bring down the tempera- ture of the product, from its temperature at the
Frozen goods warehouse.
time of entry (in the refrigerator’s cabinet) to the final desired temperature.
Tests with VCCs have shown a 20 per cent av- erage pulldown time reduction compared to the on-off ones. These working modes also con- tribute to the energy saving versus the fixed speed compressors: the VCC reaches rapidly the stabilized conditions, in which it runs at a low (energy saving) speed.
CLIMATE CONTROL NEWS SEPTEMBER 2021
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