ENERGY SAVING
with optimised performance, for using an on-off high efficiency R290 compressor, the energy consumption reduction was 32.6%, in an ambient temperature of 20°C, when using an Embraco variable speed compressor with Smart Drop In (SDI) control logic, without any other system optimisation (graphic opposite).
Quicker recovery of the heat load. VCCs recover from door openings much faster. By overdriving to higher RPMS these compressors are able to quickly regulate the delta between product and ambient temperatures. It also has a quicker average pull down time, which is the time required to bring down the temperature of the product, from its temperature at the time of entry (in the refrigerator’s cabinet) to the final desired temperature. Tests with VCCs have shown a 20% average pulldown time reduction compared to the on-off ones. These working modes also contribute 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.
Low noise & vibration Variable speed technology allows the applications to also generate less noise due to the fact that it operates at lower rotation speeds for longer periods than the fixed speed. In addition, there is the “soft start” characteristic, which means the compressor starts at a lower speed, ramps up to full speed within a few minutes and continually adjusts current to provide needed power depending on the system’s conditions, with less vibration and noise. At speed over 3000 RPM, the VCC noise is equivalent to an on-off compressor.
Life cycle
Because of the way a variable speed compressor works, controlling its rotation speed according to the condition and the temperature needed, with long running time at low speed, its expected life will be inherently longer in comparison with a fixed speed one.
Wide voltage feature
Furthermore, the variable speed compressor has a very good behavior in severe voltage fluctuations (situations that may happen in many countries): in low voltages where an on- off compressor may not even start, a variable speed does, avoiding protector switches and motor stress and keeping the system performing also in those conditions.
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Space efficiency VCCs are not only energy efficient, they are space efficient too. That is because you can produce a smaller variable speed compressor to do the same job of a fixed speed one. During the design phase of an on-off it is necessary to project its size to withstand the highest cooling capacity peak, since it will always operate at full speed. Whereas in a variable speed, the size can be designed for the average speed that it will have for the most part of the time, which will be a lower speed. By freeing up more merchandising space in commercial cabinets without changing any external dimensions, manufacturers can more creatively design equipment and provide more flexible layout options to stores.
The use of hydrocarbons provides by itself, due to the thermodynamic characteristics of these refrigerants, an energy saving versus HFCs. In our tests, using the same compressor model, in the same application, switching only the refrigerant, from HFC R404 to natural R290, the energy saving reached up around 10%, generating the same cooling capacity. On this “natural” improved base, the VCCs add the energy saving due to their technology, as said above.
Despite the fact that the aspects highlighted here have higher impact on commercial refrigeration than in residential, the adoption of variable speed in domestic refrigeration has been high in many countries because of stringent energy consumption regulations, one example is Europe, where the labeling regulations for home appliances have been in force for many years. Meanwhile, in commercial refrigeration, the variable speed penetration -
although already important in integral cabinets for retailers - still has wide growing room. The imminent EU (European Union) labeling regulation, that shall apply on 1st March 2021, will contribute to the VCC diffusion. At Nidec Global Appliance, manufacturer of Embraco solutions for refrigeration, we perceive that in commercial refrigeration the key obstacles for the adoption of variable speed compressors are: their benefits should be better disseminated, their price is higher than the fixed speed compressor, and for many years there was the need for an additional control unit to regulate the compressors working parameters, what made the whole system more expensive.
But that is changing. Because of the evolution in the compressor’s technology and in its embedded electronics, the price difference versus on-off compressors has diminished and made VCCs more affordable. Furthermore, taking into account the energy bill savings, the investment has a fast payback – as low as six months in some applications for retailers. In regard to the necessity of a control unit, that is not true anymore. There are solutions available in the market that eliminate the need for an additional control unit. Embraco is one example with its variable speed and Smart Drop In logic, that has more intelligence inside the inverter. In this new moment in the global economy,
when protecting the environment by saving energy gains new importance, we are seeing an intense movement towards variable speed in commercial refrigeration. More and more, energy efficiency is becoming a relevant decision making criteria, and the technology for it is becoming increasingly more affordable.
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