Chiller screw compressor drives: how to improve the energy efficiency of refrigeration equipment.
One of the markets in which we are most active is refrigeration.
In this case study we talk about our collaboration with a multinational company specialized in the production of air conditioning and refrigeration equipment.
As with all manufacturers of compressors used in refrigeration and air conditioning systems, energy efficiency is a key requirement.
The use of inverters in HVAC&R market applications, and in particular in the management of chillers with screw compressors, allows a series of optimizations especially with reference to the achievement of greater system efficiency in refrigeration plants, in cases of plant operation at partial load.
What the customer asked us
To meet the customer’s needs, our technical department worked on an innovative and customized solution of an inverter integrated on screw compressors: we designed an inverter of small size but able to develop a considerable power and that could be inserted inside the compressor to drive its motor (which can be either asynchronous or synchronous).
It became possible to vary the compressor speed directly on board the compressor, even indirectly.
The possibility of inserting the drive inside the compressor opens up a range of new possibilities, all aimed at increasing the efficiency of compressors. Since a chiller operates most of the time at partial load, the system is designed to give maximum efficiency precisely in this condition.
The use of the inverter therefore allows for high energy efficiency and almost perfect regulation in every load condition. Within the volumetric compressors, precisely because of their operating characteristics, the inverter allows to obtain several advantages.
The possibility of reducing the number of revolutions and therefore the refrigerant flow rate at will, regardless of the pressure drop required, allows extremely precise power regulation.
The regulation efficiency is very high, because the reduction of the volumetric flow involves a decrease in the condensing pressure, an increase in the evaporation pressure and therefore a higher Eer value.
More generally, the advantages of using the inverter are related to better temperature control and greater energy efficiency. The use of an inverter designed to be internal to the screw compressor, allows the drive to be placed inside the compressor to drive the motor. This solution makes it possible to drive both asynchronous and synchronous motors.
In order to improve plant efficiency, the drive is also designed to allow the use of a single compressor, instead of multi-compressors and brushless compressors that require inverters.
The use of the drive inside the compressor opens the way to innovative solutions. The inverter inside the compressor is in fact cooled by the refrigerant gas of the compressor itself, allowing a series of optimizations of the compressor + inverter group.
The refrigerant-cooled inverter technology has been directly integrated into the design of the single screw compressor. The combination of these technologies helps increase the efficiency of compressors and chillers, with a focus on part load.
In fact, a chiller operates most of the time at partial load: to be efficient, therefore, it must have a high efficiency in this condition of use.
Each phase of this project has been carried out to meet specific market needs: higher and higher performance in compliance with regulations.
In this way, we were able to introduce a completely new single screw compressor design, which guarantees an easy installation process.
Our added value
The adoption of our inverter has brought the following benefits:
- Wide operating range
- Low starting current
- Reduced mechanical stress and therefore greater system longevity
- Reduction of over-compression with consequent efficiency in all conditions
- Possibility of modulating the capacity and the compression ratio
- Possibility to manage longer operating hours at partial compressor loads
- Reduction of power consumption over the entire life cycle of the compressor
- Elimination of current peaks
- Noise reduction at partial loads
- Improved accuracy of internal electro-cooling, which is not affected by external conditions
- Innovative cooling system, suitable for any installation
- Drive characteristics are not affected (e.g. Derating) by outside temperature or sea level, making it ideal for applications in mountains or special conditions.
- Higher reliability
- Fewer connections