For decades, plastics processors have had to select chillers based on their maximum cooling-capacity requirements. While this approach ensures plenty of chiller capacity, it is not always energy efficient. That is because typical chillers are equipped with fixed-speed compressors (fixed-speed motors and compressor scrolls) that operate at maximum speed and capacity regardless of the load. To avoid excessive cooling on less-than-full-capacity loads, most chillers utilize a hot-gas bypass to introduce an additional, artificial cooling load. As a result, power consumption with these chillers remains fixed at a high level, regardless of actual process cooling requirements.
To provide more energy-efficient process chilling for less-than-full-load chiller capacity, auxiliary equipment makers have sought out and implemented new compressor technology. The first advance, involving digital-scroll compressors, began in the early 2000s. Digital-scroll compressors were the first that enabled chillers to unload cooling capacity, serve smaller loads and reduce power consumption.