In order to understand how to save energy with a commercial refrigeration system, you need to know a little about the technology involved. A commercial refrigeration system usually will be custom-designed by a refrigeration engineer or equipment supplier and will consist of components from a variety of manufacturers shipped separately to the site and assembled into a working system by a refrigeration contractor. There are a variety of different electromechanical devices and many different ways to configure and control them in these larger commercial refrigeration systems, and consequently, many ways to use, and therefore save, energy.
There are three main pieces of equipment that are part of a typical system: the compressor, the condenser, and the evaporator. Here is a brief description of each.
Types of compressors:
Hermetic and Semi-hermetic Reciprocating Compressors
For over 100 years reciprocating compressors have been the main technology for refrigeration compressors. Most are similar to an internal combustion engine in which a motor’s rotary motion is converted by a crankshaft into the up and down motion of a piston to compress the refrigerant. However, there are newer designs for “scroll” compressors that do not use this reciprocating action. Compressors originally were “open”, but the various exposed fittings meant to contain the refrigerant gas were too imperfect to prevent leaks. Now, a hermetic compressor is manufactured in a one-piece welded casing that is never intended to be opened, while a semi-hermetic compressor can be opened for repair. Both offer less opportunity for leakage, than does an open compressor. Household refrigerators use hermetic compressors almost exclusively. Commercial compressors can be of either type.
Compressors and condensers are often located together in a single condensing unit, sometimes called a packaged refrigeration system. On larger installations, the two components will often be separated and installed on a building’s roof or on the ground beside it. Condensers can eject a great deal of heat into the surrounding air, and if located inside a building, this heat can have both positive and negative effects. In winter, the heat can help with heating the rest of the building. In summer, the heat can make air conditioning of the building difficult and less efficient. If the heat is allowed to build up in a small space, the refrigeration system itself will become less effective and efficient. For this reason, condensers and condensing units are usually located outside.
Evaporators deliver to the cooled space the “cold” that the compressor and condenser make possible. They are always located within the cooled space and hang from the ceiling in room-sized spaces. Evaporator units contain the coils through which the refrigerant passes and around which metal fins are pressed to give added surface area for absorbing heat from the air being drawn through by running the evaporator fan motors. There are sometimes electric heaters mounted in the evaporator coils to remove any ice or frost that forms during the normal operation of the system.
There are numerous smaller devices and components, like thermostats, switches, timers, valves, pipes, and fittings, needed for the proper functioning of different complete refrigeration systems. In addition to the components that are responsible for driving the refrigeration process, there are other components that comprise the refrigerated space itself, like ceiling and wall panels, and reach-in and walk-through doors. Future blogs will discuss many of these things in more detail.