Duty Cycling
Duty cycling is a low cost method of reducing capacity of equipment. Some industrial applications permit on/off cycling of equipment to achieve energy savings and match the capacity to the load. In the case of refrigerated storage facilities, the control system provides the capability of cycling zones off at regular intervals. An override feature will restart refrigeration if the zone temperature rises significantly. Adjustable refrigeration on/off schedules are easily entered from a graphic screen. A typical schedule would only operate the evaporators a small fraction of the time.
Does your facility have equipment that can be duty cycled? How much could your efficiency be increased using this simple technique?
Demand Refrigeration
Demand refrigeration is a method of saving large amounts of energy on facilities that permit turning off the refrigeration system for several hours at a time. This technique is different from duty cycling where refrigeration is shut off in individual zones on scheduled intervals to reduce energy consumption. With demand refrigeration, the entire facility's refrigeration system is shut down when all the zone temperatures are reasonably close to setpoint. The system remains off until any single zone requires refrigeration again, indicated by a rise in temperature. At that point, refrigeration is resumed in the entire system until the zones are all back to the desired temperatures. This cycle is continuously repeated.
Intelligent Engine Room Control
You won't believe how simple it is to select capacity control and compressor sequence parameters to fit your plants changing control needs. You decide which compressors will run under different load requirements - even define parameters for auto-suction pressure reset control. Make sure that you have the capacity you need, when you need it, without wasting energy and without accumulating unnecessary run hours on compressors.
If you don't use wet-bulb approach to determine optimum discharge pressure, you are undoubtedly working your compressors harder than necessary. Efficient condenser control is as simple as tracking ambient wet-bulb temperature (the ideal limit of evaporative cooling) and continuously resetting the discharge pressure setpoint to utilize the currently available condensing capacity. Just add variable speed control of condenser fans and really achieve optimum energy efficiency.
Load Shedding
Load shedding is another energy feature offered by Techni-Systems. Selected loads can be cycled off at a preset time of day, and back on at a later time to reduce energy consumption and time-of-day demand charges. One set of times may be used for weekdays and another for weekends. This same scheme can be used to lower fan speeds or whatever makes sense for your plant operation.
Demand Limiting
In order to reduce demand charges, the rate of kilowatt usage can be monitored by the system, and control algorithms implemented to keep the demand from exceeding a maximum limit. As the electrical demand approaches the limit, certain equipment can be inhibited from starting or further loading. If the demand rises above the limit, equipment will begin to be unloaded or cycled off. When the facility load returns to a normal level, the equipment will return to normal operation.
Intelligent Defrost Control
Refrigeration systems typically defrost evaporator coils at preset intervals. This often results in unnecessary defrosting, which actually adds heat to the refrigerated space and reduces the time available for product cooling. In some cases, defrost cycles have the effect of reducing the moisture content of highly perishable products. Automated on-demand defrost control can not only save energy but also improve product quality and weight. On-demand defrost control is designed to hold off defrost cycles until they are necessary as indicated by the performance of the evaporator coil. A demand defrost condition is detected when the zone temperature is above setpoint and the temperature drop of the air passing through the coil is less than normal. If these conditions exists for a preset delay period, a defrost cycle is initiated.
Improving energy efficiency is our bag, and we've got lots of tricks! Techniques such as duty cycling, demand refrigeration, intelligent engine room control, load shedding, and, of course, variable speed control will greatly reduce your energy costs. Many facilities have been using these techniques for years. How about your plant?
