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- EXTRA EDITION
Energy consumption is predicted to increase 50 percent in the next 20 years. If this prediction is accurate, demand would outpace supplies, resulting in much higher energy costs.
To tackle this problem, the energy efficiencies of the three top culprits in energy usage in supermarkets - refrigeration, HVAC, and lighting - must be addressed.
Managing energy information is key to controlling and reducing these top supermarket energy consumers. There are several methods to obtain and utilize this data, but the key steps are to measure, monitor, maintain, and improve the operational systems in a facility.
IDENTIFY THE ENERGY CULPRITSThe first order of business is to identify the major energy culprits and measure the amount of energy being consumed. Start by installing meters on the main utility of the facility, each parallel refrigeration rack, each refrigeration condenser, the central HVAC unit (one or two units per store), and the lighting panels (two, three or four groups).
In these instances, the meters should provide 15-minute interval data. They can then be linked to a Web-enabled server and stored in a Web-enabled database. This data is collected to establish consumption rates, but most importantly to benchmark performance. Data is collected for at least four to six weeks to establish normal operating consumption performance. (See Figure 1.)
RECOMMISSIONINGThe next step is the recommissioning of the refrigeration systems to designed operational set points. The program of the refrigeration system microprocessor needs to be adjusted to the customer’s specifications. This includes suction set points, head pressure control, defrost schedules (number and duration), controls adjustments (TXVs and EPRs), and calibration (transducers and thermistors).
Once the major contributors of energy consumption in a supermarket are identified, then the amount of energy being consumed and in what time frame must also be identified. According to Figure 2, the highest amount of energy is consumed by the refrigeration systems, second is the HVAC systems, and the third is the lighting.
Management of the energy costs can only be developed after precisely measuring the energy consumed by each group independently and the time of use. It is also imperative to account for weather conditions (ambient temperatures), which also have a profound effect on the refrigeration and air conditioning system.
After collecting this information, a Web-based program aggregates the data and establishes a benchmark of efficient operation of the systems.
Stores that deviate from predicted energy performance are analyzed to find reasons for abnormal performance and results are communicated to the customer. The refrigeration system controls can then be interrogated independently to find the source of deviation. The same can be completed for the HVAC and the lighting systems.
Results can be resolved instantly via Internet or at the local level by the customer or by a preferred maintenance contractor.
This process ensures that the designed operating conditions can be maintained at all times.
The added advantage to maintaining systems at designed parameters is that maintenance costs are reduced. When the capacity of the refrigeration systems tracks the load requirements effectively, suction and discharge pressure remain constant. This not only reduces energy consumption, but it also reduces compressor and contactor cycling. The life cycle of the compressors and contactors are greatly increased, which reduces maintenance costs.
FINE-TUNINGAfter several months of monitoring and maintaining the systems, knowledge is gained for each system. Once the data is collected, methods to improve or fine-tune can be implemented and carefully reviewed. Some of the required changes may improve energy efficiency, but at the cost of product integrity. If those changes have adverse effects on product quality, then the parameters can change to compensate.
The technology for refrigeration system design and refrigerated cases is constantly changing to meet the marketing needs of the supermarket industry. The physical layout, size of stores, types of merchandisers, and types of equipment are ever-changing. This process of interrogating the energy information of the facility lends itself to evaluating different types of refrigeration systems and case technologies. It gives the operators the actual cost of operating the systems in each of their locations. They can make better decisions based on factual data of which systems provide them with the lowest possible operating costs and desired performance.
The customers now have the opportunity to evaluate the efficiencies and operation performance of new technologies. This gives them the advantage in understanding the unique performance of new technologies in facilities and what systems best fit operational needs.
Other areas of energy-saving features to consider are floating suction pressures, anti-sweat controls, motion sensors, product temperature control, variable-frequency drives, and ECM motors. These are just a few of the areas that can be evaluated to see what effect they offer for energy-saving programs.
MANAGING CONSUMPTIONIt is impossible to control rising energy costs, but energy consumption management can definitely be controlled effectively. Once you actively pursue new methods of integrating energy data, new areas will present themselves for future opportunities.
Publication date: 04/02/2007