Refrigeration Efficiency Upgrades for Grocery and Convenience Stores
Grocery and convenience stores have many of the same energy needs as other business sectors, but one key need that sets them apart is refrigeration. Improving the refrigeration efficiency of a store’s system, which uses almost 40 percent of total energy, is the No. 1 target for energy savings, with lighting following a close second. A report by E Source states that on average, grocery stores spend $3.95 on electricity and 24 cents on natural gas per square foot annually. And despite the fact that energy only represents about 1 percent of total grocery store costs, that amount is roughly equal to a typical grocery’s profit margin. But small percentages take on a whole new significance when a 10 percent reduction in energy costs translates into a 10 percent increase in profits.
refrigeration efficiency applies to all types of equipment—reach-in, walk-in, and under-the-counter refrigerators/freezers—as well as food and drink display cases. The following refrigeration efficiency measures are designed to help your business in reducing operating costs, saving energy and preventing pollution. While there are upfront costs, keep in mind that refrigeration system optimization can reduce energy use by 24 percent relative to standard practice.
Floating Head Pressure
Head pressure refers to the pressure of the vapor coming out of the compressor. Allowing that pressure to “float” means the pressure drops with reduced ambient temperature. Lowering head pressure reduces the temperature at which the compressor operates and increases the efficiency of your refrigeration system. It requires an expansion valve capable of operating at lower pressures and flow rates. By minimizing the head pressure, you can maximize your system’s cooling capacity and minimize energy costs. In one study, using floating head pressure reduced annual electricity costs by almost 5 percent compared to using fixed head pressure.
Ambient and Mechanical Subcooling
Subcooling is the process of reducing the temperature of liquid refrigerant below its condensation point. You can use either ambient water or air (ambient subcooling) or additional refrigeration system (mechanical subcooling) to reduce heat from the refrigerant. The colder your refrigerant, the less you need, which means bigger savings.
In dry climates with low humidity, evaporative condensers, which spray water instead of air over the condensing coils, may be a cost-effective approach. Their only downside is that they require a water supply and are more high-maintenance due to the potential for freezing, clogging and mineral buildup.
Display Case Shields
Low emissivity aluminum shields can have a huge impact on the power use and thermal performance of display cases. They reduce heat transfer and increase products’ shelf life—a win-win for groceries and convenience stores. When applied overnight, shields reduced refrigeration load by 8 percent, and when applied over a 24-hour period during a holiday, they reduced the load by a stunning 40 percent.
All of these measures are good investments, sure to reduce both energy use and operation costs. Implementing energy efficiency measures into your refrigeration systems has a positive effect on your bottom line: As your electrical needs drop, you will be met with a significant rise in your profitability.
Many utilities, such as PECO, offer small business incentives that cover a substantial portion of the cost of select refrigeration efficiency upgrades and their installation, include interest-free financing and make participation easy.