Given the state of economy, any movement towards am efficient operation translates to blessings for the operators of that business. The reduction of the load burdens on the machinery, more efficient motors, and sustainable and green products are some of the movements and innovations that are now available for the operators.
A supermarket is a multilevel operations with many high use energy components. Due to the high energy demands, supermarket operations become an excellent candidate for fine tuning for high efficient facility. While older aged facilities will benefit the most, the younger facilities will enjoy all the benefits of the new technologies and smart systems that have been implemented and utilized in the past years.
Recently, most supermarkets built were based on early and aged prototypes that were designed by engineers and architects. The design fee structure as well as the construction cost budget allocated does not permit any new innovations that in the long run are financially beneficial as well being very efficient for the building. Introduction of technology to the building produces fear into one group and rattles the traditionalists’ image in opposing such new elements into the design.
One of the benefits of the supermarket is very high attention given by the energy industry, academia, utility companies, as well as the government bodies. It was not very difficult to identify papers, articles, documents, doctoral thesis, innovation papers, and many pother related journals dedicated to high energy efficient supermarket. However, given the statements above, the today’s supermarket does not enjoy the benefits of these noted works.
In this report, this Engineer proposes to review all possibilities of the savings within the supermarket, review the energy profiles of the store, review the nearly all of the energy seeking equipment (i.e. motors, air conditioning, lights, …), and to augment the energy used by the renewable energy sources or on-site energy productions.
By review of the Figure 1, the example of the energy distribution of a typical grocery store is given. Grocery stores in the U.S. use an average of 52.5 kilowatt-hours (kWh) of electricity and 38,000 Btu of natural gas per square foot annually. A 100,000 square feet store will equate to 5,250,000 Kilowatt-hours (kWh) or 3.8 billion Btu of natural gas. Energy costs account for 15 percent of a grocery store’s operating budget. Because grocery stores’ profit margins are so thin—on the order of 1 percent—every dollar in energy savings is equivalent to increasing sales by $59. Any percentage of savings will greatly benefit the owners and consequently the greenhouse effects.
To tackle this issue, there are several mechanisms available for analysis:
• To attack the items that are considered as “Low Hanging Fruits”
The “Low Hanging Fruits” or LHFs are those that easily are accessible equipment, the ratio of KW to dollar savings are very high. In addition, the impact of the modifications to the operations are minimal to none.
Many grocery stores can benefit from low- or no-cost energy expenditure reductions. Some of the examples of the LHF’s are:
Turning Things Off
It’s the simplest of ideas. Remember that every 1,000 kWh you save by turning things off equals $100 off your utility bill. (This assumes average electricity costs of 10 cents/kWh.)
Plugged-in devices. Computers, cash registers, bar-code readers, deli scales, and deli cooking equipment should be shut off when not in use. “Smart” power strips with built-in occupancy sensors are available to shut off plugged-in devices when no users are present.
Lights. Turn off lights when they’re not in use. Occupancy sensors can help; a less-expensive alternative is to train staff to ensure that switches are off when the lights aren’t needed. Stores that are open all night may want to install dual-level switching for overhead lights, allowing some fixtures to be turned off during low-traffic hours.
Turning Things Down
Some equipment cannot be turned off entirely, but turning it down to minimum levels where possible can save energy.
HVAC temperature setbacks. During closed hours, turn temperature settings down in warming seasons and up in cooling seasons.
Special-use rooms. Make sure that HVAC settings in warehouses, stockrooms, offices, and other special-use rooms are at minimum settings.
Cleaning and Maintenance
Check the economizer. Many air-conditioning systems use a dampered vent called an economizer to draw in cool outside air when it is available to reduce the need for mechanically cooled air. The linkage on the damper, if not regularly checked, can seize up or break. An economizer that’s stuck in the fully open position can add as much as 50 percent to a building’s annual energy bill by allowing hot air in during the air-conditioning season and cold air in during the heating season. Have a licensed technician calibrate the controls; check, clean, and lubricate your economizer’s linkage about once a year; and make repairs if necessary.
Check air-conditioning temperatures. With a thermometer, check the temperature of the return air going to your air conditioner. Then check the temperature of the air coming out of the register nearest the air-conditioning unit. If the temperature difference is less than 14° Fahrenheit (F) or more than 22°F, have a licensed technician inspect your air-conditioning unit.
Change filters. Change air-conditioner filters every month—more often if you’re located next to a highway or construction site where the air is much dirtier.
Check cabinet panels. On a quarterly basis, make sure that the panels to your rooftop air-conditioning unit are fully attached, that all of their screws are in place, and that the gaskets are intact so no chilled air leaks out of the cabinet. Such leaks can cost $100 per year per rooftop unit in wasted energy.
Clean condenser coils. Check condenser coils quarterly for any debris, natural or otherwise, that has collected there, and remove it. At the beginning and end of the cooling season, thoroughly wash the coils.
Clean evaporator coils. The buildup of dirt and ice on evaporator coils slows down the rate of heat transfer and causes the refrigeration system to use more energy to maintain the same temperature.
Check for airflow. Hold your hand up to air registers to ensure that airflow is adequate. If there is little airflow or dirt and dust are found at the register, have a technician inspect your unit and duct work.
Check the refrigerant charge. Incorrect refrigerant charge can compromise refrigeration equipment efficiency by 5 to 20 percent and raise the risk of early component failure. Have a licensed technician check the refrigerant charge of all refrigerated equipment annually.
Check refrigerated cases for air leakage. Every month, inspect and replace any worn seals and gaskets on the doors and inspect the door closers for proper operation.
Check temperature settings on refrigerated systems. Energy is wasted if refrigeration temperature settings drift too low. Periodically check to verify that the appropriate temperature settings are specified.
Add strip curtains to walk-ins. Simply adding strip curtains to the doors of a 240-square-foot walk-in refrigerator reduced the unit’s energy consumption by 3,730 kWh per year—about 9 percent of total consumption!
Replace incandescent lightbulbs with screw-in compact fluorescent lamps (CFLs). Whenever an incandescent lightbulb burns out in a fixture that is on for longer than two hours per day, replace it with a CFL. They are three times more energy efficient than incandescent bulbs, last 10 times longer, and—because they give off one-third as much waste heat—increase the efficiency of walk-in refrigerators and freezers. Specify low-temperature-rated CFLs for freezer applications.
Install occupancy sensors in walk-ins. By replacing light switches with low-temperature occupancy sensors, you’ll reduce lighting energy consumption by about half.
• Ages equipment are the next candidates to be considered
There are many reasons that this category becomes a good candidate. The high maintenance cost for the upkeep of the equipment, the lack of efficiency, as well as low lack of controls and monitoring of the equipment give very high reasons for replacements. Naturally through time, the new equipment go through major transformations, namely: either new energy regulations and new state laws, higher efficient equipment, added components for measurement and verifications (M & V), interactive monitoring, and digital signatures on the machines. The hidden maintenance costs, time spent by the workforce to babysit the equipment, the frequent downtime of the machinery and lack of income from such machinery are added reasons for this category.
• To review the innovations on high energy usage categories- Refrigeration
By observing the energy distribution pie in Figure 1, the highest to smallest energy consuming components are Refrigeration, offices, heating, cooling, lighting, etc. Therefore it is natural to identify all of the available resources to review these in such order. In addition to the above stated issues (i.e. complete change-out), there are number of M & V devices that can increase the efficiency of the system by 25%. 25% of 36% is 9% of the total usage within the building and is considered to be significant. However, there are number of parameters to be considered before moving through this route. The office equipment can be the interior lighting, heating and cooling systems, as well as their general office equipment. Through the EPA’s energy star program, there can be very giood start. Demand use operation controls, as well as identifying the habits and office personnel can be beneficial. The Lighting, heating, and cooling for the entire space can be individually categorized and discussed later.
Some of the examples of activities for improving refrigeration efficiency are:
Optimize Refrigeration
The optimization of refrigeration systems can reduce energy use by 24 percent relative to standard practice. The following measures yield the largest savings.
Floating head pressure. Taking advantage of lower ambient temperatures to reduce refrigerant temperatures is a form of free cooling. One approach is to allow the pressure of the vapor coming out of the compressor (the “head pressure”) to float—that is, to drop with reduced ambient temperatures. This requires an expansion valve capable of operating at lower pressures and flow rates, and such valves are now commercially available. In addition, refrigerant pressures must be kept high enough to avoid “flashing”—the unwanted vaporization of refrigerant. In one field test, operating a system with floating head pressure reduced annual electricity costs by 4.9 percent relative to operating with fixed head pressure.
Ambient and mechanical subcooling. Reducing the temperature of the liquid refrigerant below its condensation temperature is called subcooling. This can be done either by using ambient air or water to remove heat from the liquid refrigerant (ambient subcooling) or by using an additional refrigeration system (mechanical subcooling). Colder refrigerant means either more cooling per pound of refrigerant delivered to the display case or shorter compressor run times because less refrigerant is needed, both of which can decrease energy use. Ambient subcooling is often more cost-effective than mechanical subcooling because it requires less equipment.
Evaporative condensers. Most condensers in grocery stores are air-cooled, but it is also possible to use evaporative condensers, which are cooled by water spraying over the condensing coils. Evaporative condensers are more energy efficient than their air-cooled counterparts, but they do have a notable disadvantage: They require a water supply, which often means increased maintenance due to freezing, clogging, and mineral buildup. Evaporative condensers may be cost-effective in drier climates, but the added maintenance may make them unattractive in other climates.
Heat-recovery systems. Heat-recovery systems are available that capture waste heat from refrigerators to make hot water for use in the store. A 7.5-horsepower compressor can heat all of the hot water a midsize supermarket would use in its kitchen cleanup and bathroom sinks. Often, enough waste heat is also available to supply hot water coils for space heating in cold weather.
Display case shields. Aluminum display-case shields can reduce refrigeration load from the display case by 8 percent when applied overnight and by 40 percent when applied over a 24-hour holiday, relative to the load present without the shield. Products are kept colder when the shields are attached and remain colder for several hours after the shields are removed.
Evaporator-fan motors. Replacing existing shaded pole motors on evaporator fans with electrically commutated motors will reduce the energy consumption of refrigerator and freezer cases by 40 to 70 percent. Drop-in replacement designs have made this retrofit relatively simple for a technician to perform. Additionally, most evaporator-fan motors in walk-ins run continuously even though full airflow is usually required only about half the time. Consider introducing advanced controls that slow the fans when full-speed operation is unnecessary. Annual cost savings can result in about a one-year payback for the total cost.
Anti-sweat heaters. The latest anti-sweat heater controls sense humidity in the store’s ambient air and reduce the operation of their heaters in low-humidity conditions. They promise significant savings and quick payback, and they are relatively easy to install.
“Smart” defrost controllers. When installed in walk-in freezers, a smart defrost controller monitors several variables and optimizes the number of daily defrost cycles. Adding these kits can save hundreds of dollars a year, depending on the size of the freezer.
Consider Desiccant Dehumidification
In humid climates, much of the energy used in air conditioning goes to removing moisture from the air. Desiccant dehumidification can be a cost-effective solution for removing this moisture because it uses natural gas instead of electricity. In some cases, air-conditioning equipment can be smaller sized because it is only used to cool dry air.
Focus on refrigeration for big energy savings
The key to conserving energy in any business is knowing which operations consume the most energy. Like other businesses, lighting, heating and cooling and office equipment are a part of supermarkets’ energy use profile. Typically, however, grocery stores use more energy for refrigeration than the other operations put together.
Several measures can reduce the cost of refrigeration. Some are inexpensive while others require a significant investment, but conservation in this area gives a double hit on savings. Cold air from refrigerated cases and walk-in coolers enters the store, increasing the energy needed to heat the building in winter so reducing refrigeration also translates to lower heat bills.
On the no-cost side, Energy Star offers the following refrigeration tips to help grocery stores save money and energy on refrigeration needs:
• Keep doors shut—Repeated fluctuations in temperature will damage food quality and cost money.
• Check temperature settings—If settings are lower than necessary, the system may be wasting energy. The most common recommended settings are between 14 degrees below freezing and 8 degrees below freezing Fahrenheit for freezers and between 35 degrees and 38 degrees Fahrenheit for refrigerators.
• Clean cooling and evaporator coils—Dirt accumulation impairs heat transfer and lowers the efficiency and capacity of refrigerators. Keep evaporator coils free of ice build-up. Don’t forget the condenser coils, usually located on the building roof. Also, do not put a sprinkler on the roof to help cool the condenser coil, as domestic water contains mineral that can damage the coil.
• Check door seals—Tight seals and properly closing doors prevent warm air from entering the unit, which reduces cooling energy and prevents frost buildup. If a dollar bill slides easily into the seal, have the seal adjusted.
• Maintain equipment—Performing scheduled maintenance on any type of business equipment improves an operation’s efficiency.
Simple changes prevent cooling losses
Taking common sense to the next level provides more refrigeration efficiency. Stores that do not operate 24 hours a day can save energy on their open-air cases by installing curtains to cover the case openings. This acts like a closed door on the case, sealing in the cold and significantly reducing the load on the refrigeration system.
When products are being moved to and from walk-in coolers, the doors are often left open for extended periods of time. Cold air flows into the store, creating a load on the heating system, while the refrigeration system tries to cool the space the heating system is warming up.
A simple solution is to add strip curtains. This minimizes the loss of cooling from the walk-in while the door remains open for staff and equipment to pass through. Since cold air sinks, the curtains should reach the floor to keep cold air from escaping at the bottom.
Automatic doors offer a more complete, but more expensive solution. The strip curtains should still be used with doors that close and open by a pull cord or button.
Lighting fixtures in older refrigerated cases can be big energy consumers. Many use high output ballasts because they work better at colder temperatures than regular ballasts. Try the new “cold weather” electronic ballasts that can be used with the lower wattage T-8 bulbs, measuring one inch in diameter, and 5/8-inch T-5 bulbs. These lower wattage bulbs often put out more and better quality light than older ones, and add less heat to the case. This savings potential could be as high as 10 percent.
System controls adjust energy use for operating conditions
Environmental conditions—ambient temperature, humidity, etc.—affect most electrical equipment and this is especially true of refrigerator units. Adding a variety of controller units to different system components can yield significant energy savings.
Refrigeration systems work by compressing and expanding a refrigerant. The pressure a compressor uses to develop is directly related to horsepower. So, the lower the pressure needed to cool to the desired temperature, the less energy used.
Most head pressure controls, as these are called, are set to a level that remains fixed regardless of the outside temperature. However, the system should not have to work as hard in cool weather since the condenser—the coil on the roof that cools the refrigerant—is in cooler air. By installing floating head pressure controls, the controller can automatically adjust downward as conditions allow for energy savings of 3 to 10 percent.
The condenser, which exhausts heat from the refrigeration system, and the evaporators that cool the walk-in cooler and product cases use electric motor-powered fans to cool the fins. High-efficiency motors do the same work with less energy. In the case of the evaporator, using less energy to move air generates less heat for the refrigerator to cool. Changing to energy-efficient motors can save between 5 and 13 percent per year.
Evaporator fans that operate continuously to mix cold air and distribute it to products also generate heat. Several manufacturers make controllers that reduce the fan motor’s speed to minimize the heat when cooling is not needed. The fan continues running at a reduced speed until the thermostat calls for cooling. Then, it speeds up to blow air over the evaporator coils and cool the space. Contact the Power Line for more information about this equipment.
Many freezer cases have glass doors, which are excellent at saving energy and maintaining product quality. However, when the door is opened, moisture from the warmer store air condenses on the glass fogging it, so the product can’t be seen. This is called sweating, and door manufacturers solve this by installing anti-sweat heaters to keep the door glass warm.
Glass fogs less during winter months and in dryer climates where the moisture content of the air is lower. Adjustable anti-sweat heater controls detect these differences in the environment and pulse the heaters on and off to save between 6 and 20 percent, depending on conditions. These controllers are relatively easy to install and can be adjusted automatically. In some cases, the refrigeration system may already have this feature and it just needs to be hooked up.
• The Heating and Cooling systems have their share of advances.
The use of building management systems, high level of monitoring and controls, presence of very high efficient units have produced tangible benefits to the supermarket. The word “comfort” can be redefined by the level of interaction of the operators of the building and full satisfaction of the occupants. The EER efficiency ratings from 7 to 8 have been elevated to 12 and 13, straight, 25% more efficient units. Leakage through ductwork account up to 10% of the energy losses, and the unclean plenums, and other factors minimize the comfort level for the store. Although environmental issues are not discussed in this article, there are direct secondary benefits of heating and cooling energy upgrades.
• Lighting has benefited the most in the efficiency and technology.
The lighting industry has benefited the most in the energy advancement. With very efficient ballasts, lamps, innovations on LED, reflective enclosures, motion sensors, on demand use, and intelligent timers the impact on savings are veru visible to the users and financial officers. Most important note is the synergy of other energyt useage with lighting. When the lighting loads within store is reduced, the heat created by the light fixture is also reduced, hence the air conditioning loads will reduce and frequency of their usage is reduced.
Some of the examples of improving the building lighting are:
Upgrade to More Efficient Lighting
Lighting is critical to creating ambiance and making merchandise attractive to shoppers. High-quality lighting design can reduce energy bills and drive sales. If your facility uses T12 fluorescent lamps, relamping with high-performance T8 lamps and electronic ballasts can reduce your lighting energy consumption by 35 percent. Adding specular reflectors and new lenses and reducing the number of lamps can double the savings. Occupancy sensors or timers can add further savings in storerooms and other staff-only areas. Paybacks of one to three years are common.
Changing refrigerated display-case lighting to light-emitting diode (LED) light strips saves energy and has been shown to appeal to customers significantly more than linear fluorescent lamps. LEDs are more than 40 percent more efficient than T8 lamps, provide a more-even light distribution, are dimmable, and have a long lifetime. In stores that remain opened 24 hours a day, LEDs can be tied to occupancy sensors so the display cases are only illuminated when customers are present. The waste heat from LEDs can be dissipated outside the case, something fluorescent lighting can’t do, resulting in reduced refrigeration energy: For every watt in reduced energy consumption, there is an additional 0.48-watt savings from reduced refrigeration demands.
Grocery stores with high ceilings might want to consider using T5 lamps and indirect fixtures to boost both lighting quality and lighting efficiency. T5 lamps are far more energy efficient and offer better light quality than either the high-intensity discharge lights or the older-style T12 and T8 linear fluorescent lamps typically found in high-ceilinged stores.
Use Smart Lighting Design in Parking Lots
Most parking lots are designed with far more lighting than the 1 foot-candle or lower average that the Illuminating Engineering Society of North America’s Lighting Handbook (2000) recommends. Using lower-wattage bulbs can actually increase the safety of your lot—an overlit lot can be dangerous to drivers if their eyes cannot adjust quickly enough in the transition from highly lit to dark areas. When designing lighting for a new parking lot, consider low-wattage metal halide lamps in fixtures that direct the light downward, rather than high-pressure sodium lamps. Even with a lower wattage, a grocery store could safely use fewer lamps if this choice is made. Metal halide is less efficient than high-pressure sodium in conventional terms, but it puts out more light in the blue part of the spectrum, which turns out to be easier for our eyes to see under low-light conditions.
LED lighting has emerged as an even more efficient parking lot option than high-intensity lighting. However, because the Energy Star program does not currently include parking lots in its list of acceptable LED applications and because LEDs’ high initial costs result in long payback periods, be sure to conduct a thorough analysis before you commit to LED lighting for your parking lot.
• Cooking and Ventilation are other components used in supermarkets.
The hood industry and cooking equipment have gone through some innovations. Presence of on-demand use sensors, variable frequency drive, very simple skirts on cooking hood covers (LHF item) as well as commissioning of the systems to design standads will greatly enhance the systems.
• Water Heating are considered as near 100% efficient units.
Theme is “older the water heater, the lower the water heater efficiency”. Water heaters are now near 100% efficiency with 10 years warranty. Once one combines this with other heat recovery systems from (the refrigeration systems) for the feed water, the water heating becomes extremely attractive proposal.
• On Site Energy Productions is now vital and viable.
Although solar has some set backs, they are great tools and energy source to reduce the peak demand charges by the utilities. Coupled with small cogen plant, the energy usage will decrease to only natural current baseline of the building usage.
In culmination of the above bulletins, there are many activities that can take place and create a very efficient and low energy use buildings.
The first activity for this Engineer is the Energy Audit of the site. An energy audit analyzes and evaluates existing energy-use practices with an eye toward cost savings.
Individual audits can vary, but they are likely to cover the following items:
• Baseline energy-use profile: Hopefully 15 minute energy use data
• Building envelope improvements- Possible energy leaks
• Heating, ventilation, and air-conditioning systems
o Retrofitting and replacement
o Improved schedules
o Improved placement of thermostats and air sensors
o Improved computer programs
• Lighting
o Installation of timers and automatic sensors
o Replacement of light fixtures and bulbs
o Improved scheduling
• Plumbing improvements
o Identification of leaks
o Improved pipe insulation
• Overall design of a company’s energy management program
• On Site Power generation or Co-generation-Solar power feasibility studies
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