Effective Energy Efficiency Measures for Supermarkets

Electricity bills can represent a significant portion of energy expenses at supermarkets: these buildings operate for extended schedules, and there are heat-sensitive products that must be kept in refrigerated spaces at all times, even after closing. Therefore, the most effective energy efficiency measures for supermarkets are normally those that improve lighting, HVAC and refrigeration.

Advantages of LED Lighting in Supermarkets

LED lighting has two notable characteristics: energy efficiency and product variety. Supermarkets using fluorescent lighting may achieve energy savings above 40% if they upgrade to LED fixtures, and savings of over 70% are possible when replacing metal halide fixtures.

Other than offering energy efficiency, LED lighting can also be a marketing tool for supermarkets: no other lighting technology offers the same flexibility in terms of color temperature and optical design. For example, it is possible to use a warm white color where products such as apples or oranges are being displayed, making them seem more appealing. Another marketing application of lighting is drawing attention to specific products using spotlights in strategic locations.

Electronically Commutated Motors for Efficient Refrigeration in Supermarkets

Fans play two important roles in refrigeration systems: they make sure that cool air circulates inside refrigerated spaces, and they also provide a flow of air for the condenser to reject heat outside. Normally, these fans are cycled on and off according to the load, but using speed control is much more energy efficient:

• For example, assume a fan operates all the time, but it is possible to meet the total load with only 80% of the air flow.
• If the fan operates with a duty cycle of 80%, the energy savings achieved are around 20%.
• However, if the fan is driven at 80% speed, savings of nearly 50% are achieved, because fan power is proportional to speed cubed.

Electronically commutated motors (ECMs) offer exceptional energy efficiency and speed control characteristics, and are a great alternative to the traditional motors used in supermarket refrigeration systems. There are now ECMs that even surpass the efficiency of NEMA Premium motors.

Anti-Sweat Controls

Supermarkets make extensive use of refrigerated cabinets for product display, and it is very important to control condensation on their doors: it reduces product visibility, it can lead to mold formation, and it is even possible for it to freeze and seal the door. Refrigerated cabinets normally use anti-sweat resistance heaters to control condensation on their doors, but this has two drawbacks in terms of energy efficiency:

• Part of that heat is released inside the cabinet, increasing the refrigeration load.
• There may be conditions when indoor moisture is not enough for condensation to occur, and the door heater can be turned off safely.

Anti-sweat controls can be an effective energy efficiency measure, making sure the doors of refrigerated cabinets only generate the necessary amount of heat to prevent condensation, but not more. Since these doors emit heat in both directions, this reduces the load on both refrigeration and air conditioning equipment.

Energy Management Systems for HVAC Control

HVAC represents a significant portion of energy expenses at supermarkets, but this also means that the potential for energy efficiency in this area is significant. There are several viable measures to improve the performance of HVAC systems.

• Using speed control for air-handling units can yield significant savings, comparable to those of ECMs in refrigerating systems. The main difference is that the horsepower of these fans is often higher than what ECMs can handle, so variable speed drives with three-phase motors are used instead.
• When the outdoor air is dry, it is possible to use an economizer and meet a part of the AC load with evaporative cooling, reducing the load on compressors and improving energy efficiency.
• HVAC schedules in supermarkets can be controlled by a building management system, making sure these units only operate for the required time to meet their load.

Energy management systems can achieve great synergy with other energy efficiency measures.

For example, there are cases when the energy savings of an LED retrofit at a supermarket can be duplicated when the upgrade is complemented with automation. And the reduced lighting heat output also contributes to a lower cooling load.

Scott Van Kerkhove is the CEO of EnergyWise and writes on issues surrounding energy management, energy efficiency and sustainability.

Find us on Google+  –  Author: Scott Van Kerkhove

LED Lighting Has a Short Payback Period

Even when dealing exclusively with energy efficiency, it is important to plan the order in which different measures will be deployed. In many cases, the best starting point is to upgrade the existing lighting to LED technology because LED lighting has a short payback period.

Before carrying out an energy efficiency or renewable energy project in a building, it is important to determine which measures are viable and the optimal order in which to implement them. For example, if a manufacturing company is considering premium efficiency motors for all of its processes and power generation from biomass, it makes sense to go for the motor upgrade first so that the biomass plant can be sized smaller.

Why LED Lighting is a Great Starting Point for Energy Efficiency?

The advantage of starting with energy efficiency measures that have shorter payback periods is that they reach positive cash flow relatively quickly, and their savings can then be used to help cover the cost of other measures. The payback period of an LED retrofit depends on several factors, but it rarely exceeds four years, and can even be less than one year if project conditions are favorable. The following are some factors that reduce the payback period of LED lighting upgrades:

• Having rebates from local utility companies to reduce the upfront cost.
• Receiving federal grant funding via the REAP Grant for energy efficiency
• Upgrading to LED from an inefficient lighting technology, such as metal halide or T12, yields higher savings than upgrading from more efficient lighting types such as T5.
• Having long operating schedules – for example, a company that works 24 hours a day with multiple shifts will save three times as much energy per month with LED lighting, compared to a company with a normal 8-hour schedule.
• High electricity prices translate into more cash savings per each kilowatt-hour of energy.

LED Lighting Can Provide Air Conditioning and Refrigeration Savings

When estimating the savings of LED lighting, calculations are often based on the direct reduction in lighting power. However, in air-conditioned or refrigerated spaces, there can also be significant indirect savings thanks to the reduced heat footprint of LED fixtures. This effect is minimal in homes and small businesses, but can be significant in large commercial buildings with thousands of fixtures.

• In order to illustrate the concept with an example, assume a large commercial facility has 4000 fluorescent fixtures that consume 90 watts each, for a total of 360 kilowatts.
• If all these fixtures are replaced with an equivalent LED product that only consumes 50 watts, total power consumption is reduced to 200 kilowatts.
• In other words, 160 kilowatts of heat are no longer being released indoors, and the air conditioning system no longer has to handle that cooling load – this is equivalent to slightly more than 45 tons of refrigeration.

Companies with warehouses that have cold-storage areas can also achieve significant cooling savings with LED lighting: unlike the AC systems in most commercial buildings, these cold-storage rooms never stop operating.

If there are plans to upgrade air conditioning systems, carrying out an LED retrofit and improving the building envelope first is highly recommendable: then it will be possible to install a new AC system or energy management and building control system that creates temperature and usage savings.

Concluding Remarks

When an LED lighting retrofit is carried out as part of a broader energy efficiency project, there are two strong reasons to make it the starting point: the payback period is short, and it can provide significant indirect savings in air-conditioned or refrigerated facilities.

There are also emerging technologies that will only be possible with LED lighting, such as visible light communication (VLC), which is much faster than traditional Wi-Fi. This means LED lighting will soon be capable of improving the networking and automation capabilities of buildings, in addition to making them more energy efficient.

Scott Van Kerkhove is the CEO of EnergyWise and writes on issues surrounding energy management, energy efficiency and sustainability.

Find us on Google+  –  Author: Scott Van Kerkhove