Daylighting controls, Electronics and office equipment, Fans, High-bay lighting, HVAC distribution systems, Industrial and manufacturing, LEDs, Light sensing and switching, Lighting, Metal halide lighting, Pumps and motors, Refrigeration, Roofs, Variable-frequency drives (VFDs), Warehousing and storage
Nonrefrigerated warehouses in the US use an average of 6.1 kilowatt-hours (kWh) of electricity and 13,400 Btu of natural gas per square foot annually. Lighting and space heating account for approximately 76% of total energy use (figure 1), making these systems the best targets for energy savings. In comparison, refrigerated warehouses use much more electricity, consuming an average of 24.9 kWh of electricity and 9,200 Btu of natural gas per square foot per year.
Average energy-use data
Energy costs typically account for 15% of a warehouse’s operating budget. To better manage your building’s energy costs, it helps to understand how utilities calculate these charges. Most utilities bill commercial buildings for natural gas based on the amount of energy delivered. On the other hand, utilities charge for electricity based on consumption and demand. The consumption component of the bill is the amount of electricity in kWh that the building consumes during a month. The demand component is the peak demand in kilowatts occurring within the month, or for some utilities, during the previous 12 months (figure 2). Demand charges range from a few dollars per kilowatt-month to nearly $20 per kilowatt-month.
Because energy costs can make up a considerable percentage of your expenses, try to reduce peak demand whenever possible. As you consider the following recommendations to manage energy costs, keep in mind how each one will affect both your consumption and your demand.
Turn things off
Turning off equipment when not in use is the first strategy any energy auditor will recommend. For facilities that don’t operate constantly, one way to identify energy-efficiency opportunities is to walk through the facility after hours. Much of the equipment employees leave on overnight in an empty building is a good candidate for saving energy by switching it off.
Computers and office equipmentModern warehouses use a lot of IT equipment. The typical desktop computer, monitor, and shared printer together draw about 120 watts. If left on overnight and on weekends, a single computer setup could add $30 or more to your energy bill each year. Most modern IT equipment has the ability to enter a low-power sleep mode after a period of inactivity, but users don’t always enable this feature. Desktop computer manufacturers have started enabling power-saving options by default. If your facility has networked computers, you may be able to control power settings at the server level by installing parameters known as group policy objects (GPOs). The US Environmental Protection Agency offers a free online tool, EZ GPO, to help network administrators create GPOs. In addition, if your system has multiple types of hardware and operating systems on the same network it may be worthwhile to purchase power management software. ENERGY STAR lists several of these products on its web page, Activating Power Management: Commercial Software Packages.
LightsTurn off lights when they’re not in use. Occupancy sensors and timers can help, but a less expensive alternative is to educate and motivate employees to turn off lights at the end of the day. Sections of your facility may have more lighting than necessary, so removing or disabling some fixtures (known as delamping) in those areas could be an easy energy-saving option.
Controlling outside-air intakeMany warehouses have rooftop units for heating, ventilation, and cooling. Some are equipped with exhaust fans that bring in outside air for ventilation. These should be set to run only when the spaces are occupied.
Perform regular maintenance
MaintenanceMaintain your warehouse’s HVAC and refrigeration systems and change filters regularly to improve efficiency and save energy.
SealsOne major source of energy waste is air infiltration through gaps around doors on the loading dock and into refrigerated spaces. To save energy, regularly check for and repair gaps in door seals and make sure employees keep the doors closed.
Heating and cooling temperature setpointsReview temperature setpoints each season in nonrefrigerated warehouses and make adjustments using programmable thermostats. For refrigerated warehouses, make sure that the setpoints comply with storage requirements. Where possible, divide the space into multiple zones so each one can be adjusted separately.
Although the actions described in this section require more involvement or investment, they can dramatically increase the efficiency of your warehouse.
Install an enterprise energy management system
It’s impossible to optimize what you don’t measure. An enterprise energy management (EEM) system makes it easy to track your facility’s use of electricity, water, compressed air, gas, and steam. An EEM system combines data-acquisition hardware and software to offer a broad understanding of how your facility uses energy. The data an EEM system collects allows energy managers to track costs, identify anomalies, and automate participation in demand-response events. You can also use an EEM system to benchmark a variety of parameters ranging from outside-air temperature to the quantity of packages processed or stored. You can use these insights on performance to compare one facility to another or to look at how performance varies over time. An EEM system can also help you determine the actual payback periods of implemented efficiency measures.
Upgrade to more-efficient lighting
Lighting is one of the largest energy consumers in a warehouse, so it can often be the best opportunity for finding savings. Look for lighting savings in two areas: using the most appropriate lighting technology and controlling it effectively.
In a warehouse with old probe-start metal-halide lamps, you can save energy by installing newer, pulse-start lamps. Go a step further by choosing fluorescent lamps or LEDs. High-intensity discharge (HID) lamps (high-pressure sodium and metal halide) were the mainstays of high-bay lighting for years, but technological advances in performance and color quality have made LEDs the most efficient, cost-effective choice in many cases. LEDs offer other advantages, including longer life, better light distribution patterns, better dimming options, better color rendition, and more controllability. LEDs also perform better in cold conditions than other types of lamps.
A large warehouse might have the lights on throughout the entire facility, even if employees occupy only a small portion at any given time. In these cases, you can save a substantial amount of energy by turning lights on only when needed. You can install occupancy sensors and timers, but they need to be combined with lighting systems that are effective when controlled. For example, HID light sources have long start-up and restart times. They can’t be shut off based on occupancy, but they can be dimmed to about 50% of initial power. Fluorescent lighting is a better choice for controllability due to its faster start-up time, but frequent on-off switching can reduce its life span. LEDs are the best choice to control. They react instantly and suffer no degradation of life with frequent switching. And LED prices have fallen drastically in recent years.
In some warehouses, skylights and daylighting controls, which take advantage of natural lighting, can be a big energy-saver. Rather than relying on employees to remember to turn lights off, these systems automatically turn interior and exterior building lights on and off based on a preset schedule.
Because they operate for long hours and have low occupancy, warehouses are also good candidates for networked or advanced lighting controls, which use multiple strategies to reduce energy consumption. Networked lighting controls can save 70% to 80% of energy consumed in warehouses. In addition to indoor lighting, upgrading outdoor lighting to LEDs will result in more than 30% savings.
Although refrigeration systems in warehouses are often specialized for each facility’s unique needs, consider adopting these technologies to save energy:
- Moderately oversized evaporative condensers controlled by variable-frequency drives (VFDs) can be highly effective in refrigeration units.
- Properly sized evaporator coils cooled with VFD-controlled fans can optimize the energy performance of refrigeration units.
- Proper insulation and efficient compressor motors are almost always cost-effective efficiency investments.
- Controllers that initiate defrost cycles based on actual ice buildup are more effective than those that run on timers.
- Waste heat from condenser coils can be recovered and used for domestic water heating.
Install a cool roof
In warmer climates where space cooling represents a large portion of energy use, consider installing a cool roof. These products have a surface coating that reflects solar radiation, reduces the need for cooling, and reduces temperatures near the ceilings in unconditioned warehouses. A roof renovation could also be a good time to add insulation.
Minimize air infiltration
One major source of energy loss for warehouses is air infiltration through open loading docks and doors. Similarly, refrigerated areas within warehouses lose a lot of energy when doors are left open to allow forklifts to come and go. These losses can be minimized by making sure that doors are closed and sealed whenever possible. But this can be easier said than done. Employees working on loading docks find it tedious to open and close doors several times a shift, so they save time by propping the doors open. One solution is to install specially designed doors that open and close quickly (but safely) and encourage employees to use the doors whenever possible. In doorways with so much traffic that even rapidly opening warehouse doors would be too slow, adding strip curtains is an inexpensive way to reduce energy losses.
Use radiant heaters
One challenge with efficiently heating a warehouse is the wide range of functions and spaces in the facility. If a large warehouse has a small section used as an office, people working there will expect a reasonable indoor room temperature year-round. The same applies to individuals working on a loading dock on a cold winter day. Maintaining a comfortable temperature throughout the entire large—and mostly unoccupied—space can be costly and inefficient. In these situations, you can mount gas or electric radiant heaters (also known as beam radiant heaters) above the areas that require heat, keeping workers comfortable even with the building air as low as 40° Fahrenheit (F) (4° Celsius [C]). These devices provide warmth to people within line-of-sight, but they aren’t designed to raise the space’s overall air temperature.
Install destratification or high-volume, low-speed ceiling fans
Improving air circulation with high-volume, low-speed (HVLS) fans, such as those described on Washington State University’s High-Volume, Low-Speed Fans web page, can be an effective way to save energy. They provide better air circulation and greater energy efficiency compared with multiple smaller, high-velocity fans. In air-conditioned spaces, HVLS fans save energy by improving air flow, which allows you to raise the temperature in your facility by as much as 4.5°F (2.5°C) while still maintaining occupant comfort. If your facility is heated, warmer air will naturally stagnate near the ceiling. HVLS fans will circulate that warm air vertically.
Use electric forklifts
Diesel- or propane-fueled forklifts require extra ventilation in your facility, which adds to the HVAC load in conditioned spaces and makes the forklifts less cost-effective. Electric forklifts have higher initial costs (capital and installation) but lower energy and total operating costs, so the total life-cycle costs are comparable. One unexpected cost with electric forklifts is increased utility demand charges, but you can avoid these by using a timer to charge the forklift batteries during off-peak hours. Another option is to use fuel cell–powered lift trucks, which use hydrogen to create electricity.
Using variable-frequency drives, which adjust motor speed to suit production needs, can save energy in some applications. They’re less likely to be cost-effective on conveyors—where the power requirement is linear—than on pump and fan systems, for which the power requirement increases exponentially with the motor speed.
Install high-efficiency motors
Some warehouses use electric motors for applications like distribution systems. High-efficiency motors can pay for themselves in electricity savings, and diagnostic systems identify when motors need maintenance. Electronic motor starters have built-in programming that communicates with a facility’s EEM system and notifies facility managers if a motor isn’t performing as expected.
Install HVAC controls
Consider installing HVAC controls that monitor indoor conditions using sensors and run HVAC components when required. Economizer controls regulate outside-air intake based on temperature. If your warehouse uses packaged rooftop units, advanced rooftop controllers can improve functionality and save energy. The US Department of Energy’s Advanced Rooftop Unit Campaign mentions that these controls can reduce energy needs by 30% to 50%. Energy-saving features can include variable-speed or multispeed supply-fan control, demand-controlled ventilation, and improved economizer control. These controls can also facilitate demand response, remote monitoring, and fault detection and diagnostics.
Participate in demand-response events
Warehouse owners can participate in utility demand-response events to save energy and perhaps even receive credit on utility bills. Some strategies include:
- Turning off or dimming lights
- Adjusting temperature setpoints in nonessential areas to reduce dependence on HVAC
- Precharging batteries and switching off charging stations
- Cooling refrigerated spaces before the event and shutting down compressors
- Temporarily disabling electric defrost systems
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