If high-intensity discharge (HID) light fixtures are still providing your warehouse lighting, a retrofit or replacement could provide multiple benefits. They include lower energy consumption, lower utility bills, reduced maintenance costs, and better quality lighting. And better lighting will, in turn, improve aesthetics, safety, security and quality control. Old HID sources typically include metal halide and high pressure sodium fixtures.
Plan out your warehouse lighting retrofit
Finding an effective warehouse lighting solution requires careful planning. There are a number of new industrial lighting technologies to choose from, but the latest and greatest might not meet the specific warehouse lighting requirements. A lot depends on how various spaces in the warehouse are laid out and what kind of tasks take place there. The challenge is to choose lights, ballasts and fixtures that provide the lumens, life, color and other criteria that meet your performance objectives while still providing energy savings and an acceptable payback on your investment.
Until recently, metal halide or highi pressure sodium high bays were the standard luminaires for open warehouse lighting, but they present a number of challenges. Because they have a long re-strike time, they can’t easily be switched off when areas are temporarily unoccupied. They are fragile when compared to newer technologies and need frequent replacing. That entails bringing in a lift, which is costly and disruptive to a warehouse’s workflow. HIDs are also much more energy-hungry than newer technology.
Fluorescent Warehouse Lighting
The most common alternative at this time is pendant fixtures with T8 or T5 fluorescent lamps, which provide better energy efficiency and a better color-rendering index. They work well with occupancy sensors and require less maintenance. They maintain lumens for a longer period of time than HID lights, and are less likely to flicker and buzz. The T5 high-output lamp is suitable for ceiling heights greater than 15 feet; T8s may be more appropriate for ceilings lower than that. For instance, a 400-watt metal halide can be replaced by a four-lamp T5, which consumes roughly 232 watts without any reduction in light levels.
Induction Warehouse Lighting
Another alternative for a warehouse lighting retrofit/replacement is induction. The technology for these industrial lamps is not new. Basically, they generate light via a gas discharge through simple magnetism. Fluorescents, in contrast, use electrodes to strike the arc and initiate the flow of current through the lamp. Each time voltage is supplied by the ballast and the arc is struck, the electrodes degrade a little, eventually causing the lamp to fail. Since induction lamps do not have electrodes or filaments, they can last up to up to 100,000 hours, with the lamp producing 70% of its light output at 60,000 hours.
Though not as efficient as fluorescents, induction lights generate more lumens per watt compared to 400-watt and 2500-watt metal halides and they start and operate at extremely low temperatures, providing an advantage over fluorescents in cold storage areas. They are also available in higher wattages than T5 lamps. With T5’s, you have to use multiple tubes together to increase the total lumen output, thereby increasing your materials cost.
LED Warehouse Lighting
A third alternative is LED warehouse lighting. LED’s use much smaller watts of power than other lights and do not heat up when they are on. They are resistant to damage and basically maintenance-free. There has been a great deal of improvement in their color rendering and brightness in recent years, and they are environmentally friendly. A 400-watt metal halide can be replaced by an LED consuming a little over 200 watts, while a 250-watt metal halide can be replaced by an 80-watt LED. And both will maintain over 90 percent of their output at 60,000 hours.
On the downside, the cost of LED high bays is still pretty steep. This could result in an unacceptably long payback. One redeeming factor might be the extremely long life of an LED fixture, which translates into significant reductions in maintenance costs, especially in hard-to-access areas. Another might be the generous rebates that are available for LEDs from some utilities. For example, PSE&G in New Jersey is currently offering a $150 rebate per fixture for high-bay and low-bay LEDs. Your equipment manufacturer or distributor can tell you what rebates are available from your utility company.
Warehouse Lighting Controls
In addition to specifying luminaires, a warehouse lighting design may also include some type of control systems. One type reduces lighting when areas are unoccupied, and can work in several different ways. Switching systems turn lights on and off by connecting or removing lighting sources from the power supply. This type of system is simple, cost-effective, and useful in areas where an abrupt change in light levels will not be frequent or noticeable to occupants. Dimming systems adjust light output and power input over a specified range. A third option is “step-switching.” This is where multiple lamps in a single light fixture can be switched on and off independent of each other. This allows for a couple of steps between full and zero light output.
Daylight harvesting increases efficiency
Another type of control system to consider is daylight harvesting, which involves installing photosensors near windows and skylights. Daylighting control systems dim or shut off lights when there is a sufficient amount of ambient light available.
Determining the energy savings potential of any control strategy depends on a building’s space and lighting characteristics. But properly installed and adjusted, most control systems reliably save a substantial amount of energy.
Obviously, in addition to meeting your lighting needs, your warehouse lighting retrofit must also make sense economically. If your lights are obsolete, but the utility rates in your area are so low that the energy savings from a retrofit would be negligible, you might be looking at a 15- or 20-year payback on your investment. However, if light levels are so poor that they are adversely impacting the work environment, retrofitting or replacing the lights will still make sense if viewed as an upgrade as opposed to an energy-savings project.
To summarize, these are the steps that will lead to an effective commercial warehouse lighting project:
- Determine the application needs based on what makes the warehouse run smoothly and efficiently
- Evaluate specific conditions – dirt, temperature concerns, space characteristics, tasks taking place in those spaces, your ability to service fixtures and lamps
- Consult with the manufacturer or distributor to find the fixtures that best meet those needs and conditions as well as your payback criteria – take into account all available utility rebates
- Determine how controls can further impact performance and energy savings