Efficient lighting systems save electric energy, require less frequent maintenance and emit better quality light, which can enhance workforce performance. The greatest financial advantage is in energy savings delivered from reduced input wattage and decreased hours of operation. Strategies to reduce energy consumption range from lamp replacement to building design.
Retrofitting existing facilities
Selecting a lighting system isn’t always an easy decision. Facility managers must first consider the appropriate design for the area to be illuminated and the light levels recommended by the Illuminating Engineering Society (IES), and then select an efficient light source and fixture.
The high indoor spaces typical of warehouses and factories have traditionally been dominated by high-intensity discharge (HID) light sources. More recently, improved fluorescent lamps and high-intensity fluorescent fixtures have made fluorescent lighting the more cost-effective alternative. Additionally, fluorescent lights are easier to control using occupancy sensors. Motion sensors make particular sense in areas with intermittent occupancy, such as warehouses.
There’s more to upgrading a lighting system than just swapping out a lamp. Lighting efficiency depends not only on the lamp but the fixture itself. “A fluorescent lamp at 95 initial lumens per watt is very efficient unless the fixture only allows 50% of the light out of it,” according to Peter Morante, director of energy programs at The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute.
If fluorescent lighting is preferred, T8 lamps with electronic ballasts are more efficient than T12 lamps with magnetic ballasts, and they have more light output. They also have a longer life and are subject to less lumen depreciation. “Changeovers pay for themselves in a very reasonable period of time,” says Morante. “Some utilities also offer rebates.”
Daylighting for new facilities
Morante would love to see plants go back to using daylighting in new factories. Daylighting minimizes the need for electric light by introducing natural light into the building. Designed correctly, this technique can reduce electricity consumption for lighting and cooling, reduce peak energy loads, reduce the number of installed lighting fixtures and reduce lamp replacement and maintenance costs.
“Daylighting can serve at least 50% of the lighting needs for a single-shift operation,” says Morante. “The percentage goes down as shifts are worked into the night, but the savings are still impressive. There are new ways to control daylight and eliminate glare that make this an increasingly practical option.”
Daylighting works best when integrated into a building’s original architectural, engineering and landscape design, rather than offered as an option afterward. Because daylighting decreases lighting loads, cooling needs can be reduced by as much as 20%, and HVAC requirements can be planned accordingly. If daylighting is added later, it’s unlikely the HVAC equipment will be downsized, and the total savings potential may never be realized.
Imminent innovations:
Electricity dimming ballasts use less energy than standard ballasts but are four to five times more expensive. Because smooth dimming is less important in industrial environments, Morante recommends incorporating standard ballasts with photosensors to detect the light level on the work surface instead of using the IES recommended lighting level. The sensor would dim or switch off all or part of a fixture in proportion to the amount of available daylight. LRC is in the advanced stages of developing a self-commissioning photosensor that allows digital dimming and switching, and supports automatic self-calibration.
Replacing instant start ballasts with load shedding ballasts can reduce the demand from light load by one-third –- without affecting lamp life. The LRC is in the demo phase of a new technology that allows a power line carrier to signal load shedding ballasts to dim. The ballasts also can be configured to receive automatic signals from energy management systems. When the signal isn’t present, the fixture automatically reverts to regular light.
Putting it together
Imagine having the ability to monitor and control all fixtures, switches, occupant sensors, light sensors, power meters, temperature sensors, and motorized blinds from a central point. The Lighting Research Group at Lawrence Berkeley National Laboratory is leveraging advances in digital networking technology to integrate building system controls from various manufacturers. The Integrated Building Environment Communications System (IBECS) is intended to provide economical building system control through the Internet, and give occupants supervised control over their own personal comfort and lighting requirements.
E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at [email protected].