Saving energy with smart lighting
One of the best ways to save money on an electric bill is to reduce the amount of energy used in a facility, either through the use of more energy-efficient devices or through intelligent building-control systems. While specific energy-efficient devices directly cut costs, intelligent building controls leverage new or existing technology to reduce energy consumption through advanced load-management strategies.
Three main load types dominate electric use in commercial facilities: lighting, HVAC, and power plug loads (from office devices and computers). Combined, these three represent almost 85% of all electric energy consumed by commercial customers. According to the U.S. Energy Information Administration, 39% of commercial-building energy is used for lighting, 28% for HVAC, and 33% is used for computers, office devices, refrigeration, and other electrical equipment.
This first part will explore ways to save money by specifying energy-efficient lighting options.
Saving energy with smarting lighting: LEDs
LED lighting fixtures are increasingly common in commercial and industrial applications. They function by passing dc voltage and current through a P-N junction in a semiconductor material. When the turn-on threshold is passed in the device, light is emitted at a frequency and color based on the band-gap of the semiconductor used. The LED is housed within a reflective cap, and can be mounted in any plastic housing that fits the application. Uses include surface-mount indicators for printed circuit boards to fully housed commercial lighting fixtures.
Estimated opportunity: Lighting loads in commercial facilities represent almost 40% of the total load. A typical commercial facility can have hundreds or thousands of lighting fixtures, all of which consume an amount of power based on the type of luminous device used. When compared with traditional incandescent, halogen incandescent, or fluorescent lighting systems, LED lighting provides dramatic savings in energy and maintenance.
Consider a single, traditional incandescent lamp of 100 W, which produces approximately 1,600 lumens. If this light were left on for 6 h every day for a year, the lamp would annually consume:
100 W x 365 days x 6 h/day = 219 kWh
Almost 90% of the energy of incandescent lamps is lost in the form of heat; only a small fraction goes to producing light.
Return on investment (ROI): With a combination of direct energy savings and fractional maintenance costs, LED lighting fixtures are attractive and economical.
If a given facility has 100 luminary units, at 12 cents/kWh, 100 units of the 1,600-lumen LED fixture will cost $528/yr to operate. That is $72 less than the fluorescent fixture, $1,488 less than the halogen incandescent, and $2,100 less than the traditional incandescent annually. The traditional incandescent lamp costs roughly $4 while the LED costs $40. At 10 times the expense, factoring in only the energy savings, the payback period for the cost of the LED fixtures is just 2 yr.
LED fixtures have a lifetime of approximately 50,000 h, compared to roughly 2,000 h for incandescent lamps and 10,000 h for fluorescent lamps. When an LED reaches end-of-life, it simply becomes dimmer, rather than “burning out” like a traditional lamp. These differences drastically reduce maintenance costs—spanning both materials and labor—for commercial facilities.
Advanced lighting control systems are also increasingly prevalent. Energy-efficient control solutions include:
- Occupancy/vacancy sensors to ensure lights are not in use when rooms are empty
- Daylight harvesting to employ natural lighting to minimize artificial lighting needs
- Personal dimming to allow individuals the option to directly control the lighting in a room or space
- Plug load control to ensure devices are not powered when they are not in use
- Lighting control circuit breakers to reduce waste via intelligent, building-wide control systems.
Estimated opportunity: Lighting controls save energy by ensuring lights are off when they are not in use or reducing the amount of power being consumed to light a given space.
ROI: Energy savings from lighting controls are dependent on the specific applications and site utilization rates. If a room is used 100% of the time, occupancy sensors will not reduce energy use. However, at 50% usage, significant energy and monetary cost will be saved. Selecting the right technology for your application is key. A 1- to 5-yr ROI is typical.
Daniel J. Carnovale is a senior member of the IEEE and the manager of Eaton’s Power Systems Experience Center (PSEC), where he develops and teaches technical seminars on power systems and power-system analysis and conducts power-quality site investigations for commercial, industrial, and utility power systems. Ansel Barchowsky is a doctoral student in electrical engineering at the University of Pittsburgh, a student member of the IEEE Power Engineering Society and IEEE Power Electronic Society, and a design consultant for Eaton’s PSEC. Brianna Groden is an engineer at Eaton’s PSEC, responsible for teaching power-quality and power-distribution topics, running demonstrations, and designing and managing the installation of new demonstration projects.