Posted in: Features, November/December 2014
To reduce energy use in existing buildings, few systems can have the same impact as lighting and lighting control retrofits. According to the U.S. Department of Energy, buildings consume 39 percent of the total U.S. primary energy. In commercial buildings, 28 percent of the energy use is devoted to lighting, which makes lighting an obvious target for gaining energy efficiencies.
There are a number of ways to reduce energy use but most involve sacrificing something in return. Lighting control strategies actually enrich the building environment by delivering both cost and energy savings while increasing occupant comfort and enhancing productivity. Additional savings can be realized by using wireless control to reduce installation costs and minimize the impact on occupants in the space.
Let’s first look at some simple lighting control strategies that are flexible, scalable, easy-to-install, and often offer payback times of just a few years. One quick tip – individual strategies, such as occupancy/vacancy sensing, can make significant contributions to energy savings by themselves, but the greatest value is realized by layering control strategies, which typically delivers lighting energy savings of up to 60 percent or more.
Each of these strategies can be implemented in conjunction with efficient new sources including a wide variety of LED lamps and fixtures. Be sure to work with a controls manufacturer that has tested many combinations of controls and sources and makes that compatibility information readily available to its customers. Ensuring compatibility between controls and light sources is critical to achieving expected dimming performance.
Digitally addressable fluorescent ballasts and LED drivers allow the lighting in the space to respond to automatic control strategies to achieve maximum lighting efficiencies. In many cases, dimming electric lights also reduces demand on HVAC systems, translating to even lower operating costs.
Basic lighting control strategies can be easily implemented in virtually any size space to deliver immediate lighting energy savings.
1. High-end tuning (sometimes called high-end trim) limits the maximum light output for each fixture, ensuring savings even when the lights are just turned on to “full.” High-end tuning can be implemented with either digital control strategies or by choosing a dimmer that allows the installer or end-user to manually reduce the maximum light level by 10-20 percent. This is an especially effective strategy for two reasons:
2. Occupancy/vacancy sensing automatically turns lights off when a space is vacant. Additional energy savings is achieved by requiring the occupants to manually turn on the lights when they enter (vacancy sensing) or by having the lights turn on to a level less than 100 percent when the occupant enters (partial-on occupancy sensing). Vacancy-only sensors are available for areas where required by local or state code (like California’s Title 24).
3. Daylight harvesting
automatically dims electric lights when enough daylight is present. To ensure maximum savings, daylight sensors communicate light levels to digitally addressable dimming ballasts so the light can be gradually and continuously adjusted to maintain the preferred lighting level in the space without requiring any intervention from the occupants in the space.
4. Personal dimming control
allows individuals to adjust light levels to perfectly suit any task. For example, the occupant may choose to dim the light levels for computer work and raise them for reading, conversations with co-workers, etc. Giving people direct control over their own lights can reduce electricity use while increasing comfort and productivity. Personal dimming can be as simple as replacing a standard switch with a dimmer or can be tailored to the environment with individual,
wireless remote controls that maximize the occupant’s ability to set the lighting to the perfect personal light level.
Consider more advanced lighting control strategies to maximize energy savings by integrating lighting control with other building management systems, automated shades, and even plug load control.
5. Controllable window shading works to reduce glare and heat, which enhances comfort and productivity. The best solutions combine automated shade control with solar-adaptive software
and cloudy-day/shadow sensors that allow the shading software to evaluate and respond to real-time daylight conditions. By using the same software to control electric light and automatic shades, the electric light can be used as a supplement to available daylight, minimizing or eliminating lighting energy use whenever possible.
6. Scheduling will automatically dim or turn lights off at certain times of the day. With scheduling, a facility manager does not have to depend on the last person who leaves a common area of the building to turn off the lights. Scheduling ensures that lighting will automatically dim or turn off at pre-determined times, such as after-hours when the building is no longer occupied, thus saving energy.
7. Demand response/load shedding reduces the overall lighting load at times when electricity costs are the highest. Many utility companies offer incentives to customers who are willing to reduce their electricity use during peak demand periods, i.e. during normal office hours. Lighting control systems are uniquely better suited to load shedding than other energy-saving technologies because they have the ability to respond quickly to requests from the utility and maintain a lower demand for a consistent and extended period of time.
8. Plug load control automatically turns off loads, such as lamps, monitors, heaters, and fans when the occupant leaves the space. These are loads that are frequently and inadvertently left on regardless of space occupancy.
9. HVAC integration controls heating and air conditioning in response to contact closures linked to occupancy sensors and/or time clock control.
What About Wireless?
Each of these strategies can be achieved using wired or wireless control, making energy retrofits easier and more cost effective than ever before. There are several different wireless technologies to choose, so it’s important to do a little investigation before choosing which manufacturer to work with. Look for products that offer long battery life – up to 10 years – to reduce maintenance costs and deliver greatest convenience to the user. Also, choose a technology that promises to operate interference free and, if desired, offers control options from a smartphone or tablet.
Wireless controls can be installed quickly and can often be programmed (and reprogrammed) with just the touch of a button. Even more important, many wireless controls can be easily relocated when space use or tenants change without having to rewire or disrupt workers in the space.
While reducing energy costs is still a primary motivator in most facilities, code compliance is also critical. Many states are adopting newer and more stringent codes, such as California’s Title 24 2013 which includes daylight harvesting requirements. When your clients need to reduce their energy use, look to lighting control for solutions that improve the working and living environment while reducing energy costs.
Brian Donlon is Sales Vice President, North America, for Lutron Electronics, an IEC National Bronze Industry Partner.