Lighting accounts for about 20 percent of the total energy usage worldwide, approximately 1,944 terawatt hours. Because lighting is relatively simple to upgrade, the trend in recent years is to switch to LEDs. Doing so greatly improves energy efficiency, mitigating global warming’s impact and reducing energy dependence on other countries.
Globally, LEDs make up less than 10 percent of lighting systems, according to the U.S. Department of Energy Solid-State Lighting R&D Plan, published in June. But the DOE forecasts LEDs to become the predominant source of illumination—for indoor and outdoor spaces—over the next decade. The DOE’s “Energy Savings Forecast of Solid-State Lighting in General Illumination Applications,” released in September, predicts that by 2035, LED lamps and luminaires will be used in 86 percent of all lighting products in the United States, compared with 6 percent in 2015. That translates into an annual savings of 1,495 terawatt hours over traditional lighting systems, nearly the total annual energy consumed by 45 million U.S. homes today. This adds up to nearly $52 billion in energy costs savings.
INCREASING EFFICIENCY AND SAVINGS
The evolution of LEDs as a source of white light has progressed dramatically in the last two decades, especially in terms of efficacy, or how well a light source produces visible light, measured in output lumens/input watts. The increase in efficacy has been achieved primarily through advances in LED chip technology, and is helping to drive LED adoption. LED products are also more affordable than incandescent bulbs over their life cycle, because their power requirements are lower and the bulbs themselves can last more than 10 years, compared with today’s incandescent bulbs they are replacing, which often last up to a year or so.
Because LEDs are semiconductor devices, integrating additional electronics in the bulbs, such as occupancy and daylight sensors connected to a network interface, provides the bulbs with new functions. This design enables, for example, the automatic dimming of lights when there’s sufficient natural light in the room, and it senses the presence of people in a room and adjusts overhead lighting accordingly. These capabilities not only provide the optimal amount of lighting throughout a building but also save energy and money.
LEDs also help lower electricity costs in exterior lighting systems. Those used in parking lots, garages, and walkways can be configured to automatically dim or turn lights off when sensors detect an unoccupied area, and much faster than today’s systems. This type of automation is an especially attractive cost-saving option for cities. About half of a city’s monthly electricity budget is devoted to keeping the streetlights on.
Moreover, LEDs serve as the foundation of networked lighting systems that also provide information to other systems connected to an internal building management network. For example, the heating, ventilation, and air conditioning systems could be alerted that certain parts of the building are empty, and could adjust the temperature or shut off the air conditioning entirely.
LEDs also are changing the way architects and interior designers use lighting. Because the bulbs are smaller and weigh less than traditional ones, LED products allow for greater flexibility and creativity in lighting venues such as concert halls, museums, and retail stores, where aesthetics are especially important, while reducing energy usage.
LEDs in malls can motivate people to linger in a store longer and therefore boost sales. The ability to adjust from warmer to cooler shades of white, referred to as color tuning—along with precise light distribution—allows the retailer to create an inviting space that could appeal to the shopper’s sense of comfort, safety, and familiarity. In the home, LED lights could automatically mimic a bright, sunny day even if it is gloomy out.
Such lighting systems will allow us to adjust our environments in ways that older technologies never could.
IEEE Senior Member Yoelit Hiebert is a senior engineer at Leidos, in St. Louis, where she is an expert on LED energy efficiency programs and policy development. She is also past chair of the IEEE St. Louis Section and a regular contributor for The Institute on LED technology.