In the past 100 years, the science and technology of illumination has taken us from candlepower to solar power. Correspondingly, lighting and lighting-control technologies have evolved. We’re affected—both physically and emotionally—by the science of artificially lighting the spaces where we live and work. The quantity and quality of light we require on a daily basis depends on many different parameters, including individual preferences, perceptions, necessities, interpretations and subjectivity. Light fixtures (luminaires) and light sources (lamps) are selected based on practicability, energy efficiency and aesthetics, among other criteria.

Lighting matters: At Indian Wells Town Hall, the conversion to Cree LR6 LED lights reduced electricity consumption by 80 percent. photos courtesy of Essential Systems Engineering

As a result of the Energy Security and Independence Act of 2007, increases in the efficiency of our current light sources are required by 2020. In response, the lighting industry has produced several alternative products with improved efficiencies, but unfortunately, these products have met with limited acceptance by the public and some lighting designers.

As the old Bob Dylan song goes, “For the times, they are a-changin’.” Directed marketing and current trends towards sustainability and “green” living are converting the old paradigms into new approaches.

For example, compact fluorescent lamps (CFLs)—despite initial problems with poor quality and disposal issues due to mercury content—are starting to replace the highly inefficient incandescent lamps in general lighting applications, and they are becoming more acceptable to the public. Linear fluorescent tubes have evolved from T-12s to T-8s and now T-5s, T-4s and T-2 minis. Each is a more compact, improved version of the other, in terms of luminous efficacy, which is the amount of light produced compared to the power consumed.

More recently, fluorescent electrode-less induction lamps have entered the market. They provide an extremely long life, vibration resistance and high efficacies. But at this point in time, these lamps tend to be very costly, and they are used primarily in specialized applications, such as roadway, railroad lighting and locations that are difficult to reach and maintain.

The current trend towards lighting future commercial and residential buildings is solid-state lighting or light-emitting diodes (LEDs). The latter offer a potential energy savings over incandescent that could have a significant impact on limiting the energy normally consumed by current, conventional lighting systems. Another benefit is the increased longevity of the LEDs—50,000 to 100,000 hours—which could potentially reduce landfill waste and other environmental concerns. (By comparison, a typical A-19 incandescent light bulb average life span is 3,500 hours and a 4-foot T-12 fluorescent lamp averages 20,000 hours.) Lighting manufacturers are currently producing LED replacement lamps for incandescent lamps in recessed downlights, halogen MR-16 lamps, street and area lights and fluorescent tubes. They also are introducing new specifically designed, “purpose-driven” LED luminaries, such as pendants; recessed downlights; cylinders; landscape accent and floods; and street, garage and display lighting, to name a few. Furthermore, LEDs are extremely tolerant of cold temperatures and have good color characteristics. Other benefits include instant on/off, vibration resistance, dimming, programmed color changes and no mercury.

Other emerging artificial lighting technologies that could develop into commercial and residential applications are two-photon phosphor fluorescents, fiber optics, sulfur lamps and electroluminescence, among others. These technologies have been years in the making and have modest success in specialized lighting applications. However, with the current emphasis on increased luminaire efficiencies and lamp efficacies, some designers and consumers are considering their advantages now.

Before and after: At N.C. State University, the parking deck was lit by the dingy orange glow of highpressure sodium fixtures (left); the new LEDs brighten the space and save 27 percent in energy costs.

Using daylighting techniques to more effectively and naturally light spaces deep within the buildings—by utilizing specialized glazing, light shelves, sun tubes and skylights—is the most efficient technology for lighting. If properly designed, daylighting methods and techniques can significantly reduce the amount of energy consumed by artificial lighting and decrease the overall energy use required for cooling the building.

Once the most efficient product has been chosen, the most important technique is controlling how much the lights are used. Automatic lighting controls can lead to an estimated 50 percent reduction in lighting energy. Commercial buildings are incorporating Direct Digital Control (DDC) systems that can be programmed through the Energy Management System (EMS) to reduce lighting energy requirements through the use of occupancy sensors, photocells and timers.

When considering cost, a general rule of thumb is that the installed cost of fluorescent over incandescent can range upward from 15 to 50 percent for an individual fixture and 10 to 30 percent overall on a per-project basis, depending on the number of fixtures installed. In contrast, at current price levels, LED fixtures cost 300 to 500 percent more than incandescent. Payback periods can range from three to 10 years depending on the cost of the installed fixtures, hours operated per year, annual maintenance and operational costs and the local cost of energy.

In the future, the art and science of illuminating living/working spaces will be done with energy efficiency in mind. Lighting will become automatic and regulated. Buildings will be oriented and configured to take advantage of natural sunlight. Lamps and luminaires will require less maintenance and become recyclable. Technology will develop lighting that is cooler to operate, with more flexibility to personal preferences. As energy costs increase, owners will recognize marketable benefits and increased profits.

Dale F. Reynolds, PE, LEED AP, BSEE N.C. State, is vice president of Essential Systems Engineering, PA and has provided design and consulting services for building lighting and electrical distribution systems for 10 years.