Lighting - Energy Consumption

Energy Consumption

Artificial lighting consumes a significant part of all electrical energy consumed worldwide. In homes and offices from 20 to 50 percent of total energy consumed is due to lighting. Most importantly, for some buildings over 90 percent of lighting energy consumed can be an unnecessary expense through over-illumination. The cost of that lighting can be substantial. A single 100 W light bulb used just 6 hours a day can cost over $25 per year to use (.12/kWh). According to the UN Environment Programme/Global Environment Facility en.lighten initiative, by simply replacing all incandescent lamps with energy efficient compact fluorescent lamps globally, 409 TWh per year would be saved, which is approximately 2.5% of global electricity consumption. This is equivalent to the combined yearly electricity consumption of the United Kingdom and Denmark.. Thus lighting represents a critical component of energy use today, especially in large office buildings where there are many alternatives for energy usage in lighting. There are several strategies available to minimize energy requirements in any building:

• Specification of illumination requirements for each given use area.
• Analysis of lighting quality to ensure that adverse components of lighting (for example, glare or incorrect color spectrum) are not biasing the design.
• Integration of space planning and interior architecture (including choice of interior surfaces and room geometries) to lighting design.
• Design of time of day use that does not expend unnecessary energy.
• Selection of fixture and lamp types that reflect best available technology for energy conservation.
• Training of building occupants to use lighting equipment in most efficient manner.
• Maintenance of lighting systems to minimize energy wastage.
• Use of natural light - some big box stores are being built (ca 2006 on) with numerous plastic bubble skylights, in many cases completely obviating the need for interior artificial lighting for many hours of the day.
• Load shedding can help reduce the power requested by individuals to the main power supply. Load shedding can be done on an individual level, at a building level, or even at a regional level.

Specification of illumination requirements is the basic concept of deciding how much illumination is required for a given task. Clearly, much less light is required to illuminate a hallway or bathroom compared to that needed for a word processing work station. Generally speaking, the energy expended is proportional to the design illumination level. For example, a lighting level of 80 footcandles might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 40 footcandles could be selected for building hallways. If the hallway standard simply emulates the conference room needs, then twice the amount of energy will be consumed as is needed for hallways. Unfortunately, most of the lighting standards even today have been specified by industrial groups who manufacture and sell lighting, so that a historical commercial bias exists in designing most building lighting, especially for office and industrial settings.