Principles of Environmental Chemistry by James E. Girard

Author:James E. Girard
Language: eng
Format: epub
Publisher: Jones & Bartlett Publishers, Inc.
Published: 2013-06-15T16:00:00+00:00

Energy-Efficient Lighting

According to the last Residential Energy Consumption Survey, U.S. households have, on average, 5.4 indoor lights that are on 1 or more hours per day and 8.9 lights that are on 15 minutes or more per day. They use 940 kilowatt-hours of electricity for lighting and spend $83 on electricity for lighting each year. U.S. households’ expenditures on electricity for lighting represent approximately 10% of their total electric bill. Most of the lights used for residential purposes are inefficient incandescent bulbs. Changing to more efficient lighting would result in significant reductions in electrical demand.

In an incandescent lamp, electric current heats a metal filament in the bulb, making it glow white hot and give off light. The problem is that only 10% of the electricity is used to make light—the rest ends up as heat. In the European Union, a ban on the sale of certain incandescent bulbs began in 2009. In the United States, the Energy Independence and Security Act of 2007 established efficiency standards for lighting that would start with a ban on the sale of 100-W incandescent bulbs. The new standards were originally planned to take effect in January 2012, but when the U.S. House of Representatives passed the final 2012 budget legislation, it delayed their implementation until October 2012.

Compact fluorescent bulbs, and LED lights, are much more efficient at turning electricity into light. A typical compact fluorescent is a one-piece light that holds both the fluorescent tube and the electronic ballast that controls the electric current. It is designed to screw easily into a standard incandescent fixture without modification and can be used outdoors as long as it is protected from the weather; thus it is suitable for use in barns and storage sheds. In very cold weather, a slight delay occurs before the fluorescent reaches full brightness.

The compact fluorescent lights are more expensive than standard incandescent lights, but if they are in use for more than 6 hours per day, they will pay for themselves within 2 years. Because they last eight to ten times longer than incandescent bulbs, there is a further savings in the labor needed to replace the lights. Compact fluorescent bulbs need approximately one third of the power required by incandescent bulbs to emit the same amount of light.

Larger incandescent fixtures, such as pole lights or floodlights, should be replaced with more efficient lights such as sodium or metal halide lamps. These are designed specifically to cast a lot of light over a wide area but with significantly less energy consumption. These lights, which require unique fixtures, are typically seen in streetlights, modern warehouses, and large stores.

The environmental benefits of making the change are considerable. Replacing a 75-W incandescent light with a 20-W compact fluorescent saves approximately 550 kilowatt-hours over its lifetime. If the electricity comes from a coal-fired generating plant, the savings represents approximately 1,300 pounds of carbon dioxide and 20 pounds of sulfur dioxide that would have otherwise been released into the atmosphere.

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