Over-illumination

An office building is illuminated by high pressure sodium (HPS) lamps shining upward, of which much light goes into the sky and neighboring apartment blocks and causes light pollution, in Nijmegen, the Netherlands. A satellite image of Earth at night. A composite image of the Earth at night in 1994–95. Over-illumination is the excessive use of light. Specifically within the United States, over-illumination is responsible for approximately two million barrels of oil per day in energy wasted. This is based upon U.S. consumption of equivalent of 50 million barrels per day (7,900,000 m3/d) of petroleum.[11] It is further noted in the same U.S. Department of Energy source that over 30% of all energy is consumed by commercial, industrial and residential sectors. Energy audits of existing buildings demonstrate that the lighting component of residential, commercial and industrial uses consumes about 20–40% of those land uses, variable with region and land use. (Residential use lighting consumes only 10–30% of the energy bill while commercial buildings major use is lighting.[12]) Thus lighting energy accounts for about four or five million barrels of oil (equivalent) per day. Again energy audit data demonstrates that about 30–60% of energy consumed in lighting is unneeded or gratuitous.[13] An alternative calculation starts with the fact that commercial building lighting consumes in excess of 81.68 terawatts (1999 data) of electricity,[14] according to the U.S. DOE. Thus commercial lighting alone consumes about four to five million barrels per day (equivalent) of petroleum, in line with the alternate rationale above to estimate U.S. lighting energy consumption. Over-illumination stems from several factors: Not using timers, occupancy sensors or other controls to extinguish lighting when not needed; Improper design, especially of workplace spaces, by specifying higher levels of light than needed for a given task; Incorrect choice of fixtures or light bulbs, which do not direct light into areas as needed; Improper selection of hardware to utilize more energy than needed to accomplish the lighting task; Incomplete training of building managers and occupants to use lighting systems efficiently; Inadequate lighting maintenance resulting in increased stray light and energy costs; "Daylight lighting" demanded by citizens to reduce crime or by shop owners to attract customers;[15] Substitution of old mercury lamps with more efficient sodium or metal halide lamps using the same electrical power; and, Indirect lighting techniques, such as lighting a vertical wall to bounce photons on the ground. Most of these issues can be readily corrected with available, inexpensive technology, and with resolution of landlord/tenant practices that create barriers to rapid correction of these matters. Most importantly public awareness would need to improve for industrialized countries to realize the large payoff in reducing over-illumination.