Wireless Sensor and Actuator Networks for Lighting Energy ...

Figure 2-1 Primary energy consumption in commerical buildings.
Figure 2-2 Primary energy expenditure in commercial buildings.
2.1.1 Environmental Impact of Commercial Buildings
Lighting consumes more than 2,000 terawatt-hours (TWh) of electricity
globally, which corresponds to about 1,800 million metric tons of carbon dioxide (CO 2 )
emissions per year, and 48% of the lighting electricity is attributed to the commercial
sector [18]. In the United Stats, the 640 TWh lighting electricity demand in buildings
alone contributes to about 115 million metric tons of carbon dioxide emissions per year
[16], which accounts for almost 40% of greenhouse gas emissions [20].
Office buildings are the single largest energy user in the commercial sector as
shown in Figure 2-3, and can therefore play a major role in increasing energy efficiency
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