energy generated energy input from fuel power plant efficiency : 660 GJ = energy input from fuel 0.38=- energy input from fuel =1.74 x 1012 J= 1.74 TJ 1.74 x 1012 J amount of coal required 232,000 kg 7.5 x 10 . kg As you can see, the amount of coal that could be saved is quite large! Before you get on an elevator next time, think about the amount of fuel-–not to mention the pollution-that can be saved if people just walk up a floor!
we determined the power required to move 30 people, with an average mass of 61 kg per person, between two floors of a building: a vertical
distance of 5 m in 2 s. The energy and the power requirements were 90,000
J and 45,000 W, respectively. Moreover, we estimated savings in energy if 1
million people decided to walk up a floor instead of taking the elevator on a daily basis. The minimum amount of energy saved during a year, based on an estimate of 220 working days in a year, would be 660 GJ. Let us now estimate the amount of fuel, such as coal, that can be saved in a power plant, assuming a 38% overall efficiency for the power plant and a heating value of approximately 7.5 MJ/kg for coal.
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