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Homework Help: Percent efficiency of three power generators need help

  1. Nov 7, 2007 #1
    A coal power plant with three power generators is used to power a small city. If each generator uses 1.22 X 10^8 J of chemical energy in the coal every hour, and the average annual energy consumption of the city is 1.61 X 10^12 J. What is the efficiency of the generators?
    (Assume the generators run 24 hours a day 365 days a year)

    SO here's what I've got so far:

    (1.22 X 10^8 J)(3 generators)= 3.6 X 10^8 J used per hour for 3 generators.
    (3.6 X 10^8 J)(24H)= 8.6 X 10^9 J consumed in 24 Hours or 1 Day.
    (8.6 X 10^9 J)(365 Days)= 3.14 X 10^12 J consumed per year.

    So I know how much energy the generators consume but how do I figure out the annual energy output of the generators, and what kind of energy would it be?

    1.61 X 10^12 J= Cities annual energy consumption
  2. jcsd
  3. Nov 7, 2007 #2
    The question gives no information about loss or conversion going from the generators' output to consumption in the city so you have to assume there is none; they are the same in both size and "kind of energy"; what comes out of the generators is consumed in the city.
  4. Nov 7, 2007 #3
    so there is really no answer for this question then because there is not enough information?
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