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Homework Help: How to Convert $/Energy to $/Power

  1. May 23, 2014 #1
    1. The problem statement, all variables and given/known data

    Convert: $29/MW-h to $/W
    That is, convert energy to power

    2. Relevant equations

    energy = power * time
    power = energy / time

    3. The attempt at a solution

    $29/MW-hr x 1MW/1,000,000W = $2.9e-5/W-hr

    However I feel that this is wrong, and it also still has hr in the solution.
    I don't see how I can convert energy to power given the value also has dollars.
    Any help would be appreciated.
    (Also this is for a nuclear energy conversion problem)
  2. jcsd
  3. May 23, 2014 #2


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    Hello saqib, and welcome to PF.

    This is a non-starter: If this really is the full rendering of your exercise, it is simply wrong.
    There is no way you can change the dimension money/energy to money x time / energy if you have no time at hand.

    Likewise income and wealth: converting someones income to someones wealth is not possible. If I earn $ 10 per hour, that says nothing about my bank balance. Only if I tell you that I've worked 40 hours a week for twenty weeks and brought all of that to the bank you can multiply $/h x h/wk x wk to get $.
  4. May 23, 2014 #3
    I'm slightly confused. You want to convert Dollars/Energy into Dollars/Power? Are you sure that's what the question stated?

    Based on your calculations, it looks like you are doing everything right. I think the initial question is wrong.
  5. May 23, 2014 #4


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    You cannot directly "convert energy to power" because, just as you say here, the don't measure the same thing! power= energy/time. To convert energy to power you will have to give a specific time interval. That will clear the "hr in the solution".
  6. May 23, 2014 #5


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    This is why we ask that posters to the HW forums post the complete problem, even though they may have questions on one or two minor points. In the long run, it saves everyone time by not having to go round and round trying to figure out all the details, when they should have been provided initially, if only as a courtesy to those who are volunteering their time to help those seeking help.
  7. May 23, 2014 #6


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    Well, there's three times no way for you!

    If I tag along with the nuclear energy conversion problem remark: Could it be that you want to know how cheap solar power (in $/W) has to be to be able to compete with nuclear power plants that can produce energy at a cost of around $ 29/MWh ? Because then it becomes really interesting ! Even then: we still need to bring in something with the dimension of time, though: physics is tough, but it's physics.

    [edit]Now even his majesty blows off some steam. HE's absolutely right of course (Always so with kings). Fortunately, I'm not here to save time... more of the opposite :smile:
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