# Homework Help: Power Output & Thermodynamics

1. Apr 23, 2010

### planke

1. The problem statement, all variables and given/known data

At a coal-burning power plant a steam turbine is operated with a power output of 491 MW. The thermal efficiency of the power plant is 39.0%.
(a) At what rate is heat discarded to the environment by this power plant?
______ GW

(b) At what rate must heat be supplied to the power plant by burning coal?
______ GW

2. Relevant equations
e = W/Qh = Qh-Qc / Qh

3. The attempt at a solution
I don't know how to approach this problem. Is there some equation for power to use for thermodynamics?

Thanks!

2. Apr 23, 2010

### rock.freak667

Start with the definition of efficiency η.

Remember power is nothing but the rate of change of energy. (1 W = 1 J/s)

3. Apr 23, 2010

### planke

I think this problem should be really straightforward, but I am still having trouble understanding how to solve it.

4. Apr 23, 2010

### rock.freak667

In your relevant equations you posted

e=W/Qh

So what is Qh ?

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