Problem 55PE

A large electrical power station generates 1000 MW of electricity with an efficiency of 35.0%. (a) Calculate the heat transfer to the power station, Qh , in one day. (b) How much heat transfer Qc occurs to the environment in one day? (c) If the heat transfer in the cooling towers is from 35.0º C water into the local air mass, which increases in temperature from 18.0º C to 20.0º C , what is the total increase in entropy due to this heat transfer? (d) How much energy becomes unavailable to do work because of this increase in entropy, assuming an 18.0º C lowest temperature? (Part of Qc could be utilized to operate heat engines or for simply heating the surroundings, but it rarely is.)

Solution 55PE

a) Heat transfer to the power station in one day is

Qh = 2.47 x 1014 j

b) the heat transfer to the environment in one day is

Qc = 1.06 x 1014 j

c) total increase in entropy is

2.85 x 1010 j/k

d) the unavailable work is

8.29 x 1012 j