Example from Physics, 12.4 Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators

Daily Work Done by a Coal-Fired Power Station and Its Efficiency (part 1)

A coal-fired power station is a huge heat engine. It uses heat to transfer energy from burning coal to do work to turn turbines, which are used then to generate electricity. In a single day, a large coal power station transfers $2.50 \times 10^{14} J$ by heat from burning coal and transfers $1.48 \times 10^{14} J$ by heat into the environment. (a) What is the work done by the power station? (b) What is the efficiency of the power station?

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Strategy
We can use $W = Q_{h} - Q_{c}$ to find the work output, W, assuming a cyclical process is used in the power station. In this process, water is boiled under pressure to form high-temperature steam, which is used to run steam turbine-generators and then condensed back to water to start the cycle again.
Solution
Work output is given by

$W = Q_{h} - Q_{c} .$
12.24

Substituting the given values,

$W = 2.50 \times 10^{14} J - 1.48 \times 10^{14} J = 1.02 \times 10^{14} J.$
12.25

0 of 2 steps open

How did it go?

Strategy

Solution

Strategy

Solution