Question

Nuclear Versus Natural Gas Energy Because of safety concerns and other constraints, nuclear power plants must be run at lower efficiencies than natural gas-fired power plants. The efficiency of a particular gas-fired power plant is 43.2 % and that of a nuclear plant is 33.5 %.

For every 1.00 kJ of mechanical work (to generate electricity) produced by the gas-fired power plant, how much energy is exhausted as waste heat?

How much waste heat is generated for every 1.00 kJ of work produced by the nuclear power plant?

What is the percentage increase of waste heat generated by the nuclear plant over the natural gas plant as a result of the lower efficiency?

Answer 1

part a:

efficiency=output/input

given that output=1 kJ

efficiency of the gas-fired plant=0.432

then input=output/efficiency=1 kJ/0.432=2.3148 kJ

then energy exhausted as waste heat=input-output=1.3148 kJ

part b:

for nuclear plant, efficiency=0.335

then input=1 kJ/0.335=2.9851 kJ

then waste heat=input-output=1.9851 kJ

part c:

percentage increase=(waste heat by nuclear plant-waste heat by gas plant)*100/(waste heat by gas plant)

=(1.9851-1.3148)*100/1.3148=50.981%