The Nuclear Reactor — Question 10

Question 10

Annual energy production separates efficiency from availability

A station has rated electrical output 800 MW and operates at full output for 85 percent of a 365-day year, with zero output otherwise. Its operating thermal efficiency is .350.

1. Calculate annual electrical energy in TWh and average electrical power.

2. Calculate annual thermal input and explain why the .85 factor is not a thermal efficiency.

Question 10 - Solution

Annual energy production separates efficiency from availability

(a) Method and calculation

$$t_{\mathrm{yr}}=365(24)=8760\,\mathrm h\Rightarrow\boxed{E_e=.800(.85)(8760)=5956.8\,\mathrm{GWh}=5.9568\,\mathrm{TWh}}.$$$$\boxed{\overline P_e=.85(800)=680\,\mathrm{MW}}.$$

(b) Interpretation and further calculation

$$\boxed{E_{\mathrm{th}}=E_e/.350=17.0194\,\mathrm{TWh}}.$$$$\boxed{\text{availability}=t_{\mathrm{on}}/t_{\mathrm{year}};\qquad\eta=E_e/E_{\mathrm{th}}}.$$

Physical check

Availability compares operating time with calendar time in this ideal on/off model. Efficiency compares output energy with input energy while operating.