Xcel Energy's Comanche 3 Power Plant in Pueblo, CO

[Winzer]

Homework Statement

The Comanche 3 power plant currently being constructed in Pueblo, CO, by Xcel Energy will
produce 750 MW of power. This plant uses supercritical boiler technology which will boost the
thermal efficiency to 42%. The plant uses Powder River Basin coal from Gillette, WY, that has a
heating value of 8,500 BTU/lbm. Find the amount of coal burned in this plant each year.

Homework Equations

$$n=\frac{what you get}{what you paid for}$$

The Attempt at a Solution

So I made the conversion from 8500 BTU/lbm to 19.7710 MJ/kg (megajouls)
I did 750E6 times .42 which is 315E6 MW.
I did $$\frac{315E6 MW}{19.7710 MJ/kg}$$ which is 15.932 kg/s
I times that by 3600*24*365 to get g in a year and get 5.024E8 kg.
The answer is 2.86x109 kg, what did I do wrong?

 

[mgb_phys]

You need to divide by 0.42 not multiply.
You want to know how many MJ of coal your are paying for, not what you get out of it!

 

[Moetasim]

Your calculations seem to be correct. However, there may be slight differences in the actual amount of coal burned in the plant each year due to various factors such as maintenance, operational efficiency, and variations in the energy content of the coal. It is also important to note that the amount of coal burned may change over time as the plant's operations and technology evolve. Overall, your calculations provide a good estimate of the amount of coal that will be used by the Comanche 3 power plant each year.