Question

A coal-fired power plant operates at an efficiency of 38%. If the facility produces 6TWh of electricity per year, what is the rate of coal consumption in kg/s. Approximate coal as pure carbon.

Answer 1

Plant efficiency = 38%

1 unit electricity = 1 KWh

1 KW = 3600 KJ/hr

i.e., to produce 1 unit electricity 3600 KJ energy is required (for 100% efficiency)

For this question, to produce 1 unit electricity 3600/0.38 = 9473.684 KJ energy is required.

Heat value of pure carbon = 32.8 MJ/kg = 32800 KJ/kg [Ref: https://www.engineeringtoolbox.com/fuels-higher-calorific-values-d_169.html]

32800 KJ energy is produced from 1 kg pure carbon

9473.684 KJ energy is produced from (9473.684/32800) =0.29 kg pure carbon

Now, To produce 1 KWh electricity 0.29 kg pure carbon is required

to produce 6 * 10⁹ KWh electricity (6 * 10⁹ * 0.29) = 1740000000 kg carbon is required

1740000000 kg coal is consumed in 1 year

coal consumed in 1 sec = 1740000000/(365_days * 24_hours* 3600_secs) = 31536000 kg

Ans: 31536000 kg/s