Natural Gas Calculation

Dear Editor,

In Tuesday’s edition, I see that emerging oil producing countries like Guyana are at risk of over-supply of natural gas. Let me use S.I. units to show how much natural gas would be needed using GPL as an example. (The International System of Units (SI, abbreviated from the French Système international (d’unités)) is the modern form of the metric system. It is the only system of measurement with an official status in nearly every country in the world). It follows that I shall be using cubic metres, megawatts and megajoules in the following simple calculation.

Let’s say GPL generates 125 MW of electricity at an efficiency of 25 percent.
This means that a thermal input of 500 MW is needed to get a 125MW output.
Natural gas has an energy content of 40 MJ (Megajoules) per cubic metre.
A MW is the rate of producing or using energy and it equals 1 MJ/second.
A thermal input of 500MW therefore requires (500 divided by 40) cubic metres of natural gas per second, which is 12.5 cubic metres per second. This works out at one million and 80 thousand cubic metres of natural gas per day.
Or, a thermal input of 500MW requires just over 38 million cubic feet of natural gas per day.
These figures can be pro-rated to any thermal process or application.
I hope this helps.

Robert Perks B.Sc. Fuel Science