Monday, January 29, 2007

I’ve got a lot of gas

No, it’s not what you’re thinking. I’m talking about natural gas – the fossil fuel.

I happened to be writing about natural gas recently and needed to explain that one company’s proven reserves totalled one trillion cubic feet.

That’s really hard to visualize, so I wanted to provide some way for the reader to imagine just how large those natural gas reserves really are.

Part of the issue is that one trillion – one million times one million – is a huge amount of anything. One million seconds, for example, is 11.57 days, but one trillion seconds is more than 31,000 years.

And the metric itself, the cubic foot, is also difficult to grasp. People know what a linear foot is. And square footage is pretty familiar if you’re ever purchased real estate or flooring, but people aren’t often called on to think in terms of cubic feet.

Just how large is one trillion cubic feet? (Referred to as “one Tcf” from now on because I’m sick of typing “one trillion cubic feet”)

A simple cube root calculation shows that one Tcf would be a cube about 1.8 miles long, 1.8 miles wide, and 1.8 miles tall, but I wanted to see if I could paint an even clearer picture.

So I got the on the web and found out a few things. One Tcf of natural gas would fill:

• The Empire State Building more than 27,000 times. Piled on top of each other, a stack of 27,000 Empire State Buildings would be 6,000 miles high.



• About 11 million regulation Olympic-sized pools, or just one such pool – if it were 14,000 miles deep (but the center of the Earth is only 4,000 miles deep).
• A balloon measuring 7.3 miles in circumference (assuming the balloon was a sphere). That would be one mammoth balloon – a surface area of 17 square miles. Filled with natural gas that balloon could detonate in one colossal explosion.

Ah! An explosion. That sounds interesting. How much energy could you get out of one Tcf of natural gas?

Turns out – a lot.

Measured in BTUs (British Thermal Units), one Tcf of natural gas would provide enough energy to:

• Melt 3.6 billion tons of ice, enough to cover a skating rink of 53,000 square miles one inch thick – a rink that would actually be bigger than the state of Alabama.



• Bring 763 billion gallons of 50-degree water to a boil – enough water to fill more than one million of those Olympic-sized pools. Or enough to fill only one of those circular above-ground pools to a depth of 5 feet, but it would have to be a big pool, with a diameter of 30 miles.
• Drive a car 163 billion miles if you got 20 miles per gallon. That’s far enough to drive around the world more than 6.5 million times (but only 6.33 million times if you fill up on premium).
• Chop wood by hand 16 hours a day for 100 million years (I’m allowing seven hours a day for sleep and one hour a day to pack in the 7,500 calories needed to work that hard).
• Generate enough electricity to power one million homes for more than 34 years (or one home for 34 million years).

But what about that explosion I was taking about earlier? What if I wanted all that energy at once?

Well, one Tcf of natural gas would be the equivalent of 17,000 atomic bombs of the kind that exploded over Hiroshima in 1945 (but sadly, only the equivalent of around five of the largest thermonuclear weapons ever tested).

In the grand scheme of things, however, one Tcf of natural gas doesn’t provide much energy at all – only enough to power the Sun for a paltry 0.00000000284 seconds (In other words, it would take the equivalent of a billion trillion cubic feet of natural gas to power the sun for 2.84 seconds).

Anyway, next time you have something complicated to explain, try to help your reader visualize it. And have fun. I did.

Posted by Richard Bloch

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