Tag Archives: Metrics

Sit in a darkened room and light a wooden match. Watch it burn. You may not feel the heat. The light it emits may not create more than a glow around your hand. You may or may not smell the slight sulphur tang, and the trail of smoke will surely be tiny. When it burns out, you have consumed a unit of energy called a British Thermal Unit, or a BTU.

Technically, a btu is the amount of energy required to heat a pint of water from 39 to 40 degrees Fahrenheit. But a wooden match burning in a darkened room provides a more concrete image.

Much of the discussion here on Quads will be about how many BTUs per capita people consume in different countries. The U.S. consumed 330 million BTUs per person in 2008, down from a peak of 346 mbtus per capita in 1989, but still an impressive figure.

By contrast, Denmark consumed 152 mbtus per person in 2008, also down from their peak of 186 mbtus in 1996. And China, despite being the largest consumer of energy in the world, spreads that consumption across a larger population–their per capita consumption has grown steadily for decades but only amounted to 65 mbtus per person in 2008.

As you will no doubt tire of reading if you spend much time on this weblog, one of the central questions of this century will be how China develops–if they aim for an American level of energy consumption, they will consume 459 quads per year when they have developed to America’s current levels. If they instead target a Danish lifestyle (which in many ways is materially better than that of America’s), it will be 211.

Picture a train car, filled with anthracite coal. Let’s be picturesque and go back to the 1970s, when smaller and weaker train cars held about 100 tons of coal. Back then, they typically formed trainsets of 100 cars, each holding 100 tons of coal, for 10,000 tons in total. One of the longest trains in history was on the Sishen-Saldanha Railroad in South Africa, operated in August of 1989. It used 7 diesels and 9 50-kV electrics to move 660 cars, a tank car, and a caboose. It traveled 535 miles in 22 hours and 40 minutes. It took a whopping 4.3 miles to stop the train. The train was over 6 miles long.

Now, picture a longer train. Imagine the longest train ever conceived of—one with 378,000 cars loaded with anthracite coal. Although coal cars vary in length, you can often estimate about 100 cars to a mile. So picture a train 3,780 miles long—the distance from Dublin to Kandahar, or from Albuquerque New Mexico to Anchorage Alaska. It is 1,500 miles longer than the tar sands oil pipeline from Alberta to Texas that is being so vigorously disputed as I write this in January of 2012.

If you burn all the coal in that train—each of the 100 tons in each of the 378,000 cars—you will have consumed 1 quadrillion BTUs. And we give the energy liberated from that incredible quantity of coal a cute little name. We call it a ‘quad.’

In 2010, the world consumed energy equivalent to the coal loaded onto 500 of those trains. The world as a whole consumed 500 quads. And despite progress in getting power from nuclear, hydro, wind and solar, in actual fact 143 of those imaginary trains filled with coal were not imaginary—they actually were filled with coal.