The Oil Drum

When we talk about Energy, it is often hard to get a good feel for the quantities that we are talking about. The United States uses about 100 Quads of Energy a year where a Quad is a quadrillion Btu’s. When I first saw that, I had to go away and look up how much a Quadrillion was, and could barely remember a British Thermal Unit (Btu) from when I was in school. And given that we are now thinking of using Exajoules instead (a Btu being roughly 1,000 joules), life seems to be getting a little beyond the stretches of my imagination.

Units tend to be something that was originally almost an arbitrary choice. For example, when I want to cook fish, I know that it takes 10 minutes per inch, and so I use the first joint on my forefinger to see how thick the fish is and to decide how long to cook it. (And it works out quite well). When I need to buy something to length, I can get a first sense of how much I need by spreading my palms and touching my thumbs and from one side of one hand to the other side of the other is close enough to a foot. But a Quadrillion (1,000,000,000,000,000 in the US – add 000,000,000 to the end for the British system) is a little hard to visualize. Showing the volume occupied by a quadrillion pennies doesn’t really help much. And as for the Btu, well it’s the amount of heat required to raise the temperature of 1 lb of water by 1 degree Fahrenheit. Which would be good to know if I could remember how much volume there was in a pound (Oh! Yes there are 8 fluid ounces to a cup). So how can we get a real sense of how much energy we are talking about? After all we measure natural gas in thousands of cubic feet (or meters), coal in tons (or is it tonnes); oil in barrels; while wind, solar, nuclear and hydro usually are given in either billion kilowatt hours a year or in megawatts (though sometimes acre-feet has an impact on hydro). So how do we decide if spending $138 million on a wind farm in New Zealand that will produce 88 megawatts, or one that will generate 132 megawatts in Maine is a better idea that, say, installing an LNG vaporization plant that will produce 400 million cubic feet of natural gas a day in Connecticut. Well to begin with it would help if we could reduce all the different terms to a common comparative base. And so that is what this post is about.