When looking at energy sources, fossil fuel is a good place to start – over 80% of the world’s energy production is from fossil fuel, coal, oil and natural gas. All in all, a conversion chart to normalize primary energy volume would have BTU’s, which economists love, expressed in quadrillions, along with “million ton oil equivalents” or MTOEs, then billion cubic meter quantities of natural gas, followed by gigawatt-years of electric power, million ton quantities of coal, and anchored by million barrel quantities of oil.
It’s interesting to note that one quadrillion BTU’s, or British Thermal Units (one BTU is the theoretical amount of energy necessary to heat one pound of water by one degree farenheit) is equivalent to about 25 million tons of oil, 28 billion cubic meters of natural gas, 33 gigawatt-years of electricity (a gigawatt-year, which we prefer as a unit of electrical measure, is equivalent to 8.7 billion kilowatt-hours), 60 million tons of coal (although that is on the low end of the scale, high-quality coal can deliver a quad btu with as little as 40 million tons), and 180 million barrels of oil.
Keeping a chart like this around would probably do no harm when considering options towards a transition to a world where nobody gets to use oil, gas or coal… Is the United States importing 12 million barrels of oil per day? What percentage of total energy consumption does that represent? With this chart, these calculations are easy. For example, the USA consumes just over 100 quad btus per year; if US oil imports hit 12 million barrels per day (4,380 mm bbls/yr), and since roughly 180 million barrels equals a quad btu, then US oil imports should represent 25% of all US energy consumption.
For electrical calculations the conversion efficiency is an obvious question – if you put a billion cubic meters of natural gas into powering an electric generating plant, how much energy in the form of electricity comes out the other end? In the case of a modern natural gas power plant, about 60% is recovered. In all cases conversion efficiency between the amount of energy locked into the raw fuel and the amount of energy the end-user consumes is an important factor. With modern cogeneration equipment, natural gas pumped into commercial buildings can be 90% efficient.
With this chart, however, you can begin to calculate most any macroeconomic energy trade-off. Should Californian’s build a liquid natural gas terminal off their central coast? Sounds good to me – a heckava lot more energy can be imported from the abundant natural gas in the world than from biofuel feedstock, which requires rainforest destruction in order to be grown in significant quantities.