alternative energy and shale gas encyclopedia pdf
Everything we make, bend, heat, cool, cut, fasten, grow, harvest, move, or shape requires energy. That is, when we do anything to anything, we use energy. If we do it by hand, the energy source is the sun which produces the food we eat. The human labor part of the energy picture, however,
is minuscule. Let me elaborate. The best coupling between man and machine is to put a person on a bicycle seat to use the strong leg muscles to push the pedals (which in turn might turn an electric generator).
Whereas a good athlete might produce a few hundred watts—perhaps as much as
a thousand watts—over a short period, it is a real chore to produce 100 W on a continuous basis for hours at a time. If we produce 100 W for a 10-hour period, the amount of electrical energy produced is 100 W × 10 hours, which is 1000 Wh, or 1 kilowatt-hour (kWh), for which the average price in the United States is about a dime. Not many people would be willing to work that hard, that long, for a mere 10 cents. For another comparison, a 2000-Calorie1 daily diet is equivalent to about 100 W.
To expand that perspective just a bit, let us look at the amount of energy—over 100 exajoules2—used in the United States every year. Averaged over the 31.6 million seconds in the year, and over the roughly 315 million US citizens, our rate of energy consumption is about 11,000 W per capita,
about 110 times as much power as the average human produces in the form of heat, or our athlete produces while on the bicycle seat.
Alternatively, one may think of our energy consumption as being equivalent to having 110 servants tending to our needs night and day. This is why we can accurately say that human labor is a minuscule part of the energy picture. Over 90% of our energy comes from petroleum, natural gas, coal, and uranium. Of the 9% contribution from renewable energy sources, the venerable ones—hydro and biomass—provide over 80%.