Natural Energy Sources

One can wonder how practical it is to satisfy the human demand for energy with some of the suggested alternatives to fossil fuels. Aside from how practical it may be to use the alternative sources, there is even the more fundamental question of just how much energy is available in each suggested source.

The rate at which the entire human race burns energy in food eaten is about equal to that required to keep a billion 100-watt light bulbs burning. The current worldwide power demand to meet all needs of civilization is about one hundred times larger. To avoid hard-to-visualize big numbers, it is useful to talk about the size of potential power sources in terms of the current worldwide demand.

In those terms, some renewable sources of energy clearly are lacking in the ability to solve the world's energy problem, even though they can be important local sources. An example is the power available in tidal flow that could be extracted at places like the Bay of Fundy or Cook Inlet. But the total tidal power available is only about one-ten-thousandth of the human energy demand. If all the energy in ocean currents and the waves at coastlines could be tapped, it would supply less than a hundredth of the total human demand.

If one could extract all the energy of motion (kinetic energy) from all water, including falling rain, it would supply only a tenth of the worldwide energy demand, whereas the energy available from the traditional damming of rivers can supply only a hundredth of the demand. Other sources such as wind power, the biological conversion of manure, plant wastes and garbage into gaseous fuels, and geothermal power each fall short, by a factor of ten or more, of being able to supply the current total world demand.

A bigger source of power is the solar-powered temperature difference with depth in the oceans. It is equal in size to the current world demand, as is the photosynthesis that occurs on farmland and in the world's forests. Ten times larger is the energy converted by photosynthesis in the oceans.

The biggest natural source of all is the sun. It provides to the earth's surface ten thousand times civilization's worldwide demand. Even at Point Barrow, the most northerly community on the North American continent, more solar energy falls on the roof of a house over a year than is needed to heat that house for the year.