ALTERNATIVE ENERGY SOURCES
ABHIJIT MITRA, SUFIA ZAMAN, NABONITA PAL
Even if further research significantly improves the use of fossil and nuclear fuels, it is nonetheless clear that other energy options are needed. Fossil fuel resources in the United States are running out faster than nuclear fuels can replace them and the growing reliance on nuclear on nuclear fuels could be dangerous and environmentally damaging. Many alternative ways to obtain energy are conceivable, and they are all ultimately derived from four natural sources of power: the radiation of the sun, the energy of the tides, the heat inside the earth, and the energy stored in the atomic nucleus more than 10 billion years ago when our galaxy was formed.
The energy radiation by the sun is immense and is constantly being replenished. The power of the tides is also a renewable resource, estimated at 3 billion kilowatts. The rate of the heat convection to the surface of the earth from geothermal sources is not well known, but is estimated to be about 300 million kw. Much more power, however, could be extracted from geothermal deposits created during earlier ages. Some fraction of the geothermal resource is renewable while the rest is depletable. The energy of the atomic nucleus is certainly depletable-fission fuels are getting scarce- but if fusion can be proved the supplies will last a million years or more.
Of the three major alternatives to the proven sources of power, fusion is the only one that is now adequately funded (at about $65 million per year), geothermal research is funded with a few modest programs, and solar research is almost completely neglected. Yet solar radiation is man’s greatest resource. Solar energy not only heats the earth’s surface, but drives the rains, winds, and ocean currents, and provides the energy for all plant and animal life-cycles through photosynthesis. In units of a billion kw, the total power continually radiated from the sun and intercepted by the earth is 173,000, while the power used by all the industrialized societies of the world is only about 6 (The United States consumes about 2 billion kw in all forms of energy). About half the sun’s radiation is converted directly to heat at the earth’s surface, about one-fourth is reflected into space, and about one-forth is spent in evaporation and precipitation cycles, which-among other things-provide the energy of currents in streams and rivers. A very small fraction of the earth’s total solar radiation drives the atmospheric and oceanic circulations and convections (370 billion kw). An even smaller amount (which is nonetheless 40 times the world’s power consumption) is captured by the chlorophyll in plants and sustains photosynthesis.