Republicans and Democrats are currently at loggerheads in the Senate over a bill to require the nation's utilities to draw a fixed percentage of their electricity from so-called "renewable energy."
The Democratic bill, sponsored by Democratic Energy Committee Chairman Dave Bingaman, of New Mexico, would have utilities get 15 percent of their electricity from wind, solar and other "renewable" sources by 2020. This version seems to be one vote short of beating a promised Republican filibuster.
Republican Senator Pete Domenici, also of New Mexico, has offered an alternate bill that would keep the same requirement but allow nuclear power and -- bizarrely -- "clean coal" to be included under the rubric of "renewable." That bill was soundly defeated, 56-39, with seven Republicans joining the Democrats to defeat the measure. A special committee is now trying to work out a compromise.
There is only one small point that makes this whole discussion rather irrelevant. According to the laws of physics, there is no such thing as "renewable energy."
The Second Law of Thermodynamics, developed during the 19th century, is said to be the only principle of Newtonian physics that survived the Einsteinian revolution. Therefore it is worthy of respect. The Second Law is expressed in a variety of ways -- "entropy," "disorder," the "dispersal of energy," the irreversibility of time. For the sake of this discussion, one of its principal corollaries is more than sufficient -- "Energy cannot be recycled."
The First Law of Thermodynamics (actually discovered after the Second Law) says that energy is always conserved and never destroyed. This seems to suggest perpetual motion. If we could only keep recycling the same energy, we would never run out.
The Second Law -- first posited by Sadi Carnot in 1824 -- contravenes this possibility. It holds that as energy is used to do work, some of it inevitably becomes irrecoverable. Energy is never destroyed. It transmutes from one form to another -- heat to mechanical motion to electricity to mechanical motion and perhaps back again to heat. In the process, however, some of the energy inevitably becomes inaccessible as "waste" or low-grade heat. Once dispersed, this energy achieves a state of high disorder or entropy. It cannot be reused, renewed, or recycled because it would take more energy to reassemble it than could be recovered.
The gasoline in your automobile engine, for example, transforms into mechanical motion. As it is consumed, however, some energy is inevitably thrown off as engine heat or friction against the road. Eventually all the momentum of your car will eventually be transformed into low-grade heat. The energy is still out there but it cannot be recycled or renewed. Therefore you will need a refill.
Calling some sources of energy "renewable" suggests that they can be used over and over, as opposed to other forms of energy, which will eventually run out. This is very misleading. What we really mean is that some forms of energy are inexhaustible, at least for our purposes. The energy of the sun is inexhaustible with respect to life on the planet. But it is not infinite. The solar energy falling on New York would not be enough to run the city, even if 100 percent of it were utilized. Therefore it must be collected elsewhere and transported, which itself consumes energy. The sun may come up day after day, but it does not provide unlimited amounts of energy.
Most "solar energy" actually comes to us in indirect forms, where the gathering and transporting is the limiting factor. Hydroelectricity derives from the sun's power to evaporate water and return it as rain. Yet there are only so many good dam sites. Hydro power supplied 20 percent of our electricity in 1980 but only 10 percent today, since most of its potential has been used. Wind comes from the sun's uneven heating of the atmosphere, but wind power is highly dispersed and must also be gathered and transformed. The wind is unpredictable and cannot be relied upon for large amounts of dispatchable electricity. Once wind reaches 20 percent of a grid, it begins to create voltage balance problems.
Direct solar electricity is free for the taking but does not arrive in very large amounts. The solar energy falling on a square-meter card table is enough to power one 100-watt light bulb. At best it could probably provide our indoor lighting. It is not enough, however, to run industrial machinery or highly sophisticated electronic networks. The great advantage of solar electricity is that it is strongest when it is needed most -- on hot summer afternoons when electrical demand peaks. Solar electricity could definitely relieve natural gas peaking plants in powering our summer air conditioning.
Fossil fuels are stored solar energy and renewable over the geological ages. We just don't have time to wait around for them to renew. Oil and gas supplies are somewhat limited and now lie mostly in countries that are politically unpredictable. We have so much coal in the U.S. we will probably never run out, but it is the prime source of air pollution and greenhouses gases. "Clean coal" is extremely expensive and will create huge problems in trying to bury whole oil fields worth of liquid carbon dioxide deep in the earth.
"Biofuels" are a gray area. They are "solar" and "renewable" but only within very strict limits. Sunshine is just one contributing factor. Much more important are land, water, fertilizer and other agricultural resources. Growing energy will compete with growing food. Nor are biofuels "carbon neutral." Burning this year's crop instead of leaving it in any of the numerous carbon sinks -- plant material, soil, the food chain -- increases the amount of greenhouse gases in the atmosphere. Calling biofuels "carbon neutral" is just poor accounting. They will both strain agricultural resources and contribute to global warming.
There is one other source of energy that is close to being as inexhaustible as the sun. That is nuclear power, which might be called "terrestrial energy." Our planet generates huge amounts of heat. The temperature in its interior -- 7,000 degrees C. -- is hotter than the surface of the sun. What is the source of this heat? Some of it comes from the pressures of gravitational collapse, but almost half is generated by the disintegration of two tiny elements, uranium and thorium.
Terrestrial energy is tapped at geothermal sites, where heat from the earth's molten core comes in contact with groundwater. We perform this same heat exchange in what is called a "nuclear reactor." A nuclear plant is simply the duplication of a geothermal site under more controlled conditions.
Terrestrial energy is not infinitely renewable, but then neither is any other source of energy. It does not rely on solar energy stored in carbon bonds and therefore does not put carbon dioxide back into the atmosphere. It is about as "green" as energy can get. It can probably stand by itself but is definitely worth including in any portfolio of "clean, renewable energy."