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What does one do with 174 peta-watt-hours of solar energy that the sun bathes the earth with every hour; that is 174 followed by 15 zeros. You can fry anything with that much energy, if you can focus it, including all of humanity. 174 quadrillion watt-hours, that is. In fact, this is humanity's present energy availability-beyond fossil fuels, hydro, nuclear, wind, geothermal, and tidal power. To help the boggled mind, the typical household electric heater consumes 1000 watts. Imagine the heat put out by 174 million-million such heaters. This solar energy is there for the converting.

There is just one minor problem: it bathes earth in the form of electromagnetic radiation, otherwise known as solar energy. And that is the catch. Mother nature is very good at converting radiation into food and fuel, but humanity is not, at least not yet.

Billions have been spent chasing the holy grail of limitless energy. For as long as humanity can live on earth, only the sun is a ready source. For perspective, let us review the power turf briefly.

  • Carbon fuels have brought us this far. Petroleum and coal together powered the industrial revolution and sustains societies today. For horizons beyond our noses, other sources will be needed. Carbon fuels add to the green-house gases, another reason for limiting their use. Since conflicts over carbon resources dominate the news and our thinking, an alternate inexhaustible source seems necessary before peace can reign on earth.
  • Fermenting various food crops can produce bio fuels, such as ethel alcohol, would have to utilize acreage now devoted to food production. Moreover, it is a poor use of land better used to grow crops. Corn is being subsidized for alcohol production, but is not the most efficient source material. Special interests are interfering with this technology. Bio-fuel via photosynthesis would seem to be a panacea, but as it works out, it is very inefficient, only about one percent of the impinging solar energy becomes a usable fuel.
  • Hydro power is already largely tapped out at the cost in land area that could sustain two or three nations.
  • Tidal and wave power, while significant, is limited to certain coast lines and is limited in any event.
  • Geothermal power is more limited than other green alternatives.
  • Wind power is coming into its own and will be an important energy source as long as the world turns. It is supplying an increasing fraction of power used today in many developed nations.
  • Nuclear power is basically safe enough, but only under ordinary conditions. But it produces radioactive by-products that stay hot for millenia. And who wants to store hot waste in their own back yard? Hot structural materials have to be secured when a plant is decommissioned. Moreover, when an unexpected event exceeds a power station's integrity, spilling radioactivity into the air, what then? Will a nuclear power plant survive an earthquake of magnitude 10 or greater? What about a Tsunami? Maybe an out-sized meteor is so rare as to be discounted, it is still possible. So fission nuclear power has its problems.
  • Fusion power has been a disappointment. No one is predicting its use for at least 3 decades. While clean compared with fission power, fusion power nevertheless would leave tons of radioactive material at decommissioning time. That feature seems inescapable.
  • Breeder reactors, the only process that creates more energy than it consumes, produces radioactive wastes that are difficult to store safely. In whose backyard? Standard fission reactors have the same problem, not to mention proliferation of weapons that attend each. A thought there is to bury all unusable waste in a subduction zone in an ocean. There must be better alternatives.
  • Pioneering work by Kanan and Nocera may result in a successful effort to mimic nature, in the sense of converting CO2 to O2. Their technique involves a catalyst that reduces the electrical potential necessary to separate oxygen from water containing phosphate and CO2. How important this new technology might be remains to be seen. Conceivably it could lead to hydrogen and oxygen separation by electrolysis somewhat cheaper than is possible now, but that is very unlikely anytime soon. See page 10572 of 22 Aug 2008 issue of Science Magazine
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With all their drawbacks, most of the above will be developed further. Without drastic changes in the living habits of humanity, they simply do not assure sufficient power even for the foreseeable future.

Solar power by direct photoelectric conversion is another story, simply because the sun provides continuous free energy to half of the world. It has none of the negative features of conventional sources. Its main drawback is a low capacity factor of only 14% arising from latitude, nights and cloudy days. A second drawback is its impact on the local ecology by shading the ground that would otherwise bathe the ground with sunlight. A possible upside in time could be the opportunity of biota to evolve into this new niche. That feature might take a million years to be full realized.

Nevertheless, theoretically, the entire world's energy needs could be generated by an area only a fraction of the size of the Sahara desert. All major land masses have their desert regions. Vast regions of the Mojave Desert in California and Nevada have been claimed by various energy companies, based on this possibility. These guys are not noted for rubber stamping failed technologies or dubious business prospects. But they are relying on Moore's Law which predicts exponential growth in technology derived from new science--at least for a time.

Aside from the capacity factor, the technical barriers to photovoltaic conversion remain considerable, even though the exponential ramp up in solar panel deployment has already begun. Part of the remaining cost barrier to wide-spread use of solar energy will disappear as energy costs continue to escalate as they must--as long as they are largely non-renewable in origin. Equally important, experimental cells with conversion efficiencies now exceed 20% when 15% or even 10% would do in applications. Moreover, manufacturing costs are steadily declining as well. So we can have considerable confidence that solar power will come of age in the next decade. As one might expect, the current leader in shipping solar panels is in China.

Petroleum products have long been expensive in Europe, so it should be no surprise that European use of solar power exceeds that of the US.

There is hope, therefore, that the energy motive for violence will be reduced in the coming decades as wind and solar power gradually supplant carbon as the fuel sustaining human society.


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