hiya morfe,
some sources for thee...
there's an excellent overview (albeit almost 7 years old now) of the hydrogen issue at:
http://www.cnie.org/nle/eng-4.html
(a pretty dispassionate and unbiased report on the issue made to the US Congress)
although they certainly don't dismiss the "solar hydrogen" scenario, i'm of the opinion that the most important point in the report is:
"Although it is the universe's most abundant element, hydrogen is present in the atmosphere only in concentrations of less than one part per million. Most of the Earth's hydrogen is bound up in chemical compounds. Hydrogen for large-scale use must therefore be extracted from a source such as water, coal, natural gas, or plant matter. It cannot simply be produced from a mine or a well. Since considerable energy is consumed in the extraction process, hydrogen should properly be considered an energy carrier rather than an energy source; the energy released when it is finally used is just the energy that was invested in its original manufacture (minus any losses). Recognizing this fact is of critical importance..."
so when's all said and done, the really vital point is that in a world without fossil fuels, when we have to replace all of our current hydrocarbon usage with "something else", where is the large _additional_ chunk of power going to come from just to produce all the hydrogen?
regarding solar (PV) cells, check out some of the articles on http://www.dieoff.org/ - there are some that claim there's a future for PV technology, but most that don't. however, some hurdles that need overcoming:
in Howard Odum's "Environmental Accounting: Emergy and Environmental Decision Making" he (allegedly... it costs $140 so i'm relying on someone's citation here!) calculates that in 1993 the total USA fuel use was 4.78 x 10e24 sej. However, total net solar radiation absorption for Alaska and the lower 48 States was 4.48 x 10e22 sej. This means that the USA is presently using fossil fuels more than 100 times greater than the total absorption of solar radiation across the entire USA! (so not 2 earths as i said previously, but 100 USAs). of course, you cover that much of the planet with PV and you gotta wonder where we're going to grow all our food, and stuff like that...
the calculations which demonstrate that PV uses twice as much energy to build, situate and maintain than you get out of the stuff are here: http://dieoff.com/pv.htm
note: i do not understand these calculations. however, when they were submitted to the energyresources mailing list, all but a few "solar rollers" (as they are known by some... i'm a "windie"; not sure which is worse ;-) who understood the numbers agreed that they demonstrated the deficit.
Jay Hanson's summary of the matter is this...
"H.T. Odum's solar "eMergy" (eMbodied energy) measures all of the energy (adjusted for quality) that went into the production of a product. Odum's calculations show that the only forms of alternative energy that can survive the exhaustion of fossil fuel are muscle, burning biomass (wood, animal dung, or peat), hydroelectric, geothermal in volcanic areas, and some wind electrical generation. Nuclear power could be viable if one could overcome the shortage of fuel. No other alternatives (e.g., solar voltaic) produce a large enough net sej to be sustainable. In short, there is no way out."
that's pretty bleak, and there are plenty of people clued up to the looming fossil fuel crunch who don't think it's as bad as all that. i simply know that it's a little silly to believe that we can replace the accumulated millions of years of stored sunlight that was our fossil fuel resources with the relative drip-feed that trickles down from above.
i think it's a tragedy as it happens. the more i've learnt about oil, the more i've realised what a unique and precious resource it is. if we'd truly been an intelligent race, it could have taken us to the stars...
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