[ RadSafe ] SOLAR as a replacement for fossil fuel?

[Michael LaFontaine, P. Phys.]

Interesting work Ted, however, for those of use who experience a real 
winter 4 to 6 months of the year, 1/4" (6.4mm) of ice or snow on a 
photo-voltaic, i.e., solar panel, effectively reduces its electrical 
output to zero - much like wind mills not turning without wind. 
Nuclear has to stay in the mix. I agree, solar is not practical - yet.

Michael

At 05:33 PM 20/03/2011, you wrote:
>Sorry folks - my calculator an I just aren't getting along today - 
>my previous numbers were wrong - too low.  Here's the whole thing 
>redone and triple checked.
>
>I welcome comment/correction - there ARE assumptions in here!  BUT 
>bottom line - whatever form of prompt (solar cells or focusing for 
>steam generation) or near prompt (bio fuel or wind or wave or hydro 
>- yes hydro is solar powered too) - it would take harvesting ALL the 
>solar radiation from just too much of the earth's surface area (6.4% 
>if by land - 1.6% if by sea too for bio fuel - the cheapest way to 
>cover the most area) and thus would be also too costly.  Its just 
>not practical.
>
>I found this an interesting exercise to assess potential.
>
>Here are ALL the calcs:
>
>Consumption:
>
>ref 1:
>Oil 85,000  thousand barrels per day
>
>ref 2:
>160 e15 btu/yr
>coal 95e15 btu/yr
>gas  95e15 btu/yr
>
>Oil energy equivalent /barrel (42 gal crude 44 gal processed)
>1.7 MWh
>5.8 e6 BTU
>6.1178632e9 J
>
>surface of earth
>
>50.25 e6 sq mi
>1.396 e14 sqm
>
>oil usage:
>
>6.8 of 44 gal barrel NOT used as fuel
>
>((44-6.8)/44) used as fuel = 0.8454545455
>
>Solar
>
>1.4 kw/sqm at noon at the equator at the summer solstice
>avg sun 12 hr/day.
>
>So - fossil fuel
>
>85,000*1000*5.8 e6*0.8454545455*365.25 = 1.52 e17 btu.yr
>or 160 e15 = 1.6 e17 as stated in the other reference
>so data is consistent
>
>
>Or using the the 1.7 MWhr number (1.7e3 KWhr)
>
>1.7e3*0.8454545455*8.5e7*365.25 = 4.46e13 kWhr/yr for oil
>PLUS 95/160*4.46e13 = 2.649e13 for coal
>PLUS 95/160*4.46e13 = 2.649e13 for gas
>
>= 9.76e13 kWhr/yr total fossil fuel
>
>Solar
>
>use 1.4 kW/sqM at noon solstice
>Assume 12 hr/day
>Assume AVG sunlight through day through latitudes ~ 1/3 max constant use .5
>(requires ALL tracking solar collectors)
>.5*1.396e14*12*365.25 = 3.059e17 kWhr/yr
>
>THUS
>
>3.19 e-4 (.0319%) of earth surface required at 100% efficiency
>0.319% @ 10% - (1.276% of land only) (best solar cells currently 10%)
>1.595% @ 2% (bio fuel grass) - (6.38% of land only)
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Michael LaFontaine, P. Phys.