[ RadSafe ] SOLAR as a replacement for fossil fuel?

[Ted de Castro]

Well - that is PART of reducing the solar constant from 1.4 at the 
equator to 0.5  for my calcs - a guesstimate that could sure use 
refinement.  In Berkeley, CA - the solar constant doesn't even peak over 
0.75!!

It would be nice to know a better number for a world average - or ring 
the area between the tropic of cancer and the tropic of capricorn with 
PV!!  Now THERE's a project for full time employment for quite a while!

BTW - even on a cold day with snow and ice - if its sunny the PV will 
work - assuming to brush the snow off of it!! <grin>

So anyhow - maybe the correct world average solar constant is 0.25 - 
which doubles all the space needed!  Also since I came up with bio fuel 
as the best option for solar conversion - and I mean the grass - not 
corn that will compete with food!!! - you would still have a shortened 
growing season too.

Sounds like rapidly approaching 20% land coverage - wide scale 
aggressive harvesting of sea growth would probably result in all sorts 
of extreme environmental havoc.

As the article linked on another post said - stay with nuclear and hire 
more engineers - not regulators.

And put more effort into fusion research so that MAYBE we can have that 
in 25-50 years.

I just don't see how we can live WITHOUT nuclear (fission) for the next 
few decades at least.

The oil runs out in 20 years!

On 3/20/2011 2:56 PM, Michael LaFontaine, P. Phys. wrote:
> 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.  
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