# 12257 bywlm_efn@... on Feb. 8, 2012, 3:50 p.m.
Member since 2021-10-03
I wrote a program for estimating the amount of land required for
ground-based solar to supply the total energy needs of the U.S.
Here it is.
of 90 exajoules consumed in 2005):
AllEnergyAnnual = 105e18 = 1.05e20 J
Average solar energy flux in the U.S. is given in this map,
in Kw-h / m2 / day:
[]
Value used:
KWHPerDay = 5.0
Joules per kilowatt-hour:
JPerKWH = 3.6e6
Days per year:
DaysPerYear = 364.25
Factor for extra land area required, for solar array support
structures, maintenance roads, power lines, etc.
Extra land for latitude adjustment is not required because of this:
ExFactor = 1.5
Conversion efficiency of solar energy to electricity:
ConvEfficiency = (see table below)
Energy-delivered efficiency, factoring in wastage involved with
ground-based energy being stored for day/night sunny/cloudy
weather or summer/winter cycles, or transmitted over long distances
through the U.S.:
DelEff = (see table below)
The above values were plugged into these equations:
JPerAnnual = KWHPerDay * JPerKWH * DaysPerYear
JAdj = JPerAnnual * ConvEfficiency * DelEff
Area = AllEnergyAnnual / JAdj
Area = Area * ExFactor
AreaKM2 = Area / 1e6
And got this table for land area required for ground-based solar,
for it to supply the total energy for the U.S., in thousands of
square Km:
Conv .... Delivery Eff%
Eff% .... 30 .. 40 .. 50 .. 60 .. 70 .. 80
10 ... 800.7 600.5 480.4 400.4 343.2 300.3
15 ... 533.8 400.4 320.3 266.9 228.8 200.2
20 ... 400.4 300.3 240.2 200.2 171.6 150.1
25 ... 320.3 240.2 192.2 160.1 137.3 120.1
30 ... 266.9 200.2 160.1 133.5 114.4 100.1
35 ... 228.8 171.6 137.3 114.4 098.0 085.8
40 ... 200.2 150.1 120.1 100.1 085.8 075.1
45 ... 177.9 133.5 106.8 089.0 076.3 066.7
50 ... 160.1 120.1 096.1 080.1 068.6 060.1
55 ... 145.6 109.2 087.4 072.8 062.4 054.6
60 ... 133.5 100.1 080.1 066.7 057.2 050.0
65 ... 123.2 092.4 073.9 061.6 052.8 046.2
70 ... 114.4 085.8 068.6 057.2 049.0 042.9
# 12258 bywlm_efn@... on Feb. 8, 2012, 3:53 p.m.
Member since 2021-10-03
Correction, here's the page (in the brackets).
--- In spacesettlers@yahoogroups.com, "William" wrote:
# 12259 bywlm_efn@... on Feb. 8, 2012, 3:59 p.m.
Member since 2021-10-03
Conversion of 10 percent are common for basic silicon PV's today.
This has the potential to go up -- very much -- in the next few
decades.
high-voltage DC power lines for long-distances. This has the potential
to go up as well.
Also: although only in the lab right now, there are technologies for
direct conversion of solar energy to hydrogen, methane and methanol
fuels. Something SSP can't do.
--- In spacesettlers@yahoogroups.com, "William" wrote:
# 12260 byalglobus@... on Feb. 9, 2012, 3:07 a.m.
Member since 2021-10-03
On Feb 8, 2012, at 7:59 AM, William wrote:
> This has the potential to go up -- very much -- in the next few
> decades.
>
There's stuff in the lab that, if memory serves, gets up to around 42%.