Land use requirements for ground-based solar

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.

Total energy used by the U.S. (estimated, based on Wikipedia figure
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