Correction in my figures for the land area required for SSP. It's 0.96
percent not 8 percent, to supply all the energy needs of the U.S. The
rectenna installations described in the various SSP studies would
deliver 5 Gw of power, not the 500 Mw I used.

105 exajoules total energy consumed by the U.S. in 2009 = 1.05e20 J.

1.05e20 / 31.4e6 seconds per year = 3336.4 Gw total power needed.

efficiency factor used for energy storage and transmission of
of the electricity for transportation, heating, etc. = 90%

adjusted power = 3336.4 Gw / 0.90 = 3701.1 Gw

3707.1 Gw / 5 Gw per installation = 742 rectenna installations
required.

rectenna installation area = 102.1 km2.

total area needed = 742 * 102.1 = 75.7 thousand km2.

lower-48 area = 7882911 km2

percentage = 100 * (75e3 / 7882911) = 0.96 percent.

sources:
1. Wikipedia for energy used by the U.S., and land areas.
2. Satellite Concept Power Systems Definition Study, by Nasa
http://www.nss.org/settlement/ssp/library/NASACR3317-
ExecutiveSummary.pdf

The 105 exajoules is based on today's energy usage, which includes
a huge amount of inefficiency in converting thermal energy from
fossil fuels into electricity and kinetic energy for transport.

--- In spacesettlers@yahoogroups.com, William wrote:

Correction again: the dimensions of the rectenna array installations
are 12 x 15.8 km, not 10 x 13. (An exclusion area outside the arrays
themselves.)

The land area required goes up, by 50 percent.

rectenna installation area = 158.3 km2.

total area needed = 742 * 158.3 = 117393 km2.
lower-48 area = 7882911 km2
percentage = 100 * (117e3 / 7882911) = 1.489 percent.

Or, about the same land area as the state of Virginia.

--- In spacesettlers@yahoogroups.com, "William" wrote: