= Transport Energy Comparison =

Energy comparison of transporting a solar panel from China, compared to launching server sky thinsats on a Falcon 9 rocket.  

||                       || "260W"  || Server Sky || Server Sky ||
|| ballast source        ||         || ground     || space      ||
|| conversion efficiency ||  15.5%  ||   15%      ||   15%      || %       ||
|| December insolation   ||  100    ||  1200      ||   1200     || W/m^2^  ||
|| Weight                ||  21.2   ||  0.005     ||   0.001    || kg      ||
|| Area                  ||  1.68   ||  0.025     ||   0.025    || m^2^    ||
|| Weight/Area           ||  12.6   ||  0.2       ||   0.04     || Kg/m^2^ ||
|| Watts/Area flat       ||  15.5   ||  180.0     ||  180.0     || W/m^2^  ||
|| Watts/Area tilt       ||  28.5   ||  180.0     ||  180.0     || W/m^2^  ||
|| Watts/kg   tilt       ||  2.31   ||  900.0     || 4500.0     || W/kg    ||
|| Transport Energy      ||  7.03   ||  1800.0    || 1800.0     || MJ/kg   ||
|| Transport Payback     ||  35     ||  22        || 4.4        || days    ||

=== Solar Panel Characteristics ===

For reference, I assumed a quality panel such as the [[ http://www.solarworld-usa.com/system-designers/~/media/Global/PDFs/datasheets/sunmodule-solar-panel-260-mono-ds.pdf | Solarworld Sunmodule 260W ]], but made in China and transported to the US.

Without some magic system for season-to-season energy storage, solar panels must be provisioned in abundance to provide barely-adequate power in December, from New Mexico solar farms.  100W/m^2^ assumes huge amounts of energy storage to average the power over a month (which we also don't have, but perhaps ecologically-damaging peaking hydro is sufficient).  

This does not include site prep, stands, wiring, grid power interface, maintenance, and power line losses.   All these will add greatly to the costs and subtract from efficiency.  This also does not include manufacturing costs for either the solar panels or server sky.

The server sky insolation numbers are a bit of a cheat - in December, server sky insolation is higher than shown, but in spring and fall near the equinoxes the eclipse times are longer and the insolation a bit lower.   Individual solar sky arrays shut down in eclipse, but other operating arrays are still visible from tropical latitudes at midnight, away from zenith.  

=== China to New Mexico transport energy cost ===

||        || distance || J/kg-km || MJ   ||
|| Rail   ||  3000 km ||   210   || 0.63 ||
|| Ship   || 10000 km ||   160   || 1.60 ||
|| Truck  ||  2000 km ||  2400   || 4.80 ||

Assumes sourced from western China, by ship from Shanghai to LA, overland by rail where possible, by truck where not.

=== Space Transport Cost ===

See SpaceX for assumptions leading to 500kWh/kg energy cost (fuel plus rocket materials) to orbit.  Rocketry is expensive because very low launch volumes support an expensive standing army of launch experts.   The energy costs are a tiny fraction of the total.  The "space ballast" source is space debris collected with refuelable VASIMR rockets;  I assume we can actually build thinsats with 90% ballast, but collecting that ballast will require shipping up more argon fuel for the VASIMR space tugs.