Digest Number 509

--- In ssi_list@... Ian Woollard
>
> >Lasers are not much use, because the rectenna would simply be PV
arrays are low conversion efficiency.
> >
> Do you have a reference for that low conversion efficiency? The
best PVs
> are now at about 30% when used with sunlight,

True enough, but I'm not ready to accept that a SPS will be using
the most efficient PV available because if they have to be
constructed from orbital resources, I wonder if we'll be able to
acquire the Group III or V periodic table elements to alloy with
gallium arsenide, indium, copper indium diselenide, gallium indium
phosphide, and germanium.

I think it more likely that a simpler silicon PV cell will be used
because it will be more easily manufactured from lunar silicon using
the Czochralski or float zone method in a zero-g or lunar
environment.

I think that there is a chance that PV technology and solar
thermal/sterling engine may not even be used. With the abundance of
ilmenite in the lunar regolith, after we extract the iron and an
oxygen atom we'll be left with titanium dioxide, which when
impregnated with a dye can replace the semiconducting material used
in PV cells to create a voltage. This may be a cheaper technology to
implement than large scale crystal growth in orbital or lunar
facilities.

TangoMan