# 22300 byhkhenson on March 8, 2009, 4:43 p.m.
Member since 2022-08-22
> Last I heard, PVs generate potential differences in the 5 Volt range.
>How do you get plasma arching at that low a voltage?
You don't. But you have to stack them in series to get the voltage
you need to run the transmitter.
Consider a 5 km x 5 km PV power sat wing.
From the end it might look like this \_/\_/\_/\_/\_/ where the
slanted section are coated with aluminized Mylar to give a mild 3x
solar concentration. You almost get the concentration for free since
the structure has to have some thickness to resist bending. Five
km/3 is about 1600 meters. Each of the 5 flat sections would be
about 330 meters wide.
To keep down conductor mass and reduce I^2R loses, the voltage across
the whole array of cells could be up in the 100,000 volt range. (If
so, the current from a wing would be 50,000 amps or ten amps per
meter.) Each of the 5 sections of cells would need to generate
20,000 volts or 60 volts per meter. That would take about 123 cells
per meter in series--which is not far from current
practice. http://www.amsolar.com/am100.html
Before getting into the complex problems of insulating the PV strings
from the power sat frame, and conducting the power to the transmitter
to and through slip rings, you need to think about a production
target of PV cells of around a GW/day--though it probably would start
smaller, maybe 1/4 to 1/2 GW/day and is further reduced by the
concentration factor.
Between jet engines and steam turbines the world is not that far from
a GW/day production of rotating machines.
Keith
# 22301 byhkhenson on March 8, 2009, 7:03 p.m.
Member since 2022-08-22
> Last I heard, PVs generate potential differences in the 5 Volt range.
>How do you get plasma arching at that low a voltage?
You don't. But you have to stack them in series to get the voltage
you need to run the transmitter.
Consider a 5 km x 5 km PV power sat wing.
From the end it might look like this \_/\_/\_/\_/\_/ where the
slanted section are coated with aluminized Mylar to give a mild 3x
solar concentration on the flat areas. You almost get the
concentration for free since the structure has to have some thickness
to resist bending. Five km/3 is about 1600 meters. Each of the 5
flat sections would be about 330 meters wide.
To keep down conductor mass and reduce I^2R loses, the voltage across
the whole array of cells could be up in the 100,000 volt range. (If
so, the current from a wing would be 50,000 amps or ten amps per
meter.) Each of the 5 sections of cells would need to generate
20,000 volts or 60 volts per meter. That would take about 123 cells
per meter in series--which is not far from current
practice. http://www.amsolar.com/am100.html
Before getting into the complex problems of insulating the PV strings
from the power sat frame, and conducting the power to the transmitter
to and through slip rings, you need to think about a production
target of PV cells of around a GW/day--though it probably would start
smaller, maybe 1/4 to 1/2 GW/day and is further reduced by the
concentration factor. It would still take a heck of a lot of growth.
Between jet engines and steam turbines the world is not that far from
a GW/day production of rotating machines.
Keith
# 22302 byGARY ANSORGE on March 9, 2009, 12:25 p.m.
Member since 2022-08-22
:,,,the voltage
> you need to run the transmitter."
>
That doesn't compute. I thought mr Tesla already solved that problem(transformers). Hooking up solid state devices in series to generate 20 to 100 k voltages should result in cascade failures, ie, arching thru the PV junctions. I rather thought we would tap off the low voltages and amplify the voltage with transformers.
GAry 7
# 22303 byhkhenson on March 9, 2009, 2:14 p.m.
Member since 2022-08-22
>:,,,the voltage
> > you need to run the transmitter."
> >
>That doesn't compute. I thought mr Tesla already solved that
>problem(transformers).
transformer, have to convert to AC to do that.
>Hooking up solid state devices in series to generate 20 to 100 k
>voltages should result in cascade failures, ie, arching thru the PV junctions.
No PV junction sees more than half a volt and that is from what it generates.
>I rather thought we would tap off the low voltages and amplify the
>voltage with transformers.
I have never seen this proposed for a power sat.
>Another point if favor of a thermal generating system???
Perhaps. The whole thing needs more engineering work, especially
considering a lower lift cost to GEO. Super conductors could be an
option to get the power to the transmitter.
I would actually suggest parallel development tracks and even build
both versions. That way something like a huge fire at a PV plant
doesn't shut down power sat construction.
Keith