High efficiency solar cells and battery charger

I'm working on a Uni. project in which I need to build the power system for
a micro satellite. It is in the form of 10x10x10cm cube.

* Where can I find high efficiency solar cells in Australia? (6 surface x
10x10cm)
* Can some one suggest a solar cell powered battery charger circuit ?
* What difference does it makes in terms of effieceny and life time for
solar cells when they are on the earth surface or in the sky?

 

Which uni?

UNSW has the best silicon solar cells around..... At a price.

Mike

 

Search for Martin Green. He is a professor in Australia who specializes in
advanced solar technology.

 

Talk to the folks at Amsat

 

You should ask these Qs on the alt.solar.photovoltaic newsgroup.

--
@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@

 

Whatever cells you use, add unfolding reflectors to increase the incoming
light so you can get a little more power out of them. Silver Mylar reflectors
weigh very little.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

Moving parts on a sat gives rise to a hole lot of other issues.

Mike

 

Sorry some additional stuff. Martin Green is at UNSW. Blue sat at the same
uni is using the good cells (space rated). If by some chance you are in the
Sydney region UNSW has an open day this Saturday where among other things
blue sat will have a display along with the solar car which as some similar
( and other very different) issues.

High energy particles ( ~10MeV IIRC)will eventually degrade the performance
of cells in space. LEO will have less particles around but it still a nasty
place.

Every component that goes into a bird will need to be space rated, and
that's where you need to talk to people who know a damn sight more about
this stuff than I.

Hope this helps

Mike

 

Reflectors will not help.

This is a 6-sided application that will most likely rotate in an uncontrolled
manner. Any reflector extending out will cast a shadow on at least
part of another surface (except for the instant one surface is perpendicular to
the sunlight). To get any useful voltage each side must have multiple solar
cells in series. With cells in series, the current fron the least illuminated cell
will be the limiting current. The negative effect of shadowed cells is thus
multiplied by the number of series cells.

A good design would be to wire the outputs of the six multi-cell cube sides
in parallel. Even better would be to have maximum power point tracking
for each of the six sides, but the size/weight constraints combined with a
possible rapid rotation would make this impractical.

Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA

 

Are there antennas or other things extruding from the cube, that might
cast a shadow on some narrow areas of a single panel ?

I assume that you must use separate diodes for connecting each panel
to the main bus to prevent the dark cells from discharging some of the
currents. But how about the shadows from narrow objects such as
antennas that might cast a shadow on an otherwise illuminated cell ?

I assume you would have to use multiple series strings with separate
isolation diodes to avoid a narrow shadow from taking out a complete
panel ?

With multiple independent strings on each side, this would require 12,
24 or even more regulators.

Paul

 

So does that mean they blow away easily in a light breeze?



--
@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@

 

Oh, indeed they do- making them ideal for use in a vacuum, of course.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

The thermal control systems to dissapate the heat however don't.

Mylar degrades rapidly due to free O.

Reflectors mean accurate pointing, otherwise it'll simply shade as often
as not.

 

You can check with UNSW, as others have suggested, but to my knowledge
none of their cells are radiation hard. The main US suppliers of
space-rated solar cells are Tecstar, Spectrolab, and Emcore.

Efficiency will be a bit less in space, since the UV light filtered out
by the Earth's atmosphere will still be present in space. However, the
light intensity is about 35% higher in space, so total power output for
a given cell will still be higher in space. When investigating solar
cells, look for efficiency under AM0 test conditions and assume 1353
W/m^2 insolation. Efficiencies under AM1.5 test conditions are useless
to you. If AM0 efficiency is not specified, the cell is probably not
space-rated.

As for lifetime, electron bombardment is the primary degradation
mechanism in Earth orbit. Cells can be designed to minimize the effects
of this degradtion on efficiency, but those designed for terrestrial use
will not survive long.

A guy named Rauschenbach from the Jet Propulsion Laboratory published a
couple of books on solar array design for space in the 1970s. They might
be a little outdated now, but the basics are still be pretty solid. If
you can't find them in a library or via interlibrary loan, I suspect
they can be purchased from www.ntis.gov.