Alt-BEAM Archive
Message #10964
To: beam@sgiblab.sgi.com
From: Wilf Rigter rigter@cafe.net
Date: Sun, 27 Feb 2000 13:15:56 -0800
Subject: [alt-beam] Re: Solar Cell tests
Just some simple ideas to increase the effiency of series connected unequal
solar cells:
The best method may be to use a high current solar cell in series with a
"switched" low current/high voltage "booster" cell. The higher internal
series resistance of the low current cell is bypassed with a reverse biased
parallel germanium / schottky diode (or better yet a mosfet) during the
initial part of the charging cycle when the voltage on the storage cap is low.
When the voltage on the cap approaches a crossover point where the current is
lower and the voltage drop across the internal resistances is smaller, the
booster cell generates the "top-up" charging current towards the open circuit
voltage. This should result in a dual or triple slope charging curve with the
first part a fast exponentially tapering curve and the middle part a fairly
linear constant current curve and the last part again exponentially tapering
towards zero. This can be tested using the real thing or with a couple of
batteries and resistors to simulate the solar cells and the additional
diode/mosfet and cap. Of course anyone with a linear circuit simulation
program can also try this out from the keyboard.
regards
wilf
CyberBug wrote:
> Sorry, forgot the images....
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