[amsat-bb] Hot solar panels

Bob Bruninga bruninga at usna.edu
Sun Jan 16 08:45:18 PST 2011



I read in the recent AMSAT journal about the new AMSAT Cubesat.  It will
have deployable solar panels.


For what it is worth, we have just completed our in-depth thermal analysis
of the 4 deployable solar panels on our cubesat (Psat) and were shocked to
learn how hot they will get.  Probably 90C or nearly boiling.  This probably
not a problem for space-rated cells, but we fly tedlar coated cheap
terrestrial cells and they have real problems at those temps.


Also, the nearly 2 volt drop in output at those elevated temperatures from
8.4v to 6.4 v or so has forced us into a complete re-design of our power


The reason these temps are such a surprise to us is because in the past, all
of our solar cells were body-mounted where they can conduct  their heat
away.  But with "deployed" panels, there is nothing but emissivity off the
back side to get rid of heat.  They will get very hot, and 45 min later get
very cold.  This thermal cycling is an order of magnitude worse than with
the body mounted cells too, leading to life concerns.


So, hope you are taking all this into consideration.


Just a thought

Bob, Wb4APR






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