From: henry@spsystems.net   
      
   In article ,   
   Keith F. Lynch  wrote:   
   >Why not use *vaccum* cells?  Light hits the cathode, and knocks   
   >electrons out of it with enough momentum to reach the anode against a   
   >moderate voltage gradient.  Should work at any temperature, so long as   
   >the components aren't white hot.   
      
   According to a rather old reference...  The working temperature is quite   
   limited because the best cathode and anode materials are complex alloys   
   involving alkali metals, which melt or decompose at modest temperatures.   
   Moreover, under good conditions the attainable efficiency is about 2%,   
   with an increase by perhaps a factor of two thought conceivable -- but by   
   no means certain -- with extensive development.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)