From: ems@michael.apple.com (E. Michael Smith)
Newsgroups: sci.energy
Subject: Re: Why not 120 VDC ?  Why invert?
Date: 25 Jan 93 01:49:43 GMT
Organization: Circle 'C' Shellfish Ranch, Shores-of-the-Pacific, California

In article <1jr751INN16a@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes:
>In article <1993Jan23.000753.14523@michael.apple.com>, ems@michael.apple.com (E. Michael Smith) writes:
>>Pondering this ...  Why not just use a 120 VDC battery pack and use
>>120 VDC for a bunch of stuff?  Lightbulbs don't care if they are
>>AC or DC,
>
>Well, actually, the fluorescents with transformer ballasts *DOL* care.  They
>need the AC for the transformer to work right.  

They are inductor ballasts rather than transformers, but that is splitting
a hair...  I'd use electronics anyway ...

>Now, incandescent lamps will
>handle DC quite well, and fluorescents with electronic ballasts want DC, I
>think (but not necessarily 120-volt DC).

The ones I dissected took 120 VAC and ran it through a bridge.  They 
should work on 120 DC, since I say no voltage doubler or indications 
that the peak, as opposed to RMS voltage was used.  Other brands may
differ.

>>nor do electric stoves and ovens or other resistive heat
>>sources.
>
>True.  However, if you care anything at all about energy efficiency, you don't
>use resistive heat sources.

Blanket statements don't always hold ...  speaking of which, what 
non-resistive electric blankets are you aware of? ;-)

There ARE places where resistive heat continues to make sense...

>>Some tools have AC/DC motors.  120 VDC was a common motor
>>type not too long ago, so I'd expect some motors to be available
>>for things like house fans.
>
>But it doesn't work very well for driving synchronous motors.

Neither my HVAC unit nor my table saw have a synchronous motor.
Nor do my clocks, come to think of it .. wonders of the 
electronic age ...

>>Yeah, I know, you shouldn't have an electric stove or oven.  But
>>the house already has one and my wife doesn't want to learn to 
>>cook on gas.  (though I think it is really 220 ... more batteries...)
>
>Cooking with gas it a lot easier than cooking on an electric range.  

I think so, my wife does not.  In my experience, it depends on what
you were raised with.  Most folks seem to like what they learned on.

>>So why not?  Why not have a 120 VDC battery bank directly running 
>>the incadecent lights, and any easy to change motors like heaters,
>>and any suitable electronic ballast CF bulbs?  Then you only need
>>an inverter for the electronic stuff, some general purpose outlets
>>in the kitchen and other parts of the house, and maybe the fridge.

>Switching
>to DC means you've probably got to replace your refrigerator, your vacuum
>cleaner, your television set, your stereo....

Um,the original posting stated clearly that I was looking at a mixed
mode system.  (In particular, I stated that an inverter would be
needed for electronics, misc. electrical outlest {like for the vac}
and the refridgerator).  

I'm not looking for a one-size fits all.  But that may be the answer
as to why 120 VDC isn't used.  Folks seem to want exactly that, one
size fits all.  ALL inverter, or ALL 12 VDC... 

BTW, to all the folks who wrote the virtues of gas stoves:  I LOVE GAS
STOVES (I was raised with one)!  It is my wife who wants electric...


-- 

E. Michael Smith  ems@apple.COM

'Whatever you can do, or dream you can, begin it.  Boldness has
 genius, power and magic in it.'  -  Goethe

I am not responsible nor is anyone else.  Everything is disclaimed.