D.C. pumps and motors... [RE-wrenches]

[Travis Creswell, Ozark Solar]

Dankoff's centrifugal might be just the ticket for you.  Check them out but
maybe Windy or Kim will reply to this thread.

Travis
----- Original Message -----
From: "Carl Emerson" <freepower at freepower.co.nz>
To: <RE-wrenches at topica.com>
Sent: Tuesday, May 22, 2001 4:02 AM
Subject: Re: D.C. pumps and motors... [RE-wrenches]


> Steve...
>
> Thanks for the response.
>
> As I suspected the DC option wins every time if the issue is only
efficiency.
>
> Now to the second part of my question...
> Some DC motor manufacturers are closing down. Apart from getting a motor
that
> might be specifically designed for a fork lift or a golf cart where can
one get
> a supply of DC motors ??
> Typically my clients demand energy efficiency and luxury. They are often
> wealthy green professionals who have escaped from the US and want heaven
in
> clean green NZ.
> They typically want large pools that require lots of pumping. Commonly
these
> pumps will draw about 2.5 kW AC
> As I normally use a 48 Volt battery bank I would like to run the pool
pumps
> with 48 Volt DC motors but have found them hard to obtain.
>
> As a second option, is there a controller available that will reduce the
power
> requirement of an AC motor after start-up ?? I have heard of such a unit
being
> developed but nothing concrete.
>
> Any thoughts welcome...
>
> Cheers
>
> Carl E
>
> info at backwoodssolar.com wrote:
>
> > There is still quite an efficiency difference, partly due to DC and
partly
> > due to positive displacement versus centrifugal.  Easy to calculate:  A
> > Grundfos 120 volt AC well pump lifts 5 gpm 200 feet using about 750
watts
> > from battery to inverter I have measured.  Lets convert that to
equivalent
> > of 150 watts for each 1 gallon per minute lifted 200 feet.
> >
> > A Shurflo 9300 DC pump delivers about 3/4 gallon per minute if operated
on
> > 12 volt DC at 200 foot lift.  It uses about 25 watts.  That is about 33
> > watts per gallon per minute delivered.  Even if these numbers are a good
> > deal off, the difference is clear.
> >
> > But the other argument is that the Grundfos AC pump will go nearly
forever
> > without service, and gives water recovery more quickly.  I think this
> > explains why people with 2500 to 4000 watt inverters are choosing the AC
> > pumps, not that they are getting more efficient. Notice where people's
> > hearts really are.
> > Steve Willey
> > Backwoods Solar Electric Systems www.backwoodssolar.com
> > ----- Original Message -----
> > From: Carl Emerson <freepower at freepower.co.nz>
> > To: <RE-wrenches at topica.com>
> > Sent: Monday, May 21, 2001 3:19 PM
> > Subject: Re: D.C. pumps and motors... [RE-wrenches]
> >
> > > Hullo there...
> > >
> > > I have noticed that it is getting harder to obtain DC pumps and DC
motors
> > in
> > > general.
> > >
> > > There used to be quite an efficiency advantage over AC but recent
> > > developments in inverter efficiency and motor design would seem to
have
> > > resulted in a swing back to AC and in fact some prominent DC motor
> > > manufactures are closing shop.
> > >
> > > I would appreciate some discussion about this. Clearly the DC option
> > allows
> > > the inverter to remain asleep while pumping. Have DC motors had their
day
>
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