[RE-wrenches] PV driven air compressor

Howie Michaelson howie at suncatchervt.com
Tue May 25 22:18:22 PDT 2010


Phil,

Thanks for the info.  The pump being considered is a Gast 22D 1180 series,
either the 1002 (12v) or the 1005 (24v) - see attached spec sheet (I think
I can attach now?).  I was assuming that using a linear current booster
with a voltage limit such as:

http://solarconverters.com/ppt7.htm
model PPT 12/24-7V M24

will protect against over voltage.  I was assuming undervoltage wouldn't
hurt the pump much (like using PV direct with an "El Sid" for SHW
pumping), and the LCB will provide the higher current potentially
necessary to start the pump.  Am I wrong about these assumptions?  I am
leaning toward the 24v pump, since it gives me more overhead with a
smaller LCB.

Always appreciate the wealth of experience and knowledge this list avails me.

Howie
-- 
Howie Michaelson
NABCEP Certified Solar PV Installer™

Sun Catcher, LLC
Renewable Energy Systems Sales and Service
VT Solar & Wind Incentive Program Partner
http://www.SunCatcherVT.com
(cell) 802-272-0004
(home) 802-439-6096


On Wed, May 26, 2010 12:51 am, Phil Undercuffler wrote:
> In my experience, there's few problems in the world that can't be solved
> with more PV -- including running pumps with permanent magnet/brush motors
> array direct.  However, there's a couple things to be aware of -- first,
> sizing the array.  Although the pump may be rated to draw 90 watts when
> running, you need to oversize the array to ensure 90 watts will be
> available
> under normal daily conditions.  The exact amount of oversizing depends
> upon
> many factors, but without further testing I'd ballpark an additional 30%
> over rated running watts.  Also, the array needs to be larger if the pump
> starts under load, which is highly likely with an aerator (probably
> doesn't
> have an unloader valve, if those work with aerators at all).  So far,
> everything leads one to say, rock on with the 180-200 watt modules.
>
> But, it's sometimes not so easy.  Most 190-200 Watt modules available
> today
> have 60 cells, and don't nicely align with 12 or 24V "nominal" voltages.
>  Does your aerator come in two flavors, 12V or 24V, please specify your
> preferred voltage upon order?  Or does it have electronics built in, and
> will take anything in a range between 12V and 24V (unlikely, but
> possible)?
>  If the former, then you really need to find some module combination that
> provides 36 or 72 cells in series -- otherwise, you'll either run the pump
> under or overspeed, which will impact longevity and performance.  If the
> latter, make sure it will be happy with the voltage the module puts out --
> over the full range of conditions.
>
> Empirical testing can sometimes be the best approach with a project like
> this, but it's a good idea to do a little homework beforehand, to best
> know
> what the expected behavior should be.  Good luck with it, it sounds like a
> fun project!
>
> Phil Undercuffler
>
>
>
>
>
>
> On Tue, May 25, 2010 at 9:30 PM, Howie Michaelson
> <howie at suncatchervt.com>wrote:
>
>> Hi all,
>>
>> I have a project to provide PV power for a small diaphragm air pump (1/8
>> hp, 12 or 24 vDC, 6.2 or 3.5 running amps, 90 watts).  As it turns out,
>> pricing from my distributor is cheaper for 180-200 watt modules than for
>> anything smaller.  I don't spec PV driven pumps except for SHW, so I'm
>> just checking for any reason to not use the larger modules.  The pump is
>> being used to aerate a pond, so no problem with excess pumping.  I will
>> most likely use a linear current booster to improve output, but mostly
>> to
>> limit voltage.  Any advice would be welcomed.
>>
>> Thanks,
>> Howie
>> --
>> Howie Michaelson
>> NABCEP Certified Solar PV Installer™
>>
>> Sun Catcher, LLC
>> Renewable Energy Systems Sales and Service
>> VT Solar & Wind Incentive Program Partner
>> http://www.SunCatcherVT.com
>> (cell) 802-272-0004
>> (home) 802-439-6096
>>
>>
>>
>>
>>
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