pv powered pool pump

 Does anyone have any experience running a swimming pool pump directly off
PV?  I currently have a 1Hp AC pump that is running 8-10 hours a day.   It
occurred to me that switching this pump out for one that is powered directly
off PV would be the cheapest way to start using PV power.  It wouldn't need
to be grid tied.  It wouldn't need battery backup, etc.

It seemed silly to pay for a grid tie 1500watt PV system if the pool pump is
already pulling more power than it would generate.

Are there any negatives to my plan?   Any guesses on what it would cost?

thanks again,

mike

 

  Hi Mike,

  The group talked a bit about this with spa pumps and other
motors. The starting current is the big issue. If you are keeping
the existing motor, you have to have a way to meet the starting
current specification, which is usually a lot higher than running
current. You would probably need batteries to supply this current,
or have to pay for many more panels, which would be more
expensive and would not provide you with any run time when
cloudy.

 
Would it work if I switched out the AC pump motor for a DC pump?   Is the
only downside no pumping on cloudy days?

mike




  Hi Mike,

  The group talked a bit about this with spa pumps and other
motors. The starting current is the big issue. If you are keeping
the existing motor, you have to have a way to meet the starting
current specification, which is usually a lot higher than running
current. You would probably need batteries to supply this current,
or have to pay for many more panels, which would be more
expensive and would not provide you with any run time when
cloudy.

 

  There are large DC motors, but they require large start currents also. =

If it were brushless DC, that is essentially a permanent magnet
AC motor and would require a special "soft start" vector controller
to keep the startup current managable. I would still think that you =
would
need batteries for take up the startup surge, but others may have more
experience in this area.

 
I hadn't thought about the pool pump itself, which I run at night if I'm
not in the pool, but I did want to add a solar heat system for the pool.
It seemed natural to me that solar power for a pump for solar heat went
hand in hand, but the feedback that I get is that the solar system needed
for the pump would be too large to be economical as a standalone system.

Converting a domestic water supply pump to solar usually involves a greatly
reduced flow rate in a DC pump, instead of AC, and a storage tank.  i don't
know if you can effectively reduce the flow rate for a normal pool pump.

A one horsepower pump draws at least 750 watts, more at startup.  
My 1HP motor has a 9.0 Amp rating on the label.

That's a substantial solar system.  You're asking for 6-8kWh per day.
I would guess $10,000 grid-tie, $15,000 off-grid.  but what do I know? ;-)

If you go that big, why not do a grid-tie?  Run the pump at night.
Then there might be some credits and rebates available, depending on where
you live.

You need some batteries, at least to smooth the startup current, if it's
a standalone system.  A battery system could be handy in power outages as
well.  Instead of running the pool, you could run household items.

http://www.green-trust.org/2003/pvsizing/default.htm
http://www.kyocerasolar.com/products/pv_calculator.html

--
Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5
http://cdold.home.mchsi.com/Solar-generation.htm