# Forum Home Renovation Solar Electrical Systems  Stand alone solar system for pool filter and solar heating pump

## Poolsun

Hi all. First time on! Is it possible to have a stand alone Solar PV unit that could power an existing pool pump and solar heating pump. Or do I need to change both?

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## Wombat2

Short answer is Yes - but not as simple as hooking a an inverter to a PV panel and plugging the pump into it. 
With our grid connect system I've learnt a lot - eg (for Queensland ) they suggest divide your usage by 5 and that gives the output you need from the PV array. ( being 5 hours a day of usable sunshine) So 3Kw of panels = 15KwH output - which we get as a daily total but with output spread over 10 hours we average 1.5Kw per hour and either end of the day are a lot lower than that. So you will need a battery bank to store your power and even it out - and an inverter capable of STARTING your motor - in other words possible as much as 3 times the size as the motor to take the start current.

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## applied

Why stand alone, just get a small say 1.5kw grid connect it would attract govt subsidy and would be cheaper than a standalone system with less maintainence issues also it would cover a large majority of the energy required. 
My solar system covers the energy used by the tumble drier with the bonus of not having to go outside to get one off the line :Biggrin:

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## Johning

> Why stand alone, just get a small say 1.5kw grid connect it would attract govt subsidy and would be cheaper than a standalone system with less maintainence issues also it would cover a large majority of the energy required. 
> My solar system covers the energy used by the tumble drier with the bonus of not having to go outside to get one off the line

  I totally agree with Applied (first paragraph) with the added bonus that you may generate enough energy in the day to qualify for the premium feed in tariff. Nearly fell off my chair when reading the second paragraph, until I saw the smiley. Good one.

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## dynamictiger

First off let me say I am in teh swimming pool industry, however not usually involved in domestic systems so please do not ask me domestic questions. 
However, I did start in domestic side of this business. 
For several years now I have been conducting thought experiements on alternative solar powered swimming pool pumps and how these may work, what issues they may face and what could work.  After considerable thought, and perhaps it is appropriate to say I have designed a new pool heater for Rinnai, designed a childrens water playground for Kalgoorlie Oasis when the consultant couldn't, etc.  The design I have arrived at should work, although I have not had an opportunity to test it. 
If anyone is that interested I can go into all the reasons why this should work, however I think this is both beyond my intended scope here and interest of nearly every reader except me and my cohorts. 
First off you need a second pump.  This pump is most likely sold as a fishpond pump and would be in the range of the pool volume divided by 6-8 as we want to acheive around 8 hours tuirnover.  So if your pool was say 60 000 litres this would equate to about 10 000 litres per hour.  You want this flow rate at 2 or more metres.  So in pump parlance this pump is 10 000 litres per hour at 2 metres (or more) e.g. 3, 4,5 metres.  The pump selected should be able to operate outside of the pond.  Watch out many of these pumps are designed for operating fully submerged you don't want this. 
Now the plumbing bit. 
Next to your existing pool pump, place this little fishpond pump and then attach it to both the suction and discharge of your existing pump.  Unfortunately it is not that simple - nothing ever is.  You need to install check valves to prevent your main pool pump sucking this pump dry and to prevent the water simply circulating through your pool pump.  The sketch I have done attached should help explain this. 
Now the operation is very straight forward.   
Your solar panel will drive the pond pump and unlike a pool pump that is drawing perhaps 1.5 kW the pond pump will draw something like 685 watts.   
Your pool circulation pump is only run when you either need to clean the pool and it is cloudy etc or when the pool is in use. 
Negatives with this approach are:
-Can't run an automatic cleaner - not enough grunt
- May need to run your pool pump an hour or so a day to give the chemical levels a boost(don't know that is the issue with thought experiements)
- You still need to run your main pump for a period post pool use.  This time will vary with use and I cannot tell you what that is
- Salt chlorinator outputs may need adjusting
- Some pond pumps may not tolerate chlorine
- Can't run pond pump and main pump at same time 
Positives anticipated:
- No need to run main pump when pool not in use significant reduction in power consumption
- 8 hours is typical older syle commercial pool turnover time - will work for lightly loaded domesitc pools
- Better filtration - do you really want to know why
- Possible reduction in backwash frequency requirements 
HTH

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