Help with small system sizing!

5 Posts
Jan 11, 2008 05:03 pm
Help with small system sizing!

Hey guys. I am trying to size a small PV system for a battery bank to power my 2 pool pumps. I have never sized a battery bank and need some help.

Here are my loads:

Pump 1-      1 1/2 HP  230V 12A
daily operating time 10 hrs.

Pump 2-      1 HP  230 V 12 A
daily operating time 6hrs.


I am assuming my surge requiremets for each will be Wattage x 3.

I need to know how to size a battery bank for this with some flexibility (possible 2 day autonomy here and there during pool season)

How to size the according array and and what operating voltage to set the array/ bank to.

Any other controllers, protection, disconnects that may apply.

Can anyone help me with this or give me some help. Once again any help would be greatly appreciated.

 
163 Posts
Jan 12, 2008 09:16 am
Re: Help with small system sizing!

Hey guys. I am trying to size a small PV system for a battery bank to power my 2 pool pumps. I have never sized a battery bank and need some help.

Here are my loads:

Pump 1-      1 1/2 HP  230V 12A
daily operating time 10 hrs.

Pump 2-      1 HP  230 V 12 A
daily operating time 6hrs.

That is quite a large system. Here is how you can start. 1HP = 745 watts, but the HP rating on motors can be quite nominal sometimes. My 1HP pool pump runs at a measured 1200 watts, so lets use 1800 watts for your 1.5HP pump.

1800 watts for 10 hours is 18 kilowatt hours per day. Now add on another 8 kilowatt hours for your 1HP pump. To get that from a 12V battery you will need 24000/12 or 2000 amp hours of battery life. That would be 20 batteries of 100AH capacity each, but since you don't want to discharge your batteries more than 50% then you need 40 batteries. That then becomes 80 batteries if you want reserve power for 2 days.

I would estimate that you will need around 10kilowatts of PV power to run that system.
 
462 Posts
Jan 12, 2008 11:07 am
Re: Help with small system sizing!

Jeffery, before you invest in a large system, what I tell homeowners who want to reduce their electric bills associated with pool pumps is that first you should minimize usage. Determine how much water you pump can pump. Gal/min etc. Then figure out how many gallons there are in you pool. It should then be easy to see how long it would take to filter your pool twice. If it comes out to be less time than the time you run the pumps now, you might be able to reduce filtering time. Then you can add an appropriate sized timer (Watts) and filter the pool at night, when it is cooler, to make the pump run more efficiently.
 Filtering the pool while it is being used, especially with kids stiring it up, is usually the best time. Just turn the filter on manually while it is being used.
 After time notice your savings and usage and then you can probably purchase a smaller, move affordable PV system if you still choose to.
 
163 Posts
Jan 12, 2008 01:11 pm
Re: Help with small system sizing!

Judging from the size of the pumps and the number of hours run, I was guessing this to be some sort of community pool.
 
5 Posts
Jan 13, 2008 10:08 pm
Re: Help with small system sizing!

Hey guys, I am now seeing this may not be the most efficient way of going about this project. For one, batteries are expensive and I would need alot. Another is the pumps are not efficient and would need a considerably large array to charge the batteries.Another is the system would only be used 4 months out of the year so why not install the system and pump the electricity back to the grid year- round. This is not a community pool but I guess they are some pretty large pumps. The pool is abot 22,000 gal.

Now I am leaning towards solar efficient pumps and running the pumps during the sun hours. This should be efficient enough especially since I am finding that the solar pumps (DC) have AC backup just in case.

If anyone has any input on this project feel free to reply.

 

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