Off grid system help

[Lilfella87]

So my well is solar 4 320 watt panels. I only have to run the pump every 2 weeks if not more.
What would be a good setup to use them for off grid system?

 

[FilterGuy]

@Lilfella87
Could you provide more info on the current well set-up? What solar chargers, batteries, inverters and other equipment is in the set-up?

 

[Lilfella87]

@FilterGuy the panels are REC 320NP QTY 4 PMPP 320 IMPP 9.37 VMPP 34.2.
They go into groundfos CU 200SQflex.
There are no batteries

 

[FilterGuy]

That is an interesting system. I had not seen that before.

You mention that it only runs every couple of weeks. Do you manually turn it on or does it take that long to refill the well?

 

[Lilfella87]

Manual, we have a 2500 gal holding tank. I'll try to post some pictures.

 

[FilterGuy]

OK..... that is a fairly integrated system. Trying to use the output of the 200SQflex would be impractical so what would be needed is to switch the solar panels over to a separate system when you are not using them for the pump.

Tell me more about what you want to power with the off-grid system? Do you have an idea of how much power you need?

 

[Lilfella87]

That's what I figured or a spliter to power both at once.

Really dont have a idea on power consumption yet. I know that doesn't help much.
I guess my question would be what charge controller would be good. We are in northern Arizona fyi.

 

[FilterGuy]

That's what I figured or a spliter to power both at once.

Really dont have a idea on power consumption yet. I know that doesn't help much.
I guess my question would be what charge controller would be good. We are in northern Arizona fyi.

Before you start buying any equipment, you should get an idea of what you want to do long term. This thread may help:
https://diysolarforum.com/threads/energy-audit-and-system-sizing-spreadsheet.3552/

 

[kernel]

4 panels could make a decent system. Forst i would find out what voltage they are wired in order to determine what controller you would need and if anything else needs to be in place to use the power from them.

Even if all four are wired in series you will find a controller to get it to your battery at its voltage.

From there, as filterguy says you will want to determine the extent of the project. If younare building based on 4 modules and all they can give, without looking to increase system size too much or at all, it becomes easier.

From knowing the amount of time it generally takes to fill the tank amd how often, you can find the average duration of power available in a given season (300 days of sun?) and size the battery from the leftovers as large as it can be and still be charged reliably, then thats your system.

The battery size could limit reasonable inverter sizing.....
Or the battery can be larger and just not cycled so deeply that it may not see a full charge enough to be useful (lithium) or see a full charge every few days or so (lead).

If you leave room in the cc and battery you will habe room for expansion, if you dont need to expand dont buy more electronics and battery than you need, just size any battery so it will still do the job when down to 80% capacity due to wear.

 

[FilterGuy]

To figure out what controller you would need, we need to know how the panels are wired, what the Voc (Open Circuit Voltage) is and what the coldest it will get in your area is. (The Voc goes up as the temp goes down)

Look up the all time low for where the panels will be and let us know.

I looked up the REC40NP and the Voc is 40.8V and the Voc temp coefficient is -0.27 %/°C

Your panels are almost certainly wired in one of three ways:



Given the application, I assume it is wired like 'A' (All 4 in series). This will give the highest voltage for the run down to the pump. Assuming that is true:

• The Voc for this config is 163.2V.
• I did the math for a coldest temp of -20C (-4F) and the Voc goes up to ~183V or higher.

If my assumptions are true, you need a controller that can handle up to 183V on the input.

However, before we can go much further there are some basic questions to answer:

Will this system be totally off grid or grid tied?
Will you want to grow the system in the future?

• More Panels?
• More Storage?
• etc