Solar PV direct Pumping system. What size solar panel do I need?

[bcroe]

I do have a line of power I can hook this up to, but I want to make it fully solar.

The sun may be shining today here in Rockford, but there are plenty of days it is not. Are
you going to use line power then? Bruce Roe

[PNPmacnab]

Watts in X 85% = potential watts out. Lower the voltage and it will be capable of more current. It is the voltage and load on the motor which determines the current. Throught most of the day expect less than 50% of panels output. I would lay the panels almost flat if I had sufficient panel power. E and W also works. Crappy output but more consistent throughout the day. Check open circuit voltage of panels. Converter has to be rated for more than that voltage.

[ERIC5249]

On a bright sunny day one panel might be able to run a 100W pump for a few hours. Looking
out the window by Rockford today, it might take half a dozen or more, does it need to run
every day? You have no line power? Bruce Roe

I do have a line of power I can hook this up to, but I want to make it fully solar.

[ERIC5249]

I'd go with a $20 buck converter and buy a bigger or extra panel. A 300ish watt grid tie panel is only about $200. A buck converter will convert the panels higher voltage to the pumps lower voltage at higher current. This combination will give you longer pump running and protect the motor. Not as good at low light levels as buck converters go into a death spiral when demand exceeds available panel power for a while. Just divide in half any rating for these modules. Youtube probably has some videos on how to convert these modules into a LCB if you are handy.

For a dc-dc step down buck converter, I know it will take in the power coming from the solar panels and you can adjust the voltage to what you need. What about the current? For the pump that I am looking at getting the maximum current it can take is 6.5 A, but I need 3.3 A if I run the pump at 2.2 GPM and 10 PSI. So will the buck converter also regulate the current that is coming from the panels?

[PNPmacnab]

I'd go with a $20 buck converter and buy a bigger or extra panel. A 300ish watt grid tie panel is only about $200. A buck converter will convert the panels higher voltage to the pumps lower voltage at higher current. This combination will give you longer pump running and protect the motor. Not as good at low light levels as buck converters go into a death spiral when demand exceeds available panel power for a while. Just divide in half any rating for these modules. Youtube probably has some videos on how to convert these modules into a LCB if you are handy.

100 watts is the correct size you made it

[bcroe]

On a bright sunny day one panel might be able to run a 100W pump for a few hours. Looking
out the window by Rockford today, it might take half a dozen or more, does it need to run
every day? You have no line power? Bruce Roe

[ERIC5249]

Hello! I am working on a project where I need to pump water from one tank to another one. I am located in Rockford, IL and need to pump this system for a few hours. The pump that I am looking at using is a Shurflo 12 VDC pump (Model # 2088-514-145). I need 10 PSI and 2.90 GPM and the current needed for the pump is 5.6. I am not going to use any batteries as they are expensive, but I am wanting to use a Shurflo pump controller, 902-200 9300 series 12/24 V, to get a better performance from the pump. The one thing I am not sure of is what size solar panel do I need to run this pump? I calculated that I would need a 100 Watt pump, but I am not sure if this is correct.