Solar Pumps for Pakistan

[muddasirwaheed]

Due to extreme power outage the irrigation system largely dependent of self owned water pumps is severly affected in Pakistan

The water table in the Pujab the major agrarian province is around 60-70 feet
The deep well turbine and centrifugal pumps used by farmers cover this range and above with 20-30 HP induction motors with 1 -1.5 cusec water flow (100m3/hr)
A proposal is underway for using solar energy with government support (may be) for water pumps
The pipe diameter in most pumps and turbines is 6 inch
Now the easiest and straight forward option is to use a solar panel with 3 phase inverter (sans economy) this is the easiest and fastest solution as there could be great reluctance on part of farmer to alter their existing pump/motor set ; so direct driven dc motors (which are ususally submersible) is not an option.
Any comments or suggestions ; whether its right way to go if you donot have to alter the pumpimg infrastructure or introducing a new system would be more beneficial
(no storage/overhead/battery required,)
Regards

[thastinger]

The farmer will loose his "great reluctance" to switch to a DC pump motor once the water stops flowing. No need to reinvent the wheel here, PV and DC well pumps are used together all over the world, probably for good reason.

[Mike90250]

The farmer is going to need a pretty big field to harvest enough solar to run a 30hp pump.

[muddasirwaheed]

Why Dc motor for solar pumps

Point well taken but there is one clarification why dc? it would higher initial and maintenance cost , not sure about reliability and 3 phase motors are rugged and could be easily serviced and repaired near installation site, plus there is a constant rpm requirement (usually 4 pole , 1450 rpm type), so the farmer familiarity and existing market would be in favour of pre existing 3 phase motors , please suggest why NOT to use an inverter 3 phase.

PS it is being planned to target 12.5 acre land so even 10 HP motor could do at around 10 cusec at 70 feet depth ? is 10 HP upper ceiling workable.

[inetdog]

Point well taken but there is one clarification why dc? it would higher initial and maintenance cost , not sure about reliability and 3 phase motors are rugged and could be easily serviced and repaired near installation site, plus there is a constant rpm requirement (usually 4 pole , 1450 rpm type), so the farmer familiarity and existing market would be in favour of pre existing 3 phase motors , please suggest why NOT to use an inverter 3 phase.

The answer to your question is simple but not obvious. A DC pump can run at reduced speed and output when the available current is not enough to run it at full power.
An AC pump driven by an inverter will always try to run at full power and the inverter itself will shut down if not enough DC is available to power the pump at full speed.
If you used a specially engineered VFD with DC input instead of an inverter, you could get the same effect with an existing AC pump.
The power from the panels, without batteries, is not constant and is very often less than the maximum value for full sun.
So you would have to size the panel array for several times the expected load and use a specialized inverter if you do not use a DC pump.
And although some of the DC pumps that people often talk about are straight DC pumps for small (decorative pond, for example) applications, they are actually AC pumps with a built-in VFD/Inverter combination for larger sizes. (It is best if the AC pump and the VFD/Inverter are engineered to work together rather than being supplied separately.)

[muddasirwaheed]

ac motors with VFD and inveter for solar irrigation pumps

Regards,
I believe there are some latest solar inverter available 3 phase which are specialized for driving ac motors for instance they have star-delta combination built in for soft starting motors and VFD option to vary operating frequency to maintain the constant operating speed ..... I hope some one could point over this feature if with this is now comaptible with DC motor opition ?

[inetdog]

Regards,
I believe there are some latest solar inverter available 3 phase which are specialized for driving ac motors for instance they have star-delta combination built in for soft starting motors and VFD option to vary operating frequency to maintain the constant operating speed ..... I hope some one could point over this feature if with this is now comaptible with DC motor opition ?

The question I would ask is whether these inverters require batteries or can operate directly from the panels. I have not seen them described. If batteries are required, the cost of the system goes up a lot.

[Texas Wellman]

Franklin electric now makes a solar-ready inverter. From the information I have seen it runs a normal 3-phase motor and uses DC input as it's power. I'm not sure if it goes up to the HP you require. Perhaps you should contact them and see if they have something for your application.

PS...You're going to need a lot of panels either way.

[Texas Wellman]

I just checked...looks like franklin only goes up to 3 HP 90 GPM pumps. http://solar.franklin-electric.com/products.aspx#Tab4

Franklin electric now makes a solar-ready inverter. From the information I have seen it runs a normal 3-phase motor and uses DC input as it's power. I'm not sure if it goes up to the HP you require. Perhaps you should contact them and see if they have something for your application.

PS...You're going to need a lot of panels either way.

[muddasirwaheed]

no batteries with soalr pump

no sir no battries are required, all we need is PV and directly operatedy 3phase inverter with built in functions? any suggestions?

[SunEagle]

no sir no battries are required, all we need is PV and directly operatedy 3phase inverter with built in functions? any suggestions?

It is not going to happen. Your 30hp AC pump is too big to run directly off of a PV system without the requirements for a battery / inverter hardware.

[Texas Wellman]

PM Sent. I would like to see if anything comes of what I sent you so keep me informed.