Anyone use PV to run a motor? Customer would like to run a 0.5HP motor off of PV panels. I suspect a VFD (low startup torque is OK and would minimize starting current) fed with 200 VDC from four panels might work and would eliminate an inverter. Batteries are not desirable. Obvious need to monitor for adequate voltage, but prefer to not rely on the VFD to make that decision. Any suggestions? Thanks.
PV for motor
- Thread starter sgunsel
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K8MHZ
Senior Member
- Occupation
- Electrician
Take a look at solar attic fans. You may be able to just scale up from there.
petersonra
Senior Member
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- Northern illinois
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- engineer
there are solar powered well pumps that run directly off of PV panels.
I would just get a dc motor.
I would just get a dc motor.
- Location
- Placerville, CA, USA
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- Retired PV System Designer
For best performance over a range of panel output power (resulting from differences in weather, time of day, etc.) with a simple DC pump you will need to install a linear current booster between panel and pump. This will allow the pump to deliver the optimum flow rate as the available panel current changes while the maximum power voltage of the panel stays the same.
Solar powered well pumps that run directly off the panel output usually include such a device (or a DC-input VFD driving an AC motor.)
petersonra
Senior Member
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- Northern illinois
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- engineer
The OP did not mention what the motor was.
A half HP motor would be a very small well pump.
The direct driven DC well pumps I was referring to are designed to run continuously at very low flow.
A lot would depend on just what the application is that the guy is suggesting.
In any case, doing anything like this off of PV without batteries is often an exercise in futility.
A half HP motor would be a very small well pump.
The direct driven DC well pumps I was referring to are designed to run continuously at very low flow.
A lot would depend on just what the application is that the guy is suggesting.
In any case, doing anything like this off of PV without batteries is often an exercise in futility.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Quite true. Some form of energy storage is often needed. But it can be in the form of batteries to run the pump when needed or in the form of pumping when energy is available to fill a water storage tank.
One complete exception is a swimming pool filter, where you need to run a certain volume of water per day and do not much care when.
broadgage
Senior Member
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- London, England
IF this is for a well pump, then I would agree that a dedicated PV pump is the way forward.
0.5 HP is almost certainly ample even for a large house or modest size farm. Remember that a typical line powered residential well pump runs on demand and must be able to supply enough flow and pressure for perhaps an effective shower and a dishwasher at the same time, this requires at least 1HP and sometimes more.
A PV well pump normaly runs continually during sunlight and fills an elevated water tower or tank, therefore a much lower HP suffices as it only has to meet the average water demand not the peak.
If this is NOT for a well pump, then you may need a battery.
The output from a PV array is very variable and PV well pumps are designed to make best use of this variable input.
For most other applications the motor speed and output HP will vary too much without a battery to provide a roughly constant voltage.
0.5 HP is almost certainly ample even for a large house or modest size farm. Remember that a typical line powered residential well pump runs on demand and must be able to supply enough flow and pressure for perhaps an effective shower and a dishwasher at the same time, this requires at least 1HP and sometimes more.
A PV well pump normaly runs continually during sunlight and fills an elevated water tower or tank, therefore a much lower HP suffices as it only has to meet the average water demand not the peak.
If this is NOT for a well pump, then you may need a battery.
The output from a PV array is very variable and PV well pumps are designed to make best use of this variable input.
For most other applications the motor speed and output HP will vary too much without a battery to provide a roughly constant voltage.
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