Guru
Joined: 09/08/2007
Location: AustraliaPosts: 4406
| Posted: 03:57am 26 Aug 2019 |
Where there is plenty of sun, there is no problem driving a pump.
The difficulty is the start up current and maybe priming the pump if its a deep well.
In very heavy overcast the pump may not be able to even start, it will just pull the solar panel voltage down to almost nothing, well below any usable power curve.
So basically nothing at all will be pumped.
If you have a bank of ultracaps and allow them to charge, that might take several minutes. Then hit the pump with that. It should start but only run for perhaps a few seconds, but at least you will get something.
The more ultracaps, the longer the pump will run for each time, but it also will take correspondingly longer to recharge.
If you need 1Kw to lift water to a fair height, and there is only fifty watts of solar, it will only run for about 1/20th the time it takes to recharge. But you WILL get your miserable 50 watts worth of water pumped, even if the sky is evil grey for a week.
The VFD method would be much more appropriate for a higher voltage, much higher powered system. But at ultra low turning speed, it may still not develop enough torque to raise water to a sufficient height. Short bursts at near full power may be more effective.
For a really small low power system a 24v or 48v positive displacement pump running intermittently, and some ultracaps and a couple of panels could probably all be done at a tolerably low cost.
Edited 2019-08-26 15:08 by Warpspeed
Cheers, Tony.