Anyone here using a borehole pump running directly off PV?
The one side of the coin is just use a traditional AC pump on your inverter and use the money you save on more panels for your main system. Plus if the pump isn’t running then you can use that PV capacity for something else in the house.
However if you go beyond the typical 5 or 10 kl tank for home use, if you have 50, 60 kl of water storage capacity which you use for irrigation on a big veg garden and fruit trees, so a lot of pumping basically, then my thinking is that a direct PV pump might just be worth it since you’ll have to pump water practically every day for a few hours, Working on 5 kl extraction per day.
The panels dedicated to this will be 1.5 to 2kW, so let’s call it R10k.
The solar pumps is around R15, R20k more expensive than normal AC pumps, rough estimate, plenty variables.
For R30k you can add a good amount of extra panels on your main system. But for R30k you won’t be able to add more inverter capacity plus more panels to your main system, capacity which will anyway be tied up by the borehole pump for the majority of the day.
Yes, I have done it with a very small pump (300W’ish). I can’t remember exactly the specs.
About a 90m head, probably delivered around 400l p.d. It had a built-in MPPT, so it connected directly onto 2 x 240W panels.
It worked for about a year. I haven’t pulled it up to see what is wrong, but they supplied a second internal rubber “thingy” with the pump. So I guess that part wears out.
I’d go the conventional 1ph AC route given a choice in future.
What intrigues me with these dedicated solar devices is whether they are improving the efficiency compared to the mains version.
I recall years ago the ‘alternative energy’ market (in the US) pushed for more efficient fridges. And then suddenly fridges became a lot more energy efficient.
The journey of energy efficiency and your grasp of it is intrinsic to RE. The energy that RE produces isn’t abundant so you need to utilize it efficiently. This means managing your loads as well.
It is for a farm, grid tied and who knows, maybe even eventually off grid.
The direct solar pump makes more and more sense to me, especially because of the volume of water / duration in a day the pump will have to run.
Making provision for a AC pump on the main system will let’s say mean having to size up from a 5 kVA Multi to a 8 kVA Multi, along with the additional PV which goes with the bigger inverter, such a upgrade will get quite expensive.
Hence my thinking to rather just spend money on a solar pump with a couple of panels for it. It can do its own thing at its own time, pump threw an entire day as long as the sun shines for all I care, and I don’t have to worry about it taking up capacity on the main system.
Because of the water storage volume, it won’t be a train smash if we can’t pump for a week because of no or low sunshine, even more so if it rains during that week or even longer. And should the brown stuff really hit the fan, there will always be AC backup, most of those pumps can run on AC as well.