Bringing my second-generation solar system up

[MichaelK]

We own a piece of land up in the mountains where we're creating an off-grid organic homestead.  For the last few years, a 400 watt solar system supplied a bit of power at our cabin.  But, a long-term goal of mine was to design and build a much larger system capable of powering my 240VAC well pump.  This would reduce fuel consumption on the homestead significantly for our orchard/garden irrigation.

Using a clamp meter I determined that the 1.5hp pump was using 10 amps to run.  This Fluke meter also has "in-rush" capability, and measured that starting amperage at 37-38 amps (500 mSec).  That means I needed a substantial inverter to supply that much power.  I selected Schneider's XM6848 120/240VAC inverter that has up to 12kw of surge (5 seconds).

I coupled this to 15-300watt Renogy panels, wired three in series per array, a 3S5P configuration.  The 115VDC from each array was funneled through a combiner box which feeds a Midnight 200 charge controller.  The Midnight charges a bank of 8 L-16 batteries wired in series for 48V.  Here's a pic of the array frame, made out of welded unistruts. 
(attachment 1)

The frame fits over a single steel pipe sunk in 48" of concrete, which allows the array to track the sun left and right.  The horizontal stabilizers at the bottom also allow for season angle changes.  Here is the array with the panels installed.
(attachment 2)
Though I did most of the wiring myself, my BIL is a retired electrician, so I had him inspect my work.

Last month we flipped the breaker to start the well pump, and the XM powered it up with ease.  I'm now in the performance qualification phase of the system.  My rule of thumb is to run the pump only while the panels are capable of making >2400 watts of power.  This happens after about 9:30 in the morning.  If the arrays are swung over to face SE, the batteries are mostly charged by then.  By noon though, there's enough excess power to bring the batteries up to float.  I position the arrays manually to track the sun when maximal power is needed.  On days I’m not pumping water I can just lock the arrays in a south-facing position and forget about them.

[ClassicCrazy]

Looks good !  You did your homework and it paid off with that nice installation.

Larry

[Westbranch]

Like. 

Your lead in suggests you have a question, or ??

[CDN-VT]

Nice & Like

Large LPG tank there also

VT

[russ_drinkwater]

Maybe, he is concerned about the storage capacity of the trojans.
Especially if the pump is having to operate at night.

[MichaelK]

Maybe, he is concerned about the storage capacity of the trojans.
Especially if the pump is having to operate at night.

No questions?  I most definately will not be running the pump at night!  Way too much of a power hog to run without active solar coming in.  I am experimenting a bit though with how long in the afternoon I can keep the pump running.  My rule of thumb is to allow the pump to run if the incoming solar is ≥ 2200 watts.  That's from about 8:30am till about 3:30pm. 

In my last experiment, I ran the pump till 5:30pm, measuring SG every 15 minutes.  I stopped with SG dropped to 1.265 (90%).  That's very conservative, and I can go lower, but I don't want to go overboard just yet.  My plan is to pump until I've drained the batteries to a manageable level, bulk charge early in the morning, then get the pump running again as soon as the watts are available.  As long as the sun's up, I can still get the batteries fully charged again before noon.

This is of-course while we are still just using the cabin on weekends.  After retirement I'd expect to run the pump as needed on any day of the week its convenient.  For now its simply "how many gallons can we squeeze out of a weekend.

[Westbranch]

Have you measured the load ,supplied by the batteries, as the pump starts up?

I had a harebrained idea that you could start the pump from the generator and the after the pump is running and a god BULK charge has been added, switch off the gen power and let the batteries spin the pump... I am assuming that the pump runs continuously... that might give you more late afternoon run time before hitting your target SoC ...

[MichaelK]

I had a harebrained idea that you could start the pump from the generator and the after the pump is running and a god BULK charge has been added, switch off the gen power and let the batteries spin the pump... I am assuming that the pump runs continuously... that might give you more late afternoon run time before hitting your target SoC

I actually considered that idea in the design phase of creating my new system.  I was very concerned that whatever inverter I got wouldn't handle that half second of 9kw.  I spoke with a Magnum technical rep that thought their 4448 model wouldn't be able to handle it.  The Schneider rep though responded yes in less than a heartbeat.  Since I knew the generator could handle the starting surge, I thought I might just run it for 5 minutes just to start the pump, then shut the gen back off.

The very first time I flipped that switch, I had a fire extingisher within reach.  Talk about naive!  I am just so impressed now with the capacity of the XW.  Guess this is what engineers refer to as overbuilding.  Starting with full batteries, I think it's realist to get 9 hours of pumping in a day (well, maybe not in November), without the generator running at all.  This is the first time I can remember driving up to the cabin without bringing a 5 gal can of gasoline with me!

[russ_drinkwater]

Have you considered a direct power pump.
Many of the bores over here have a dc pump, controller box and 2-12 panels depending on job.
The pump fires up when enough amps are being generated by the array and then shuts off when PV
drops off in the late arvo.
You can submerge them in a bore or have them on float in a dam etc.
Number of panels depending on the head and volume of water required.

[MichaelK]

I'm totally satisfied with my system as is now.  I intend to keep it this way till the pump dies of old age.  When if finally comes time to replace the pump, the first I'd consider is Grunfos' AC/DC compatible 4" pump, the 6 SQF-3.

[tecnodave]

MichealK,

Very nice.....looks like that homework is paying off...



I'm doing something similar but have a slightly different solution.. My main inverter is a MagnaSine MS-4024-AE. It will rum my 1.5 hp. Deep well submersible, but has a real hard time starting the pump. I have an Onan 6.5 kW 120/240 volt generator which will run the pump with ease. Starting the pump with the generator and allowing the pump to run for 5 minutes then shutting down the generator to cause the MagnaSine to start does not work due to the high rotating mass of the generator wind down causes the voltage to drop too far for the MagnaSine to pick up the load. I needed a faster switchover so I rigged a magnetic contactor to switch the pump load from the generator to the inverter. The inverter/charger input from the generator is switched off to keep the inverter running with a 1 kW dummy load so it's ready to go. At changeover time the multi contact contactor switches the pump from generator to inverter and dumps off the dummy load. Presto....the inverter does not see the high start surge of the deep pump and it works fine.  The well and pumping system was in place when I acquired the property.

If I built from scratch I would do a DC pump with a current booster for water pumping, but this is working just fine.

David

[mike90045]

I'd rig up a Sync Lamp, so that you are switching over without a big glitch from phase imbalance of the 2 sources.

https://en.wikipedia.org/wiki/Synchronization_(alternating_current)#Synchronizing_lamps
https://circuitglobe.com/generator-synchronization.html

single phase only needs one lamp, 3 phase needs 3

[CDN-VT]

If you use the pump starting switch to signal a system to have a generator to fire up & be online when your pumping should start.

Photo cells to pick sun out , day timer to pick daylight time , AGS system to a inverter charger , then that could be the start of a system. All in series so each sensor / timer is met.
Tweaks and once a day fills could work.

VT