Big pump on Solar

[Plaashaas]

Good morning Gents

A friend of mine is looking to go off grid. The biggest problem he has is the 18.5kW pump he uses to pump water from the river to a dam. 

My suggestion, get a smaller pump and pump every day instead of every 3rd day. Maybe a 10kW?
Setup a 3 Phase system cosisting of:
2x KING 5kW on P1
1x KING 5kW on P2
1x KING 5kW on P3

4 arrays consisting of 10x380W (2S5P)

Battery bank, 5x US3000, with the option to excpand later.

Other than normal house loads, Solar geyser, gas stove, most of the loads including the pump can be run during the day. 

 

Any thoughts on this?

 

[Louisvdw]

You get solar pumps that are specific to pump water using panels. No batteries required. If the sun shine they will pump. They are expensive, but from what I heard they work well. I know OmniSolar in George did extensive tests one these. It might be worth while contacting them for information.

Then you can just spec the rest of the system as you would normally do.

[___]

4 minutes ago, Louisvdw said:

specific to pump water using panels

They use a VFD/VSD (variable speed/frequency drive). They can drive the pump slowly when you don't have too much sun (by changing the frequency), or at full speed when there is more sun. They are a kind of inverter that work directly from sunlight, which they can because they can adapt the speed of the pump to the available sunlight. This kind of setup should be way more efficient than putting down batteries and inverters.

Talk to @anotherbrownbear, or contact All-Electrical in Port Elizabeth. They specialise in this stuff.

With that concern out of the way, you can probably get away with the usual Voltronic money-savery...

[Plaashaas]

Thank you for the reply guys. 

I will look into the Solar pumps. 

The problrm I have with them it is allot of captal and then it is dedicated to pumping water only. Adding that same capital to a normal Solar system does give you a bigger and better system with witch you now have more capcity to be used as you please. Lets say he needs to do a bit of welding and grinding, he can then just switch off the pump and use that energy. Or am I missing something?

[___]

12 minutes ago, Plaashaas said:

dedicated to pumping water only

You may be right. If you want to keep the 20kW pump, I'd suggest definitely going with a dedicated solar setup for that. 20kW is such a big blob of the whole that the "I want to maybe use some of that for welding" is just a weak excuse. But if you make the pump smaller, then the game changes a bit.

What I would do in this case, is I'd install 3 x 10kW Victron inverters (or maybe 8kW, or 5kW depending on loads), and then I'd AC-couple a 15kW three phase PV-inverter to the output.

The reason for going blue (other than... you know... cause they are my boys), is because this is a low-frequency inverter that allows you to AC-couple PV on the output. The reason for AC-coupling the PV is that most of it will be used directly during the day for pumping water. Then downsize the pump as suggested, and put up around 15kWp of PV. Battery bank would probably be the same as you suggested.

Using PV-inverters like this (eg Fronius, ABB aka FimerSpa) would be more efficient for daytime loads.

[phil.g00]

AC coupling is nice, but along with the 1:1 rule ( Victron to PV inverter) there is a battery size component as well.

If I recall correctly it is:

1kW PV inverter for 5kVA battery for lead acid & 1.5kW PV inverter for 5kVA Lithium.

15kW of PV inverter adds up to a pretty sizeable battery bank pretty quick.

As much as I like Victron equipment, an SMA Sunny Island + Sunny boy combination may be worth looking into as well.

SMA may also have a similar requirement, but they seem to allow a higher ratio of AC coupled inverters.

 

Edited August 26, 2020 by phil.g00

[___]

46 minutes ago, phil.g00 said:

they seem to allow a higher ratio of AC coupled inverters.

They do. I think they allow 2:1.

I think you are probably correct to advise more battery for such a setup, double at least. So maybe DC-coupling will be better on those grounds. Given the amount of money that's going to be spent, I'd really push for a better inverter. You know... something with a 5 year warranty

Besides, isn't the king the one with the 0-second transfer double-inversion architecture? If you want to save money here, should you not go for the more off-grid oriented models?

If this is purely off-grid (no generator backup), you could further save money by using Victron Phoenix inverters (no transfer switch, no AC charging).

[phil.g00]

2 minutes ago, plonkster said:

If this is purely off-grid (no generator backup), you could further save money by using Victron Phoenix inverters (no transfer switch, no AC charging).

I was going to suggest that myself, you can also AC-couple to Phoenix inverters. Although, have Victron just come out with a new range?

My phoenix inverter has a Multiplus firmware chip, I have always wondered if I could parallel it to a Multiplus? 

Thereby adding AC charging/blending, albeit a lesser amount.

This would allow a smaller generator to supplement to the power.

With Victron multiple 5kVA's also deliver more power as they start to derate at temperature, than a single big boy.

9 minutes ago, plonkster said:

I'd really push for a better inverter. You know... something with a 5 year warranty

I agree with you on this point. This ain't going to be cheap, if it's going to last.

[___]

21 minutes ago, phil.g00 said:

Although, have Victron just come out with a new range?

There's the small Phoenix inverters, which can't be made into a three-phase setup. Then there's the new Phoenix Smart models, which can be made into three-phase, but they only go up to 3kVA. Then of course there is the older models, that as you noted has the same inverter component as the equivalent Multi (to the extent that in some Venus firmware versions they were misidentified), but no transfer switch or charging.

I doubt you can combine Phoenix's with a Multi. If it is at all possible in a three-phase system, I would expect that the Multi would have to be on L1. Even if it works, I'm unsure if this is supported.

You can build a three-phase setup with three Multis/Quattros, and put a single-phase supply on just one of them. This is one way to make a 3-phase supply from a single phase supply.

 

Edited August 26, 2020 by plonkster

[phil.g00]

3 minutes ago, plonkster said:

Then of course there is the older models, that as you noted has the same inverter component as the equivalent Multi (to the extent that in some Venus firmware versions they were misidentified), but no transfer switch or charging.

Yes, I returned a second Phoenix inverter ( of the old type) because it could not parallel with my existing one. Bizarrely, the firmware difference was related to the transfer switch size of their respective Multiplus firmwares. As you state, Phoenix inverters don't have transfer switches, but there you go.

Are the older 5kVA Phoenix's now phased out?

I wish Victron would announce their end of line dates on products, as the ability to parallel and grow a system is a big selling point.  They are pricey products and I am sure people plan to expand their systems, and rely on procuring parallel components in the future. At least if they know something is becoming end-of-line they can maybe move up their plans and get the component they will rely on in the future.

 

[___]

7 minutes ago, phil.g00 said:

Are the older 5kVA Phoenix's now phased out?

Not as far as I know. They older 5kVA Quattros are still being built, and the same inverter component is used in those. eOrder shows a little over 200 in stock.

[phil.g00]

2 minutes ago, plonkster said:

eOrder shows a little over 200 in stock.

I assume "eOrder" that is something Victron lets you see? Or is it visible to us mere mortals?

I've had a helluva time over the years with ensuring firmware compatibility. Does what you see let you see firmware versions, or is it potluck?

AFAIK, the firmware version is not visible on the box, and many resellers are reluctant to open the box, once you point out the importance of firmware compatibility.

I know Victron advises that multipluses destined for paralleling should be bought together, but that is hardly a practical solution given their price.

Or what would one do if a muliplus in a parallel or three phase system needs replacing?

Dealings with resellers in the past, enlightened me that they didn't even know firmware versions existed.

 

 

[___]

12 minutes ago, phil.g00 said:

I assume "eOrder" that is something Victron lets you see? Or is it visible to us mere mortals?

eorder.victronenergy.com. Most people will however buy from a reseller in their own country. I don't know if stock levels would be visible to "mere mortals".

14 minutes ago, phil.g00 said:

I know Victron advises that multipluses destined for paralleling should be bought together, but that is hardly a practical solution given their price.

Yeah, I know...

[phil.g00]

20 minutes ago, plonkster said:

eorder.victronenergy.com. Most people will however buy from a reseller in their own country. I don't know if stock levels would be visible to "mere mortals".

Apparently not.

How does one go about ordering a specific firmware version?

Or is there a serial number visible on the box, that can be checked against a database?

[___]

56 minutes ago, phil.g00 said:

Apparently not.

How does one go about ordering a specific firmware version?

Or is there a serial number visible on the box, that can be checked against a database?

I honestly don't know. Since most people order through resellers, and the reseller himself rarely knows or cares what is in the box, I admit that it is a problem.

[phil.g00]

I know people have complained about them but Segensolar came through for me, confirming parallel compatibility of two 8kVA Quattro's on the bench beforehand.

(I don't know if I could've specified the firmware I wanted, to expand my system in the future though).

AC/DC didn't have a clue, just tried to upsell me a Venus as the cure-all.

So credit where it is due.

 

 

 

 

[Coulomb]

On 2020/08/25 at 4:58 PM, Plaashaas said:

The biggest problem he has is the 18.5kW pump

That's a monster motor/pump. Usually the startup surge of a motor is some 7 x the operating power, so that's a staggering 129.5 kVA! It would take 13 5 kW inverters (at 200% load for a short time) to start that pump's motor. The battery needed would be huge.

18.5 kW is 6.2 kW per phase, so even 4 5 kW inverters won't work, even if there wasn't a startup surge at all. That's also ignoring power factor, which is likely around 0.8, so that's ≈7.7 kVA per phase.

Your friend will definitely need a smaller pump to go off-grid.

[phil.g00]

8 minutes ago, Coulomb said:

That's a monster motor/pump. Usually the startup surge of a motor is some 7 x the operating power, so that's a staggering 129.5 kVA! It would take 13 5 kW inverters (at 200% load for a short time) to start that pump's motor. The battery needed would be huge.

18.5 kW is 6.2 kW per phase, so even 4 5 kW inverters won't work, even if there wasn't a startup surge at all. That's also ignoring power factor, which is likely around 0.8, so that's ≈7.7 kVA per phase.

Your friend will definitely need a smaller pump to go off-grid.

Agreed it's going to have a fair surge, as pumps need to be primed so they start under load.

I would be pretty confident he already has a star/delta starter for a pump that size, so it may not be as  bad as you say.

Best thing is to measure it.

Edited August 26, 2020 by phil.g00

[Plaashaas]

On 2020/08/25 at 8:58 AM, Plaashaas said:

My suggestion, get a smaller pump and pump every day instead of every 3rd day. Maybe a 10kW?

Guys you are missing this part. Yes the 18.5kW will not be viable off-grid, that we all agree on allready. I am even thinking 7.5kW might do the trick with an added soft start?

[phil.g00]

14 minutes ago, Plaashaas said:

Guys you are missing this part. Yes the 18.5kW will not be viable off-grid, that we all agree on allready. I am even thinking 7.5kW might do the trick with an added soft start?

Basically, you have between 10AM to 2PM when solar can really work. That's four hours, I think the minimum pump size has to be governed by its ability to achieve what it needs to do in those four hours.

[DeepBass9]

Check how much power the pump is actually drawing. Just because it is rated at 18kW, doesn't necessarily mean it is using that amount. 

[jykenmynie]

2 hours ago, DeepBass9 said:

Check how much power the pump is actually drawing. Just because it is rated at 18kW, doesn't necessarily mean it is using that amount. 

With most pumps though, the running rating is one thing, but starting it is another. It might draw 5-7 times its running wattage for a few seconds starting up. Most inverters can only surge 2 times their kVA. That pump might ask for 112 - 160 kVA starting up (assuming a power factor of 0.8). You will need a small army of inverters.

It really doesn't seem like an efficient solution.

Even a smaller 10kW pump (let's say 12 kVA) would still ask for 60 - 84 kVA starting. I really think you should rather consider plonkster's suggestion of a dedicated solar pump.

Edited August 26, 2020 by jykenmynie

[Gerrie]

2 hours ago, Plaashaas said:

Guys you are missing this part. Yes the 18.5kW will not be viable off-grid, that we all agree on allready. I am even thinking 7.5kW might do the trick with an added soft start?

I’m no expert when it comes to VSD’s but I’m wondering what if you put a 18KW VSD drive on that 18KW motor but only run it at say, 50% (max) power from a 8KW solar inverters and stay within the solar inverters capacity. It will pump slower but might still do the trick, Or you might even get away with fitting a small VSD of say 8KW, but limit it to not overload on the 18KW motor. One thing the motor might overheat as it is normally air cooled and supposed to run at full speed, but you can always put a small electric fan to force cool it, i have seen this on small motors turning big gearboxes and been force cooled. I have played around some years back with VSD’s and have connected oversized motors on small VSD’s and it did work. 

Anyone that think it might work or have done something like it before?

 

[phil.g00]

31 minutes ago, jykenmynie said:

With most pumps though, the running rating is one thing, but starting it is another. It might draw 5-7 times its running wattage for a few seconds starting up. Most inverters can only surge 2 times their kVA. That pump might ask for 112 - 160 kVA starting up (assuming a power factor of 0.8). You will need a small army of inverters.

It really doesn't seem like an efficient solution.

Even a smaller 10kW pump (let's say 12 kVA) would still ask for 60 - 84 kVA starting. I really think you should rather consider plonkster's suggestion of a dedicated solar pump.

Things have come a long way since star/delta starters I see.

From what I understand a soft starter (cheaper) should halve the standing starting current surge, and a VFD (more expensive) could possibly limit it to 110% of full load.

I have never used either, but it would be worth a few bob, if they can.

Edited August 26, 2020 by phil.g00

[jykenmynie]

14 minutes ago, phil.g00 said:

Things have come a long way since star/delta starters I see.

From what I understand a soft starter (cheaper) should halve the standing starting current surge, and a VFD (more expensive) could possibly limit it to 110% of full load.

I have never used either, but it would be worth a few bob, if they can.

Definitely, if you are going to try and start such a massive motor, you have to get more efficient technology if you are going off-grid. Grid-tied, the grid can just start it for you, cheap.

The numbers I quoted was explained to me, but I do not have any practical experience with these things myself.