Help required to design off grid system

BB.

Re: Help required to design off grid system

That is really neat!

Watch the solar panel to VFD input voltage--You don't want something to happen and over voltage the input of the VFD (solar panels with no load have higher Voc --voltage open circuit--than when they are under load).

I too am waiting to see the details of your installation.

-Bill

stephendv

Re: Help required to design off grid system

Yep you've cracked an important problem that many people would benefit from: direct solar pumping using off the shelf reasonably priced components. Agree with bill that the thing to watch is the voltage, you can increase the number of parallel pv strings to increase the available current, that way you can extend the run time into earlier and later during the day and in cloudy weather. If you have two parallel arrays might be worthwhile putting one in SE and the other in SW orientation to have a longer and more constant solar day.

Nice work!

inetdog

Re: Help required to design off grid system

syedbukhari wrote: »

Kindly advice can i use different power and different specification panels in a system or the specification and the power should be same every time to extend the system power.

Here are four general guidelines to help you determine all of your panel array expansion options:

1. Always make sure that adding a panel to each string does not cause the cold-temperature Voc of the string to excede the maximum input voltage rating of any of your equipment, from wiring to circuit breakers to VFD input.
2. You can add new panel strings in parallel with your existing ones as long as the Vmp of the new string is within about 5% of the Vmp of the existing strings. Make sure that the Voc of the new string is not too high (see #1). The current values or number of panels for the new string do not have to match the old string. Just the total voltage.
3. You can add additional panels to a series string as long as the Imp of the new panel is at least as large as the Imp of the existing panels. To avoid wasting power, the Imp should not be too much higher (~10%?) than the Imp of the existing panels. The voltage does not need to be matched. (but see #1)
4. Try not to add panels into a location in which they may be shaded at a time when the existing panels are not shaded. Mixed shading conditions will not hurt the panels, but will result in less power then you would get from the new strings under ideal conditions.

syedbukhari

Re: Help required to design off grid system

Can i upload the video directly or first i have to upload it on you tube?

BB.

Re: Help required to design off grid system

We do not host videos here... Youtube (and a few others?) can host a window here.

Otherwise, links to other services are fine too.

-Bill

syedbukhari

Re: Help required to design off grid system

BB. wrote: »

We do not host videos here... Youtube (and a few others?) can host a window here.

Otherwise, links to other services are fine too.

-Bill

Youtube is blocked in our country as soon as it opens i will share the video on this forum.

BB.

Re: Help required to design off grid system

If you have it posted on a video site others can access, please feel free to post a link to it.

-Bill

PS: I should add, you can post photographs here too (keep the resolution down--We don't support high resolution photos).

-Bill

syedbukhari

Re: Help required to design off grid system

PS: I should add, you can post photographs here too (keep the resolution down--We don't support high resolution photos).

-Bill

Here are two photos i will try my best to upload video as soon as possible.

BB.

Re: Help required to design off grid system

Very neat!

Have you attracted any attention from others in your area interested in reproducing your setup?

-Bill

westbranch

Re: Help required to design off grid system

what is the output of that PV/pump system per hr or day? Very nice looking...

syedbukhari

Re: Help required to design off grid system

BB. wrote: »

Very neat!

Have you attracted any attention from others in your area interested in reproducing your setup?

-Bill

Yes now i starts marketing and installed 10 HP motor to a customer. He is also quite satisfy with the working of the motor and enjoying free water all the day.

syedbukhari

Re: Help required to design off grid system

westbranch wrote: »

what is the output of that PV/pump system per hr or day? Very nice looking...

I use 20 Pannels in this system. Capacity of each pannel is 220 watt.
It starts working from 9 A:M and countinue working till 4 P:M these days. In summer it will start working from 7:30 A:M and will continue to 6 P:M.

stephendv

Re: Help required to design off grid system

That's a beautiful sight seeing so much water being pumped in a dry region -all from solar! Any chance you could post a photo of the VFD and connections? I sent you my email in a private message if you want me to upload the video for you.

syedbukhari

Re: Help required to design off grid system

Hello
Once again I need help from this forum
Please advice can I get better results if I use 5 Hp Dc motor instead of AC motor in my deep well system.

I listen from some one the water pressure can be increased if I use 2800 rpm Ac motor instead of 1400 rpm motor in 5 Hp.
And water pressure can also be increased if we use Dc motor in 4000 rpm with same power (5 Hp) even with less wattage of solar panels.

Please guide

BB.

Re: Help required to design off grid system

syedbukhari wrote: »

Please advice can I get better results if I use 5 Hp Dc motor instead of AC motor in my deep well system.

A "permanent" magnet motor may be ~20% more efficient. You could also see if you can find a "synchronous" motor (may be more efficient than induction motor too, but probably not as efficient as a permanent magnet motor). Either motor should work with your VFD (starts at 0 Hz / cycles per second, then ramps up to full RPM--PM and Synchronous motors need "help" to get to operating RPM, induction motors "slip" to start--the other motors are "locked" to frequency). Don't buy anything yet--There is a lot of research to be done first.

I listen from some one the water pressure can be increased if I use 2800 rpm Ac motor instead of 1400 rpm motor in 5 Hp.

Note: You are using 50 Hz which is 1,500 RPM if a "synchronous" type motor... That 100 RPM "slip" is the the "loses" that are being used to create a magnetic field in the rotating armature of an induction type motor.

Regarding pressure--For solar/cost efficient energy usage, you only want to have the "minimum" pressure required to operate your water distribution system. If you double the pressure, you will double the amount of power (watts) needed to run the pump. Nothing is "free" on the energy side.

Depending on your heeds... Say you use a well pump to move lots of water to a holding pond. High volume, low/minimum pressure--Most water for the minimum amount of power (solar array, vfd, pump motor, etc.).

And lets say you need some water to pump through sprinklers (irrigation) and you need more pressure for that. It might be more efficient for you to setup a second pump to provide only the power/volume of water needed for that application rather than "burden" your main well/transfer pump with the high pressure for 10% of water usage.

Also, pumps designed to work below water level (i.e., not lift water from source, but have some positive pressure on the pump inlet because the water level is higher than the pump), are more efficient than those designed/operated where the pump has to suck water up above the level of the pond/tank/etc. Also, over all, pumps with positive inlet pressure tend to have "less problems" overall (air leakage, cavitation, plugged inlet screens causing loss in pumping, etc.).

And water pressure can also be increased if we use DC motor in 4000 rpm with same power (5 Hp) even with less wattage of solar panels.

There are many different types of DC motors... A whole forum worth of details.

The standard type of DC motor that we usually see is like those used in electric hand drills, mixers in the kitchen, etc... These are typically called "universal" motors or brushed motors with commutator.
Brushed DC electric motor - Wikipedia, the free encyclopedia

While these are nice motors, have lots of different configurations, and have been used for over 100 years--I would suggest you would want to stay away from these. A brushed motor can avoid the use of a VFD, for your application you would need a linear current booster or something similar (large ones, if available, probably cost more than a VFD).

But the big draw back is the brush/commutator. Brushes would only last (perhaps) 6 months, and you would need to pull apart the motor and turn the commutator on a lath every so often to keep it smooth (brush wear, arcing from rotation/electrical current, etc.). I would usually avoid this for a large/permanently installed pumping system.

So, your best bet, my guess, would be a 3,000 RPM induction motor (if you can find one--larger ones may be difficult to find) or go with a permanent magnet or DC Slip Ring type motor. These are really 3 phase (or other combinations) type motors that should work well with your VFD. Permanent Magnet motors are just that--They have magnets in the armature so it "locks" to the rotating field supplied by the three phase field (and your three phase VFD). A synchronous motor with slip rings is similar--But instead of induction magnetism or permanent magnets, the rotor's field is supplied by DC current fed through slip rings to the armature (identical to the alternator on your car).

So, as I said before, nothing is "for free". If you want more volume and/or more pressure, then the pump (water side) needs to be sized to the expected water flow/pressure--And the motor (electrical side) needs to drive the shaft at the RPM and torque required (i.e., horsepower/kWatts). The first part is then to look at the pump requirements.

Once you have the pump side defined, then you can look at the motor side and pick a motor that will meet those needs in a cost effective manner. I.e., a PMA (permanent magnet armature) motor may cost more but because it is ~20% more efficient may let you use fewer solar panels/smaller VFD.

Anyway--Sorry for all the "word salad" here... It is a complex, and interesting subject. I have not worked very much with PMA Motors, so I am of limited help here. Check with your VFD manufacturer/supplier and see if they can give you come guidance. I would be very interested to hear what you find.

Also--More information/pictures on your existing setup (VFD information). Hope all continues to work well for you and your new customers. It sounds like a very satisfying job/commitment bringing water to people who need it.

-Bill

PS: I should add... Many motors are specified to run on both 50 and 60 Hz... So you may be able to "crank up" your 1,400 RPM motor to ~1,720-1,800 RPM without too much problem (may need more solar panels in parallel to supply additional current).

You could also check with the motor mfg. and see what their maximum rated RPM may be... It is possible you can just crank up the VFD to higher RPMs safely (again, more power needed, possibly more wear on bearings/pumps--everything needs to be double checked).

High RPM's may not be your friend here... Water pumping could have significant cavitation problems at higher RPMs (just guessing here).

syedbukhari

Re: Help required to design off grid system

Thanks Bill for sharing information. I hope these will help me.
Yes you are right there is much more cousion for research then implementation.

syedbukhari

Re: Help required to design off grid system

I need once again your help.
In most areas the water table is about 50-60 ft in depth. many people use induction motor. They place these motor in the depth of above 5 ft of the water level by digging the well. I just wants to know if we use submersible then
Will the submersible require same power to pull the water or it will work with less power than the induction motor for the same volume of water?
Which is more efficent in general?

Cariboocoot

Re: Help required to design off grid system

Submersible pumps are more efficient. They don't have to 'lift' water, just push it up. That 'push' begins at whatever height the water table is, as opposed to having to 'suck' the water up to the pump level first.

syedbukhari

Re: Help required to design off grid system

Hello every one

Can we use two strings of different ampare and voltages?
For example
A string having
V 600
Amp 6.7
and other having
V 300
Amp 6.7

westbranch

Re: Help required to design off grid system

you can if you use 2 Charge Controllers, one for each string.

syedbukhari

Re: Help required to design off grid system

Hello every one
Glad to come once again after a long time.
I have to install two different systems
in one system the distance of the charge controller from the array is about 30 ft and in second system the distance is about 250-300 ft.
We can not reduce the distance.
The system configuration is as follows

System Battery Voltage 48 V
Panel power 240 watt
Total number of panels 6 Nos.
Panel Voltage 30 V
Panel Amp 7.85 A

Kindly suggest me the appropriate wire gauge so that to control the wire losses.

BB.

Re: Help required to design off grid system

Do you have an MPPT charge controller you like (typical Vmp would be around 90 volts @ Vmax~140-150 VDC; Midnite, Outback, Schneider/Xantrex)--You can get "high voltage" controllers with Vmax of 200-250 VDC (Midnite classic) or even 550-600 VDC (Schneider/Xantrex).

And what is the minimum/maximum temperatures you would see.

-Bill

westbranch

Re: Help required to design off grid system

Can you also tell us what this particular application will be? More water pumps?

syedbukhari

Re: Help required to design off grid system

it is totally a DC system in which we have to charge the batteries only. By the way all of my pumping systems running very well by virtue of this forum.
Yes i have a MPPT controller but its voltage range is only upto 95 V
The temp. goes up to 50 in summer and goes down to zero maximum in winter.

BB.

Re: Help required to design off grid system

At this point, I don't see you can do what you want with the compnents available to you...

For a 95 VDC maximum input controller, you are looking at a maximum Vmp-array~63 volts (Voc-cold must be less than 95 VDC).

And to reliably charge a 48 volt battery bank, you need ~70 VDC for Vmp-stc (standard test conditions)...

Your two panels in series with Vmp-array=60 volts is too low for a 48 volt battery bank. And three panels in series for Vmp-array=90 volts is too high for a 95 volt input max controller.

A low tech solution would be to put three panels in series, connect to the battery bank (with a blocking diode per string). And get a Dump/Shunt type controller to dump excess current to an electric heater.

Otherwise, you will have to make changes--24 VDC battery bank, different charge controller (you may find PWM controllers with high enough input rated voltage to use with 90Vmp array--But you will lose almost 30% of the array's output power because of the miss-match between Vmp~90 volts and the Vbatt~60 volt charging).

Also, I am still very interested in your water pumping solutions--I think that a solar array + VFD + 3 Phase Pump would be very helpful to large parts of the world where water is hard to get and utility/battery power is not affordable.

-Bill

syedbukhari

Re: Help required to design off grid system

BB. wrote: »

Also, I am still very interested in your water pumping solutions--I think that a solar array + VFD + 3 Phase Pump would be very helpful to large parts of the world where water is hard to get and utility/battery power is not affordable.

-Bill

Yes off course i will be very pleased to help you out in this matter.
In water pumping solution you just need solar array, VFD, 3 Phase motor only. The configuration of the array depends upon your VFD. It generally ranges from 300-680 Volts arrangements. A is aid befor it purely depends upon your VFD.

syedbukhari

Re: Help required to design off grid system

BB. wrote: »

At this point, I don't see you can do what you want with the compnents available to you...

For a 95 VDC maximum input controller, you are looking at a maximum Vmp-array~63 volts (Voc-cold must be less than 95 VDC).

And to reliably charge a 48 volt battery bank, you need ~70 VDC for Vmp-stc (standard test conditions)...

Your two panels in series with Vmp-array=60 volts is too low for a 48 volt battery bank. And three panels in series for Vmp-array=90 volts is too high for a 95 volt input max controller.

A low tech solution would be to put three panels in series, connect to the battery bank (with a blocking diode per string). And get a Dump/Shunt type controller to dump excess current to an electric heater.



-Bill

I am using dry batteries (VRLA GEL) so i think for this type of battery i do not need 70 V.
I also use three panels in series to increase the voltages up to 90 Volts it works well in Summer but it becomes over voltage in Winter.
I am also facing a problem with battery voltages and SOC.
When we charge the batteries from grid SOC shows 100 % capacity as we switch off the main supply SOC suddenly drops to 80-85 %. Same is the case when we charge it from solar. Please also advice in this matter. The batteries are brand new.

BB.

Re: Help required to design off grid system

If your panels are Vmp~30 volts, two panels in series running at normal operating temperatures in full sun will probably have Vmp at ~52 volts. That is pretty low for charging even VRLA batteries... However, the Vmp curve is relatively rounded, you can still get significant charging current to the batteries (especially if the batteries are warm too).

Regarding State of Charge--How are you getting the 85/100% readings? Measuring the voltage is, at best, only a rough estimate, and you usually cannot measure specific gravity in sealed/VRLA batteries (which is more accurate). I would not be surprised if you have a voltage based charger (or SOC meter) that changed readings when you cut utility charging current/switch things around.

Regarding the VFD and water pumping... Did you have to modify the VFD or were you able to just connect the solar array directly into the AC input of the VFD? Any modifications to the VFD?

-Bill

westbranch

Re: Help required to design off grid system

syedbukhari wrote: »

When we charge the batteries from grid SOC shows 100 % capacity as we switch off the main supply SOC suddenly drops to 80-85 %. Same is the case when we charge it from solar. Please also advice in this matter. The batteries are brand new.

You need to let batteries rest for 3 or more hours before testing their voltage ('at rest'), that is when you can measure their 'true' voltage.
I am thinking that they are not getting a proper charge if they drop right away. They should be at 100% for a short time after charge is stopped.

What are the charger settings?

syedbukhari

Re: Help required to design off grid system

BB. wrote: »

Regarding the VFD and water pumping... Did you have to modify the VFD or were you able to just connect the solar array directly into the AC input of the VFD? Any modifications to the VFD?

-Bill

Sorry Bill for responding too late. Regarding to your question yes we modify VFD to some extent but now a days many Chinese are producing pumping inverters without battery support. These inverters are also basically new form of VFD please visit the site for more information
http://www.sacredsolar.com/index.aspx?menuid=12&type=introduct&lanmuid=87&language=en

I hope it will help you. I will try to help you in this matter.