Why is this setup failing?

Izwbusr

Hi:

For a school project, we need to use solar panels to power a water pump.  Something is wrong with our setup and it is not working; pumps (we tried two different models) are not starting; no movement at all.  I would greatly appreciate any pointers in helping us figure out what is wrong.

We are using two solar panel that produces 12 V and 10 Watts (Eco-Worthy from DC House).  The two water pumps we have tried are (Uniclife 10L/min DC 12V Brushless Water Pump Submersible oil pump 16ft 20W) and (Hanperal 12V 5M Pumping Head Mini Submersible Motor Garden Fountain DC Brush Water Pump).

We have tried the water pumps individually with one solar panel and with two solar panels connected in parallel.  The pumps do not even start! 

With a multimeter I have confirmed that the voltage coming from the solar panels (using only one or two in parallel) is about 20V without anything else connected.

I feared that the pumps might not lift the water the whole 5 meters they claimed, but I surely thought that they would move!

Any help is greatly appreciated.

Thanks,

Rodrigo

mcgivor

Let's use the Uniclife pump as an example, because we know the wattage, 20W.
The panels are rated at 10W, but will most likely produce about 75% or 7.5W in direct sunlight, so even with both in parallel it is not enough to achieve 20W. Having about 40W worth of photovoltaic  (PV ) modules would be what it would take to power the pump, but there is a catch, the voltage will be higher than the pumps rated voltage, so a means of regulation is required, such as a dc-dc converter, something like this https://www.amazon.com/DROK-Converter-Regulator-1-5-24V-Adjustable/dp/B00KL7I9XC as an example.
What is happening is the panel or panels cannot support the load, so when connected the voltages will collapse from the 20V you read, to below the requirements. Hope this helps, feel free to ask questions.

Photowhit

You might try first reducing the load, if the pumps are designed to run dry, just spin them up. Then reduce the height that they must push the water.

Also, a solar panel is designed to charge a nominal voltage battery. To charge a 12 volt battery, they need to produce 17-19 volts. This can sometimes be too high for some motors. If they have some type of regulator, the VOC can be as high as 23 volts.

I've run a small water pump off of a 55 watt 12 volt nominal, to run a 12v hydroponic system. This pump which has lower requirements than yours.
https://www.ebay.com/itm/Magnetic-DC-12V-Electric-Brushless-Centrifugal-Water-Pump-3M-Fountain-550L-h-/400666077637?ssPageName=STRK:MERWX:ACTPNL:LNLK:ITM&nma=true&si=VotiF5cvBDSzN9rmgEBcp2RDynw%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Typically the flow rate is for a minimal head height and it become less the higher it has to pump with the max height being very minimal.

Izwbusr

Thank you all for your reply.  A couple of comments:

- I am trying to test the pumps without ANY load.  Just trying to make them spin first.  Nothing happens.  You could easily think somebody cut the cables.  

- Though I understand that solar panels might perform under the advertised wattage, I did expect for the pump to work, even if with less water pressure than advertised maximum.  So, the pumps say they can pump water 5 meters vertically, how about 30 cm horizontally?!

- I am using TWO solar panels (each rated at 10W) connected in parallel.  So I should have enough power (20W) for the pump to work at full power.  But it does not even start.  I am trying with these two pumps individually (not both at the same time):

- Pump one says:

Power consumption: 20 W 

Rated voltage: 12V DC 

Rated current: 1.1A

- Pump two says:

Rated voltage: 12V 

Working voltage 6-15V 

Rated current: 1.2A 

- When connected in parallel, the two solar panels show 19V.  I connect to pump and voltage collapses to close to zero.  Why?

- I am guessing the solar panels are producing amps significantly below advertised.  How can I test if this is the case?  I have a multimeter but not sure how to test for amperage.  I think the load has to be connected for a proper test.  Is this right?

Thank you for your help!

Estragon

The first thing I would try is hooking up each pump to a known voltage/current source such as a 12vdc power supply or battery(s). This takes panel issues off the table for now and confirms the pumps work. As mentioned earlier in the thread, the uncontrolled voltage from panels may have been too high and the pumps may be damaged.

To check the panels, you could test output with a small 12v automotive light bulb? Some multimeters can check current up to ~10a. I would check the pumps first though.

mike95490

DRY pumps may not spin, if they rely on water as bearing lube

littleharbor2

Maybe a dumb question, but I have to ask. Are the solar panels actually in the sun? While you can get some voltage from panels even indoors under artificial light you will get no appreciable current. Are they oriented correctly and in full sun?  The rated amperage should only be expected in full sun and will be substantially less with poor orientation. Are the panels a long distance from the panels, and if so what gauge wire are you using?

Horsefly

Estragon said:

The first thing I would try is hooking up each pump to a known voltage/current source such as a 12vdc power supply or battery(s). This takes panel issues off the table for now and confirms the pumps work. As mentioned earlier in the thread, the uncontrolled voltage from panels may have been too high and the pumps may be damaged.

To check the panels, you could test output with a small 12v automotive light bulb? Some multimeters can check current up to ~10a. I would check the pumps first though.

I agree with @Estragon. Hook the pump up to a car battery, verify the pump turns, and measure the actual current. I am guessing you are still expecting more from the panels than they will produce.

mcgivor

@Izwbus said

- When connected in parallel, the two solar panels show 19V.  I connect to pump and voltage collapses to close to zero.  Why?

The panels are rated at 10W but you will rarely approach that figure, unless in freezing temperature under noon sun directly hitting them at 90°, usually you can expect to see 75-80% of that figure. Once a load greater than the panels output is applied, the voltage will collapse, read post 2, I've pointed this out previously, you would need more PV to accomplish what it is you're attempting.

Estragon

I also think the pv (especially direct to load) is likely a problem. It may not be the only problem though, as voltage between Voc and Vmp may have damaged one or both pumps. At least one appears to have a 15v max IIRC. It/they may be damaged, or as @mike95490 notes, may have something to prevent them running dry. In any case, it makes sense to me to make sure the pumps will work independent of pv issues.

Being a school project, I assume learning about the various issues involved is at least as important as actually getting working pumps.

Izwbusr

Thank you all for your kind and helpful comments

We tested the pumps with a car battery.  They both work fine.  The problem is definitely the solar panels. 

I live in the Andes on the Equator line and I have tested the panels at noon without a cloud in the sky and perpendicular to the sun.  The pumps don't even squeak.  It seems the panels are very likely way below the rated 10W, which is quite disappointing.

So, I am thinking that I should buy more panels to make sure I have enough Amps to power at least one of the pumps.  I could also try another brand and model.  So, my question is if it is better to stick to the same model if I will be connecting them in parallel to increase Wattage?

Thank you all for your help.

Rodrigo

westbranch

I would see what is available and post what you can readily source and we can help you choose a panel or 2 that will work for you,.... hopefully.
I suggest you look for ~ 100 watt + panels as they should be more common and more available.

Izwbusr

Hi:  I found a 12V, 50W panel.  I am thinking that should be fine.  Right?

westbranch

Possibly, in solar installations we derate the panels rating to go from Panels through the Charge Controller , to battery through inverter, If there is one, to the end use by > 0. 72 +-.
Without knowing exactly all the data for each component it would be wiser to use that number and hope/expect for better achievement so at the optimum you should get +- 36W from one panel.  Is the panel local?  Can you 'get a test' with the panel and the motor  before purchase?

bill von novak

Izwbusr said:

I feared that the pumps might not lift the water the whole 5 meters they claimed, but I surely thought that they would move!

Consider a linear current booster (LCB.)  Google them for a list.  They take high voltages from a panel and drop them to a low voltage at much higher current to start and run the pumps.  With one of these, the pump speed will match the amount of solar radiation received.

BB.

An LCB would be too expensive for a class project (I believe).

You tried the two panels in parallel driving one pump?

The problem with solar cells is that they are "current sources" (more or less), not voltage sources (like a battery).

Basically, your panel would output ~1.1 amps in full noon-time sun... Between zero volts and ~17.5 volts (Vmp--Voltage maximum power).

Most motors require higher current to start--And what probably is happening, is your pump(s) are trying to draw >1.2 amps for a few seconds, which causes the output Voltage of the solar panel(s) to fall... Remember that Power = Voltage * Current.... If the voltage of the array falls to (for example) 3 volts--3 volts * 1.1 amps = ~3.3 Watts -- and not enough current (or even voltage) to start the pump.

If you had >40 Watts minimum @ ~12-15 volts Vmp (per pump, 2-5x running load), you should have a good/reliable starting point.

-Bill

Note, a pump with "5 meter lift"--Probably near zero volume flow @ 5 meters. At least one of the pumps is a centrifugal pump (not a positive displacement pump).