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Charge Controller

10/02/2017 1:19 PM

I am designing a RO water purification system to be used in remote village where electricity is not readily available. So I thought of using solar panels? The pumps are 24v DC. Can we connect direct to solar panel or do we need a charge controller?

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#1

Re: Charge Controller

10/02/2017 1:59 PM

I suppose you could consider this:

(1) solar array produces electric power

(2) Motor designed for 24V DC runs when power is available, drives high-pressure hydraulic pump

(3) Output of hydraulic pump goes directly to hydraulic accumulator

(4) Hydraulic motor drives RO pressure booster pump to correct pressure for flow rate of RO unit, and required net driving pressure.

(5) RO unit switches on/off dependent upon pressure available in hydraulic accumulator, and thus runs within a stable operating window.

(6) Around sun-down each day, the RO goes through a "normal" full shut-down with RO permeate rinsing the membranes down.

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#2
In reply to #1

Re: Charge Controller

10/02/2017 2:12 PM

I'd want more voltage.

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#3
In reply to #2

Re: Charge Controller

10/02/2017 2:35 PM

There are up converters for that, but I think there are plenty of 24 VDC motors that will run a hydraulic pump. Putting the hydraulic energy source between the RO and the energy collection will prevent flow/pressure mismatch during production.

It has been done before. It has even been done without PV panels, but with large solar brine ponds that deliver some 110 °C water to the cylinder jacket of a large piston engine, with supercritical CO2 operating inside the cylinder. Switch back to cold water to return piston to top of stroke.

Piston engine drives hydraulic pump that operates hydraulic motor for seawater RO.

Pretty slick way to get things to happen. No fuel burn needed. Especially made for Baja peninsula, but should work in any high solar input area such as Arabia of India or Saharan Africa.

Using such a system, you could get by with a smaller PV panel that just pumps the solar brine and cold water supplies around on your 24 VDC system, and does so at relatively low pressure.

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#6
In reply to #3

Re: Charge Controller

10/02/2017 3:26 PM

Thank you for the suggestions. But here I am talking of small systems below. 500W.

Cost factor also is important. This is for rural community. Most of them happen to be at the low end of income spectrum.

That is the reason I prefer to run a low. Cost 24 or 29V DC (may be even 48V DC ) water pump directly off a solar panel or solar panel+ charge controller combination.

Your contribution is highly appreciated.

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#7
In reply to #6

Re: Charge Controller

10/02/2017 3:32 PM

that is partly why I included reference to the piston engine type, simply because a solar brine pond is far cheaper to build than the cost of PV.

The locals could volunteer to provide most or all of the labor.

You still might need a small (300-400 W solar PV) just to move water from A to B.

Are you sure these rural communities actually need RO purification, and not just several steps of filtration with UV?

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#9
In reply to #7

Re: Charge Controller

10/02/2017 3:41 PM

There have been frequent deaths due to chronic kidney disease of an unknown etymology. Several studies suggested that ground water laden with Cadmium, Arsenic, Calcium, Magnesium, Glyphosates and fluoride are the causative factors either singularly or in combination.

Only way to get rid of these elements is Reverse Osmosis

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#10
In reply to #9

Re: Charge Controller

10/03/2017 3:47 AM

So water tests have been performed? Could you copy the results here so that we can have a better idea what you are dealing with?

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#11
In reply to #10

Re: Charge Controller

10/03/2017 4:43 AM

http://dailynews.lk/2017/03/09/features/109851/chronic-kidney-disease-uncertain-aetiology-ckdu-sri-lanka-war-kidney

This explains everything

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#13
In reply to #11

Re: Charge Controller

10/03/2017 5:03 AM

The link explains that clean water is necessary for recovery. The big factor that is still missing is what exactly the quality of water is at the location of concern.

If you install an RO system at a location that already has clean water, the investment of time and money is misguided.

What do you know about the water quality at the location of concern?

.

That there are no paediatric cases and cases are mostly in male farmers, sometimes clustered in families seems to point toward something like argochemicals and not water.

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#14
In reply to #13

Re: Charge Controller

10/03/2017 5:12 AM

Quality of Raw water changes from area to area. Therefore we design the pretreatment plant to match individual sites

RO module is common for most of the sites.

We are fully aware of the water chemistry and the technology in purification.

My question is whether I could directly connect a solar panel with 24 V DC pump.

After reading the comments of all I think it is undesirable and also considering the fact that we can buy a charge controller from China at cheap price I think we will go ahead with the charge controller

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#21
In reply to #11

Re: Charge Controller

10/03/2017 12:53 PM
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#22
In reply to #21

Re: Charge Controller

10/03/2017 1:23 PM

So the end conclusion may well be other environmental or work related sources of exposure to toxic elements, since most of the ground water/surface waters were below the threshold values?

Makes a good case for providing well-filtered water, and not much if anything beyond that.

Also makes a good case for work hygiene, hand washing, etc. Carrying toxins from skin to mouth when eating by hand is a concern, especially if the folks there have been working in the fields, and not washing up before eating.

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#4

Re: Charge Controller

10/02/2017 2:59 PM
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#5
In reply to #4

Re: Charge Controller

10/02/2017 3:21 PM

The second link is not for an RO or other desalination, it is a solar powered water filtration system that utilizes UV disinfection as final step. Not bad at all, where the water is moderately low TDS (total dissolved solids), 0-600 mg/L or so. Much higher than that, and one would probably desire to de-salt the water.

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#12
In reply to #4

Re: Charge Controller

10/03/2017 4:50 AM

Thank you for the response.

First link is about large scale RO systems. Here we are trying to build small systems which can be used in remote villages where the requirement is 2000 to 5000 litres per day. Sophistication is undesirable.

The second link is about UV sterilization which does not apply in our scenario but thank you for this link as I learnt something which can be made use of during a disaster situation such as floods

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#19
In reply to #12

Re: Charge Controller

10/03/2017 10:12 AM

The link wasn't presented as a turnkey solution, but as an example that direct solar to pump is done....I believe that was your question.....another interesting aspect of the system referenced is that instead of batteries for storage the system uses overproduction and tank storage as energy storage..........certainly this can be scaled to suit...good luck

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#8

Re: Charge Controller

10/02/2017 3:37 PM

To more fully answer your main questions:

(1) yes you can make use of PV panels.

(2) if you choose direct connection, you could either overload the pump motor due to drawing down the voltage under load, and burn it up, or you could over-drive the membranes and produce too high pressure for the water and system design, and have quality issues in the future.

(3) membrane systems will foul if water such as dirty surface water is fed directly to them, usually there is a sophisticated upstream filtration of the water. RO is only needed when the water is too salty (brackish) for human use.

(4) Larger factor connected with human disease in water supply can be addressed with the proper filtration/sanitation system Solar Eagle mentioned.

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#15

Re: Charge Controller

10/03/2017 8:06 AM
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#16

Re: Charge Controller

10/03/2017 8:46 AM

You need a few batteries to make the charge controller work( Hence Charge controller) and to absorb the fluctuation in sun intensity. Then maybe a light sensor so your RO system won't discharge the batteries. You can use several methods to compress the water to force it through the membrane, even a hand pump or water tower. Do remember to prolong the membrane life by filtering the water with aggregates and /or simple home made charcoal filter, first. Got to get the chunks out. You have a noble project and I would like to help. FB JEVCO.

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#23
In reply to #16

Re: Charge Controller

10/04/2017 1:02 PM

I appreciate very much your response. I think charge controller with 2 x12v batteries connected in series will work in our case.

Just to keep everyone else on this thread informed the treatment plant is designed to suit site water conditions and generally consists of a pressure sand filter, activated carbon filter and softener.

In most of the areas electricity supply is readily available but there are a few pockets of remote areas where still it is a luxury. This project is an attempt to serve those areas.

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#24
In reply to #23

Re: Charge Controller

10/04/2017 1:34 PM

Yeah, all well and good, but won't do squat if the water is near any active volcanism, and thus contaminated with arsenic.

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#25
In reply to #24

Re: Charge Controller

10/04/2017 1:42 PM

..."Source of Arsenic

Arsenic (As) is not easily dissolved in water, therefore, if it is found in a water supply, it usually comes from mining or metallurgical operations or from runoff from agricultural areas where materials containing arsenic were used as industrial poisons. Arsenic and phosphate easily substitute for one another chemically; therefore, commercial grade phosphate can have some arsenic in it. Arsenic is highly toxic and has been classified by the US EPA as a carcinogen. The current MCL for arsenic is 0.05 mg/l, which was derived from toxicity considerations rather than carcinogenicity.

Treatment of Arsenic

If in an inorganic form, arsenic can be removed or reduced by conventional water treatment processes. There are five ways to remove inorganic contaminants; reverse osmosis, activated alumina, ion exchange, activated carbon, and distillation. Filtration through activated carbon will reduce the amount of arsenic in drinking water from 40 - 70%. Anion exchange can reduce it by 90 - 100%. Reverse Osmosis has a 90% removal rate, and Distillation will remove 98%. If the arsenic is present in organic form, it can be removed by oxidation of the organic material and subsequent coagulation.

Products Related to Arsenic Water Treatment

http://www.aquapurefilters.com/contaminants/107/arsenic.html

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#26
In reply to #25

Re: Charge Controller

10/04/2017 1:57 PM

No arguments there, yes, I understand that AC can reduce arsenic (and others), but it depends on how much alkaline earth metal is retained in the carbon, and also on the service throughput of the bed. After a long time, AC has a habit of releasing a higher concentration once it is saturated with a contaminant, under certain conditions.

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#17

Re: Charge Controller

10/03/2017 9:43 AM

Dear sir:

You mention Cadmium, arsenic etc. And you mention Ground water.

Is the ground water source from a well, surface runoff, streams, ponds or man made reservoirs ?

When you flush the reverse osmosis membrane, what process will you use to contain the effluent waste ? Portable tank to dump waste at a different site ? Containment and or evaporation pond ?

If you use an evaporation pond, how will you process the dried waste products if they are indeed contaminated with high levels of Cadmium, Arsenic etc ?

If you transport waste products to a remote area, has a study been done to determine what the effect on the local environment will be. Is there a chance of polluting the ground surface, subterranean, and or a migration plume

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#18

Re: Charge Controller

10/03/2017 10:06 AM

What is the source of the water? If the water can be elevated 160 ft or more will provide pressure for RO. I have seen where pipe was ran up a creek bed to elevation to provide water and a water pressure for remote cabins.

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#20
In reply to #18

Re: Charge Controller

10/03/2017 11:19 AM

With the above in mind, these are inexpensive and very effective pumps: https://en.wikipedia.org/wiki/Pulser_pump https://en.wikipedia.org/wiki/Hydraulic_ram

Here is an R.O unit with high production rate at a reasonable price: https://www.amazon.com/Aquatic-Life-Reverse-Osmosis-50-Gallon/dp/B00DOG63OY/ref=sr_1_1?ie=UTF8&qid=1507043896&sr=8-1&keywords=ro+buddy

Good luck with your project & please keep us updated!

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#27

Re: Charge Controller

10/05/2017 3:38 PM

a charge controller for the PV panels would be a good idea. PV panels have various voltage outputs during the day due to anything (clouds, dust ,etc) blocking incoming light. This varying voltages is not good for simple motors. adding a charge controller and matching deep discharge batteries will keep the whole thing in better shape for the long run.

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