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Old 27-01-2018, 20:01   #46
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Re: Is this a crazy idea?

Not much cheaper, couple gallons per day, 135lbs and no indication of power consumption.
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Old 27-01-2018, 21:11   #47
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Re: Is this a crazy idea?

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Originally Posted by wsmurdoch View Post
With shipping that is over $2,000. If you read the thread above, you'll see I can't drop $2,000 on a water maker, so I can't drop $2,000 on this either. And this isn't going to fit in a void in my boat, either
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Old 27-01-2018, 21:41   #48
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Re: Is this a crazy idea?

In today's research I talked to an engineer who has overseen industrial scale desalination in South Africa. Most of his knowledge isn't relevant, but there were definitely some ideas that he had which scale very small.

It seems the weakness of dehumidifier-based systems is they are constantly starved of water to condense. If they get airflow to solve this, it is high enough that it evaporates the difference. The trick is to prevent starvation of gas state water by increasing humidity and managing the air path.

He suggested using an ultrasonic humidifier, and having a channel long enough that all the water evaporates and all the salt precipitates. Then directing that ultra-humid air over a large surface area cool element. He advised the element be a tube with baffles inside it to create a lot of turbulence to the airflow. The salt should not precipitate back into the source water.

I'll draw a diagram tomorrow of what he described, then take constructive feedback.
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Old 28-01-2018, 02:13   #49
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Re: Is this a crazy idea?

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Originally Posted by PEACEMAKER 455 View Post
Hi all I am thinking of installing a CJD WATERMAKER NZ DESIGN AND BUILD I hear they are used o VOLVO ROUND THE WORLD. anyone have experience with these units ?
The Volvo racers use Spectra Cape Horn watermakers. 18 amps @ 12 volts for 16 gallons/hour.

Spectra Ventura produces 6 gallons/hour with 9 amps/12 volts.
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Old 28-01-2018, 02:39   #50
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Re: Is this a crazy idea?

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The problem is that RO watermakers are simply out of my price range. I cannot afford $2,000+ just for a small system.

My usage is on a 25' cuddy cruiser, 1 or 2 people (2 max). It has a 20 gallon tank. With real world usage for us, that is 3 days. I don't want to carry more than 20 gallons as that is heavy and kills fuel economy. I'd like to extend the water capacity to about a week.

A week's consumption is 50 gallons, or 6.66 gallons a day. Assuming a solar system, I would need to produce 1/2 a gallon per hour for 12 hours.

I bought and took apart one of those peltier element dehumidifiers that makes about 500ml/24 hrs to see what was going on. The design was just two small heatsinks, a peltier element, and a small fan. It struck me that blowing air over the cooling element increased airflow but also caused some evaporation. Disabling the fan reduced output by about 10%, but this was caused mostly by the case design, which limited airflow. Evaporation also increases when the water becomes heavily beaded and has the highest surface area.

It seems that on the cold side, condensation is at first rapid, then slows down. The water condenses and gives its heat up to the plate, which warms it. Enough water has to condense to create running drips before there is any output. Also, surface area increases output.

It seems the optimum approach is to have an automated wiper that removes all the condensation rapidly. This reduces evaporation to almost zero. Also, passive airflow is required. The cooled air should fall out of the bottom of the unit, drawing in warm, humid air at the top. Once the unit reaches steady state, this is the most efficient method.

I have designed a prototype that has a peltier element in the center of a round PCB, surrounded by two tracks which power it. The PCB is turned by a tiny motor, and has a small wiper on both sides. I've ordered the PCB and parts, and hope to test this to see what output vs. consumption it provides.

The main thing about this design is the disk and wipers are removable and disinfectable.

I'll report back after more testing.
OK, that's a rather special situation. No chance to simply obtain potable water in your area? I guess in a powerboat the solar still is off the table, so to speak.
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Old 28-01-2018, 03:28   #51
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Re: Is this a crazy idea?

Other than the mold, dust, and bacteria in the collected water it is a great idea.
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Old 28-01-2018, 06:55   #52
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Re: Is this a crazy idea?

Sometimes plans change and people sell items cheap. I bought an unused Katadyn PS 40e for a third of the MSRP, one year old but still in the box. Produces slightly more than the rated 5.6 l/h eating 4A @ floating charge voltage (13.x Volt). Booster pump is almost never required.

Can't really beat that with experiments. So if all you want is drinking water then just watch craigslist and similar sites.

If you want drinking water and a hobby there are instructions on the web how to make your own high output AC watermaker from a few industrial parts and a disposable pressure washer. Won't be cheaper than a second hand Katadyn but you want a hobby.

If you just want the fun of a new hobby without guaranteed outcome then your approach might be a fun experiment. Noting wrong with this, but I'm sure you won't save money or produce significant amounts of drinkable water.


BTW: What happens if I put my worn stinking socks near the air intake of your condensing unit. Will the result be drinking water or smelly something? I don't know, want to give it a try?
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Old 28-01-2018, 09:15   #53
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Re: Is this a crazy idea?

After just a little testing, the round PCB being turned with wipers idea doesn't work. The tracks carrying power to the peltier element become wet. The condensate is so pure it acts as a modest insulator and the peltier element loses capacity. Either the sliding contacts need to be on the hot side, or some other arrangement is needed. I will explore other avenues first.

For the interested:

Current draw: 4.15A @ 12.25v
Temp: 72F
Humidity: 65%
Dew point: 59F
Panel temp: 36F once steady state achieved
Panel surface area (3" disk): 28.3 square inches
Production: 280ml/hr (1.77G/day)
Wiper on one side only.

It seems increasing the area to 6" disk (113.1 sq in) would give a panel temp of around 46-48F and a production of around 6-7 gallons a day?
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Old 28-01-2018, 12:31   #54
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Re: Is this a crazy idea?

So, in round figures, 100 a/h to make 10 litres. A long way to go to match a second hand RO system.
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Old 28-01-2018, 12:49   #55
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Re: Is this a crazy idea?

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The problem with AC condensate is that rather quickly it picks up things like Legionnaire's Disease as bacteria, mold, other nice things start to grow in it, especially in the coil fins. That's why it is not done. You can certainly set up a solar still, but that is a small output and requires a fairly level and steady platform as well.

There are reasons why people either buy water, or pay for the watermaker. Still no practical alternative on the market.
Quantity of condensate aside, lets be clear, there is negligible legionella present.
There is a naturally high legionella present in ground and thus in ground water, but it likes to live in dirt. Sediment is where it breeds if you have the right temperatures.
A/C coils should be pressure washed annually. as well as the drain tray and pipework cleaned. That will eliminate legionella.
The nasties we often hear of are the legionella in cooling towers. There are designed to evaporate water - which leaves behind solids/salts. We bleed a quantity of the condenser water to waste to limit the Total Disolved Solids and we treat with a biocide. As such, you would not want to wash in, or drink the condenser water from a tower. We also sterilise the towers quarterly, pressure wash and dose the systems.
Condensate is not related to condenser water in any shape, form or pollution, other than the fact it is water with stuff in it, not much stuff if you clean the a/c coil and tray. It will be relatively clean and probably cleaner than what comes from a tap in many places.
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Old 28-01-2018, 15:46   #56
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Re: Is this a crazy idea?

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So, in round figures, 100 a/h to make 10 litres. A long way to go to match a second hand RO system.
Show me a second hand RO system that has no moving parts, can be serviced with a paper towel and a spray of bleach, and costs under $100 brand new, including solar panel
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Old 28-01-2018, 16:05   #57
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Re: Is this a crazy idea?

The point is your on-the-hook energy system will cost thousands, no net savings.

Unless you have mains power, but then fresh water is readily available.

Just acknowledge it's a fun science project, if it by some miracle has a practical result you can say I told ya so.
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Old 28-01-2018, 16:41   #58
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Re: Is this a crazy idea?

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Also, please ask your friends or next of kin to promise to let us know what happened after you die of toxic substances from your project.

Do you use aluminium or ss pots or copper pipes or pvc pipes or uhmpe pipes or ?...I constantly piss myself laughing at people who drink bottled water out of plastic bottles at least here when you have good water treatment. I can understand in the US where you have lead piping & high levels of arsenic etc although we have had some pollution issues here too in places with inadequate treatment.. It seems that Mr pix has a handle on the hazards & he has stated often enuough he can't afford an RO setup
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Old 28-01-2018, 16:49   #59
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Re: Is this a crazy idea?

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The point is your on-the-hook energy system will cost thousands, no net savings.
You keep asserting that. A fogger piezo transducer is $2 wholesale. A 5A 12V peltier element is $1.60 wholesale. If we allow $20 for ABS moldings, $2 for a lead free ENIG PCB to CE standards, and $0.05 of lead free bismuth-based solder, we have a grand total of $25.65 in parts for a single unit. Those costs would drop about 60% for mass production.

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Just acknowledge it's a fun science project, if it by some miracle has a practical result you can say I told ya so.
I think I have restated that many times. It's just a case of retargeting well understood device and technology to maximize a particular aspect of its function.

It's not rocket science.

So far I have spent $65 or so on this, and already have something that works quite a lot better than nothing. That $65 included the solar panel. It produces enough water to actually keep a person alive. That's something.
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Old 28-01-2018, 16:59   #60
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Re: Is this a crazy idea?

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Show me a second hand RO system that has no moving parts, can be serviced with a paper towel and a spray of bleach, and costs under $100 brand new, including solar panel
One of these elements and a 80w solar panel could probably make up a nice emergency watermaker to keep one person alive. But not much more.


Based on your figures:

Your element makes 280ml/h or 1.77g/d while eating 4.15A @ 12.25V.

Based on nominal 12v this is 101AH for 1.77g or 6.7 liters.

To keep two people happy you need maybe 30 liters per day (or replace with your figure). That is 452 Ah @ 12V, or 5.42kWh.

What amount of solar do you need to reliably produce that amont? No clue, maybe 3kWp?

3kWp solar panels & charger cost more than the watermaker you are trying to replace, and won't fit on your boat or most other boats but very large catamarans.

Don't forget the additonal battery capacity required to run the elements 24h. Costs another 500 at least.


So unless you are happy with 2 liters per day, or you can optimize your process by an order of magnitude this idea is not fit for the job.

EDIT: I must stress that the idea is excellent for an emergency watermaker for those folks who depend on their watermaker, especially if they have enough solar anyway. If the main WM breaks on passage just hook up your device and survive. Smelly but alive, better than nothing.
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