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Author Topic: Improved DIY Solar Seawater Desalination  (Read 917 times)

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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #20 on: February 05, 2018, 11:48:11 am »
To make it more simple for everyone I added a calculator to estimate the size of the solar panel needed (I was previously lazy and just referred people to an existing calculator in a previous article).

I was a bit more conservative with the numbers, so now that should make everyone happy :thumleft:  :bueller: O0

http://offgriddiy.co.za/diy-design-for-solar-seawater-desalinator/
« Last Edit: February 05, 2018, 11:48:40 am by alanB »
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Offline LeonDude

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Re: Improved DIY Solar Seawater Desalination
« Reply #21 on: February 05, 2018, 12:46:10 pm »
Alan, I've left a reply on your website.
I'm going to post that reply here too though, because I'm not sure if I'll get any feedback on that site. If you do reply, please let me know or post here.
Quote
If I might make a suggestion. I would move the outlet of the pipe taking the seawater from the bucket to the heater to the top of the bucket.
My reasoning is that the sea water will heat up as the steam cools, and the warm water will naturally rise to the top. So by removing the hot sea water from the top, you are feeding pre-heated water into your water heater. This will also ensure that you don't bleed off your cold water from the bottom, leaving your water cooling system less efficient.
This, of course, will only work if you can keep your sea-water bucket topped up high enough for the outlet point to be submerged at all times.
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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #22 on: February 05, 2018, 12:57:58 pm »
Alan, I've left a reply on your website.
I'm going to post that reply here too though, because I'm not sure if I'll get any feedback on that site. If you do reply, please let me know or post here.
Quote
If I might make a suggestion. I would move the outlet of the pipe taking the seawater from the bucket to the heater to the top of the bucket.
My reasoning is that the sea water will heat up as the steam cools, and the warm water will naturally rise to the top. So by removing the hot sea water from the top, you are feeding pre-heated water into your water heater. This will also ensure that you don't bleed off your cold water from the bottom, leaving your water cooling system less efficient.
This, of course, will only work if you can keep your sea-water bucket topped up high enough for the outlet point to be submerged at all times.

Thanks for the interest Leon

The bin water will heat up, how much it would heat up depends on the size of the bin relative to the panel. I'll maybe add a calculator for the bin size when I get a chance.

But in any event, it would be better to let the water run out the bottom of the bin because that is more fool proof - ie tolerant of unforeseen issues. I realise water in the bin will naturally stratify etc so the water at the bottom will be a bit cooler. But overall that plays a small role in the design, the small quantity of water in the collector has no where to go so it heats up fast from the incoming solar energy. A few degrees here or there in terms of its starting point is not going to make a big impact on the yield I don't think.

If you do have time to build even a scaled down version (say with a 1 square meter collector I would be thrilled to hear how it goes BTW  :thumleft:)

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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #23 on: February 06, 2018, 06:40:24 am »
OK I added a calculator to estimate bin size given the target yield in distilled water (depending also on solar energy available at your location).

I also downgraded the target yield of the design to 5-10 liters of drinking water a day to keep the sizes of the components manageable/practical for a small DIY system, but you can scale it up as required by playing with the numbers in the calculator.

http://offgriddiy.co.za/diy-design-for-solar-seawater-desalinator/
« Last Edit: February 06, 2018, 06:57:17 am by alanB »
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Re: Improved DIY Solar Seawater Desalination
« Reply #24 on: February 06, 2018, 06:50:31 am »
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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #25 on: February 06, 2018, 07:15:28 am »
Here is a "personal" distiller called the Eliodomestico - lots to read about it on the net, including building plans. Does 5L of fresh water a day. Cost is around $50.

http://www.core77.com/posts/20893/Eliodomestico-Solar-Household-Still-by-Gabriele-Diamanti
https://inhabitat.com/eliodomestico-solar-terracotta-water-filter-distills-5-liters-of-water-a-day/
https://www.greenprophet.com/2012/08/eliodomestico-solar-powered-desalination-99/



Ja saw that as well before. Looks quite neat! But not sure about the 5 litres per day out of such a small solar collector?
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Offline Sláinte Mhaith

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Re: Improved DIY Solar Seawater Desalination
« Reply #26 on: February 06, 2018, 07:17:13 am »
Here is a "personal" distiller called the Eliodomestico - lots to read about it on the net, including building plans. Does 5L of fresh water a day. Cost is around $50.

Interesting.  :thumleft:








 

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Re: Improved DIY Solar Seawater Desalination
« Reply #27 on: February 06, 2018, 07:17:36 am »
Ja saw that as well before. Looks quite neat! But not sure about the 5 litres per day out of such a small solar collector?

The designer seems sure enough, the science is all out there on the web. Check it out.
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Offline Sláinte Mhaith

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Re: Improved DIY Solar Seawater Desalination
« Reply #28 on: February 06, 2018, 07:24:02 am »
http://www.core77.com/posts/20893/Eliodomestico-Solar-Household-Still-by-Gabriele-Diamanti

This link refers to a desalination system that can do 250l/h. They also mention 24h operation. That sounds like an economically viable solution for water supply.

 

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Re: Improved DIY Solar Seawater Desalination
« Reply #29 on: February 06, 2018, 07:28:18 am »
http://www.core77.com/posts/20893/Eliodomestico-Solar-Household-Still-by-Gabriele-Diamanti

This link refers to a desalination system that can do 250l/h. They also mention 24h operation. That sounds like an economically viable solution for water supply.


There are small desalination plants for sale on Alibaba.com - Starting from $1500 to $10000 and running 125L and up. Not so much cash to lay out if you can afford it...

https://jzwater.en.alibaba.com/product/1515371942-220591004/1500_GPD_Small_Desalination_Plant_for_Domestic_Use.html
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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #30 on: February 06, 2018, 08:13:31 am »
http://www.core77.com/posts/20893/Eliodomestico-Solar-Household-Still-by-Gabriele-Diamanti

This link refers to a desalination system that can do 250l/h. They also mention 24h operation. That sounds like an economically viable solution for water supply.



That looks like a reverse osmosis set up?

I posted a brief discussion on the pro and cons vs distillation a while ago http://offgriddiy.co.za/diy-design-for-solar-seawater-desalinator/
« Last Edit: February 06, 2018, 08:14:50 am by alanB »
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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #31 on: February 10, 2018, 11:37:59 am »
After looking at the size of commercially available flat plate water heaters, and the size of the bin needed for that, it struck me that you could use one of those very easily together with a wheelie bin.

Just a thought?

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Offline barry13

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Re: Improved DIY Solar Seawater Desalination
« Reply #32 on: February 26, 2018, 10:36:54 am »
Loving the innovation here :)

What do you think of the idea of using a vacuum tube type collector running a closed loop glycol mix as a heat source rather than running the sea water through the solar panel ?
These collectors tend to get up to very high temperatures.
We could use a small 12V solar powered circulation pump to drive the heated mix through a heat exchanger in the sea water boiler tank.
The sea water boiler tank would then be smaller and fed from a refillable sea water reservoir.
Steam would be produced and collected at the sea water boiler tank and perhaps the condensate could be returned via the sea water reservoir for cooling.
May give longer cycles between cleaning and less blockages.

I am very keen to pursue the solar desalination idea as we have many local properties with salt or brak water available.
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Offline alanB

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Re: Improved DIY Solar Seawater Desalination
« Reply #33 on: February 26, 2018, 06:47:23 pm »
Loving the innovation here :)

What do you think of the idea of using a vacuum tube type collector running a closed loop glycol mix as a heat source rather than running the sea water through the solar panel ?
These collectors tend to get up to very high temperatures.
We could use a small 12V solar powered circulation pump to drive the heated mix through a heat exchanger in the sea water boiler tank.
The sea water boiler tank would then be smaller and fed from a refillable sea water reservoir.
Steam would be produced and collected at the sea water boiler tank and perhaps the condensate could be returned via the sea water reservoir for cooling.
May give longer cycles between cleaning and less blockages.

I am very keen to pursue the solar desalination idea as we have many local properties with salt or brak water available.

I don't see the need for/benefit of adding another boiler tank, with a glycol loop and pump etc?

You may as well just feed the sea water directly into the vacuum tube heater and let it boil in the heater directly. The only thing is that you would have to raise the bin sufficiently so that water flowed out of that into the vacuum heater under gravity. Should work fine, especially because those vacuum collectors are so efficient, as you point out. You would have to flush the heater periodically to remove salt build up. Plus its important to focus the heat captured from the sun on a small quantity of water to get it boiling in a reasonable time period (thereafter as the water boils off it gets replaced automatically by new water from the bin). In my collector design this was less than a litre at a time (depending on the size of the flat plate collector used).
 
On my DIY site I have a policy of going for the cheaper solutions to help people keep costs down, which is why I use a DIY design for the flat plate panel. But any type of solar water heater, which is large enough will work.
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