Waynes solar salt factory

I turned a stainless steel insulated buffet server into a solar dehydrator, to turn seawater into salt. Its pretty self evident when you see the 2 pictures. If anyone is interested,  check back to see the progress.

That looks promising, but have you figured out a way to deal with corrosion of the metal? I noticed from the first photo that there already appears to be some rust in the tray--makes me wonder if that is an inferior quality stainless. Or is that just a stain from food spills?

First photo was as i bought it. Its been cleaned and no evidence of more showing up.

The first batch of salt was boiled down in a ss pot and it did leave a very small rust ring around the the top. Im hoping by not boiling, that this doesn't happen.

I need to tweek the design. Water is condensating and falling down the glass from inside. My first design was to capture this via a gutter, making salt, mineral rich water, and distilled water. My rush to get it done before going out of town led to this design. I think if i add a small fan and solar cell to the upper hole, the vapor will leave before it can condensate.

I also lack solar heat sinks. Something that can absorb the heat. Maybe some dark rocks put in the water. Right now everything is reflective.

I made one change. I put the seawater in a pot, placed the pot inside. I can block off the ventholes now, let the water condensate on glass, then fall back into basin, not pot. Temperatures should increase with the vents blocked.

In essence, distilled water will collect in the basin.  Theres a drain with ball valve on bottom. Allowing me to collect the distilled water.

I need another pot to get the rest of the seawater out. I doubt we will see the sun over the next few days.

Hi Wayne, Neat idea.

Maybe consider switching over to an enamelled pot for the salt water, rather than steel. It should help avoid the corrosion problems.

Also, you will probably find it helpful to let the distilled water drain out, so that the solar energy is focused on evaporating the water from the salt pot. A tiny, tiny hole in the lowest corner will do it.

Theres a bottom drain and i attached a ball valve to it, allowing me to place a bucket underneath.  Can let it drain, or drain it once a day.

I have to get the rest of the seawater out of the basin before i can collect the distilled water.

Enameled makes sense. Wish i had one. Cast iron and stainless is what i have. I do have graniteware turkey roaster i dont use. My homegrown turkeys dont fit in it, had to buy a bigger one. Im off to fill it up.lol. thanks!

how about circulating the seawater in black polypipe placed in the sun to get the water a lot warmer before entering the still. You will get a multiple of performance by increasing the cost a tiny fraction. I've never understood why glass is used for stills instead of black polypipe, especially when corrosive salts are concerned. I don't think your stainless steel will last long. Its most likely 200 series or if you're lucky 304 grade, much less resistant to corrosion than marine grade (which still rusts). Maybe a black plastic liner could be used?

I personally consider plastics something to scour from design for sustainability. I use pyrex to take my lunch to work, and the glass lids have silicone gaskets. If water is to be harvested, I would avoid plastics wherever possible.

-CK

I placed a couple 1 gallon mason jars inside  full of seawater. It wont rust. I dont see temps getting past 120-140 f so it should make it just fine

Still waiting for sunlight. I have a bar b q temp gauge mounted now. Ill report back with temps.

When i did this before (on stovetop) i had visions of scraping the salt out of the pot. Literally scraping. This wasnt the case. The salt just formed, like "poof" theres the salt. I was able to scoop it out with my hand. If true, somebody here posted this, the salt is the first to appear. Other minerals come after further evaporation. So once i scoop out the salt, i should have a salt free, mineral rich water to put on the ground. Or maybe add to sheep and cattle water troughs for minerals. Its pretty exciting stuff.  No energy costs will be accrued to aquire the products. If its kept going, even salt blocks can be switched over to the excess salt.

Steve, assuming i can get a cooler chest full of saltwater once a month, i have a month to evaporate it. Theres no big need (for me)  to expedite the process.

wayne fajkus wrote:. If true, somebody here posted this, the salt is the first to appear. Other minerals come after further evaporation. So once i scoop out the salt, i should have a salt free, mineral rich water...

Yup that was me: https://permies.com/t/56498/Salt-soil#638470 By the way, I really like your dehydrator setup!

I just sent you a thank you pie. Do you have further info, like the order of appearance?

Hey thanks for the pie Wayne!! No, I don't know the order of which minerals come out of suspension after salt.

The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is:
Calcite (CaCO3) and dolomite (CaMg(CO3)2)
Gypsum (CaSO4-2H2O) and anhydrite (CaSO4).
Halite (i.e. common salt, NaCl)
Potassium and magnesium salts

Evaporite Deposits

Nice find michael

I opened my vents back up. I didnt build it to allow the water to condensate and fall back in. It has to travel over wood and will probably rot out quickly. With the vents open the vapor leaves and it is working well enough. I need to put a screen on the venthole though.

Just as an fyi, at 80 degrees outside it got to 125 (f) inside. This is vent closed but its not a tight seal between glass box and table.

I'm really curious how much salt you get from a given quantity of water

Depends on the salinity of said water. If it's really brackish, or closer to brine, you'll get a lot more mineral content.

-CK

Next batch i can do premeasured test. This batch went thru to many changes. Partially evaporated  in basin then moved to pot.

Seawater is typically about 35g per liter of water.

If you are just seasoning your meals you might get through a kilo or two per year. If you are preserving foods - for example making saukraut - you will need a lot more.

Lets say that 40 liters gets you around 1kg of salt, allowing for some wastage. Lets say a family needs about 10kg per year (normal food, but also some preserving) and you are looking at 400 litres of seawater to collect and evaporate. Pretty big investment of effort for a project that produces a commodity that is dirt cheap (£1.00 per kilo or there abouts). I'd say that it was worth doing if you lived somewhere with super easy access to the salt water - but it wouldn't make sense to go out of your way to collect it, given vehicle fuel costs and time.

According to united nations,  40% of the world's  population is within 100 kilometers of the ocean

Bad picture, expand it and you can see the salt

I scooped out the bottom basin. 1 and 1/3 cups of salt. The other pic shows the remaining water between glass and stainless pots.

once i get through this ill have a better plan on the future. There really wasnt enough rust in the basin to worry about. The pot (same i used before) is definitely rusting.

Wayne, it's rad.    

A chemist would definitely be using a flask, or a wide mouthed beaker in a situation like this. It would be really awesome if we could think of something that already comes bathtub shaped and made of glass--and the battle would be won.

How about it, everybody?

Long term, you're looking for something eniterly inert. I know it's a lot less cool and a lot more trouble, but you could blacken the inside of the chamber, then fill it with smaller glass vessels--like sawed off topo chico bottles, or some such--and you would get the surface area to evaporate enough to be worth your while. But getting the salt out of three hundred little jars would be a terrible pain.  

How about....a sporty windshield? Could you lay your hands on something like this?

The lack of volume in a windshield could be a problem. Glass is usually easily obtained.  1 gallon pickle jars come to mind. Smaller jars like spaghetti sauce hold a decent volume.

Lets say i use all spaghetti jars. As it evaporates i would keep condensing it. When 50 jars are half full i would repour until i have 25 full, then 12 full, etc. At the same time I'd put fresh seawater in the empties.  Doing this would get a sizable qty from each jar. Im not sure the ratio, but a one quart  jar would be evaporating 2 gallons of seawater, not just the quart. So hopefully i am not getting 1/2  teaspoon per jar, but something worth scooping out.

It would be really awesome if we could think of something that already comes bathtub shaped and made of glass--and the battle would be won.

I'm not so sure you would want glass inside a greenhouse. I suspect sooner than later, the temperature flux would warp the glass something fierce and become a shattering / cracking hazard all winter long (sunny days + cold air = extreme heat differences). But I sort of think you answered your own question. A bathtub would be perfect. Many are coated in porcelain or enamel, and I suspect that would work out perfectly.

That being said, I'm not sure volume is really what you're after. You want surface area and low volume to encourage evaporation and reduce thermal mass (and then keep refilling as wayne mentioned). An old school enameled bed pan or baby tub would probably be ideal, although I'm not sure how to even find those.

I'm impressed with the amount of salt you've been able to harvest so far! I would  have thought it would take a very long time to get that quantity of salt. I know for how I cook, that'd last me quite some time.

Kyle, once you have a source you start looking for uses. Take eggs an example. I encourage people to raise their own eggs because it can change a person for the better. Because you have eggs, your next goal is to use the eggs. So now your dietary habits change. Instead of "just add water" pancake mix, you are now making pancakes from scratch. If you microwave a jimmy dean egg/sausage patty in the morning,.....you question why to buy them anymore cause you got eggs.

So now you have salt. Smoked salt is very expensive.  Maybe you smoke some and sell it at a farmers market. Maybe you sell it to the local deer processing plant, right next to the liquid smoke (still dont understand why that exists, ick!) for jerky in a dehydrator. I see it for sale, but ive never seen it marketed as a jerky salt. That could be HUGE.

If you have sheep, goats, cows you now make your own salt lick. It doesnt have to be in a block. Maybe you put a little salt water right in their water supply.

And theres the ultimate use that makes it viable for everyone with a yard or acreage. Dilute seawater 10:1 and apply it to the ground to remineralize. If its in its salt form, ALL the minerals are there, you could easily calculate a ratio of this salt to water and apply to the ground.

I reached 125 f with the side vent opened. Outside temp is 87 f.  No water is condensating on the glass with it open. A few rocks were added yesterday since basin was dry. They are very hot to the touch. I am currently filling the glass jars from the stainless pot as it evaporates.  To bug proof it, i stapled window screen to the vent hole.

Only other thing i might do is ad a solar fan. I got a computer case fan. I tried to wire it to a solar panel used to charge a gate opener 12v battery. It didnt spin. I hooked it straight to the battery and it did spin. Its 12v. The amperage was something like .58a. I was surprised the solar panel didnt spin it.

I plan to use this for dehydrating food also. Thought the fan would help, but may not be needed since the glass is not fogging. We get plenty of full sun days.

What are the rocks for?

Hold heat

An update.  I thought i was getting a brown mineral coming out. It turns out it is rust. The reasoning is it is in the stainless pot, not the glass jar. I think im convinced glass will be the way i go forward with this.

I'm consistently hitting 150 degrees f each day (sunny, 90 degree f days). Bar b q thermometer is used, unsure of accuracy. With one screened vent about 1.5" diameter, i am getting no fogging on the glass panes.

Once this batch is done, i will post the starting water amount and the accumulated salt total. I did lose some as i switched around from basin to stainless pot to glass

A solar cooker still!  I have been thinking about creating one of these to distill water... but you have thought about the opposite end of the same idea, gathering salt!  Very cool!

I actually have an annual project for my high school students to see who can build the most efficient solar cooker.  Here are some suggestions for you:

Paint the inside of your cooker matte black.  The shiny stainless steel is actually reflecting most sunlight back out, and it is this energy that is converted into heat to raise the temperature.  Black will absorb the most light and convert much more into heat.  If you are getting 150F now while actually losing most of your light, you can probably come close to boiling your water if it is painted black.  High heat spray paint, the kind designed for wood stoves, would be perfect.  If you want to avoid paints, black paper or cardstock would be the next best thing, but getting black paint on the metal itself would be leagues more efficient at conducting that heat into the metal and raising temperatures higher.

Get rid of the rocks.  Although they hold heat, they are not increasing the temperature to promote evaporation.  All they are good for would be holding the temperature higher for slightly longer once the sun goes down, acting as a thermal battery.  The rocks, being a lighter color, will also block and reflect light from hitting your newly painted black floor, limiting the amount of light turned into heat.

Definitely use glass containers instead of metal, you are on the right track.  Otherwise your salt will be contaminated with various oxidized metals.

Keep us updated!

I like the idea of the "solar cooker still"!!
It multi-tasks one appliance... whenever you aren't "cooking" you can be "distilling/evaporating"... or maybe even do both at once? (mason jars of sea water in the corners, dinner in the middle?)

I think the glass containers are best, although ones with more open surface area (like a casserole dish) would be more efficient.
(you could use the lid for a "casserole door rocket batch heater!") ;-)

Another way to boost the heat would be to make a solar hot air collector below and in front of the basin (easy to just lean it there), or to the left adjacent to the input vent.
Input air enters the solar collector to be preheated, then exits into the evaporator.

Chris Kott wrote:I personally consider plastics something to scour from design for sustainability. I use pyrex to take my lunch to work, and the glass lids have silicone gaskets. If water is to be harvested, I would avoid plastics wherever possible.

-CK

Understood and agree. I would be more cautious of stainless steel than plastic for contaminating the salt.. the glass jars seem ideal. My water from air prototyping has brine in plastic pipes but the water is
evaporated and condensed. It then goes into pvc pipes as used for mains plumbing but the key thing is the harvested water is not touching the polypipe exposed to high temps after it is condensed. Its an abundance of overcaution as the water is for irrigation, not drinking.

wayne fajkus wrote:An update.  I thought i was getting a brown mineral coming out. It turns out it is rust.

The rust is one thing but you're also getting highly toxic chromium compounds, solids and gases, coming out of stainless steel.

wayne fajkus wrote:I'm consistently hitting 150 degrees f each day (sunny, 90 degree f days). Bar b q thermometer is used, unsure of accuracy. ...... Once this batch is done, i will post the starting water amount and the accumulated salt total.

Thats a great result. What part of the system is the thermometer reading? Looking forward to reports on quantities of water thruput. Id be interested in amount of distilled water collected too.

Steve Farmer wrote:



Thats a great result. What part of the system is the thermometer reading? Looking forward to reports on quantities of water thruput. Id be interested in amount of distilled water collected too.

Thermometer is up high in what was the top vent hole. Its in open air. I have to rebuild the top to collect distilled water. Right now the water would fall down the glass and have to travel over painted wood to get back to bottom.

Kenneth Elwell wrote:

I think the glass containers are best, although ones with more open surface area (like a casserole dish) would be more efficient.
(you could use the lid for a "casserole door rocket batch heater!") ;-)

Yes and no. 20 1 gallon mason jars will have the same surface area, yet provide a deeper depth (hold more water) than a casserole dish. 20 gallons is the amount of seawater i get at a time. I doubt that could be accomplished with the dishes.

Bell Cedar Farm wrote:

Get rid of the rocks.  Although they hold heat, they are not increasing the temperature to promote evaporation.  All they are good for would be holding the temperature higher for slightly longer once the sun goes down, acting as a thermal battery.  The rocks, being a lighter color, will also block and reflect light from hitting your newly painted black floor, limiting the amount of light turned into heat.

With 20 1 gallon mason jars, the heat holding capacity will be much greater than now. I have access to granite slab scraps. I think im going to cut a black 7/8" thick piece and place on bottom shiny side down. Its free and it can scald you just sitting in the texas sun. The white paint should reflect it down.  My goal is no paint though(white, black)if i evolve to distilling