Cities need Freshwater to Grow


Almost everyone did this on the islands i lived on. Water for plants and animals came from the large tanks sitting under the air conditioners. It’s not as clean as the RO or distilled water, it contains some metals from the ac unit, as well as stuff out of the air as it’s blown thru the unit, and then molds that grow on that residue, but dogs are hardy beasts, and the plants didn’t seem to mind. If you have ever done ac repair, you have seen mold and fungi inside those things that will give you nightmares, you need carbon/RO/UV post-distillery, but the good news is that there’s virtually nothing left for those post filters to remove, so they can last forever.


Guys, for crying out loud,…

Stop bickering and reinventing the wheel and just plan to use existing proven technology that works and is available on the market today.

Watermakers+solar panels+wind generators+a bank of batteries+storage tanks=fresh water. Daahhh,…


Also, we need to make sure our pumps work OK with salt water. Even marine ones will have some problems with it, the less mechanized stuff the better. KISS: Keep It Simple, Stupid.


A simple cheap pvc and rubber flapper wave operated pump can feed a distiller. After the distiller, you can use any water pump you want because there’s no salt in the water.


Works well enough for me.

(Bob LLewellyn) #66

[quote=“octavian, post:62, topic:621”]
Stop bickering and reinventing the wheel[/quote]
That’s not what we’re doing. :smile: It’s Saturday night, we’re sitting around having a drink and comparing notes with friends about an up coming project. Most likely we will use several ideas and find out which one works best then make more of them.

Brainstorming this way is slow but it has the benefit of re-reading for clarity and others can come along and catch up to where we are instead of having to go over the same stuff.


Thanks the numbers. For now, let’s focus on just what we need.

I think the 4-6 gallons a day does not include cleaning, showers or laundry. I.e. the people are doing sun showers or sponge baths.

Can you do laundry with salt water, or does it need to be fresh? How much water is needed? I assume in our city we need to do sheets and towels once a week, plus light clothing unless everyone is a naturist like me. Eating places need to be kept clean and scrubbed. Can you mop a floor with salt water, or does it need to be fresh water?

Octavian care to guess what laundry and cleaning would add to that; maybe 8 gallons a day? or do you think 6 will do it?


Oh, I know the answer to this one. For wells 30-80 feet you use a jet pump. These are pretty cheap. My well on my acreage was 65 feet deep. A jet pump is located above ground. It sends water down a tube, and around a brass valve at the bottom. The valve has a venturi principal cone so water is jetted to the surface. More water comes up than you send down. You have to prime the down pipe with several gallons of water that needs to be sterile to avoid contaminating the well. After that it cycles the water down and brings it up. My jet pump ran about $600 for the surface part, and $50 for the valve, plus two runs of tubing. So less than $1000 total. This is great system for lifting water up to 80 feet and keeping a tank at 60 psi water pressure. That’s one thing I miss about the well is being able to set my showers to really spray. Oh, and the free water.


LOL, what “cleaning, showers or laundry” on a sailing boat?? Who has time for that while fishing and drinking rum?? That’s it. 4-6 gal. a day all included :slight_smile:

But,… if “showers” are “really needed”, couple of buckets of seawater will do the trick and after that you wipe your body with a moist fresh water towel. “Laundry”?? OK,…if you insist,…You put your dirty cloth in a net and you drag it astern in the wake for 15 min, rinse them with 1 gal of fresh water and than dried them on the lifelines. Half an hour max and “laundry” is done.

But that’s for sailors,… :slight_smile:

For a seastead maybe you should allow 20-30 gal/person/day to be in the safe side and than whatever is needed for commercial activities. What also matters is how fast your seastead is growing in terms of population and what industries are running aboard.

For a seastead start up of 100-200 people and light economics I’d definitely get a 10000 gal/day watermaker from the start.
Even if you grow fast, just keep on adding this size units. It’s better to have several units instead of one big one for back up purposes,…


[quote=“ForexBob, post:66, topic:621”]
That’s not what we’re doing. It’s Saturday night, we’re sitting around having a drink and comparing notes with friends about an up coming project.
[/quote]OK, I got you. Let me grab a cold one and join the effort :smile:


I definitely agree. All my research indicates that solar power (or wind or whatever) running a membrane style desalination unit is the most efficient existing technology.

For those who are still working on solar still, how much solar area is needed to get 4000 gallons per day (20 gallons each for 200 people)?

I think what I found yesterday was a square meter per gallon; so that’s 9 square feet. So you need 36,000 square feet of solar still for 200 people. Does that sound right?

I’d like to continue to calc through the numbers. One thing I haven’t started yet is the power generation needs. Figure the desalinization unit, hot water, cooking, a bit of pumping for water pressure and for sewage treatment. Luckily with LED lights there isn’t much need for lighting power. Computers. Satelite internet. And finally, someone mentioned A/C. Do you know how much power A/C needs? Maybe we can use swamp coolers. Anyway, it would be good to get a working number, like that we need 20Kw for the city or something like that.


I want to know how efficient those wind turbine condenser things Ellmer was talking about are. (Scroll way up). If those work well enough, that would be pretty helpful. Reverse Osmosis may be the most efficient method currently, but we should still look at other options.

Also, use passive solar design ideas to seriously reduce AC energy use. Overhangs on windows so direct sun is kept out between 12 and 4 or something like that; good insulative windows, making roofs white to reflect heat, ect…

Using solar heating tanks for our hot water would be good.Literally just black drums on the roof filled with water works pretty well.


Maybe 100KW for a 100-200 people seastead start up would be more than enough,…

(Wilfried Ellmer) #74

@ForexBob, Bob i actually have quite an insight on the subject i am involved in Michael Edwards RioJuntas project in Ecuador where the building of sustainable dome structures is a key ingredient. In 2012 we got quite a demand on “prepper domes” - a spin off of this (packing a 4 head family into a 12m dome under earth with 100% independent food and water) was a project in Chile where Michael would buy and and develop a piece of the Atacama Desert. The key to this development would be a “WATERDOME” a shell building with glass surfaces to produce water out of oceanic moist. Supply fresh water in the middle of the desert was the core of the business plan we can use that technology with a few modifications for Marinea.


Octavian this is really a good call. I was reading up last night, and found that a good Solar rule of thumb is 10 watts per square foot. So 100KW (100,000 watts) is roughtly 10,000 square feet of solar. The DeltaSync plan uses a 50m x 50m square platform (160x160 feet) so that’s 25,600 square feet. So a roof area equivalent to 40% of the platform size is right.

I’m even more excited about solar embedded in windows. This has a lower conversion ratio, only 7%compared to 20%. So figure only 4 watts per square foot. Also it impedes the light. Like sunglasses, only 60% of the light and heat goes through. So solar windows would be like sunglasses for the residents. You would still see outside, but a lot of the light and heat would be reduced. The buildings on a 160 x 160 foot platform might easily exceed 15,000 square feet. Which means there would not be visible solar panels at all. The windows alone are enough to generate power for the residents.

With that much power, membrane desalinization is a no-brainer. Also hot water, flush toilets, and even my favorite, a marine gyroscope sufficient to stabilize the rocking motion. We might even get some A/C units going, or at least swamp coolers.

I still see no reason to clutter the sea with a football field size solar still, which needs nearly daily maintenance, when the windows of your apartment power a high technology machine that only needs a hour maintenance every month. Just my opinion.

(Bob LLewellyn) #76

Dehumidifiers, There should be a fairly strong breeze with natural cooling from the water. When the surface of the water evaporates, it takes up energy from the surrounding air which makes the air cooler but wet. If anything electrical is needed, it will be dehumidifiers. They should be built in. The moisture captured from the units should be channeled to the holding tank for doing laundry.


The numbers i get are one square meter per 8 hour day will supply heat of vaporization for one gallon of water. One square meter is ~11 sq ft, so you need solar input on 44,000 sq ft for 4000 gallons per day. That does not mean the distiller is that big, it means the heat collected is piped over to the distiller. Coincidently, 44,000 sq ft is an acre, ~210 x 210 feet. Basically, you roof over everything, and put solar panels of some flavor on all of it. If the living space for a person is 20x20 and the roof is covered in flat plate collectors for heat, a good guess during a sunny 8hr day is their distiller can make 36 gallons. I have not calculated the extremely variable variables and inefficiencies and parasitic loads.


I wouldn’t use only solar panels, but also wind generators. Keep in mind that for alternative energy sources of 100KW you will need huge battery banks and inverters, and it might be very expensive to start up with alternative only. I would go with a solid diesel generator backed up by solar and wind, and do a gradual transition to alternative only.


One of the alternatives I see is wave power. For a city at sea, waves are constant. The platforms are always being pushed and pulled relative to each other.

I’ve seen online an “engine” that converts random motion to a spinning flywheel. It basically catches the motion in the right direction, and makes a wheel spin. The engine I saw catches 3-d motion, so it has three catch mechanisms to transfer power to a single flywheel.

I’ve seen other opportunities where wave motion drives a piston to pressurize air, and the air is then stored and used to generate power.

Wave power would generate 24x7 except on calm seas. This contrasts to Solar which generates 8 hours a day, with lower generation on cloudy days.

(Irene DeBlasio) #80

The island of Bermuda collects rain water by using slanted limestone roofs to catch rainwater. Is this feasible for seasteading in addition to desalination plants?