Cities need Freshwater to Grow

(.) #81

The specific gravity of freshwater is less than saltwater,
after rain in the see, the top layer of water is freshwater.
I red this in some navy survivalist literature.

(Irene DeBlasio) #82

Bermuda houses have layered limestone roofs – the layers help to catch nearly every drop of rain water due to the architectural design. You could use salt water in homes for bathing. Rain water could be stored for drinking.

(Matias Volco) #83

Thank you so much Irene! I’m looking at it right now:
It is imperative we look at real life situations where this kind of challenges have already been solved. Bermuda is such a good example as perhaps the most developed isolated island.


You can use any roof material that is compatable with your impurity removeal system.


Some areas of Australia are also mandatory-catch. The usa’s King Bush #2’s Texas “ranch” has rainwater collection and a cistern in the basement. Pretty much anyone who doesn’t want to pay for water, like me, uses a collection of some sort. Some places in Oregon(?) offer tax rebates for water collection systems on houses.

(Byron Kay) #86

there are several businesses down the street from where I work that take deep seawater and turn it into bottled water and concentrated (by this I mean really really concentrated) brine. They sell the bottled water to the japanese and the brine to the chinese as a pickling solution. the brine is more valuable than the water I was told. the deep seawater is high is potassium and low in sodium salt. I talked to one of the guys from a plant and he said he learned how to de-salinate using reverse osmosis on navy nuclear subs and they employ a similar technique here. Kona (where I am) has electricity that is 4x more expensive than the average cost in the mainland US. Our power costs 44 cents per kw/h. I could poke around and try to find out more if you like.

I know they have desalinization units on large ships so I could imagine something like that would be economical and is already in-use. Perhaps a combination of catchment and desal would make sense with the desal coming on to meet demand when catchment falls short. Of course the desal water would cost quite a bit more and so would have to be billed at a much higher rate to justify its creation.

We also have a lot of off-grid homes with catchment. My mother-in-law has a tank since she cannot get water any other way. She catches it on her roof and it goes into a tank that is well covered to keep out ligh and debris and it gets pumped into a presurrized tank. Its rather high in nitrate and not the best drinking water but it can be used for showering and washing.


Freedivehi , filters are fairly easy to install and keep working. Everything you need is on ebay.

(Larry G) #88


Based on the review and discussions, the following could be concluded;

  1. The Saltwater Greenhouse systems showed significantly higher distilled water output
    especially adopting technological aspects compared with conventional systems under the
    same operational conditions.
  2. Some of the reviewed technical developments are in research stage or/and are in a small
    scale. So, a lot efforts are required in that field
  3. The distillation process uses very little energy; it needs about 2 kW to drive pumps and fans
    for each 1000 m2
  4. When the solar still is integrated with greenhouse, distillation took place after solar noon and
    during the night due to the low absorption of solar irradiation contrary to what happens in
    traditional solar stills.
  5. The suggested system for irrigation is based on dual using of solar energy in electricity
    generation and brackish water desalination. That system can offer a fresh water for an
    irrigation to an area about 2333

Wind energy systems adapted to the seawater greenhouse desalination unit designed for arid coastal countries

"Only a small fraction of sunlight is useful for photosynthesis. Sunlight is selectively filtered by the roof elements in order to remove radiation that does not contribute to photosynthesis. This helps to keep the greenhouse cool whilst allowing the crops to grow in high light conditions. "


This current study has analyzed the feasibility of an innovative autonomous wind/ solar powered seawater greenhouse desalination unit. The examination of the data collected during the operation of the SWG confirmed that it is technically feasible to take advantage of renewable energy in order to ensure the autonomy of the SWG. It was found that the use of wind/solar system can produce fresh water without the back up support of fossil fuel energy sources. This was justified by the fact that in only eight hour (between 09.00 and 17.00); the greenhouse produced 98% of total fresh water required. This interval corresponded to the duration of the solar sunning and wind efficiency interval."

(Larry G) opened #90

(Larry G) #91

Tried to capture the high points of discussion here: