Seawater Greenhouses

February 19th, 2009 | Posted by paul in Uncategorized - (Comments Off on Seawater Greenhouses)

Unlimited energy. Fast-growing fruit. Free air-conditioning. John Pia Craven says we can have it all by tapping the icy waters of the deep. (See Wired Magazine Article).


This particular technology will work well in arid locations by the ocean.  The technology is called Ocean Thermal Energy Conversion (OTEC), and promoted in Marshall Savages, Millennial Project: Colonizing the Galaxy in Eight Easy Steps (See Millennial Project 2.0Living Universe Foundationand their blog).  It’s kind of the reverse of geothermal, using deep cold ocean water as the differential, rather than hot underground land water.  Combining the prospects of Deep Geothermal and OTEC could do a lot to bring the world vast amounts of clean energy and water, whether it’s along the Sahara coastline, or in central Iowa.


“Water Production and Water Savings

The Seawater Greenhouse converts sea water into fresh water, providing a unique local desalination capability. The water is condensed from water vapour in the air, in much the same way as dew. It is pure distilled water, produced without chemical treatment. The quantity produced depends on the climate – the hotter and sunnier, the more water.

The air entering the Greenhouse is both cooled and humidified. High humidity and low temperatures (the Greenhouse operates at approx. 90% relative humidity) reduces plant transpiration substantially, by up to 80%. This reduces irrigation requirements. The irrigation rate in Tenerife averaged 1.2 litre/day/m2 against 8 litres/day/m2 used by local farmers.

The impact of a new source of water on a local area can be highly beneficial. In Tenerife, a barren area ‘turned green’ as seepage from irrigation reversed saline intrusion and enabled new plant growth.

Of even greater importance is the effect the Seawater Greenhouse can have on reducing demand for mains water and reserves of ground water. Around 8-10 litres per m2 per day can be saved which, on a macro scale, will have an immense impact, freeing existing water supply for other uses.”

Construction and Materials –

The Seawater Greenhouse has a specific function – to produce fresh water and cool air while allowing maximum light penetration. The choice of materials is guided by the level of performance required – and cost. Various specifications of Seawater Greenhouse are available.

Low-cost solutions give excellent results. The design requires a light steel structure with polythene covering, cardboard evaporators and a plastic condenser. ABS and MDPE plastics are used for plumbing. Polythene films are cheap and effective. They are specially treated to incorporate ultraviolet-reflecting and infrared-absorbing properties and can be 100% recycled at the end of their useful life.

The cardboard evaporators are strengthened by a surprisingly effective process. They crystallise calcium carbonate from the sea water and harden like sea shells. The process is controllable and the results indicate that the life of the evaporators can be extended almost indefinitely.”



moisture_vaporatorI was going through my garage last night and found an old box of files I kept of magazine clippings. There were are all sorts of interesting nuggets in there, especially this one:

Popular Science, Oct. 1992, the article Pyramid Power. In this case, the power of pyramids in question is their ability to provide drinking water. Here’s a sample:

Squeezing blood from a stone is beyond the scope of modern science, but a trio of engineers in Seattle claim they have figured out how to get water from rocks. Jose Vila, a retired Boeing Co. engineer, says that pyramids made of loosely piled stone can be used to capture enough moisture to provide ample drinking water for a small community. Such pyramids, called aerial wells, use the daily cycle of solar heating and night-time cooling to create condensation.

Aerial wells are actually a centuries-old idea. In the late 1800’s, archaeologists at the site of the ancient Greek city of Feodosiya, in what is now Ukraine, discovered the 2,500 year old ruins of a water supply system consisting of 13 limestone pyramids, each nearly 40 feet tall. Based on the size of its tile pipes, the system may have produced as much as 14,000 gallons of water a day.

I kept waiting to hear more about it, and finally in 1995 I made some calls, checked white and yellow pages and found Jose Vila himself and called him up. He took down my address and sent me a letter and some background research. He was applying for an additional $250,000 in funding from the National Science Foundation at the time. I got the impression from talking with him, that he was quite elderly. So if he is deceased that may explain the lack of follow up R&D, as I have found only one mention of it on the entire net.

Just imagine if you could build an aerial well, producing for you lots of water out of the air like Tatooine Moisture Vaporators, giving you lots of water where there may be little or none available through traditional welling.