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RT-101

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  • A. QUICK REPLY:1. A fan is best way to make lots (GPH - gallons per hour) of water. You need to move 1500 SCFM (standard cubic feet per minute) of air through a 10 inch (25cm) diameter plastic pipe of 150 ft. to make about 12 GPH of water. That much air through 10 inch pipe makes the air velocity at 55 MPH (miles per hour) which is very fast to chill the air down by dumping heat through plastic pipe into colder ground. If you use metal pipe you only need about 100 ft. instead of 150 ft. length.2. It's very hard to generate free convective air movements without a fan. You need to move lots of moist ambient air over 30 meters and that's hard to do using just free convection. If you want to eliminate fan, you need very large diameter pipes or a cave that allows natural air movements into ca…

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    A. QUICK REPLY:1. A fan is best way to make lots (GPH - gallons per hour) of water. You need to move 1500 SCFM (standard cubic feet per minute) of air through a 10 inch (25cm) diameter plastic pipe of 150 ft. to make about 12 GPH of water. That much air through 10 inch pipe makes the air velocity at 55 MPH (miles per hour) which is very fast to chill the air down by dumping heat through plastic pipe into colder ground. If you use metal pipe you only need about 100 ft. instead of 150 ft. length.2. It's very hard to generate free convective air movements without a fan. You need to move lots of moist ambient air over 30 meters and that's hard to do using just free convection. If you want to eliminate fan, you need very large diameter pipes or a cave that allows natural air movements into cave to chill air against cold rocks and get water. My system is not designed for this and trades off large caves with natural convective air movements for 10 inch narrow pipes and a high pressure fan to pump the right amout of air through pipe.B. DETAILED REPLYHi Kalina,Unfortunately engineering is a very exacting procedure and to make machinery work properly requires geometries and fan blowers designed for specific sizing. Without a high power fan capable of moving about 1500 SCFM of moist air from ambient surroundings through your pipes, your system simply won't work to produce about 12 GPH of condensed water for drinking. You can't rely on natural convective air currents to move that much required moist air through 90 ft (30 meters) of 4 inch (10 cm) diameter plastic pipe. And even if it's 40 inch (110 cm) diameter piping, and you probably sized for free convective air movement, its way too large pipe for the forced convection that uses a fan and only needs 10 inch diameter pipe. My system design is not based on free convection air movement which you realized needs large size dimensions to naturally move small amounts of air. Moving and chilling small amounts of air using natural convection will only yield droplets and not gallons of water over an hour's time. And such natural convective systems need very specific geometry and proper wind conditions that would force air into a cave opening whose internal cold rock walls are mostly underground and chill the air and create water droplets. This air would then need some large cave exit flow to keep it's draft moving in and out while slowly creating water droplets. One can build such air inlet and exit draft cave structures using huge piles of rocks. But don't confuse this with my "active" or dynamic fan air design, which uses minimal volume space and no caves, without cave-stone like structures. They are different entities.It takes a very powerful fan using about a 1.25 HP (1000 watt) electric motor to push 1500 SCFM of airflow through a 10 inch (25 cm) diameter pipe. That airflow and pipe diameter over a 150 ft length of buried pipe will yield about 12 GPH of condensed water. Water yields will vary with ambient relative humidity, pipe length and diameter, and amount of air pushed through pipe. The longer the pipe used to better chill the moist air, the more water generated but at the expense of a more powerful fan as greater pipe length means more power needed to push air though. Metal pipes need shorter lengths than plastic pipes. With less airflow you get less water. Decreasing the pipe diameter will also reduce airflow capability, for a given size fan, and reduced water generation. It's all a technical balancing act that requires either engineering knowhow or lots of trial and error to get it right.In technical terms the fan must be capable of generating 1500 SCFM of air flowing through 150 ft of 10 inch diameter plastic piping. That takes a fan air pressure capability of about 10 inches of water column (iwc). You need to move your humid air at speeds of about 55 MPH inside the plastic pipe to chill air down and get 12 GPH water. Your free convective system is similar to a fan capable of only 0.05 iwc at a flow of maybe 1 SCFM. Yielding no condensed water. Decreasing the pipe diameter causes more airflow pressure drop and needs an even more powerful motor to get your 1500 SCFM of airflow and yield 12 GPH water. Lesser fans yield lesser pressure drop and less generated waterflow. Cutting the airflow rate in half yields half the condensed water and requires a smaller cheaper fan.Unfortunately, my 1500 SCFM fan with 10 iwc costs about $4000.RegardsHerman Vogel

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  • Hi Chris. I can show you how to fish (show math equations on calculating pressure drop and fan size) or just give you the fish (answers), which do you prefer? Fan pressure needed is based on multiplying a known fan pressure drop (base on flow, pipe-length and diameter) by ratio of new pipe-length to diameter used. Then multiplying that by ratio of new to old flow rate squared. Units don't matter since its a ratio as long as they're consistent ones. Result is a needed fan pressure drop for pipe length, width, and airflow rate. This drop is the fan pressure needed to flow your air. In my case a 200ft long pipe 0.75ft diameter (9inches) yields about 10iwc (inches water pressure) drop. I'm flowing 1500CFM of air. This yields about 12 GPH of water under conditions I noted in my report. Now a …

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    Hi Chris. I can show you how to fish (show math equations on calculating pressure drop and fan size) or just give you the fish (answers), which do you prefer? Fan pressure needed is based on multiplying a known fan pressure drop (base on flow, pipe-length and diameter) by ratio of new pipe-length to diameter used. Then multiplying that by ratio of new to old flow rate squared. Units don't matter since its a ratio as long as they're consistent ones. Result is a needed fan pressure drop for pipe length, width, and airflow rate. This drop is the fan pressure needed to flow your air. In my case a 200ft long pipe 0.75ft diameter (9inches) yields about 10iwc (inches water pressure) drop. I'm flowing 1500CFM of air. This yields about 12 GPH of water under conditions I noted in my report. Now a fan this hefty with about 1ft diameter blades will cost ~$2000. Keeping my same geometry pipe, and cutting the air flow rate in half (750CFM) yields ~half the GPH water or 6GPH. And fan air pressure drop lowers to (750/1500)^^2 x 10iwc = 2.5iwc from 10iwc, which is a much cheaper fan power, but only yields 6GPH water generated.Careful about using corrugated plastic tubing. Corrugations add perhaps another 30% to pressure drop and requires a more powerful fan. Your needed tubing length is based on heat transfer equations relying on air flowrate, tube diameter, underground dirt temperature (Your case pile of rocks), and the inlet air temperature. RH also enters these equations. But don't worry, using some of these basic ratios with some trial and error will get you started on track.NOTE: Measure your pile of rocks' internal body temperature and compare to 5ft under dirt temperature. Colder is better and needs less airflow and RH to get more drinking water. Old air well structures of rock were cold to touch and usually well hidden in grottos from direct Sun.Mahalo.

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  • Sorry about too many details. Needed to get message across. Questions, just ask!

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  • Glad to help, keep me informed of your efforts/challenges.Key Points:1)GeneratingLarge GPH: To generate ~12GPH (gallonsper hour) of water you need a costly, high performance fan to produce aflowrate of 1500CFM at a pressure drop of about 10 iwc (inches of watercolumn). The pressure drop is rating is calculated based on flowrate, pipediameter (~10 inches), and pipe length (~ 200 – 250 feet). Generated water is scaledby the flowrate, so that same geometry at 750CFM you get ~6GPH. Typically,water generating systems use lots of electricity to create only a few gallonsof water per day and not per hour. Our system efficiency uses the chillingtemperature of the underground instead of an electric cooler to make the water.We are MUCH cheaper with larger water volume production.2)WindspeedVERY IMP…

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    Glad to help, keep me informed of your efforts/challenges.Key Points:1)GeneratingLarge GPH: To generate ~12GPH (gallonsper hour) of water you need a costly, high performance fan to produce aflowrate of 1500CFM at a pressure drop of about 10 iwc (inches of watercolumn). The pressure drop is rating is calculated based on flowrate, pipediameter (~10 inches), and pipe length (~ 200 – 250 feet). Generated water is scaledby the flowrate, so that same geometry at 750CFM you get ~6GPH. Typically,water generating systems use lots of electricity to create only a few gallonsof water per day and not per hour. Our system efficiency uses the chillingtemperature of the underground instead of an electric cooler to make the water.We are MUCH cheaper with larger water volume production.2)WindspeedVERY IMPORTANT: Your math will find that for the pipe diameter and air flowrate,you will get about 55MPH air velocity through the pipe. This means that thecondensed moving water droplets won’t be able to adhere to pipe walls and will getsucked up with the windflow. So to capture these droplets suspended in windflow,and to collect them into the cistern, you must have a porous, fiberous splash-surfacelocated inside the cistern for the wet wind to splash upon, condense and form thewater droplets for collection in the cistern. Otherwise, the exhausting wet airflowexiting the cistern and dumping into the general ambient will cause local “rainfall”to occur. You actually have your own weather machine that locally creates rainfor your crops! Make sure you have an umbrella! 3)ProduceCooler Byproduct: Keeping farm producein a cooled, air conditioned warehouse is another benefit and byproduct of yourwater generating system. Our water generator has the capacity to act as acooler. Remember you’re using underground pipes to chill airflow down byperhaps 15 F lower thanambient (deeperunderground pipes provide more chilling). Since this cooler exhaust air “must”be continuously dumped somewhere, why not dump it into a warehouse to get freeair conditioning and preserve your produce!

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  • I looked at the youtube video link and agree thatit doesn't math out! The rebuttal mentioned it very nicely. The diagram shownwill generate some marginal water, maybe a gallon a day, but such passivesystems are not designed for high capacity throughput, and require multiplecells for generating reasonable quantities of water. You need a hefty airmoving fan rated at ~1Kw to move at least 1500 CFM (cubic feet per minute) ofmoist air to generate sufficient water as reviewed in my report. At thatairflow rate and a pipe diameter of about 10inch, plus 150ft long, you couldgenerate a hefty water supply of 12 GPH. I've created a design code based onfundamental heat transfer engineering principles that addresses the necessaryvariables needed to create XX GPH of water, but didn't include its designp…

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    I looked at the youtube video link and agree thatit doesn't math out! The rebuttal mentioned it very nicely. The diagram shownwill generate some marginal water, maybe a gallon a day, but such passivesystems are not designed for high capacity throughput, and require multiplecells for generating reasonable quantities of water. You need a hefty airmoving fan rated at ~1Kw to move at least 1500 CFM (cubic feet per minute) ofmoist air to generate sufficient water as reviewed in my report. At thatairflow rate and a pipe diameter of about 10inch, plus 150ft long, you couldgenerate a hefty water supply of 12 GPH. I've created a design code based onfundamental heat transfer engineering principles that addresses the necessaryvariables needed to create XX GPH of water, but didn't include its designprocedure in this report.Takes several weeks to dig ~150ft treansh and laydown 10inch-dia piping, plant a say 50gallon sisterm down about 10ft, and getan electric fan capable of pushing that much air through ~150 of piping. Suchfans easily cost several thousand.Good concept, but convective draft of suchchimneys are minor compared to the required ~10iwc draft pressure drop.Good thinking, but we need about 150ft of 10inchpiping burried about 5ft underground where the soil is cooler.

    I was email contacted by some green movement society in Germany who applied this concept and claimed to successfully create water. My friends and I built a small test model in an indoor warehouse. Instead of burying plastic pipes, we submerged them in an above ground swimming pool whose water was chilled to simulate the cooler temperatures existing with underground pipes. We used a cheap fan that couldn't blow enough humid air through our 100 foot 10-inch ID pipe to condense out very much water droplets. We made only a little condensed water in the pipe because of our small amount of pipe airflow created. However, the idea was proven and by math-scaling my results we would generate the GPH shown in my Instructables model.

    I was email contacted by some green movement society inGermany who applied this concept and claimed to successfully have created water. Myfriends and I built a small test model in an indoor warehouse a few years back to prove a point. Instead ofburying plastic pipes, we submerged them in an above ground swimming pool whosewater was chilled to simulate the cooler temperatures existing with undergroundpipes. We used a cheap fan that couldn't blow enough humid air through our 100foot 10-inch ID pipe to condense out very much water droplets. We made only alittle condensed water in the pipe because of our small quantity of pipe airflowcreated. However, the idea was proven and by math-scaling our results we proved we couldgenerate the GPH shown in my Instructables model.

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  • Good concept, but convective draft of such chimneys are minor compared to the required ~10iwc draft pressure drop.

    Yes copper is much better and would improve our 1500CFM airflow design system by reducing the length needed for heat exchange of a 10inch diameter pipe, from a PVC length of 150ft down by more than 50%. BTW: the airflow moves at about 35MPH and won't get heated by friction but rather loose its heat by convection with pipe.

    Sorry! NEVER meant intentionally. Had lots of personal issues plus changed my email contact, while sadly forgetting to notify Instructables how to get in touch with me.

    Takes several weeks to dig ~150ft treansh and lay down 10inch-dia piping, plant a say 50gallon sisterm down about 10ft, and get an electric fan capable of pushing that much air through ~150 of piping. Such fans easily cost several thousand.

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  • Hi wkg4,Yes it would work, but the resultant updraft would be ~1/10 to 1/100 of what we need to generate 10 to 15 GPH of drinking water at ~10 inches of water column pressure

    Yes, agreed if you had no power. But with power (solar cells, etc.), I want at least 1500 CFM through a 10-inch plastic pipe (for making 10-12 GPH drinking water) to run moist air at ~45MPH. Under such air speeds you don't even need a sloped pipe. You could use a horizontal pipe and need a water catcher screen at the dump-exit to catch condensed water droplets mixed with and moving with the airflow that will drip into the cistern collector.

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