I see photographs, from time to time, of old windmills that at one time were common on farms and ranches across the U.S.A. Is there a rule of thumb about how much wind it takes to pump water with a windmill?
I see photographs, from time to time, of old windmills that at one time were common on farms and ranches across the U.S.A. Is there a rule of thumb about how much wind it takes to pump water with a windmill?
I found this site.
https://www.agritechtomorrow.com/article/2018/03/using-windmills-to-deliver-water/10595/
A typical windmill with 8' diameter wheel can lift water 185 feet and pump about 150 gallons an hour in 15 to 20 mph winds when using a 1 ¾ "pump cylinder.
An average windmill with the blades spinning in a brisk breeze of 15 to 20 MPH will pump about three gallons a minute whenever the wind blows. The wind blows about 35% of the time in many areas, which will produce around 1500 gallons of water a day.
Another site mentioned that they can generally start pumping water with winds from 3-8mph (depending on the size & type of windmill).
There is no rule of thumb. It's just physics. X amount of energy to lift Y amount of water.
Increasing the sail size to convert more energy into the pump.
Increasing efficiency of the pump, and reducing weight of the sail/vane can shrink the size required to get the job done.
Theoretically, even a one mile per hour wind can get the job done if the system is efficient enough.
Plus it must be taken into consideration how deep the water table is. You can get more water out of a shallow well than you can from a deep well with the same amount of pressure.
Compare trying to pull water from a straw, then repeating it through 10 meters of surgical tubing.
repeating it through 10 meters of surgical tubing.
Well, it will depend on whether all 10 meters of tubing is completely vertical and if not where in reference to the water source.
Of course raw pressure is not the only solution to raising water. You could also use an Archimedes Screw. Of course, I have no idea what would be the relationship between the length of the screw and how much energy it takes to turn it.
A windmill would be well suited to driving an Archimedes Screw assuming the energy requirement is not too high.
Compare trying to pull water from a straw, then repeating it through 10 meters of surgical tubing.
If it's nearly vertical you will suck only vapor because the theoretical maximal suction height for water is about 10 meters (depends on air pressure and water temperature).
Look at any commercially offered pump, their suction heights are only a few meters to avoid cavitation.
They usually provide a diagram showing the relations between pumping height and pumped volume, and their max. pumping height. There is also a maximum pump speed, above which you get cavitation which will finally destroy the pump.
HM.
If it's nearly vertical you will suck only vapor because the theoretical maximal suction height for water is about 10 meters (depends on air pressure and water temperature).
Here we are getting a bit technical, but the limit is actually how much suction can be created. And the human mouth is just not a very efficient suction pump.
And pressure matters a lot, as does temperature. Many do not know that you can actually boil water just above freezing, simply by reducing the pressure. Which is why recipes for higher altitudes need to be adjusted.
But all of this is getting way too technical, and to be honest I think beyond the understanding (or interest) of most readers.
https://www.youtube.com/watch?v=hHNoHhbfFDQ
but the limit is actually how much suction can be created
Wrong. Any suction creates lower pressure and you'll get the water boiling creating vapor if you use a powerful suction pump.
10 meters are the theoretical maximum height you can suck water up. In real world applications it's quite less. For more you have to have the pump near or below the surface and press the water up to the desired height.
HM.
the human mouth is just not a very efficient suction pump
Well, I've hit 0.1 bar; cheeks braced by jaws and teeth, pipe to gauge braced against front teeth, tongue used as a combination of a flexible piston and a valve. Not very pleasant, wouldn't cope with continuous flow, but useful for the check I was doing and much quicker than digging out and setting up the vacuum pump.
You aren't sucking the water up.
Atmospheric pressure is pushing the water up.
How far it can push depends upon the difference between atmospheric pressure and the partial vacuum you create.
That said, a windmill pump does not usually "suck" - but instead, the pumping mechanism is down in the well below water level, so the lift limit depends mostly on how much power you can supply to it.
How far it can push depends upon the difference between atmospheric pressure and the partial vacuum you create
Right, and when you create a nearly 100% vacuum, the atmospheric pressure at sea level can only push it up about 10 meters.
HM.
Posting this reply to the topic as I couldn't work out the best post to post it to as a response.
In regards to how far you can get water from below the ground level there are three major systems used for deep wells on farms etc. today:
1. The water is under high pressure and the natural pressure pushes it up through the pipe.
2. The electric pump is actually at the end of a long tether and power cable to push the water up from the bottom as the pump is lowered into the water table itself.
3. Twin pipe mechanical pump where one pipe is simply a long rod attached to an offset gear at the top and the rod goes up and down to work a mechanical pump at the bottom of the shaft. These have been around for a couple of hundred years and are usually run by wind and is the common type of small windmill often seen on farms.
There are many other systems in use, and have been used over the years, but these are the three most common on small operations due to the low cost and maintenance involved.