Wind Turbine Extracts Water From Air 227
An anonymous reader writes "Getting access to enough water to drink in a desert environment is a pretty tough proposition, but Eole Water may have solved the problem. It has created a wind turbine that can extract up to 1,000 liters of water per day from the air. All it requires is a 15mph wind to generate the 30kW's of power required for the process to happen. The end result is a tank full of purified water ready to drink at the base of each turbine."
see also (Score:5, Informative)
A Slashdot story from 2009 [slashdot.org] on the same idea. That one wasn't operational at the time, though (except as a research prototype), and this seems to be from a different group.
Re:"up to 1,000 liters of water per day"? (Score:5, Informative)
If you read the article you will see that an operational unit is already producing 800 liters a day consistently. I love this stuff, the energy and raw materials to sustain the human race are all around us, just waiting for the right technique to take advantage of them.
Soooo, that's arid area and probably fresh water shortages licked, what's up next.
Re:"up to 1,000 liters of water per day"? (Score:5, Informative)
Many deserts are also relatively humid.
Remember that deserts are defined by precipitation, not humidity. Deserts next to coastal areas lacking sufficient mountains to extract the humidity (such as Abu Dabi, referenced in TFA) are prime candidates.
This wouldn't work nearly as well in, say, Phoenix Arizona which is not only a desert, but is also arid and dry in every sense of the word.
Re:"up to 1,000 liters of water per day"? (Score:5, Informative)
Whew quick update - a tenth of a cent per liter would be the target
http://www.canadianclear.com/desalination.html [canadianclear.com]
so it would have to be running ~150 years to equal that kind of throughput. With that said there are plenty of places it would be useful which are not accessable to desal tech without major infrastructure investment, so I can see value, while it's not the answer to all questions on fresh water.
Re:This would also be useful on tropical islands.. (Score:5, Informative)
This would also be useful for areas such as rural parts of central Texas, where the water table is so low that drilling a reliable well is dicey, the humidity is high, and the wind is fairly constant for most of the year.
For a small farm that tries to be as off-grid as possible, other than the noise factor from windmills, this would be ideal. If the water yield is good enough, it would mean irrigation is taken care of regardless of drought conditions.
I just hope this technology doesn't just fade away as many others have in the past. There is definitely a use for this around the world, as usable fresh water becomes harder and harder to find.
Re:"up to 1,000 liters of water per day"? (Score:5, Informative)
You haven't been here in July or August, have you? Dewpoints are generally between 50 and 65 degrees F during those months (although, with an outdoor air temperature of 110F, the relative humidity is still low). Currently, we have a relative humidity of 9%, and a dewpoint of 25F, so it's pretty dry, but an evaporator operating below 25F will still condense water...
Re:see also (Score:5, Informative)
I had the same question and did a little Googling. Using some huge assumptions:
* Wind turbine complexes cost about $1.2 - $2.5 M per MW nameplate capacity. Use the high end of that range because we lose some efficiency of scale, adjust to 30kW and we have about $75K for the turbine.
* They say the Abu Dhabi has been producing 800 L / day, and the nameplate production from the spec sheet is 550 - 1200 L / day. Let's go with 800 L / day consistently on the low-ish end.
* No clue on maintenance costs or lifespan, but lets give it 10 years
$75,000 / (800 L / day) / (365 * 10) = $0.025 / L
Municipal water rates vary all over the board, but they're generally between $0.30 and $3.00 / CCF (100 cubic feet). This is about $0.0001 to $0.001 / L, or 25 - 250 times cheaper than this unit
Re:Windtrap (Score:5, Informative)
The yield must depend on moisture. Is this going to be useful in the Sahara or just outside of Las Vegas?
From TFA:
A prototype unit was constructed and erected in Abu Dhabi 6 months ago and has consistently produced up to 800 liters of water a day.
But since that could mean in the middle of the desert or on the coast, your point still stands.
However, I wonder, if it has access to salt water, why not adapt it to use ocean water instead of the humidity from the air? Is it a problem of what to do with the salt and other minerals?
Re:Windtrap (Score:5, Informative)
Abu Dhabi is a coastal city in the United Arab Emirates so it does mean on the coast.
The issue with many desalination plants is not the disposal of salts/minerals but keeping the system clean from all those salts/minerals. The issue being that salts/minerals have a tenancy to build up inside the pipes causing the system to need lots of maintenance. Desalination is a well known process and using regular turbines to power the plant is a good idea. This technology is for a different purpose.
To everyone who's getting steamed about this... (Score:4, Informative)
I don't get it. Why does it have to heat the air up ("to produce steam") ??
Why can't it just take the air and cool it down, instead of wasting energy for heating?
It claims to heat the (hot, desert) air to "produce steam" which is then condensed. The water is already in the air, you don't need to heat it, just cool it to grab the water out.
Either this is a crap article, or its one of those over-unity perpetual motion scams.
To everyone questioning the snake-oil of having to steamify this mysterious water vapour before recondensing it, please keep in mind the following:
I. Just because the water molecule is in the air (via most likely evaporation), it does not imply that the water vapor has a lot of kinetic energy (it's not hot water vapor like steam is). An analogous situation to this is how the water vapor coming out of a kettle can cook your hand, but a muggy day only ruins your hair.
II. Next, we want to consider efficiency. As this article (first link when googling for "steam condense efficiency") http://www.engineersedge.com/heat_exchanger/large_steam_condenser.htm [engineersedge.com] mentions, the laws of thermodynamics dictate that the largest temperature difference is the most efficient for mechanisms such as condensation.
III. -Finally, thermodynamics also dictates two last details about generating temperature differences:
1. That it's much more efficient to cool to a temperature close to ambient (same reason why low-TC superconducting magnets are bathed in multiple blankets of cryo-fluids with different boiling points, rather than just liquid helium blanket and room temperature on the other side),
2. That heat is very cheap and easy to make (often referred to as the "dirtiest" form of energy because it's maximized in entropy).
IV. Put all those things together, and one arrives at the following:
-I want to condense water, and to do it well I need a huge temperature difference between the vapor in the air and my condenser coil.
-It's really hard, costly, and wasteful to make a super good air-conditioner inside a turbine for no reason.
-I'll just heat (remember, it's P=IR heating coil easy!) the water first, and then make a mediocre condenser, and get just the same gains as having a phenomenal condenser.
Re:Windtrap (Score:2, Informative)
There is no evaporation in modern desalanation and no heat involved. It's done with reverse osmosis - membranes permiable to water not salt and high pressure to push against the osmotic draw.
Re:Windtrap (Score:5, Informative)
Holy crap my experience as an ME comes in handy on /.
You are correct. You have to use energy to cool the air and the water in the air. But it's much easier to cool a mass of dry air than wet air. But you get less water out of dry air. You have to think of the air being cooled as wasted energy although some can be recovered by using the cool dry air to pre-cool the incoming moister air.. Also you have to cool the air to below it's dew point in order to get the water to condense. In dry air you have to cool it much further to get to the Dew Point.
Take a look at this psych chart. http://www.rfcafe.com/references/general/images/psychrom_chrt.gif [rfcafe.com]
This tells you how much energy it takes to cool air from different states.
So lets take air at Death Valley. Right now it's about 70 F and 20% Humidity.
Looking on the chart you have:
Enthalpy 20 BTU/lb
Dew Point 30 F
1 lb of air you have 25 grains (.004 lb) of water
Take Orlando. Right now 80 F and 50% Humidity.
Looking on the chart you have:
Enthalpy 30 BTU/lb of air
Dew Point 60 F.
1 lb of air you have 80 grains (.011 lb) of water
So the air in Orlando contains 3 times as much water per lb of air.
The energy required to cool it is 1.5 times as much per lb
You only have to cool 50% of the temperature difference (80-60) = 20 F vs (70-30) = 40 F.
Now lets say you want to get 1000 liters = 2200 lb of water out of the air. Assume you will be able to reduce both to a humidity ratio of 10 grain/lb.
For Death Valley you will get 15 grain/lb of air so you need to cool 1,026,666 lbs of air.
Look on the chart for the before and after enthalpy and you get (20-5) Btu/lb = 15 BTU/lb
You need about 15 x 10^6 BTU to make 1000 liters.
For Orlando you will get 70 grain/lb of air so you need to cool 220,000 lbs of air
Look on the chart for the before and after enthalpy and you get (30-5) Btu/lb = 25 BTU/lb
You need about 5.5 x 10^6 BTU to make 1000 liters.
Re:Windtrap (Score:4, Informative)
All right here it is in SI with some rounding
http://www.uigi.com/UIGI_SI.PDF [uigi.com] [uigi.com]
This tells you how much energy it takes to cool air from different states.
So lets take air at Death Valley. Right now it's about 21 C and 20% Humidity.
Looking on the chart you have:
Enthalpy 28.5 kJ/kg
Dew Point -2 C
1 kg of air you have 3 g of water
Take Orlando. Right now 27 C and 50% Humidity.
Looking on the chart you have:
Enthalpy 56 kJ/kg of air
Dew Point 16 C
1 kg of air you have 11 g of water
So the air in Orlando contains 3 times as much water per kg of air.
The energy required to cool it is 2 times as much per lb
You only have to cool 50% of the temperature difference (21 C-(-2 C)) = 23 C vs (27 C-16 C) = 11 C.
Now lets say you want to get 1000 liters = 1000 kg of water out of the air. Assume you will be able to reduce both to a humidity ratio of 1.5 g/kg
For Death Valley you will get 1.5 g/kg of air so you need to cool 6.7 x 10^5 kg of air.
Look on the chart for the before and after enthalpy and you get (28.5-(-6)) kJ/kg = 34.5 kJ/kg
You need about 2.3x10^6 kJ to make 1000 liters.
To make this in a day you need a power of 266 kW.
For Orlando you will get 9.5 g/kg of air so you need to cool 1.1 x 10^5 kg of air
Look on the chart for the before and after enthalpy and you get (56-(-6)) kJ/kg = 62 kJ/kg
You need about 6.5x10^6 kJ to make 1000 liters.
To make this in a day you need a power of 75 kW
Again you can get big efficiency gains from using the now -10 C air to prechill the incoming air so the actual power required will be less.