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How Hard is it to Get Water From the Air?

In the last few blogs, we learned we are running out of water and climate change is making it worse. We also learned almost 100% of the water we use is polluted and no one has water security and independence. We learned there is more than enough for everyone replenished every day untapped, unowned, and unused, in the air around us.

We learned about 80 Amazon Rivers of fresh, clean, pure water flow into the atmosphere every day.  We learned 80% of the world’s population has over 100,000 gals of fresh water in the air around them. We learned there are large very dry climate regions that have very high humidity, and there are numerous micro-climate coastal areas in California, Texas, the Middle East, and Caribbean, Pacific, and Indonesian islands, that are ideal for condensing water from the air. 

Finally, we learned getting this abundant water out of the air and to the people who need it will change their lives in ways we cannot imagine today.

So how do we get it?

Getting water from the air is really easy, very simple, and wicked hard. 

It’s easy because it happens naturally, without doing anything.  In fact, you can’t stop it when the air cools quickly; it rains, or you get ‘dewdrops’ on your glass of milk.

It’s simple because the physics always works and works the same way every time.  We know with great precision exactly how much water is in a specified volume of air at a particular temperature and pressure, we know exactly how much energy it takes for the water to condense from a vapor to a liquid, and we know exactly the temperature that it will occur at.  However, making that happen at the time and place you want it to happen at the highest possible volume at the lowest possible energy is a wicked hard problem.  Let’s look at that.

Let’s start with what physics, thermodynamics, fluid mechanics, and what a constellation of geniuses have learned about the whole process.  Don’t worry! This sounds terribly complicated, but we will make it simple.

Pressure Volume Graph.png

Think about turning your computer on and off. You go through four simple steps; a beginning when you get started, a transition up to get ready to rock ’n roll, a steady operation doing what you want to do, and a transition down when you want to stop.  When you want to turn your computer on again, you go through the same four steps in the same order.

When translated into geek speak, this is called the Carnot Cycle or the Carnot Thermodynamic Model (Figure 1). Below the bottom line water is a liquid, above the top the line it is a vapor, and in between it is in transition. We know exactly how much this is: 2,260 kJ/kg, which is the minimum amount of energy required.

Bottom line in getting water from the air is we need to transfer energy to change water vapor in the air into liquid water in your glass. When the air temperature is precisely at the edge of the transition point it is at the ‘dew point’, which is the temperature that water droplets begin to form.  Voila! L'eau de l'air! Did I mention that Sadi Carnot was French?

Now, the atmosphere is very extremely variable (it’s called weather) and the temperature and humidity are constantly changing.  There is a lot of heat in the air above the dew point, or it would be raining constantly.  There is a special word for that energy; ‘Sensible Heat’.

In a controlled system, like a home heating and cooling system, reducing the sensible heat to reduce water vapor takes a lot of energy.  In fact, it is one of the greatest domestic uses of electrical energy in the US. For the purpose of taking water from the air, this energy is all wasted; we don’t get any water until we get the air to the dewpoint.  99% there, which is 99% of the energy used in an air conditioner or dehumidifier, generates no water.

So, the challenge to getting the maximum of amount of water for the minimum amount of energy from the air at the right place and time is knowing and manipulating the heat of the air.  A lot of other things go into it, such as saturated vapor density, airflow, air volume and pressure, etc., etc., and the STEM is really fun if you are into that sort of thing! 

There are a couple of tricks that to meeting that challenge: precise and current measurement of air temperature and humidity in an extremely variable environment; reducing the sensible heat of the air using the least amount of energy; and controlling the airflow to control the amount of water produced.  What does all this mean for getting at all that water in the air?

·         First, it means that if you have unlimited energy just cool the air until the water forms, and you can get as much as you want. 

·         Second, it means you can do it very efficiently by continuous precise measurement and control of the air temperature and airflow and get as much as you want

But the most important thing is that it is doable!  With the right design, we can bring water security and independence to everyone!  Let’s get started!

Want to know more?  (www.waterseer.org). Want to help the world get water abundance?  (https://www.waterseer.org/foundation/). Want your own water Security and Independence?  (https://www.waterseer.org/products/reserve-your-waterseer-1-7g4nk). Want to find a WaterSeer distributer? (https://www.waterseer.org/regional-distributors/)

Sources:

Carnot, Sadi, Reflections on the Motive Power of Fire

The Feynman Lectures on Physics, Addison-Wesley Publishing Company.

Google and Wikipedia, of course.

For cool interactive graphic on the Carnot Cycle in simple mechanics go to http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/carnot.htm