One of the biggest problems for bugging in during a disaster can end up being water. We talk about finding water sources near our homes, but that isn’t always possible. Unless you happen to have a stream or pond nearby, which you can harvest water from, you might end up struggling to come up with enough water to survive.
The typical answers to this are rainwater capture and putting in a well. While both are excellent answers, there are times when they won’t work. The well may only produce brackish water and there are plenty of places where it can go months at a time without raining.
But there’s a third option which can be put into effect on your own property, especially if you live in a high humidity area. Actually, it only needs to be high humidity right about sunrise, as that’s when almost all the water will accumulate.
A number of different people have experimented with capturing humidity and turning it into water, in various parts of the world. In Etheopia, which is pretty much desert, they have towers made of bamboo and mesh, which are able to draw as much as 25 liters of water from the air every day. This is an especially good method to use in places where there is a lot of morning fog, coupled with a breeze.
The key to this is hidden in the understanding of “relative humidity.” It’s relative, because how much water vapor the air can hold depends on the ambient temperature. As the air gets warmer, it can’t hold as much water. That water has to go somewhere, so it looks for a cooler surface to condensate on. That causes water drops on our windows, car windshields and even dew on the grass. This condensation happens right about the time of sunrise, when the air is warming faster than the surfaces that the dew forms on.
All it really takes to harvest that humidity is something for the water to condense on. In most successful humidity catchers I’ve seen, this has been a polyethylene plastic mesh, stretched over a frame. Polyethylene is a particularly good plastic for this, because like Teflon, nothing sticks to it. So, the water will run off it easily.
To make a humidity catcher, start by sewing copper pipe and elbows together to form a square. The size needs to be slightly smaller than the width of your polyethylene mesh, so that he mesh can cover it. Make a bag out of the mesh, something like a pillow case, by sewing three edges together. That results in two layers of mesh that the air has to pass through. This bag should fit snug over the copper people frame, but not tight. You don’t want the stitches to pull out.
The frame then needs to be mounted in a stand, nothing more than a couple of legs, with crossbars. Set it up so that the face of the humidity capture is perpendicular to the predominant direction of the wind, so that the most possible air will go through it.
The only other thing the humidity catcher needs is some way of catching the water that will form in it. To do that, split a piece of 4” diameter PVC pipe and put caps on the ends. Cut it so that it just fits inside the stand, right below the bottom of the frame. Then add a fitting and tube for the water to flow out of, into a container on the ground.
How much water your humidity catcher produces will depend on the humidity where you live. Chances are, you’ll need several of these to harvest enough water. But once set up, it’s pretty much a set and forget method, which requires little maintenance and no power to operate.