The Water Gathering Lake

Lakes are drying up. This is because water absorbs almost all sunlight that hits it. Especially when the wind can carry the layer right above the water away, evaporation will be continuous. Of course if it can’t that layer will be saturated with water vapor, preventing more evaporation, but then the lake will get very warm.

A dew point map showing the temperature at which water condensates in the USA

The air is not dry in many places stricken by drought. That’s where all the water has gone. To get it out the air needs to be cooled to the dew point. Then the water will condensate, form droplets or a puddle. You can see it happen if you have one of those cooling bars you put in the freezer. Just take one out, put it on a plate and observe the water collecting on it, which can be quite a lot.

Dew on a cold bottle of beer suggests its coolness

In principle all ingredients for a full lake are there, especially when the lake evaporates a lot : sun, a basin, a flat surface. What to do? Build a floating heat or solar PV cooling installation on the lake. Heat based cooling uses collected heat energy to compress a cooling gas into a liquid that can then be used to extract heat from the air or maybe even the water. Using heat exchangers/condensers you can then grap a lot of water from the air, and allow it to flow into the lake. Of course you have to prevent water from evaporating at the same time. This you do by shading the lake with the floating solar or thermal collectors. You can apply a few tricks to be even more effective.

The rainmaker system uses mechanical wind energy to drive compressors to cool air and condense water out of it. But it does not seem to make any products at the moment!

Especially when it is humid and hot, a dangerous combination, cooling the humidity out of the air provides both water and dry air in which we can perspire. All lakes are fit for water gathering equipment, the question is how simple can we make it, what is the most robust and low cost mechanism. Of course we can also look into ways to get the water out of our atmosphere in other ways..

Solar panels on a lake like this heat up quite a bit. This can be reduced by putting CuO in the laminate. That sends heat right back to space!