Water Innovation

This is a video about a billboard that produces drinking water from the humidity in the air.  I am all for water innovation, and I hope this idea continues to be developed!  But, let us do a little quick math together.

One billboard produces 9,450 liters of water in three months.

That is about 105 liters a day. (Not accounting for any of the water spilling etc.)

In many relief and development contexts it would be ideal to provide 15-20 liters of water per person per day, but that includes water for bathing, cooking, washing clothes and dishes, etc.  For just drinking and some cooking you would want to provide at least 2.5-3 liters of water per person per day.

Since in the US most people are unfamiliar with liters, keep in mind, the average soda bottle is 2 liters and below is an image of a 20 liter jerry can.

So getting back to the math, the billboard can provide 7 people with 15 liters of water per day or 35 people with 3 liters of water per day.

Of course, I am totally unfamiliar with the context.  I don't know the typical local water usage per family.  I don't know what other sources of water are available. I don't know how they use the billboard water in comparison to how they use the well water.

My main question stems from the fact that the video implies they are able to provide for the water needs of hundreds of families.  But when I heard the numbers, I had to wonder how they are able to achieve that with only about 105 liters per day (a little more than 5 full jerry cans).

I had a chemistry professor as an undergrad who was a strong advocate for quick mental math and the memorization of estimates for key values in science.  He argued that as good scientists and engineers we should be able to hear a speaker or read an article and quickly consider whether their argument was reasonable based on the values they were presenting.  I have come to see the wisdom in his teaching methods.  I must admit that I have forgotten a lot of the estimates he asked us to memorize and I'm no longer as quick as I used to be with mental math, so please feel free to point out any mistakes I make.  =)  But I have become pretty familiar with basic numbers when it comes to providing safe drinking water.  So when I watch a video like the one above, I can quickly come to my own conclusions.

There was a time when solar panels were at this stage of development as well, and now they are used all over the world.  So I really do hope that engineers around the world continue to innovate and develop new ideas like providing drinking water from a billboard!