Availability of Rainwater

Rainwater is a local resource we should harness to provide potable water in our building. But it is not so easy as it may seem at first sight.

A bio-inspired water system for our building should incorporate some basic life’s principles like focusing on locally available resources and be integrated in its environment. To design it cleverly, we took inspiration in a first strategy that does work in nature: collecting rainwater. As plants do under climate with intense variations of precipitation, our building should harvest rainwater through the specific design of its roof.

We looked for data available on atmospheric precipitations in Holland and found that we could consider an average height of rainfall of 70 mm per month. In fact, the height of precipitation has important variations with the period of the year, for example, it rains only about 50 mm in March but more than 140 mm in September. We must take this into account to adapt to our environment.

With a specific design of the roof that uses the lotus effect to maximize water recovery, we calculated that we should be able to gather about 2 liters of water per day and per square meter of projected area of the roof. Unfortunately, rainwater will not be enough to provide all the water the faculty will daily need: if we tried to do so with a flat circular roof for example, the radius should be 125 m!

Then, we tried to go further and decided to exploit the fact that rainwater is almost pure. Though, turning rainwater into drinking water will need few energy and no chemical products. Our idea was to design a roof that can at least provide enough water to respond to the daily demand on drinking water. We proof this realistic, indeed a flat circular roof of 50 m radius can gather each day the water we need.

Together with the shelter-structure group, we came up to a design that uses bio-inspired technologies already available in the market to address the issue of potable water.