Designing the water collector shape

Overview

The aim of the shape design group is to construct a functional, modular water collector. We use the freely available Autodesk Fusion 360 software to make a 3D design in a collaborative fashion. Together with 3D printing, we can rapidly construct prototypes to be tested for functionality, durability, or even esthetics. The water collector is made from polylactic acid (PLA), an environmentally friendly bioplastic. The other work packages will enhance the physicochemical properties of the water collector.

Goals

1. The shape should be able to collect fog, mist, dew and rain from the air into a reservoir.
2. The collector should be modular: many collectors should be able to be combined to one large structure. On the other hand, a single collector should be able to draw a useful amount of water from the air as well.
3. The water collector should be easily transported and stored. Multiple collectors should be able to be stacked compactly.
4. It should be able to be mass produced cheaply and quickly.

Specifications

A shape for water collection

Our shape is inspired by the fogstand beetle (Stenocara gracilipes). Living in the Namib Desert in South Africa, this beetle cannot rely on rain or water bodies for its water needs. Instead, it tilts its round body towards the humid breeze. Small droplets of water in the wet air are collected against its wings. The wings contain alternating hydrophilic and hydrophobic patches. The former bind small water droplets, the latter lead larger accumulated drops towards the head of the beetle.

Our basic shape tries to emulate this process: a half sphere which collects water from the air, surrounded by a gutter to collect the water droplets. It will be investigated if additional rough spots on the dome help water harvesting by increasing the surface or 'guiding' the water downwards.

The surface of the dome

The dome of our shape is the active part: fog droplets should be collected and aggregate into larger drops. When they reach a sufficient weight, gravity pulls them down into the gutter so that the water can be collected. This dome will be coated with the Ice Nucleating Protein, which should enhance the material's interaction with the humid air to extract water.

We experimented with many ways to construct this dome, in increasing order of complexity:

1. A simple, smooth half-sphere, allowing for a surface from which the drops can glide down.
2. A sphere with small bumps to increase the roughness.
3. Small channels placed radially from the top to the bottom to guide the water downwards, allowing for a constant dry surface of the sphere.
4. A shape made of interwoven ribbons, allowing air to pass through.
5. A shape made of a complex net, providing a very large surface area for the air to interact with. This design tries to emulate the nets used for fog harvesting.

Figure 1: First prototype water collector.

Figure 2: First batch of water collectors.

Figure 3: Model with ribbons.

Figure 4: Model made of a complex net structure.

Ease of collecting water and stacking

Our collector has a top with a thread, complementary to a Coca-Cola screw cap. Likewise, in the center of the bottom, a hole with a thread is complementary to this top. This feature has two important functions: first, it allows for multiple collectors to be stacked like a tower, with the screw providing sturdiness. Secondly, it allows for the (bottom) collector to be screwed on a bottle, providing easy storage of the collected water. The water bottle can be buried in the soil, to stabilize the structure, and to keep the collected water cool so it doesn't evaporate again.

Figure 5: The water collector on the soil.

Production

The water collector is designed using Autodesk Fusion 360. Prototypes are made using a variety of 3D printers in the UGent Fablab. We would like to thank Kurt Van Houtte, Willem Van De Steene and Deepak Mehta for their support and guidance.