Solar Stills for Water Purification

Objective

To make a modular solar still (for water desalination) system that utilizes readily available materials. This system ensures that fresh clean water is produced from sea water/brackish water. The system can be modulated and made bigger/smaller, but also multiple systems can be set up easily, and run in parallel without any manual intervention.

Concepts used

Simple method of evaporation and condensation of fresh pure water, leaving behind salt from the original input of brackish water.

Materials needed

Shallow base container (made of any material such as plastic or aluminum/steel, etc.), central collection device (cup), clear plastic sheet, tape, weight. Input is sea water/brackish water.

Methodology

The explanation through the video should be followed. Nonetheless, here is an outline of the steps:

Safety precaution

Taste (sip) the condensed water in the central cup (at the end of the evaporation/condensation process) to ensure that it is indeed fresh, and without salt.

Instructions on how to build and operate

You will pour the sea water/brackish water in the shallow base container.
As you can see from the video, you will need a central cup that will be the collector, and you will need to cover the entire setup with a clear plastic sheet.
Use tape to pin down the edges of the plastic sheet.
After you assemble the setup as you can see in the video, you need to put a weight on top of the plastic sheet (over the central cup) to provide tension. You will have to try a few different weights to ensure that the plastic sheet will feel the tension, but there will be some room left for the water droplets to run down and collect in the central cup (method described below).
Put the entire setup in heat and under the sun. As you can see, droplets of pure water will form on the underside of the plastic sheet and will run down due to the tension created by the weight. The drops will then be able to go over the rim of the central cup and collect in it.
Be careful and gentle when extracting the central cup.
Our results have yielded 160 – 170 milliliters of pure water from one liter of saltwater, under heat + sun for 10 hours. If you have 6 of these setups, you can harness 1 liter of pure water every day.

English Version

Arabic Version

Schematic 1

End result showing precipitation collected on bottom surface of plastic wrap dripping into the central collection cup. You can also see the load (a piece of stone) that enables the tension and ultimate movement of water droplets downward and over the edge of the central collection cup, finally enabling dripping and capture in the cup.