Cheap, Practical Solar Still

This solar still is distilling up to 3,000 gallons of fresh water a day at Coober Pedy, a township in South Australia. The water comes from a brackish underground stream. The still was designed by the Division of Mechanical Engineering of the Australian Commonwealth Scientific and In dustrial Research Organisation. It covers 38,000 square feet and provides sufficient water for the township at a cost of $4 a 1,000 gallons. It can be doubled in size.

It is claimed that the still is cheaper in first cost and more efficient in operation than any similar still now operating, including those in the Mediterranean region and Africa. The design includes a series of metal troughs with built-in weirs so that the brackish water can flow into the troughs under gravity from a bore water tank.

The troughs are lined with black polythene to absorb the sun’s heat and also to protect the troughs from the corrosive effects of the water.

A series of glass panels is laid across the tops of the troughs which are sealed at the sides, and at top and ends, with butyl or polythene sealing strips.

The weirs are designed to ensure an even flow of water which evaporates as it receives heat from the sun. It then condenses on the under sides of the glass and trickles down into side channels and so to the tank which receives the fresh water.

The bore water is unfit for human consumption as it contains 24,000 parts per million of salt, but after passing through the still the water collected is purer than that in almost any city and contains less than 50 parts per million of salt.