Use cold surfaces for fresh drinking water from air

WHEN I drive up to my garage on a warm day, I notice a small puddle of water has formed on the driveway, caused by condensation in the car’s air conditioner. Take a look at the outside of any air conditioner and you’ll see water dripping out.

Some years ago, I installed a small, portable air conditioning unit in a friend’s flat. About the only regular maintenance it required was the daily emptying of the water container. It produced two or three litres a day.

While we’re worried about the future of our city’s water supply, we tend to look longingly at the sea because there’s a lot of potential drinking water sloshing about there.

But our experience with air conditioners seems to show there’s a great deal of water hanging about in the air too, completely unused. All we have to do to harvest it is give it a cold surface on which to condense.

We already spend a huge amount of energy creating cold surfaces. Shops operate refrigerated units, offices run air conditioners, bars run ice-making machines and almost every suburban home has a fridge with a freezer. Look at the drops of water that frost your glass of cooldrink on a hot day. Free water from the air.

We all turn off taps and save our bath water for flushing the toilet, but at the same time we are generating thousands of litres daily and letting it drip on to the pavement or driveway, where it will evaporate and return to the air unused.

It may be worthwhile to find an inexpensive way to create a cold surface, and we’d have fresh drinking water from the air.

Maybe we have plenty of cold surfaces but we’re not using them. Our dams may have run dry, but our sky is still brimful.

Wouldn’t this be a practical project for engineering students to tackle?

Design a chilling unit, preferably powered by solar or wind power, to create a surface on which moisture in the air can condense to provide potable water. I have seen adverts for commercial units that do this, but they run on electricity provided by Eskom, which is not cheap.

Find cheaper ways of chilling a surface and I’ll buy one.

I’ll raise my first glass of condensed water in a toast to the inventor.

(Of interest, I read on the internet that somebody had found a way to produce deep-fried water. Goodness knows what it’s for?)

Last Laugh

A woman went into the chemist’s shop and told the pharmacist she wanted to buy some arsenic. “What do you want it for?” he asked. “I want to poison my husband, “she replied. “Oh no, I can’t sell you arsenic to poison your husband. That would be totally illegal.”

At this, the woman reached into her handbag and produced a photograph of her husband in bed with the pharmacist’s wife.”

He looked at it for a moment and said: “Oh, I do apologise, madam. I didn’t realise you had a prescription.”