DESLEY BLANCH : Dr John Barker is a Sydney-based physicist who has an idea for providing cheap, clean water for Pakistan. He's been working in solar technology for many years and believes his simple, cheap 'solar nest' may provide a solution to the pressing need for clean drinking water.
Many years ago, he developed a durable, high-quality solar oven, but he realised the need for a similar device which was cheap. The result is his do-it-yourself solar nest, which works as an oven that can reach temperatures high enough to sterilise water or cook food. He explains his solar oven to ABC Radio's Michael Cathcart.
DR JOHN BARKER : I developed a solar oven which was suitable for what I said at the time - was for greenies and grannies and everybody in between in Australia, because it was a durable high quality product and we manufactured and sold quite a few hundred of those.
But clearly it was far too expensive for what I call the billion dollar-a-day people in the world who have got very little money and have not got those resources and they desperately need what a solar oven can provide. So as they say, after 30 years it was obvious as to how it could be done.
MICHAEL CATHCART : Well how do you build one, just take us through it?
DR JOHN BARKER : Right, well if the listeners could imagine taking, say a picture frame or something like that about half a metre by half a metre and rather than having the picture and the glass on it, just wrap some clear plastic over it so that it's essentially a double glazed window half a metre square.
You then take a heap of fibrous material, it could be, well I have got coconut fibre, but it could be straw and it could even be in countries like Pakistan, dehydrated cow dung. It's good enough so long as it is dried out and they use a lot of that dry. They generally burn it.
You turn that into what I call a nest, so you can put that half metre squared frame on top of it with a hollow in the middle. So that provides the insulation rather than using a box, you use this nest.
MICHAEL CATHCART : So that's to hold the heat in, that's the point of this?
DR JOHN BARKER : That holds the heat in.
MICHAEL CATHCART : Right.
DR JOHN BARKER : The sunlight goes through the double sheet of plastic, you put the cooking vessel or water bottle whatever you like in the nest, you put the picture frame on top of it and any sunny day over about 20-25 degrees C, you will achieve cooking temperatures within about an hour-and-a-half.
MICHAEL CATHCART : Okay, so you have made what you call a nest, which is basically a little box, that's half a metre square. It's made out of insulating material like fibre as you say and over the top, you have put a frame of plastic, two sheets of plastic. The sun shines down on this, and you say it really heats up the area that you've enclosed in the nest!
DR JOHN BARKER : Absolutely, and in fact I did a lot of tests on this, The question is, how hot will this get and how long will it take. So I did a lot of research on this, using electronic probe thermometers, and various materials and so on. The paper that I presented at the World Solar Congress in Beijing at the end of 2007 has got graphs in it which demonstrates the research that I did.
Typically remind the listener that you don't need temperatures above 100 degrees Celsius to cook. In fact anything over about 80 degrees will cook and anything over about 65 degrees will sterilise water.
MICHAEL CATHCART : Well, that's what I was going to ask you, because when we need to sterilise water, we're always told to boil it, but you're saying you don't need to boil it?
DR JOHN BARKER : Well, you don't need to. Certainly if you do boil it, then you've got 100 per cent probability of sterilising everything. If you've got the opportunity to boil water, yeah you've got gas in a billy and things like that, then I would say yes, boil it. There is nothing more to think of, after a little while your water is absolutely sterile.
But if you've got your back to the wall, limited resources, as many of these people and many people in desert countries have got, then certainly the reality is that anything over about 65 degrees -- sustain that temperature for any period of time and you'll have sterile water.
MICHAEL CATHCART : So this is a survival option?
DR JOHN BARKER : It's a survival option.
MICHAEL CATHCART : Yeah, when you say for a period of time, we're talking about hours, aren't we?
DR JOHN BARKER : No, you don't need hours to sterilise it. Holding it over about 65-70 degrees for about half an hour should do the trick.
MICHAEL CATHCART : Oh I see. So you could put a plastic bottle of water in, leave it there for half an hour and it would be safe to drink you reckon?
DR JOHN BARKER : Oh, well, not that you leave it there for half an hour, but it would need to be at -- one of these typically use a litre, a litre and a half of cooking or drinking material in it and it will take about an hour and a half to get up that temperature. You'd say after two hours, you have got your clean water.
MICHAEL CATHCART : I see, okay so you're waiting for the temperature to build to the maximum, so it does take a couple of hours. And you reckon you could cook rice and so on in it?
DR JOHN BARKER : Oh absolutely. In fact the pictures are on the ABC web site show rice as cooked. I even cooked a small roast of lamb in it. I did it to prove it.
MICHAEL CATHCART : Now, I should make it clear, you're not selling this. You are not claiming intellectual property in this. This is just -- you are giving this to the world?
DR JOHN BARKER : Absolutely and I am essentially giving myself to the world with it. If any of the aid agencies are interested, I have contacted them in the past, but I understand that they are flat chat trying to deliver thousands of tents and things like that and dealing with innovations which might seem a little bit pie-eyed is not quite their cup of tea. But I am willing, ready and able.
DESLEY BLANCH : Dr John Barker, who is an Adjunct Professor at Murdoch University and is a developer of a do-it-yourself solar nest which reaches temperatures high enough to sterilise water and will cook food.
DESLEY BLANCH : Next, we meet an Australian who is doing something about the world's shortage of phosphorous.
Dr John Barker, Adjunct Professor
School of Sustainability, Murdoch Universit,
90 South Street, Murdoch, WA 6150