Technofix
Nature’s blueprint for solar power
Jessica Hume
Last Updated: May 15. 2008 9:10PM UAE / May 15. 2008 5:10PM GMT
The solution to the energy crisis may be found in a process developed aeons before electricity, oil, and even the origin of man. Photosynthesis, the mechanism by which sunlight is converted to energy in some bacteria and plants, may provide an efficient and elegant model for the next generation of solar-cell technologies.
The photosynthetic process in plants evolved from a process first used by bacteria. In order to discover the most fundamental photosynthetic models and apply them to new technologies, scientists are studying purple bacteria for its ability to harness and store the energy from the sun.
Unlike green plants, which produce oxygen using water and sunlight, purple bacteria uses sulphide or elemental sulphur and sunlight to produce hydrogen, the cleanest fuel on the planet. It has the potential to replace fossil fuels as a major source of energy, some scientists believe.
“At the moment we’re rapidly eating our way through fossil fuels, which are essentially reflections of photosynthetic activity that went on millions of years ago,” said Richard Cogdell, a professor at the University of Glasgow department of biochemistry and molecular biology.
“We have to find some way of sustainably meeting the energy demands of mankind for the future. Hopefully, we can find a clean way to do this, one that doesn’t produce excess carbon dioxide and induce climate change.”
More solar energy hits the earth’s surface every hour than all of mankind uses in one year. The purpose of Prof Cogdell’s work is to figure out how to capture that energy with enough efficiency to meet all the energy needs of daily life.
As one of a handful of scientists working on developing a mechanism to use purple bacteria as a primary energy source, Prof Cogdell said the idea was to use the photosynthetic process to build an “artificial leaf” with which solar energy could be captured, converted to usable energy, stored and distributed.
The device would work in a similar fashion to a solar panel, only more efficiently and better able to store captured energy.
“Normal solar cells have problems with storage – energy can’t be stored for that long. But once that energy has been converted to fuel, which is what the artificial leaf would do, storage is not a problem at all, neither is transportation.”
The leaf would be similar in appearance to a normal solar device. It would have a panel on the bottom to which water would be supplied and where photosynthesis would take place and a catalytic layer which would convert carbon dioxide to fuel, Prof Cogdell said.
The fuel produced during photosynthesis could be stored for an unlimited amount of time.
“In the solar panel, you’d have a module that would be able to allow photosynthesis to occur; so it would be taking carbon dioxide, converting it from an oxidised form to a reduced form. That’s the fuel you then burn, which re-oxidises it.
“You have a cycle where the net change in carbon dioxide, or carbon in the atmosphere, is going to be zero. The artificial leaf is carbon neutral.”
The photosynthetic process would take place as the panel is exposed to sunlight. In a green plant the process involves solar energy, which is converted by carbon dioxide into carbohydrate, a fuel. In the phototrophic bacteria, purple bacteria among them, the process is much simpler and photosynthesis produces hydrogen. When hydrogen reacts with oxygen, the by-product is water.
For obvious reasons, the geographical locations most conducive to the successful implementation of the artificial leaves would be places that get at least half a day of full sunlight. The Gulf and Saharan Africa, for example, are two locations in which the technology could work extremely well.
But Prof Cogdell said the potential was there for the artificial leaf to have dramatic and positive effects all over the world.
“We rely now on oil, and that’s produced in only a few specific places. Systems like the artificial leaf could be distributed more widely but obviously it will depend on there being enough sunlight wherever you set it up. But the point is, this could fully substitute for oil.”
The price of a barrel of oil was now at an all-time high, Prof Cogdell said, and with demand expected to double by 2050 the future was not looking bright. If we were to maintain our current global levels of transportation and quality of life, other energy sources besides fossil fuels needed to be developed.
One of the greatest challenges was gathering a larger body of research: “It’s not just biologists we need to be involved in this – we need chemists, physicists, engineers. Right now we’re trying to carry over our excitement about this to other scientists.”
How soon could it become a reality? Prof Cogdell said the length of time it would take to achieve the widespread implementation of the artificial leaf depended on the amount of investment available. But the idea was catching on across the western world, he said, and in the past ten years the issue of renewable energy had become a central issue in global consciousness.
First things first, though, he cautioned: “We don’t know whether the idea is actually going to work. If we can learn how nature does it, we can duplicate it. We believe that it is possible because nature isn’t magic.”
jhume@thenational.ae
thenational.ae |
