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Wonders of a small dish
Poverty and sunlight are thought to be the characteristics of a typical third-world country. Scattered at or around the Equator, most of the developing nations receive intense sunlight almost all the year. Pakistan, for instance, has an average of 200 solar days a year. To many of us here, the scorching sun may not be something to get excited about, but some day it may prove to be a blessing in disguise.
We all know about the sun’s immense potential as a source of heat and light that can be harnessed to cook meals and generate electric power. What would sound surprising is that sunlight can also be used to perform laser surgery. A new and cheap technique that uses sunlight instead of laser beam is on its way to completion.
In the Negev Desert of Israel, a group of scientists is experimenting with solar surgery — a new kind of surgery that uses concentrated sunlight. During preliminary experiments, they have used concentrated sunbeam to burn animal tissues and studied various effects of medical importance. If proved successful, these experiments will offer a very cheap alternative to highly expensive laser surgery.
Scientists working on this project hope that in a couple of years, this technology will be mature enough to be marketed, and help in procedures not currently possible without laser surgery.
The phenomenon of laser (light amplification by stimulated emission of radiation) produces extremely concentrated, coherent and monochromatic light beam. That is, a laser gives an energy density hundreds of thousands times higher than that of ordinary light. Put in simpler words, it packs huge amounts of energy in a small area. Devices using the phenomenon of laser are called “laser devices” or — in more familiar words — lasers. Today, lasers are used in numerous devices, from CD drives to X-ray welding equipments. Surgery is also taking the advantage of lasers, but such surgical devices are so expensive that even good hospitals can’t afford them.
On the contrary, parts used in experimental solar surgery equipment are common, off-the-shelf and, for this reason, quite inexpensive as compare to laser devices. They concentrate sunlight on small panels to do the job similar to that of laser surgery equipments.
A curved, plate-sized dish concentrates sunlight on a point to serve the purpose. It increases the concentration of sunlight 15,000-fold.
“We want to concentrate sunlight back to a level it has close to the Sun,” says Jeffrey Gordon, the key investigator of the project and a mechanical engineer at the Jacob Blaustein Institute for Desert Research at Ben-Gurion University of the Negev.
The concentrated light reflected from the dish is then sent into an optical fibre which can carry it, for example, from a hospital’s rooftop to the operation theatre. Gordon believes the small will prove a cheap and readily available alternative to costly laser surgery equipments. Of course, developing countries are on the top of its potential beneficiaries.
Extraordinary concentration of energy at a small area is the key feature of laser. In general, the advantage of using laser light for surgery is not its coherence but high power density at adequate power levels. The equipments of laser surgery simply focus the light — a form of energy — to do their job. But their price tag is the major problem. That is why millions of people in third world are put at the disadvantage being unable to use it. In this regard the solar unit can match typical surgical lasers in terms of power (eight watts) and power density (ten watts per square millimetre) at a far less cost as well.
According to Gordon, a typical laser surgery unit costs 100,000 dollars or even more (around 6 million Pakistani rupees at the current rate of exchange). On the other hand, the complete solar surgery unit — even at the current experimental stage — has been developed for about 1,000 dollars. It is clearly 100 times cheaper than laser surgery setup. From the third world viewpoint, it will not only save a huge amount but also result in better and widespread healthcare facilities.
Gordon and his colleagues — including Solly Mizrahi, a liver surgeon at Ben-Gurion University — have experimentally burnt chicken liver and breast using concentrated sunlight. Mizrahi says that the effects of burning from concentrated sunlight are comparable to that of laser burning. The next step will be to perform surgery on live mice with the solar optical fiber system.
According to Mizrahi, solar surgery seems promising for treating patients with liver tumors — specially those who need keyhole surgery because open operations are dangerous to them.
Beside these advantages, solar surgery has a downside as well. It can’t work in a cloudy weather. A small cloud blocking the sunlight for a while can stop an operation right in the middle, and even can pose risk of life for the patient.
The dish could also cut the cost of solar-generated electricity, the team hopes. Existing solar cells convert sunlight directly into electricity. They are efficient, but their semiconductor materials are pricey. Focussing a large amount of sunlight onto a tiny chip should slash the price, says Gordon. Much research is underway on concentrating sunlight in this way.
In Gordon’s solar surgery setup, a small mirror is placed at the focal point of the dish — rather than a bulky solar cell that blocks out sunlight. Reflected into an optical fibre, the light is carried to cells elsewhere. Each dish generates up to five watts of power, so pieced together into arrays a handful could power a 60-watt light bulb.
Though the system is basically devised to applied in the field of surgery, but some experts think it may also be used to fulfill some the energy needs in remote areas. Agami Reddy of Drexel University in Philadelphia is progressing in this direction. He is leading a project funded by the US Department of Energy to construct a pilot installation. Another solar energy researcher, Yogi Goswami of the University of Florida in Gainesville, also finds this an appealing concept, “the concept is workable. But its success will eventually depend on whether it proves economical. If it does, they should follow it.”
Further Readings:
1. Helen Pearson, “Solar surgery hots up” — Nature Science Update
2. Feuermann, D., Gordon, J.M. & M. Huleihil, “Solar Fiber-optic mini-dish concentrators: first experimental results and field experience” — Solar Energy, 72, 459 - 472, (2002).
3. Gordon, J.M., D. Feuermann, and M. Huleihil, “Laser surgical effects with concentrated solar radiation” — Applied Physics Letters 81 (Sept. 30):2653-2655. Abstract available at
.doi.org/10.1063/1.1510942>.
4. “Solar energy engineering — A mini-revolution in Israel” — REFOCUS March 2001
5. Daniel Feuermann and Jeffrey M. Gordon, “Solar surgery: remote fiber optic irradiation with highly concentrated sunlight in lieu of lasers” — Optical Engineering, Vol. 37 No. 10, October 1998 (2760-2767)
The writer
