Concentrated sunlight could be used as an alternative to expensive laser surgery in poor countries, according to new research.
    Scientists working in Israel's Negev desert are using a curved, plate-sized dish to focus sunlight to a point, concentrating it up to 15,000 fold. A mirror directs the light into a fibre-optic cable, which could carry the beam from a hospital roof to the operating theatre.
    As well as reducing the costs of some forms of surgery, the technology could also offer a cut-price way to harness solar power, by concentrating sunlight onto small solar panels.
    In Israel's sizzling Negev Desert, scientists have been carrying out the first trials of solar surgery - burning tissue with concentrated sunlight.
    Sunbeams could one day shrivel burn away tumours, offering an alternative to laser surgery. The technology could also offer a cut-price way to harness solar power, by concentrating sunlight onto small solar panels.
    A curved, plate-sized dish focuses sunlight into a point, concentrating it up to15,000-fold. "We want to concentrate sunlight back to a level it has close to the Sun," says Jeffrey Gordon of the Jacob Blaustein Institute for Desert Research at Ben-Gurion University of the Negev.
    The dish bounces the light into a fibre-optic cable, which could carry the beam from a hospital roof to the operating theatre. Gordon thinks the dish could provide a cheap alternative to laser equipment - particularly for developing countries.
    "Most patients are deprived because of price," says Gordon. A laser unit costs more than US$100,000; the solar set-up, which includes off-the-shelf parts, is nearer $1,000.

Sun burn
    The group have tested the sunbeam on chicken breast and liver. The effects on tissue are comparable to laser burns, says liver surgeon Solly Mizrahi of Ben-Gurion University, who was involved in the trials.
    Liver tumours are good candidates for solar surgery, says Mizrahi - particularly patients who need keyhole surgery because open operations are dangerous.

A beam of concentrated sunlight burns a chicken liver.
    Emergency treatments are out, however, as a drifting cloud could shroud the sun and shut down the operating room. "It's useless if you live in London or Seattle," admits Gordon.
    The dish could also cut the cost of solar-generated electricity, the team hope. Existing solar cells convert sunlight directly into electricity. They are efficient, but their semiconductor materials are pricey.
    Focusing 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.

Sun trap
    Gordon's system places a small mirror at the focal point of the dish - rather than a bulky solar cell which blocks out its light. Reflected into an optical fibre, the light is carried to cells elsewhere. Each dish generates up to 5 watts of power, so pieced together into arrays a handful could power a 60-watt light bulb.
    Houses could use these modules to supply some of their power needs, predicts Agami Reddy of Drexel University in Philadelphia. He is leading a project funded by the US Department of Energy to construct a pilot installation.
    "The concept is workable," agrees solar-energy researcher Yogi Goswami of the University of Florida in Gainesville. Ultimately, the system's success will depend on whether it proves economical. "If it does, they should follow it," he says.

References
Feuermann, D., Gordon, J.M. & Huleihil, M. Solar Fiber-optic mini-dish concentrators: first experimental results and field experience. Solar Energy, 72, 459 - 472, (2002).