NREL Researchers Use Sunlight to Power Laser

Golden, Colo., December 14, 1995 -- Commercial prospects for solar-powered lasers recently got a little brighter when researchers at the U.S. Department of Energy s National Renewable Energy Laboratory (NREL) and the University of Chicago powered a laser with concentrated sunlight instead of electricity.

The solar laser works in the same manner as other lasers except it uses concentrated sunlight for power instead of electricity. The sunlight was supplied by NREL s High Flux Solar Furnace, a facility that uses a series of mirrors to concentrate sunlight into an intense, focused beam that reaches concentrations of up to 50,000 suns.

To create the solar laser, a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser crystal was mounted at the target of a specially designed secondary concentrator. The crystal and secondary concentrator were then placed at the focal point of the primary concentrator. When sunlight was added, this concave-convex mirror system gave birth to a solar laser.

The laser had a peak power output of 57 watts. Most conventional industrial lasers have power outputs of several hundred watts.

Our test results prove that a solar-pumped laser can achieve high powers with reasonable efficiency, said NREL s Allan Lewandowski. We achieved the highest reported efficiency for a solar-pumped laser operating at this power level.

Lasers are very energy intensive, consuming much more energy than they produce. Lasers powered by electricity operate at about 1-2 percent efficiency, meaning they require 10 kilowatts of energy to produce 100 to 200 watt lasers. NREL s solar laser has an efficiency of almost 1 percent. The efficiency is expected to improve as researchers refine and optimize the system. NREL researchers believe that solar lasers are potentially more efficient than traditional lasers.

NREL and University of Chicago researchers developed the secondary concentrator used for the solar laser as part of a collaborative effort. While early results are promising, the technology still requires significant development before it is viable for commercial uses.

Because atmospheric conditions such as variable cloud cover significantly influence laser performance, space-based applications (space communication and space power systems) may hold the most promise for solar lasers. Other potential applications include terrestrial materials processing and photochemistry.

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