FUNDAMENTAL STUDY ON POWER TRANSMISSION USING LASER BEAMS — DIRECT ENERGY CONVERTER FROM LASER ENERGY TO ELECTRICITY* CHOBEI YAMABE, TOSHIHIKO NAKAMURA, HIROYUKI ISHIHARA, SHIGEYUKI TAKAGI, HIDENORI AKIYAMA and KENJI HORII Department of Electrical Engineering Nagoya University Furo-cho Chikusa-ku Nagoya 464, Japan Abstract — A method of power transmission using a laser beam for a very long distance is proposed here- The characteristics of this method are described, and only the direct energy converter from laser energy to electricity is studied in this work. It is found that the converter energy increases with the magnetic field when the laser-produced plasma is confined by the surface magnetic field. 1. INTRODUCTION It has been proposed (5) to use a laser beam for energy transmission over an ultralong distance from a developing country which is rich in natural energy to a consuming city where there is need for large amounts of energy, or from a solar power satellite (SPS) to the Earth or between space stations. On the other hand, power transmission by a microwave beam has been proposed by Glaser (4). However, the demerits of a microwave beam are longer wavelengths and therefore the necessity of very large equipment because of the large beam divergence and the low energy transmission density due to the air breakdown by the electric field of the microwave. Not many studies on the power transmission using laser beams have been reported. The wavelength of laser light is shorter than that of a microwave beam, and the electric field for the air breakdown with laser light is higher compared to that of the microwave, therefore, the transmission energy density can be increased. Since the conversion efficiency with a laser beam is inferior to that of a microwave beam, for which the method is supported by an established technique, it is important to improve the laser device in efficiency and output power at the region of wavelength which is called “the window of the atmosphere.” It is also important to develop a high-efficiency direct energy converter from laser energy to electricity. In this paper, the direct energy converter from laser energy to electricity with laser-produced plasma is reported. A TEA CO2 laser (wavelength X = 10.6 /xm) is used and its output beam is irradiated on a solid target to produce the plasma. The energy of the initially produced plasma is changed to the expansion energy with the *Presented at the Fourth ISAS Space Energy Symposium, at ISAS, Tokyo, I March 1985.
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