0191-9067/81/010071-01 $02.00/0 Copyright ® 1981 SUNSAT Energy Council USE OF SOLAR POWER SATELLITES: EVALUATION OF THE RISKS ON HEALTH AND ENVIRONMENT LEO THOUREL ONERA-CERT/DERMO 2 Avenue Edouard Belin Toulouse. France Introductory Remarks for the Panel Session on “Impacts on Environment and Effects on Human Bodies’’ We are gathered to try to evaluate the risks for man and environment which could occur from the use of the solar power satellite. First, I think that we must lay down the problem correctly and figure out the power densities we are faced with. Happily, at the 2450 MHz frequency range, we have a lot of information available, with respect to the possible biological effects. We shall consider a 10 GW solar power satellite with a ground antenna of about 40 km2. It is easy to see that this corresponds to an average power density of 25 mW/cm2 on the antenna; however, with the 10 dB width of the satellite radiated beam being about twice the beamwidth at 3 dB, one can see that for a quadruple surface, i.e., 150 km2, the average power level will still be about 2.5 mW/cm2. A prolonged stay in such an electromagnetic atmosphere may be dangerous and consequently we can, from now on, estimate that it would be wise to forbid such an area to people within a distance of 150 km2. Technicians who would have to work on the site would have to be well equipped with protective suits. This constraint may not seem too important; however, the fact is that we must consider a few restrictions with respect to the site for the SPS stations. Desert areas will have to be found, about 15 km diameter. It must also be clear that no beam deviation can be admitted, and in case of an accident, a security system will have to cut power immediately. One can wonder what will occur to the ecology of a country as the small animals, birds, insects, and plants support such radiations. However, the most important phenomenon seems to be the side lobes of the radiation pattern of the satellite antenna; as the gain antenna must be as large as possible, the side lobe level will be high. If, and this seems reasonable, the average side lobe levels reach 20 dB, we obtain a power density of 0.25 mW/cm2, that we may also observe on a surface of several hundred km2. This is without considering the grating lobes (due to the fact that the emitting antenna is an array) which can be met very far from the site. Is this value acceptable? If not, we cannot accept the solar power satellite system as it is designed for the time being, as far as human risks and ecology of the area are concerned. May we remind you now of the agreed standards for maximum admitted power densities? Let us sum up the results obtained by scientists for power densities inferior to 5 mW/cm2 and try to conclude on the use of satellites.
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