FEASIBILITY OF SITING SPS RECTENNAS OVER THE SEA* P. Q. COLLINS Imperial College of Science and Technology Prince Consort Road London SW7 2B1, England Abstract — Due to population density, it is likely that West European countries would have difficulty in finding enough land rectenna sites to obtain a significant proportion of their power from satellite power stations (SPS). Thus the long West European coastline makes the possibility of siting rectennas over the sea attractive. However, no work has been done on this subject to date. Rectenna design is a field open to innovation, and the specifications for a marine rectenna would be different from those for a rectenna built on land; in particular, environmental requirements would be different. A number of support structures would be possible for marine rectennas; three different approaches are described here, and cost estimates given. The higher cost per unit area of the marine rectenna necessitates a reoptimization of the microwave power transmission system (MPTS), leading to a larger antenna at the satellite, a smaller rectenna and a different illumination function across the microwave beam. It is estimated that siting a rectenna over the sea would increase the cost of power generated by 10-15% and hence this option appears very promising. A number of subjects requiring more detailed investigation are discussed. Resume — A cause de la densite de la population, il est probable que les pays de I'Europe de 1'Ouest auraient des difficultes a trouver assez de sites terrestres de ‘rectenna' pour obtenir une proportion raisonnable de leurs besoins d'energie des Centrales Solaires dans I'Espace. C'est pourquoi Ie tres long littoral de I'Europe de 1'Ouest rend la possibilite de placer les rectennas sur la mer tres interessante. Jusqu'ici aucune etude sur ce sujet n'a ete entreprise. Le dessein des rectennas encourage les innovations. Les specifications d'un rectenna matin seraient evidemment differentes de celle d'un rectenna terrestre (les exigences du milieu environnant etant bien stir differentes). Plusieurs structures de rectenna matin seraient possibles. Ici nous considerons trois alternatives, en donnant des estimations des coOts probables. L'augmentation du cotit unitaire de surface du rectenna matin modifie le sous-systeme optimum de transmission de 1'energie hyperfrequence, car une plus grande antenne dans I'espace deviendra alors necessaire, avec comme corollaire un rectenna de moindre dimension et une distribution differente des ondes hyperfrequence. Nous estimons que ['emplacement d'un rectenna sur la mer augmenterait de 10% a 15% le prix de 1'energie foumie. Cette possibilite apparait done tres prometteuse. Un certain nombre de sujets meritant une plus grande investigation sont egalement passes on revue. 1. INTRODUCTION If systems of orbiting solar energy collectors, or satellite power stations (SPS), are developed as a major energy source for earth, the minimum requirement for any country to use the energy that they produced would be to have the ability to receive the power that they transmitted on the earth. As well as solving the technical prob- *Based on a paper presented at the Colloquium on Solar Power Satellite Systems held at the Institution of Electrical Engineers, London, 27/4/79.
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