43rd and 46th parallel, the average annual energies due to sun and wind, expressed in identical units, are of roughly similar magnitudes. But what really counts is the consistency of furnished energy. The Rhone Valley’s average annual energy can scarcely be utilized because it is the product of a turbulent, capricious wind that blows approximately 100 to 120 days per year, and dies down at night. (This is only a disadvantage to the extent that the wind blows stronger during the day, exceeding the maximum productivity level of the vanes. In France, only Brittany’s coastal area (with winds of relatively constant force and direction) could be exploited. Generally speaking, the most important element is not the average annual energy provided but the distribution curve of exploitable energies superior to a given threshold, for 10- 20-30 hours etc . . . without interruption. One must not forget that the problems of high-scale energy stocking have not yet been solved. The most important stocks near a total of a few hundred MW-h on the daily level and some GW-h on the weekly grade. For the present, various other problems restrict the immediate interest of such resources: investment and maintenance costs, resistance to the outbreak of storms — be they only once every five or six years — noise, wakes far downhill from the windmill (between 10 and 50 “diameters”) and the unsightliness of the machine itself. This form of energy is directly linked to solar energy and to the rotation of the Earth. Energy taken from the sea takes three forms: (a) Tidal Energy There exists only one world site in operation: the tidal power station of Rance, in France, with a capacity of 240 MW, put into service in 1966. Our globe offers about ten potential sites (with tides greater than 10 m and dyke construction possibilities). This is consequently not an abundant and well-distributed energy source!* On the other hand, the modulation consistency is perfectly predictable. This energy is not of solar origin, but originates from an initial state (planetary movement) which, in fact, results from a slowing down of planetary movement (Earth-Moon) owing to energy dissipation in an oscillating system, unmeasurable even over a century, in its present state of operation. (b) Wave Energy Although several projects, notably Japanese, have led to experimental realization, this energy, not yet in use, does not seem likely to provide a solution to the energy crisis. Its linear density is low (one must consider the wave’s’space and time intervals and be aware that this is the work of “gravity”) and the energy collecting installations needed are gigantic structures. Yet, the heterogeneous material structures may end up making this type of energy more significant. The above energy is of solar origin. (c) Thermic Ocean Energy This is the process of exploiting the difference of temperature between surface *Among the possible sites: Chansey, France: 12 GW, Funday Bay, Canada: 5 GW, A. San Bay, Korea: 2 GW; the remaining sites (Arctic Ocean, India, Australia) hardly account for more than 20 GW.
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