Energy of sea wind waves and principles of its conversion

Abstract

Editor's Note. Publishing the article of V. V. Volshanik and G. V. Matushevskii, the editor draws attention to the urgency and prospects ofworks on developing nontraditional renewable energy sources. At the same time, with respect to their technicoeconomic indices thewave power plants at present are noticeably inferior to classical hydroelectric stations.The presence of a considerable untapped energy potential of large and small rivers of the country makes their energy the main renewable source whose further development continues to remain the most important problem of hydropower engineering. Ever greater attention has been devoted recently to the possibility of using renewable energy sources. Not last among them is the energy of oceans (wave, tidal, thermal) [i]. A significant place in this field is occupied by a study of the possibilities of using the energy of wind waves (more than i000 scientific papers and about i000 patents). ENERGYThe total power of waves in the world's oceans is estimated to be from i00 million to 13]. Such large differences (by three orderes of magnitude) in the estimates are explained by the differences in the methods of determining the power of real wind waves and selection of the time at which such an estimate is made.In the present article a new method of determining the average long-term power of waves is presented and the first classification of wave power plants (WPPs) according to the energy principle of their operation is proposed. For waves of small amplitude the work in unit time (energy flow) on deep water is [3] Po = w -5-= ~ -32~ h~, (t)where W is the specific wave energy; c, phase velocity; h, X, T, wave height, length, and period; ~, water density; g, acceleration of gravity.In the International System of Units SI the quantity Po has the dimension of watts per meter of the crest (for this reason this quantity in the foreign literature is often called the specific wave power).The following method is usually used for determining the total power of waves on a certain water area, for example, [12,13]. We will examine a cell in a grid region within which the wave field can be considered uniform. Let the length of the sides of this cell be ZI and 12 and two-dimensional regular waves travel in the direction coinciding with side '~i. The wavelength is X = gT2/2~, where 9 is the wave period, and the number of waves in the cell n = 11/%. Then the total wave power within the cell is determined as Pt=Pont2. (2)Summing the values of Pt within the entire investigated water area, we find the total wave power at the time of calculation. This scheme is used for estimating the power of real irregular wind waves, the difference Being that for the energy flow is used the quantity Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 4, pp. 41-45, April, 1985.