Tidal Phase-difference Energy Between Baysand Sea

Tidal energy has huge reserves, of many forms of marine renewable energy, which can be accurately forecast and the energy density is the biggest. Therefore, it is very necessary to increase research and development of tidal energy, especially under the present prominent contradiction between energy shortage, resource development and environmental protection..The paper first put forward the brand new way of tidal energy development in use of the different tidal phase on the bay. The principle is:tidal formed significant phase difference and dynamic water head between inside and outside of the Gulf, after it spread from the open sea to the Gulf coast, due to the deformation of tidal wave caused by coastline and topography, which lead to tidal power generation. The tidal energy development technology has the advantage of higher energy density in the premise of not building dams, and both smaller environmental impact and higher resource utilization rate.Two different methods of mathematical physics are used to find analytical solutions of tidal phase-difference water head. The first method is to use the equations of hydrodynamics and Newton’s second law, and the other is the complex variable function method in polar coordinates, both considering and neglecting the resistance condition. This is the theory basis of the phase-difference energy development.Based on simplified N-S equations numerical model, the tide head numerical solution can be got under different conditions. Comparison numerical solution and analytical solution curve, results showed that the theoretical formula and numerical solution fitted well, especially considering resistance influence on. It can be drawn from this paper, the theoretical formula of tidal energy water head is reliable, which has laid a theoretical foundation but also provides technical support for the new tidal energy development.According to the tidal energy calculation formula and the total potential energy theory, mathematical formulas of maximum power and he actual installed power capacity are obtained, and hence formula of the optimal installed power.The longer the tidal current and the peninsula, the larger the water area,the higher efficiency, the greater the installed power is.Based on the theoretical research of tidal energy, the paper put forward fiour principles of site selection for the phase-difference energy development. Continuous observation for a period of one year was carried out on Sansa bay, which was selected as typical sites for tidal energy research. During spring tide period, maximum tidal energy water head is between1.7～2.2m, obtained from the observed data statistics; and from calculation of this theoretical formula, the tidal energy water head is between1.48m～2.33m. The almost same result showed reliability of theoretical formula in this paper. At the same time, the1.7m water head value is suitable for the low head turbines, which also shows more value of the phase-difference energy development in typical bay.High precision two-dimensional hydrodynamic numerical model is established in the typical Bay, to simulate and predict hydrodynamic field under different power generation condition, in order to obtain the water level, tidal flow, water head, discharge curves through power generation channel. The results showed that:①small loss of tidal energy head, and little effect on the efficiency of power generation,compared with traditional tidal energy development;②outside-to-inside flow is larger, thus inside-to-outside should be the positive power direction. Based on the calculation results of two dimensional hydrodynamic numerical model, unit selection and power generation capacity calculation are carried out. The proper power capacity in this bay is (6～10)Mw.The advantage of phase-difference energy over the traditional tidal energy is in terms of environmental impact, which can be elaborated as follows,①it will speed up the bay water exchange rate, ②it makes the content of active phosphate P in the Gulf decreases, which leads to the bay water quality improvement;(3) it increases and maintains the overall gulf hydrodynamic force;④it will be more favorable for the bottom of the Bay dredging. All in all, the phase-difference energy is a kind of environmentally favorable mode for oceanal energy development, and moreover, it provides a new method for the resource development.