TIDAL POWER

The paper reviews the physics of tidal power considering gravitational effects of moon and sun; semidiurnal, diurnal, and mixed tides; and major periodic components that affect the tidal range. Shelving, funnelling, reflection, and resonance phenomena that have a significant effect on tidal range are also discussed. The paper then examines tidal energy resource for principal developments estimated from parametric modeling in Europe and worldwide. Basic parameters that govern the design of tidal power schemes in terms of mean tidal range and surface area of the enclosed basin are identified. While energy extracted is proportional to the tidal amplitude squared, requisite sluicing area is proportional to the square root of the tidal amplitude. Sites with large tidal amplitudes are therefore best suited for tidal power developments, whereas sites with low tidal amplitudes have sluicing that may be prohibitive. It is shown that 48% of the European tidal resource is in the United Kingdom, 42% in France, and 8% in Ireland, other countries having negligible potential. Worldwide, approximately 200, 50, 27, 20, 17, 17, 15, and 14 TWh of tidal resource annually are identified at Penzhinskaya Cauba (former USSR), Mezen (former USSR), Tugur (former USSR), San Jose (Argentina), The Severn (U.K.), Turnagain Arm (U.S.A.), Gulf of Cambay (India), and Cobequid (Canada), respectively. Smaller potential tidal energy developments are mentioned. Existing tidal energy plants at La Rance (France-240 MW), Annapolis (Canada-17.8 MW), Jiangxia (People's Republic of China-3.2 MW), Kislaya Guba (former Soviet Union-0.4 MW), and others are discussed. Tidal barrage design and construction using caissons is examined, as are alternative operating modes (single-action generation, outflow generation, flood generation, two-way generation, twin basin generation, pumping, etc), development trends and possibilities, generation cost at the barrage boundary, sensitivity to discount rates, general economics, and markets. Environmental effects, and institutional constraints to the development of tidal barrage schemes are also discussed.