GB511809A - Method and system for utilising tidal energy - Google Patents

Abstract

511,809. Utilizing tidal energy. CAQUOT, A., and DEFOUR, A. June 27, 1938, No. 19013. Convention date, July 6, 1937. [Class 69 (i)] In a tidal power system in which water impounded at high tide in a storage bay operates turbines, the tail water being delivered to a drainage bay which is emptied at low tide, a third or reserve bay is employed which functions at different parts of the cycle of operations sometimes as a second storage bay and at other times as a second drainage bay. The turbines are thus maintained under a more uniform head of water and so more efficiently employed. In addition, the high water level in either or both of the storage and reserve bays may be raised, or the low water level in either or both of the drainage and reserve bays may be lowered by pumping, or both methods may be employed in conjunction. Figs. 1 and 2 show an arrangement of storage, reserve, and drainage bays 15, 16, 17, and power house 21. The head race bay 20 of the turbines communicates by sluices 19, 24, 28 with the storage bay 15, the reserve bay 16, and the sea respectively, and the tail race bay 23 communicates by sluices 26, 25, 29 respectively with the drainage bay 17, reserve bay 16, and the sea. Sluices 18, 27 respectively allow communication between the storage and drainage bays and the sea. Fig. 3 shows a complete cycle of one method of operation of the system, the heights of the tide and of the water in the storage, reserve, and drainage bays being shown respectively by a heavy full line, a dotted line, a chain dotted line and a light full line. The head of water available on the turbines is indicated by the height of the shaded area, and the different phases of the cycle are numbered 1 ... 8, correspondingly numbered arrows on Fig. 2 showing the corresponding directions of flow of the water. Commencing at the point E, the cycle comprises the following operations:-Phase 3; storage bay filled by rising tide, turbines supplied direct from sea and tail water delivered to reserve bay, the drainage bay being closed: Phase 4; water impounded in storage bay at high tide, turbines supplied direct from sea and discharging to drainage bay, reserve bay filled from sea and closed: Phase 5; turbines supplied from storage bay until level in it falls to that in reserve bay, tail water being delivered to drainage bay: Phase 6; turbines supplied from storage and reserve bays together and delivering tail water to drainage bay until the level of the water in it reaches that of the tide: Phase 7; storage bay closed, and turbines supplied from reserve bay alone, tail water being discharged direct to sea, and drainage bay being emptied as tide falls: Phase 8; turbines supplied from storage bay and tail water delivered to sea, reserve bay being emptied to sea and then closed and drainage bay being closed at low tide: Phase 1; turbines supplied from storage bay and tail water delivered to drainage bay until the level in it rises to that in the reserve bay, which is closed: Phase 2; turbines supplied from storage bay until the level in it falls to that of the tide, the tail water being delivered to both reserve and drainage bays, and the drainage bay being closed at the end of this phase, after which the cycle recommences with phase 3. Modifications of this cycle of operation are described comprising six or four phases only. Operation of the sluices may be effected automatically under the control of the water levels in the bays, or by hand. Fig. 8 shows the same cycle of operations as Fig. 3 but modified by pumping during the end of phase 3 and the commencement of phase 4 to raise the otherwise highest water levels in the storage and reserve bays by the amounts K, L respectively, and during the end of phase 7 and commencement of phase 8 to lower the otherwise lowest levels in the drainage and reserve bays by the amounts M, N respectively, which gives a net gain in the power developed. The pumps 34, Fig. 9, may be driven direct from the turbines 30, the sluice-controlled conduits 33 connecting them to the storage, drainage, and reserve bays being arranged below the head and tail bays 20, 23. Alternatively, the pumps may be independently operated by motors, in which case they may be located in the most suitable positions. For example, the pumps for supplying water from the sea to the bay 15, and for pumping water from the bay 17 to the sea, may be located in the dam 11, Fig. 1.