IES20040107A2 - Tidal current/tidal stream electrical generator - Google Patents

Abstract

A tidal current/tidal stream electrical generator, comprising of a submersible hollow platform (3) serviced by a compressed air pipe, with pylons (2) supporting a generator unit (1). Blades (4) are mounted on a central shaft (5) and turn a gearbox (6) to increase rotational speed to drive a hydraulic pump (7), which produces high-pressure fluid to drive a hydraulic motor (8), which turns an AC twelve-wire three-phase generator (9). A relief valve (10) diverts excess hydraulic fluid to a hydraulic ram device (11) to control pitch of blades, via linkages (12). The device can generate power from the tidal stream or current in both forward and reverse directions, automatically compensating for the change of the tidal direction and speed to maintain a constant power output. It effectively turns tidal power through rotary mechanisms into hydraulic power, with a system of hydraulic gearing to regulate the speed of the generator and the pitch of the blades. It can be submerged to the ocean floor to avoid marine traffic and brought to the surface for servicing and repair. <Figure 1>

Description

Tidal current/tidal stream electricity generator This invention relates to the harnessing of energy created by the movement of water in ocean tidal currents, and at the mouth of tidal inlets, using an impulse turbine device with built-in controls to turn the constantly changing tidal energy source into a regulated three-phase electricity supply suitable for grid connection.

Devices have been tested using ships’ propellers and wind turbine type blades but due to the fact that the tide reverses direction, this necessitates the whole device being turned to face the tidal flow. This invention concerns a system of blades which operate in the current equally well regardless of the forward or reverse direction of the water without the need to turn the whole device to meet the oncoming flow. A method to vary the pitch of said blades is incorporated so as to provide a constant speed at the generator and so provide regulated and usable three-phase power. The generator unit in its housing is mounted on a submersible platform which rests on the sea floor and so does not obstruct shipping lanes or general marine traffic. It has the capacity to be raised to the surface for servicing, thus avoiding the danger to divers in adverse weather conditions or deep sea application.

This invention seeks to provide constant regulated usable three-phase electric alternating-current (AC) power from a constantly changing tidal power source. As the tides come in the speed of the water increases then drops off as the water reaches high tide. As the water begins to recede, the water increases speed again until it approaches low tide and then drops off again. Wind and waves conditions also affect the speed of the water. Tidal cycles affect the speeds of the water. A spring tide can move twice as fast as a neap tide.

With its ability to be submerged and brought to the surface, this device solves the need to access the machinery for servicing and parts p replacement underwater. This feature also minimizes construction I problems associated with any marine device in adverse conditions or off $ shore-deep sea water. j Additionally, the problem of extracting energy from water hitting a set of blades from forward and reverse directions is solved by the use of a blade configuration that will reverse direction at the turn of the tide. Also, a hydraulic pump will work equally well in a clockwise or counterclockwise rotation. This makes turning the whole device to face the oncoming water unnecessary. The invention effectively turns tidal power through rotary mechanisms into hydraulic power, with a system of hydraulic gearing to regulate the speed of the generator and the pitch of the blades in T3JL8J TRUE COPY AS LODGED OPEN TO PUBLIC INSPECTION UNDER SECTION 28 AND RULE 23 JNLNo.lfijB— ΙΕ η 4 ο 1 Ο 7 automatically compensate for the change in speed in order to maintain the same output levels.

The turbine blades begin their rotation in an attitude of coarse pitch.

This utilizes all the available power of the water to turn the machinery. The rotary mechanical power is channeled through a mechanical gearbox to a hydraulic pump. This pump drives a hydraulic motor to turn the generator. As an AC generator only operates within set limits, all the power at start-up is used to get the machinery up to speed. When its lower operation rotation is met, the generator switches on. As the water speed increases, the blade speed increases and greater hydraulic pressure is provided to the generator until it meets its maximum operating speed under load. At this point the excess hydraulic pressure is now transmitted through a relief valve to a hydraulic ram device in the hub which changes the blade angle to a finer pitch, thus reducing the available power and so producing a constant self regulated speed at the generator. As the rotational speed is now reduced, the relief valve shuts and the generator runs within its operating limits. As the power from the water reduces, the blades are returned to their coarse pitch attitude ready for the next cycle. As the blades are of a simple impulse type design, they operate equally well when the water hits them either from the front or the back.

Due to the design of the invention the mounting platform is partially hollow and capable of having air pumped into it to make it rise to the surface for repair or cleaning.

The invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a view of the tidal stream/current generator as it sits on the ocean floor; and Figure 2 shows a cross-sectional view of the inner generator workings.

Figure 3 shows an expanded view of some workings from Figure 2.

Figure 1 shows a generator unit (1) mounted on a pylon (2) attached to a submersible base with hollow chambers (3) to enable it to be lowered to the ocean floor by pumping in water or raised by pumping in compressed air.

Figure 2 shows the blades (4) are attached to a central shaft (5), going through a speed increasing gearbox (6) to turn a hydraulic pump (7). The pressurized fluid is then pumped to a motor (8) to turn the hydraulic generator (9) within specified speed ranges, dependent on a 50Hz or IE Ο 4 Ο 1 Ο 7 60Hz power requirement. The generator consists of a twelve-wire AC unit producing three-phase power, the setting to be compatible with the local grid capability.

A relief valve system (10) channels excess hydraulic pressure to a hydraulic ram controller (11) unit in the hub to vary the pitch of the blades via linkages (12) so as to keep a constant speed at the generator.

Power is transferred ashore by means of underwater marine cables for grid connection.

Another configuration of this machine would be a direct-current (DC) generator being used to supply DC power to a shore based inverter or producing unregulated power for hydrogen production or water purification/desalination in a location too far from a grid connector. In a situation of multiple turbines, the combined hydraulic output of the pumps may be brought together in the platform to drive one large generator.

Claims (1)

1. Claims A tidal current/tidal stream electrical generator comprising of a mounting, submersible hollow platform (3) serviced by a compressed air pipe, supporting pylons (2) supporting the generator unit (l)(this may be contained in the platform). The blades (4) are mounted on a central shaft (5). This shaft turns a gearbox (6) to increase rotational speed to drive a hydraulic pump (7) producing high-pressure fluid to drive a hydraulic motor (8), which turns an AC twelve-wire three-phase generator (9). A relief valve (10) diverts excess hydraulic fluid to hydraulic ram device (11) to control the pitch of the blades, via linkages (12). The invention effectively turns tidal power through rotary mechanisms into hydraulic power, with a system of hydraulic gearing to regulate the speed of the generator and the pitch of the blades. The fluid to be used in this application would ideally be vegetable / mineral based oil biodegradable to avoid pollution in the event of a spill. The problem of extracting energy from water hitting a set of blades from forward and reverse directions is solved by the use of a blade configuration that will reverse direction at the turn of the tide. A hydraulic pump will work equally well in a clockwise or counterclockwise rotation. This makes turning the whole device to face the oncoming water unnecessary. The whole device can be built at a remote location and used as a modular structure to use as many or as few generators as necessary. IE 0 4 01 0 7 Alternately in a situation of multiple turbines, the combined hydraulic output of the pumps may be combined in the platform to drive one large generator.