A Brief Description of Tidal Effects

The tide rises and falls twice a day, tidal streams are created by the flow of water from one area to another. The geographical features of coastlines and estuaries cause different effects to the water flow. Due to its position and shape the Bristol Channel increases the effect of water flow and creates strong tidal streams and large tidal height ranges. These factors make the Bristol Channel one of the best locations in the world for extracting energy from the sea. The combination of strong tidal streams and large tidal height ranges makes the Bristol Channel an ideal location for the O.H.E.G. plant.

 

 

The Operating Principle of the Ocean Hydro Electricity Generator

The power plant has a bank of tidal turbines which operate when the tidal streams are flooding or ebbing. The bank of turbines is located within channel created by the outer walls of the chambers. The profile of the chambers produces a venturi effect, speeding up the water flow through the channel. The increased water speed allows more energy to be extracted from the tidal stream.

 

Turbines complete with isolation valves, located within the chamber walls, allow power to be generated when the chambers are flooded or discharged of water. The isolation valves allow the chambers to be sealed from the effects of the tide in the open water.

 

The chambers contain energy accumulators which have large mass and large buoyancy, these produce power when allowed to ascend or descend.

 

Energy Accumulator

 

Ocean Hydro Electricity Generator Sequence of Operation

Sequence started from low tide.

 

The flooding tidal stream (tide rising) would be diverted through the bank of tidal turbines creating power, the isolation valves on the chamber inlet / outlets would be closed preventing the water level to rise within the chambers.

 

As the tidal stream slows down towards high tide the tidal turbines power output is reduced, at this stage the chamber isolation valves are opened and water is allowed to enter the chambers. As there is a significant height difference between the open water and the water level within the chambers, a hydrostatic head, water rushes into the chambers driving the turbines mounted in the inlet / outlets, creating power.

 

The energy accumulators are held at the bottom of their stroke allowing the water inside the chambers to rise above them. As the water level within the chambers reaches the same height as the open water the power output of the turbines decreases, at this stage the accumulators are released and begin to rise creating power.

 

As high tide is reached the chamber isolation valves are closed, trapping water inside the chambers.

 

As the accumulators reach the top of their stroke the buoyancy force becomes equal to the gravitational force and they stop producing power. The system is timed so that the last group of accumulators reach the top of their stroke as the tidal turbines begin producing power from the now ebbing tidal stream.

 

The ebbing tidal stream (tide dropping) would be diverted through the bank of tidal turbines creating power, the isolation valves on the chamber inlet / outlets would be closed preventing the water level to drop within the chambers.

 

As the tidal stream slows down towards low tide the tidal turbines power output is reduced, at this stage the chamber isolation valves are opened and water is allowed to exit the chambers. As there is a significant height difference between the open water and the water level within the chambers, a hydrostatic head, water rushes out of the chambers driving the turbines mounted in the inlet / outlets, creating power.

 

The energy accumulators are held at the top of their stroke retaining them out of the water as the water level falls below them. As the water level within the chambers reaches the same height as the open water the power output of the turbines decreases, at this stage the accumulators are released and begin to drop creating power.

 

As low tide is reached the chamber isolation valves are closed, retaining the water at low level within the chambers.

 

As the accumulators reach the bottom of their stroke the gravitational force becomes equal to the buoyancy force and they stop producing power. The system is timed so that the last group of accumulators reach the bottom of their stroke as the tidal turbines begin producing power from the now flooding tidal stream.

 

The sequence then begins again.

 

The sequence will be timed and balanced to give maximum efficiency, operation of the valves and energy accumulators will be computer controlled.

 

Flow Diagram

Initial Testing

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