Prime-mover dynamo plants – Electric control – Fluid-current motors
Reexamination Certificate
2000-09-18
2001-10-30
Waks, Joseph (Department: 2834)
Prime-mover dynamo plants
Electric control
Fluid-current motors
C310S011000
Reexamination Certificate
active
06310406
ABSTRACT:
1. DESCRIPTION OF THE PRIOR ART
1.1 State of the Art: Tidal & Ocean Current Exploitation
A huge amount of energy is present in the world's tidal and ocean currents. Estimated is an amount of 200,000 MW for ocean tidal and 50,000 MW for ocean currents (Charlier, 1982).
However, today this vast amount of energy is hardly exploited. At present only one 250 MW tidal power scheme is in operation, in France in the estuary of the river Rance. The scheme utilises a barrage to block the tidal flow and to release it through propeller turbines, see FIG.
1
.
Devices which are yet in the test-phase are so-called free stream devices, see
FIG. 2
(adapted from IT-power News, 1993). These devices do not need a barrage but directly convert the kinetic energy of the current into mechanical energy. Their development descend from the windmill turbine technology. However, as yet no free stream device has reached the pilot-state.
Plans for large scale application are now being developed, like the Cenex (Current Energy Exploitation) plan to harness energy from the strait of Messina. The first phase of this project foresees in the installation of about 100 Darieus-type turbines.
1.2 Drawbacks
Both the barrage and the free stream devices have their specific drawbacks. The barrage systems involve large scale civil engineering works (the barrage itself). Apart from the large capital needs for the construction, these systems have a large environmental impact during construction, but also during operation. With respect to the free stream devices, it can be stated that their environmental impact is less. However, as the mechanical energy is not densified before conversion (like in the barrage type through blocking of the flow) the amount of energy converted per turbine is less. In addition, as these turbines have to operate in a hazardous marine environment, the turbines (involving numerous moving parts) are prone to corrosion and mechanical failure. As they are less easily accessible, maintenance of the underwater mechanical engineering works (rotor blades, seals, gear box, generator) is costly and time consuming.
1.3 Historic Background
The first person who became aware of the interaction between an electric and a magnetic field is Michael Faraday. As part of his experiments, he tried to measure an electrical potential, generated by the tidal flow passing Waterloo's bridge in the earth's magnetic field (Faraday, 1839). However, possibly due to the low magnetic field strength (at 52 Deg. latitude (Holland/UK), the horizontal component of the earth magnetic field amounts to 1.8 10
−5
Tesla) Faraday was not able to detect a potential difference.
U.S. Pat. No. 6,136,173 discloses a magneto hydrodynamic generator. The generator comprises a float attached to suspension means. At the other side of the suspension means, magnetohydrodynamic conversion means are connected for suspending on the float at a deep level in the sea. In us, the float is going up and down due to movement of the sea at its surface and, thus, the conversion means are moving up and down below the sea surface. Sea water is forced to flow through an outward flared opening passageway into a working volume of the converter means. Electrodes are provided within this working volume. In use, the conversion means produce a magnetic field, at least within the working volume, and an electric field will be produced between the electrodes due to the magnetic field within this working volume and the sea water flowing within this working volume. Electrical power may be taken from these electrodes.
The principle to generate electricity by moving a conductor in a magnetic field is nowadays utilised in electricity generators (dynamo-principle). Normally the electrical conductor is a copper (or aluminium) wire. In the thirties of this century systems were developed in which the conductor itself was a fluid. Specifically systems have been studied in which the conductor is a high temperature (electricity conducting) ionised gas (a plasma). The systems are intended to be used as a topping (high temperature) cycle of traditional fossil fuel plants. MHD conversion gained considerable attention in the sixties and seventies. However, the development of combined (gas and steam turbine) cycles (in which gas turbines are used as top cycles) and the decline of interest in nuclear power caused a decline in the interest in MHD conversion.
An MHD-application which is also relevant to the present invention is MHD ship and submarine propulsion. By creating an electric-magnetic field around a ship's hull, body forces are exerted on the conductive water surrounding the vessel. As a reaction the ship is propelled. As fluid body forces (unlike surface forces) may be exerted over a large distance, a large area may be swept, creating the necessary amount of impulse with a minimum amount of kinetic energy (which represents the loss). Goal was to build large (100,000 tons) cargo submarines. However, the low efficiency of the MHD propulsion system (mainly caused by the limited conductivity of the sea water and the high power consumption of the super conduction magnets) led to abandonment of the principle (Philips, 1962).
BRIEF SUMMARY OF INVENTION
1.4 Summary of the Invention
The present invention aims to directly convert the power of flowing conductive liquids, like saline waters into electrical power (without a mechanical energy transition step). The working principle is based on the interaction between an electrical field, a magnetical field and a hydro-dynamical field, see FIG.
3
. When an electrical conductor moves in a direction
1
through a magnetic field B in a direction
2
, an electrical field E in a direction
3
is created.
Therefore the invention claims a magneto hydrodynamic apparatus as claimed in claim
1
.
Whereas in known MHD converters the magnetic field lines are substantially within the construction volume itself, like between the magnetic poles shown in
FIG. 3
, the invention is based on the insight that magnetic field lines can be generated largely outside the construction volume, which is a great advantage when the converter is immersed in the flowing liquid like sea water. The converter itself can be made small while still converting energy from large amounts of flowing liquid into electricity.
As magneto hydrodynamic (MHD) forces are body forces (acting on fluid bodies, on a distance) and not surface forces (acting only on fluid surfaces in direct contact with the converter), volumes much larger than the converter itself may take part in the power conversion process. Furthermore, the conversion process works without moving, mechanical engineering components, which simplifies the maintenance. In addition, the absence of moving parts makes the canvasser more robust and reliable.
In this invention, MHD tidal and ocean current converter types are discerned with respect to the magnetic field actuation and augmentation principle.
The present invention will be explained in detail with reference to some drawings.
REFERENCES:
patent: 4151423 (1979-04-01), Hendel
patent: 4153757 (1979-05-01), Clark, III
patent: 4663932 (1987-05-01), Cox
patent: 5003517 (1991-03-01), Greer, Jr.
patent: 5136173 (1992-08-01), Rynne
patent: 5273465 (1993-12-01), Meng
patent: 5298818 (1994-03-01), Tada
patent: 5314311 (1994-05-01), Tada
patent: 2 255 947 (1992-11-01), None
Entry-Technology
Waks Joseph
Young & Thompson
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