ES2235647A1 - Hydrodynamic turbine for sea currents - Google Patents

Abstract

The invention relates to a hydrodynamic turbine comprising a rotor which uses the energy of the sea currents and which also acts as a suction pump since it is equipped with hollow turbine blades having pointed tips which, by means of the venturi and centrifugal effect, draw in an inner current at a greater velocity. The aforementioned current can be used to actuate a turbine having a much smaller diameter and more revolutions than the rotor and to which the electrical generator can be solidly connected without a mechanical multiplier, such as to produce a hydrodynamic multiplier . The fluid flow with greater energy density can be conveyed to other points of the fluid medium through tubular support structures for applications such as desalting water or producing H2 by means of electrolysis. The invention also relates to different configurations for the anchoring and self-orientation of the turbines, as well as underwater coupling systems for maintenance operations (minimal). In this way, the invention offers technology to compete with other energy sources, which also constitutes a predictable generation-type renewable energy.

Description

Hydrodynamic turbine for streams Marine

This invention is about a new design of Hydrodynamic turbine and its applications for the use of enormous energy potential of marine currents, with the in order to reduce manufacturing, installation and maintenance in the marine environment always difficult and to minimize the environmental impact, contributing to this technology being Competitive with other renewable energy sources.

State of the art

With the impulse to harness energy renewables for sustainable growth and a reduction of effects on climate change, wind energy in particular He has experienced a great technological development recently. Based on this wind experience, they are developing similar technologies for harnessing the great potential energy of marine currents.

Apart from the great ocean currents, they take into account the currents due to the tides (tidal) in locations near the coast and reaching speeds greater than 2.5 m / s (5 knots), with higher density energy than oceanic in general, although the latter move huge flows.

If we compare with wind energy, the diameter of marine rotor is of the order of 3 times smaller for the same power, since the ratio of sea / air densities is of the order of 820.

The prediction in the generation of energy by sea currents (following the rise and fall times of the tides), as well as the high capacity factor that can be greater than 45%, are other comparative advantages.

Although wind experience and technology, including offshore, it is usable for the development of this new technology, we must continue to deepen in several aspects of equipment, installation and maintenance in the marine environment, cavitation phenomena on the blades, etc.

Turbine prototypes of vertical axis (Darrieus type) for installation on the seabed or well suspended on bridges but, like wind, the largest Development focuses on the horizontal axis.

It has been installed, on the coast of Devon (UK), a 300 Kw prototype of horizontal axis with 2-blade rotor, with asynchronous multiplier and generator. Current designs consider anchoring to the seabed (30 m deep maximum) by means of a "monopile" pile that can support up to 2 twin turbines whose plane is perpendicular to the currents in both senses. This pile emerges from the surface to support the maintenance platform, through special systems of lifting the turbines, etc.

Explanation of the invention.

The innovative Hydrodynamic Turbine for Marine currents is horizontal axis (rotor axis aligned with the currents) and includes all the elements to transform the energy of the currents in "useful energy".

Referring to Figure-1, it they can see the different elements that make it up, being the most highlighted the rotor, which is usually composed of the blades (1), the hub (3) that supports the blades and the bearing (5) that supports the support structures and allows the rotor to rotate freely.

In this invention, the hub and blades are designed hollow and nozzles (2) are incorporated in blade tip, in such a way that there is an internal fluid vein between the center of the rotor and the pointed nozzles. In addition, the hub has an open area in which a crown of fixed blades (4) is inserted, integral with the hub, and It serves as a connection between the bushing and the bearing.

Rotating the rotor by currents marine on the shovels, an inner stream is created or "secondary current" at higher speed, which circulates from the center of the rotor inside the blades until the exit through the nozzles This current is caused by the centrifugal effect in the inside of the blades and the venturi effect on the nozzles, so the rotor, in addition to capturing energy, also performs The function of suction pump. The secondary current, with higher energy density, can drive a turbine impeller (6) of diameter much smaller than the rotor, which can be housed in the interior of the hub as a bulb type turbine aligned with the shaft of the rotor. Since the speed of rotation of this turbine is very superior to that of the rotor, the electric generator (7).

You can say that with this gadget you create a hydraulic jump into the sea, as a difference between the pressure hydrostatic medium (at bushing depth) and depression created in the inner fluid vein (center of the rotor).

An important advantage of this invention is that there are no torsional moments in the rotor shaft, since it is in the periphery of it where energy is captured and, in turn, is transmits to the secondary current.

Another very important advantage is to do without of the mechanical multiplier (with all its problematic of periodic maintenance, environmental impact due to the use of lubricants, etc), since the rotor converts the captured energy into another of greater density, as a "hydrodynamic multiplier".

Another advantage, as we will see later, is that The rotor is self-regulating to operate or variable speed, thus avoiding the active control systems of the blades, which They can be fixed.

In the extradós of the end of shovel resides the greater tendency to cavitation (which is one of the limitations of this technology), depending on the relative speed of the blade tip fluid and hydrostatic pressure depending on rotor depth If we properly practice grooves in these areas subject to greater depression, the internal fluid (water) will be suctioned avoiding cavitation on the one hand and creating the secondary current by another. However, if necessary a important exit area, the pointed nozzles are considered oriented in the direction of relative velocity. Because of performance, the absolute speed and direction of secondary current output match the current marine, which have relative output speeds of the order of the blade tip speed, but in the opposite direction. By therefore, the specific velocity coefficient Lambda (ratio between the blade tip speed and the speed of the stream marine) is similar to the speed ratio: Current secondary / marine current. By having the secondary current a Lambda order speed times greater, we can operate a turbine on the rotor shaft of a diameter Lambda 3/2 times less than that of the rotor, provided they are similar.

In order to appreciate the order of magnitude of these parameters, and considering a design speed of the marine current of 2.5 m / s and a rotor diameter of the order of 20 m (power of 1 Mw) to Lambda 6, the rotor is turned at 15 rpm, while the 1.2 m diameter turbine rotates at about 300 rpm. The design parameters depend greatly on the depth of bushing (rotor shaft) in the marine currents of each site.

The following are the strategies of Design for different situations.

In order to reduce rotor speed limiting cavitation, 4 blades are considered (greater strength than with the 3 blades in the wind), which also facilitates greater area of circulation for secondary current. For variable currents caused by the tides (sine speed) and with the generator connected to the network (fixed frequency, 50 Hz) and integral to the turbine, it is designed at constant speed with baffles (8) of passive input regulation to optimize performance in a certain range of flow rates requested by the rotor, the which operates at variable speed to also improve its performance in energy collection and to dampen fluctuations in currents, although there are no deviations or conditions here Extreme wind power.

The variable speed of the rotor is self-regulated to "constant Lambda", since the speed of the current marine (which generates rotor power) and current secondary (which absorbs this power and gives it to the turbine) they must remain in a constant relationship, being the relationship of rotor and turbine powers also constant proportional to Lambda3.

When the nominal power speed is exceeded, activates the power limiter valve (9) of the turbine, since the differential pressure (outside and inside the hub) would overcome the resistance of the "tared" valve spring that would allow a bypass flow input, increasing the rotor speed (although limited by the viscous medium) for dissipate excess energy.

All this leads to a generator (synchronous) of 10 pairs of poles, with which the dimensions, weight and cost are drastically reduce (in a 1:20 ratio) compared to generator directly coupled to the rotor, which on the other hand would have to be variable speed based on frequency converters 100% of the power generated.

The synchronous generator can be magnets permanent, for simplicity and to avoid thermal dissipation (rotor coils). However, at variable speed of currents and, therefore, at variable power, you could not control the generator power factor with permanent magnets (constant magnetic flux). To do this, we resort to a mains transformer with load regulation. The number of pairs of poles could even be reduced to 6, depending on the conditions of the location and arrangement of the turbine, type modified bulb, which in this case would operate at 500 rpm.

Therefore, under current conditions variable, it is considered a Kaplan turbine (impeller blades adjustable) or, at least, semi-Kaplan that would be easier by having only the deflector blades of flow (8). For constant (oceanic) currents, it is considered a Propeller turbine, which is the simplest to have the blades baffles and fixed impeller.

The consequence of the simplicity of systems, together with the use of resistant materials, is a "Maintenance free" hydrodynamic turbine.

Therefore, this design does not include a platform in surface, minimizing the environmental impact: no affect landscape, enough free depth for navigation, rotor slower than fish (in principle), etc.

Different configurations and applications, or embodiments , are described below, referring to the figures:

Figure-2 For due currents at tides, to depths not exceeding 30 m, is possible to place two twin rotors (10) at both ends of one horizontal tubular structure (11), supported in the form of "T" on another vertical structure anchored to the bottom or pile (12), on which is coupled by gravity the group turbine-generator (13). Secondary current sucked by both rotors, through the tubular structures, drives the turbine coupled in solidarity with the generator.

The guided underwater coupling system of the group consists of two or more guide wires (14) that can slide through holes (15) in the support base of the group on the pile. The lower end of the cables joins a counterweight (16) that descends by gravity to the stops (17). The extreme upper is provided with float (18), whose upward thrust is lower than the counterweight but keeps the hitch (19) at height preset, its capture being possible from surface barge. Once the hitch is taken, it rises to the surface, making cap the counterweight with the horizontal structure, so that the Tensioned cables can lead the guide points (20) of the group during lifting and lowering operations. The useful of hoisted also connects to the hitch point (21) of the group a through the guide wires. The group is coupled by gravity in its base, with lace between both pieces that prevent the rotation of the same.

Figure-3 To align the axis of the rotor perfectly with the currents, in both directions, it allows the rotor to rotate on the horizontal axis (22) of its support structure. It is placed diametrically opposite the rotor, with respect to this axis, a counterweight (23) to place the center of gravity of the set close to said axis. The center of the force axial thrust (24) of the rotor is offset from said shaft, which contains the bearing (26), so that it keeps the rotor aft Always aligned with the current.

You can also allow the rotation of the horizontal structure on the vertical axis (25), so that the plane of both rotors is self-oriented perpendicular to the sea current, due to the forces of axial thrust of both rotors, with the application point behind of the axis of rotation on the vertical structure. In this case, the Guided submarine coupling system is implemented for the set of the two rotors.

Figure-4 Configurations previously described can be used to desalinate water by reverse osmosis method, replacing the electric generator with a pressure pump (27), which drives pressurized seawater to through the osmosis membranes (28). Fresh water is collected in the tank (29) and the brine is returned to the sea, not being a Elimination problem.

Another more direct way is to do without the turbine-pump, sucking the current secondary by the tubular structure from the surface, through throttling nozzles (30), where a depression below water saturation pressure. Steam generated would amount to a condensation chamber (31), cooled by a recirculation of water from the seabed, obtaining the water desalted

Figure-5 Finally, in deeper locations (especially for ocean currents, where the rotor diameter would be larger), is presents the design of Floating Hydrodynamic Turbine, which solves the difficulty (or impossibility) of piloting in one more way simple and economical Launching is possible from the barge of the ballast (32), turbine and float (33), with the corresponding lashing cables that position the turbine constantly self-aligned with the currents, semi-floating and in stable equilibrium, with a high damping capacity of efforts

In addition, the configuration of the mooring to the ballast and the float, together with the points of application of the weight (34) and of the axial thrust (35) allows that, before an increase in the speed of the currents above design, it moves the turbine downwards away from the maximum current lines and the rotor plane is tilted projecting a smaller sweeping area in the direction of the currents, so that a certain self-control of
power.

In the case of ocean currents, or sites with a distance to land such that the laying of the submarine electric cable (36) is unfeasible, the energy produced by large parks of floating turbines can be used for the mass generation of hydrogen in Platforms
Marinas

Description of the drawings

Figure-1: Represents a section of the rotor of the Hydrodynamic Turbine, which is composed of the blades (1) with nozzles (2) pointed, the bushing (3) that supports the blades and the fixed blades (4) to the bushing that attach it to the bearing (5). The generator housing (7) supports said bearing, as well as the turbine impeller (6), which is equipped with baffles (8) of flow and power limiting valve (9).

It serves as a clarification to Claim 1.

Figure-2: Represents a mode of realization of the turbine with two twin rotors (10), whose secondary current drives the group turbine-generator (13), located vertically on the pile (12) anchored to the seabed.

The coupling system is also presented Guided submarine of the group. It is an appropriate design for not very deep water locations.

It serves as a clarification to Claim 2.

Figure-3: Same as the previous one, where the self-orientation of each rotor with respect to the horizontal axis (22) or the set of rotors with respect to the vertical axis (25) can be seen.

It serves as a clarification to Claims 3 and Four.

Figure-4: Represents a application to desalinate water, either by reverse osmosis by pressure pump turbine (27), osmosis membranes (28) and freshwater collection tank (29), or by a method evaporation in throttling nozzles (30) and later steam condensate in the condensing chamber (31).

It serves as a clarification to Claim 5.

Figure-5: Represents another mode of realization of the turbine, Floating Hydrodynamic Turbine, which stays self-oriented with the currents and in stable equilibrium, due to the ballast mooring configuration (32) and to the float (33).

It is an appropriate design for locations in deep water.

It serves as a clarification to Claim 6.

Claims (6)

1. Hydrodynamic turbine for marine currents, among other applications, whose rotor is horizontal axis and is normally composed of two to four blades (1) that capture the energy of said currents, the bushing (3) that supports said blades and the bearing (5) which allows it to rotate on its axis, characterized in that the blades are hollow and communicate with the bushing, which is also hollow, enabling an internal fluid vein from the entrance through the center of the open bushing to the streams, to the exit by nozzles (2) (or grooves in areas of blade with greater depression due to high relative velocity of the fluid medium), placed at the tip of the blades. By rotating the rotor by the action of marine currents on the outside of the blades, the internal fluid vein is suctioned by centrifugal effect inside the blades and by venturi effect on the nozzles, performing the rotor in turn the function of pump suction This results in a "secondary current" at a higher speed than the marina, which circulates radially, entering the center of the rotor and exiting through the nozzles, in a direction almost opposite to their movement. Said secondary current with higher density energetic (speed similar to the blade tip), can be driven by tubular support structures, to other points of the fluid medium for various applications, among them is the drive a turbine impeller (6) of much smaller diameter and at higher revolutions to the rotor. On the axis of said impeller of The turbine can be coupled in solidarity with an electric generator (7), pressure pump, etc., regardless of mechanical multiplier intermediate. This rotor, therefore, converts energy marine captured in another of greater density, by way of "hydrodynamic multiplier". 2. Hydrodynamic turbine according to claim 1, characterized in that the turbine-generator group (13) is positioned vertically on the pile (12) or support structure of one or more rotors (10), placed at the ends of tubular structures (11) horizontal that are supported by its central part in the pile, in the form of "T", through which the secondary current sucked by the rotors can circulate, to drive said turbine (or other device) in the most convenient place. For installation or lifting of the group (maintenance operations) the system is used guided underwater coupling, consisting of two or more guide wires (14) that can slide through holes (15) in the support base of the group on the pile. The lower end of the cables joins to a counterweight (16) that descends by gravity to some stops (17). The upper end is provided with a float (18), whose thrust up is lower than the counterweight but keeps the hitch (19) at the preset height, being possible its capture from barge on the surface Once the hitch is taken, it rises until surface, buttressing the counterweight (16) with the structure horizontal (11), so that the cables under tension can guide the group points (20) during operations of raising and lowering it. The lifting tool is also connected to the coupling point (21) of the group through the guide wires. He group is coupled by gravity at its base, with lace between the two pieces that prevent its rotation. 3. Hydrodynamic turbine according to claims 1 and 2, characterized in that it contains a plurality of rotors capable of self-orientation with sea currents. Each rotor can be oriented by rotating on a bearing (26) of union with the support structure, in an axis (22) perpendicular to that of the rotor itself. The center of the axial thrust force (24) of the rotor is behind said axis according to the direction of the currents, so that it keeps the rotor aft always aligned with the sea current, even if it changes direction. Diametrically opposed to the rotor with respect to said axis, a counterweight (23) of compensation of the gravitational moments of the rotor is placed. The counterweight and tubular structures that lead the secondary currents have hydrodynamic form, in horizontal direction 4. Hydrodynamic turbine according to claims 1 and 2, characterized in that it consists of two (or more) rotors at both ends of a horizontal tubular structure that can rotate at its central point of support on the pile, with respect to the vertical axis (25), so that the plane of both rotors is oriented perpendicularly to the sea current, due to the axial thrust forces of the rotors whose application point is behind (aft) the axis of rotation on the pile. The guided underwater coupling system is implemented for the set of rotors, in this case. 5. Hydrodynamic turbine according to claims 1, 2, 3 and 4, characterized in that the electric generator is replaced by a pressure pump (27) capable of desalinating water by the reverse osmosis method, or the turbine-generator group is eliminated so that the secondary current directly descends from the surface through the tubular structure, being sucked by the rotors. The water would desalinate by evaporation, upon reaching a depression below the saturation pressure of the water at that temperature. To the depression caused by the suction of the secondary current, the one generated by the acceleration of the water (Bemouilli effect) must be added to its passage through specific throttling nozzles (30). The steam generated there rises to a condensation chamber (31), cooled by a recirculation of colder water from the seabed. 6. Hydrodynamic turbine according to claim 1, characterized in that the turbine-generator group and the rotor are on the same horizontal axis, the turbine impeller (bulb type) being housed within the rotor hub. The generator housing supports the coaxial bearings of the turbine and rotor, as well as the ties (cables) of the ballast (32) and the float (33), which position the self-oriented system in the field of currents, counteracting the forces of drag (35) and gravity (34), in stable equilibrium. The mooring configuration itself, together with the drag and gravity forces, allows the turbine to move downwards away from the maximum current lines and, when the speed increases in the currents above the design. rotor plane projecting a smaller sweep area in the direction of the currents, so that a certain power self-control and a damping of forces is produced.