Technical Field

The present invention relates to a device for generating electricity and, in particular, to a marine hydro- generator.

Background to this Invention

Marine vessels are typically used to transport persons or objects over a body of water, such as a river, water reservoir, lake, sea or ocean, which may include, for example, ships, boats, dinghies, tugs, and so on. Marine vessels typically use low voltage Direct Current (DC) internal electrical systems that are battery powered. These systems include the marine vessel's instruments, navigation systems, communication devices and accommodation and living support such as refrigeration, pressurised water supply, entertainment and lighting. When passage making, most of the marine vessel's systems are powered up and operational. Over long offshore passages and blue water passages over several days, this can place a significant drain on the marine vessel's battery charge reserve. Solar power is a useful option to offset this, and is often adequate when at anchor with many of the navigation, communication and instrumentation systems powered down, but it is insufficient for replacing all of the charge dissipated from the batteries while under passage.

A device for generating electrical power for a marine vessel by means of a water flow over an immersed part of the device will be referred to herein for convenience as a "hydrogenerator".

Hydro-generators are a potentially effective means for maintaining the charge in the marine vessel's battery bank and powering the electrical systems on board while passage making. This avoids the redress to a fossil fuel generation method, either using a dedicated generator orthrough running the ships auxiliary diesel engine to charge batteries. The hydro-generator operates by placing a turbine into the flow of water over the hull of the vessel. Typically, the turbine is coupled to a permanent magnet generator proving a 3 phase Alternating Current (AC) output that is converted to a DC output using a controller. Permanent magnet generators are very well suited to this application, as they provide useful electrical output at low angular velocities in comparison with automotive alternators. However, unlike automotive alternators, the permanent magnet rotating field cannot be regulated. Therefore the controller, in addition to rectifying the 3 phase generator output, provides a means of dissipating excess power.

In normal operation, conditions arise when the power extracted from the turbine exceeds that required by the marine vessel's electrical systems. The battery bank in a low voltage DC system has the property of holding the voltage to a maximum level set by its internal chemistry. However, when the battery is completely charged and the marine vessel's electrical systems are being supplied with the current they require, excess energy from the generator has the effect of raising the potential of electrical charge presented at its output. This causes the voltage at the output to rise and eventually this would damage the marine vessel's electrical systems and battery bank. To overcome this, a regulation system is deployed. In conventional systems the regulator utilises pulse width modulation. This works by switching the output from the generator to a pulse train rather than a direct current. As the voltage of the pulses rises in response to the power output from the turbine exceeding the demand from the vessel, the pulse width is reduced to maintain the average voltage at the level required by the battery banks and electrical infrastructure.

A drawback of hydro-generation is drag. This is a force working against the thrust provided by the propulsion means, such as wind over the sails, or a propeller. Drag comes in two forms, static and induced. Static drag is the result of the resistance to flow over the components of the hydro generator and is minimised by streamlining. Induced drag is directly related to the proportion of power extracted from a turbine compared to its power capacity. The power capacity of the turbine is related to the area of the turbine and the speed of the fluid flowing over it cubed. The extracted power is that usefully consumed by the vessel combined with excess dumped as heat in the regulator. At any given marine vessel speed, the induced drag increases as the electrical power dissipated in the marine vessel increases. The power capacity of a hydro generator deployed on a vessel reaches maximum at the maximum hull speed of the vessel. This maximum power is considerably greater than power at lower hull speeds as a result of the relationship with the cube of the hull speed. The pulse width modulation system used to regulate the output of the generator has a maximum input powerthat it is able to switch to an acceptable level for the vessel's systems. This means that existing hydro generators have to be fitted with small turbines designed to provide a maximum power capacity at full hull speed equal to the maximum power input to the regulator so that the power extracted by the vessel is acceptable. This has two significant drawbacks. The first is that the hydro generator's power capacity falls off with cube of hull speed, so the system provides little or no useful power for the vessel at speeds below or even near maximum. The second drawback is that the pulse width modulation scheme, when delivering low power to the vessel when the power capacity of the turbine is high at high hull speed, internally dissipates a proportion of the excess power as heat. Aside from raising the temperature of the regulator, this causes drag above that resulting from the vessel's power demand.

A typical conventional hydro-generator is shown in figure 1. This shows a turbine 11 being drawn through the water by attachment to the hull of a vessel moving through the water. The turbine is directly mechanically coupled to the generator 13 via a belt or chain transmission 12. The power capacity of the turbine is therefore directly converted to electrical power capacity that is fed through the regulator 15 to the reduced power output to the vessel. The induced drag experienced by this conventional system is the ratio of extracted power from the turbine to the turbine's power capacity. The extracted power is the sum of the power consumed by the vessel and excess power dissipated as heat in the regulator 15. When the vessel's batteries are well charged, a small amount of power is taken by the vessel leaving a large amount for the regulator to dissipate. This causes excessive unwanted induced drag. In addition, the turbine's maximum power capacity must equal the maximum regulatory capability of the regulator 15. In other words the transfer function of the regulator 15, given by the power in to power out must deliver an acceptably low current at the battery bank float voltage level when the turbine is at maximum power capacity. The turbine power capacity, being directly mechanically coupled to the generator, is converted into electrical potential. The regulator 15 has to transfer a portion of this as power to the vessel, dissipate some as heat and let some remain as potential in the generator. The extracted power, from the perspective of the turbine, is always the sum of the power to the vessel and that dissipated as heat. This appears as torque on the generator shaft 14, and by direct coupling on the turbine shaft causes drag induction. With this arrangement the drag always includes the dissipation due to heat. This is unnecessary drag that can rise to very large values at high hull speed and large turbine size with this arrangement. The drag due to the vessel's consumption is working drag that cannot be avoided when generating. The total potential that the regulator is able to control to the vessel and dissipate as heat determines the maximum power capacity of the system. The maximum power capacity of the turbine is therefore set at maximum hull speed and this determines the turbine's cross sectional area. At lower hull speeds the turbine is therefore unable to provide useful output to provide electrical power for the vessel's systems, as the relationship with output to the hull speed cubed makes a turbine sized for full power at maximum hull speed useless at half hull speed. The conventional hydro generator is therefore limited in its operational range and places drag penalties on the vessel greater than that incurred by electrical consumption and efficiency, as a result of the method of regulation employed.

The present invention seeks to address, at least in part, any or all of the above described drawbacks and disadvantages.

Summary of the Invention

According to a first aspect of the present invention, there is provided a method of operating a hydro-generator system for a marine vessel, the hydro-generator system generating power for one or more electrical components of the marine vessel, the method comprising: receiving a signal indicative of a flow rate of fluid over a turbine, wherein the turbine rotates due to a relative motion of a fluid to the turbine; receiving a signal indicative of a position of a pressure compensated flow regulation valve, wherein the pressure compensated flow regulation valve controls a flow of hydraulic fluid through a first path of an outbound flow of hydraulic fluid from a hydraulic pump; determining an instantaneous extracted power from the turbine being delivered to the marine vessel; determining an instantaneous power capacity based at least in part on the flow rate of fluid over the turbine and a turbine geometry; determining an instantaneous available power based at least in part on a variable induced drag factor and the determined instantaneous power capacity; wherein the induced drag factor represents a ratio of the instantaneous extracted power, being delivered to the marine vessel from the turbine, to the instantaneous power capacity; receiving a signal indicative of an instantaneous output voltage of a permanent magnet generator of the turbine, wherein the permanent magnet generator is operatively connected to a motor that is operatively connected to a second path of the outbound flow of the hydraulic fluid from the hydraulic pump; and comparing the instantaneous output voltage to a voltage limit, wherein the voltage limit is a maximum permitted output voltage of the permanent magnet generator; wherein if the instantaneous output voltage is lower than the voltage limit and the instantaneous extracted power does not exceed the instantaneous available power, controlling the position of the pressure compensated flow regulation valve to rotate in a first direction by a predetermined amount; or wherein if the instantaneous output voltage exceeds the voltage limit, controlling the position of the pressure compensated flow regulation valve to rotate in a second direction opposite to the first direction by a predetermined amount.

In some embodiments, determining the instantaneous extracted power being delivered to the marine vessel may comprise measuring an instantaneous current output of the turbine; determining a product of the instantaneous current output and instantaneous voltage output of the turbine; and applying a transfer function of an intermediate system located between the turbine and the marine vessel to the determined product of the instantaneous current output and the instantaneous voltage output.

In some embodiments, determining the instantaneous extracted power may comprise measuring a speed of rotation of the turbine, measuring a hull speed of the marine vessel and comparing the measured speed of rotation to a predetermined speed of rotation for the hull speed.

In some embodiments, the method may further comprise predetermining a maximum induced drag limit; wherein the variable induced drag factor does not exceed the maximum induced drag limit and wherein the maximum induced drag limit may be predetermined by a user or a controller.

In some embodiments, if the output voltage is lower than the voltage limit and the instantaneous extracted power exceeds the instantaneous available power, the position of the pressure compensated flow regulation valve may be controlled to rotate by a predetermined amount.

In some embodiments, if the output voltage is within a predetermined threshold range of a voltage limit, the position of the pressure compensated control valve may be maintained.

In some embodiments, if the output current is within a predetermined threshold range of a current limit, the position of the pressure compensated control valve may be maintained. In some embodiments, controlling the position of the pressure compensated control valve may comprise sending a signal to a motor controlling the position of the pressure compensated flow valve.

In some embodiments, the method may further comprise detecting an initial current output from the turbine, wherein the initial current output indicates the turbine is generating power.

In some embodiments, detecting the initial current output from the turbine may be related to an initial rotation of the pressure compensated flow regulation valve in the first direction.

In some embodiments, the signal indicative of the flow rate of fluid over the turbine may be based, at least in part, on an alternating current waveform of the permanent magnet generator.

In some embodiments, the method may further comprise comparing the instantaneous current output to a maximum current limit.

In some embodiments, if the instantaneous current output exceeds the maximum current limit the position of the pressure compensated flow regulation valve may be controlled to rotate in the second direction by a predetermined amount.

In some embodiments, if the instantaneous voltage output is less than or equal to the voltage limit, the instantaneous current output may be maintained at the maximum current limit.

According to a second aspect of the present invention, there is provided a controller comprising: a first input configured to receive a signal indicative of a flow rate of fluid over a turbine; a second input configured to receive a signal indicative of a position of a pressure compensate flow regulation valve; a third input configured to receive an instantaneous output voltage a permanent magnet generator of the turbine; an output configured to control a position of the pressure compensate flow regulation valve; a memory; and a processor, wherein the processor is configured to implement a method according to any of the features of the method described in relation to the first aspect of the present invention.

According to a third aspect of the present invention there is provided a hydro-generator system operatively coupled to a marine vessel for generating electricity for one or more electrical components of the marine vessel, comprising: a turbine, wherein the turbine rotates due to a relative motion of a fluid to the turbine; an intermediate system coupled to the turbine, wherein the intermediate system comprises: a hydraulic pump coupled to the turbine, wherein the rotation of the turbine causes the hydraulic pump to drive a flow of hydraulic fluid through a closed circuit of the hydro-generator system; wherein the closed circuit comprises: an outbound flow of hydraulic fluid from the hydraulic pump, wherein the outbound flow is divided at least once into parallel paths, wherein a first path includes a pressure compensated flow regulator and a second path includes a hydraulic motor coupled to a permanent magnet generator of the turbine that provides an electrical output; and a controller according to the controller of the second aspect of the present invention.

According to a fourth aspect of the present invention there is provided a computer program product comprising computer readable executable code for implementing a method according to any of the features of the method described in relation to the first aspect of the present invention.

It will be appreciated that any features described herein as being suitable for incorporation into one or more aspects or embodiments of the present disclosure are intended to be generalizable across any and all aspects and embodiments of the present disclosure. Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

Drawings

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 illustrates schematically a conventional marine hydro-generation system;

Fig. 2 illustrates schematically a marine hydro-generation system according to one or more embodiments of the present invention;

Fig. 3 illustrates schematically a hydraulic circuit for regulation of the hydrogeneration system according to one or more embodiments of the present invention. Fig 4 illustrates a transom mounted marine hydro-generator system according to one or more embodiments of the present invention.

Fig 5 illustrates a marine hydro-generator system according to one or more embodiments of the present invention.

Fig. 6 illustrates an electrical subsystem according to one or more embodiments of the present invention.

Embodiments

This disclosure relates to devices for generating electricity by virtue of interaction with a liquid fluid flow, for example by immersion of at least one surface of the device in a body of liquid fluid and relative motion of that surface of the device with respect to the body of fluid. The body of fluid may be a river, water reservoir, lake, sea or ocean, and the electricity generating device may be operably associated with a marine vessel intended for use, or normally used, for transportation of persons or objects over water. For the purposes of explanation, the disclosure discusses the invention by way of example in relation to sailing vessels.

Figure 2 is a schematic block diagram illustrating one or more embodiments of the present invention. In general, the turbine is indirectly coupled to the input shaft of a permanent magnet generator through an intermediate system comprising an input shaft mechanically connected to the turbine, an output shaft mechanically connected to the generator, and a variable coupling between the input and output shafts is operated by a controller connected to the output of the generator.

The hydro-generator system includes a turbine 21, and permanent magnet generator shaft 26 between which is provided an intermediate system 23 for at least regulating power output of the hydro-generator.

The controlled dumping of excess power in conventional hydro-generator systems is replaced by regulating the generator output through delivering the required power to the generator input leaving the excess as potential in the intermediate system 23. This is achieved by controlling the torque and angular velocity delivered to the input shaft of the generator by indirectly coupling the turbine shaft to a shaft of the generator through the intermediate system 23. The turbine 21, is caused to rotate by fluid flowing over it and the turbine shaft is coupled, to the input shaft 24 of the intermediate system 23, for example, by belt 22. Accordingly, the power available at the turbine shaft is transferred, less efficiency losses, to the intermediate system 23. The intermediate system 23 has an output shaft 25 to which at least a portion of the input power can be directed through a coupling, such as a control valve 29, wherein the control valve may be a pressure compensated flow regulation valve. The output shaft of the intermediate system 25, is then directly coupled to the permanent magnet generator shaft 26.

The embodiments therefore provide a variable torque coupling between the input shaft 24 and output shaft 25 of the intermediate system 23 which provides the means by which the torque delivered at angular velocity to the input shaft of the permanent magnet generator can be controlled.

The generator provides a 3 phase AC output that is rectified in the 3 phase rectifier 27. A controller 28 receives input signals, from the rectified output of the rectifier 1 , providing voltage, and current. The output voltage and/or output current from the 3 phase rectifier are compared with values provided to the controller 28. The controller computes the required increase or decrease of power to be transferred across the intermediate system 23 and alters the coupling 29 to achieve this.

The controller 28 may determine and/or set the amount of power to be transferred to the generator from the available turbine power capacity caused by the fluid flow over the turbine. The power capacity of the turbine varies according to the cube of the speed of the marine vessel through the fluid, i.e. water. The power transferred across the intermediate system 23 is determined by the power capacity of the turbine and the position of the variable coupling 29. When the coupling is opened wide, a large proportion of the turbine power capacity is transferred across the intermediate system 23, while when the coupling 29 is closed no power is transferred across the intermediate system 23 and the turbine power capacity is converted to potential as fluid flow internal to the intermediate system 23. Therefore, the degree to which the controller 28 has to open the control valve 29 coupling the input source from the turbine to the output load at the generator shaft input is related to the extracted turbine power as a proportion of the power capacity of the turbine. When compared with the power being taken by the vessel, the instantaneous power capacity of the turbine can be determined by controller. This is achieved, for a given turbine geometry by the combination of the transfer coupling position (e.g. the control valve 29 position) and power delivered to the vessel. The intermediate system has at the turbine side variable power capacity in from the turbine and at the vessel, variable load out. Therefore at a constant load, the coupling (e.g. control valve 29) will open and close to transfer a substantially steady or constant output when the power capacity of the turbine increases and decreases. Similarly with a steady hull speed and therefore turbine power capacity, the coupling (e.g. control valve 29) will be opened and closed to maintain a steady output voltage, current or power as required in response to changes in the load provided by the vessel's electrical systems. The position of the powertransfer coupling (e.g. control valve 20) determines the proportion of power extracted from the turbine to the turbine's power capacity. Knowing the transfer function of the intermediate system 23 allows the controller 28 to determine the power extracted from the turbine. Comparing this with the coupling (e.g. control valve) position provides the other variable of turbine power. In one or more embodiments this information can be tabularised and looked up by the controller.

As the controller 28, is used to determine the power transferred through the generator from mechanical input to electrical output, it may provide additional control points forthe hydrogenerator system that was not possible in the conventional hydro-generator systems such as that shown in Figure 1. One such control point may include the maximum output voltage level of the generator. The maximum output voltage level of the generator may be set by, or predetermined from, the marine vessels electrical system and battery type. In addition, the output current delivered from the generator to the marine vessels electrical system may be controlled through the delivery of torque to the input shaft of the generator. Controlling the delivered current and voltage in this manner provides a means by which the embodiments may control the output power to a selected upper limit. A selected upper power limit may be determined by a selected maximum induced drag ratio. The induced drag ratio is the ratio of the power extracted from the turbine to the power capacity of the turbine. These are instantaneous values given at the current hull speed, which may vary as the vessel proceeds on passage. The instantaneous induced drag ratio is determined by the controller using the extracted power and the position of the coupling (e.g. control valve) to provide turbine capacity. The instantaneous induced drag factor can then be compared with the maximum induced drag factor selected. If the current induced drag factor is larger than the selected maximum, the intermediate system 23 is transferring too much turbine power to the vessel and must adjust the coupling (e.g. control valve) to reduce the transfer. Similarly, if the current induced drag factor is greater than the selected maximum, the controller 28 must reduce the amount of power transferred by adjusting the coupling. One or more of these control limits may be provided as inputs from the user, allowing the user to increase or decrease electrical consumption according to the marine vessels operating conditions during passage making. The induced drag factor is a measure of the induced drag imposed on the vessel by the generating system. Increasing the output to the induced drag factor maximum increases the drag to the selected maximum. Increasing the induced drag factor allows the system to provide higher output at any hull speed, but has the impact of increased drag. The maximum induced drag factor possible is 1, at which point the Betz limit of the turbine is approached and it begins to stall.

Figure 3 illustrates an intermediate system according to one or more of the embodiments of the present invention. In general, in the example shown in Figure 3 the intermediate system may be provided, or implemented, by a hydraulic circuit comprising an input shaft driving a hydraulic pump, and an output shaft from a hydraulic motor. In parallel with the hydraulic pump, there may be provided a flow bypass which may be controlled using a flow control valve. The flow control valve may be operated by a motor from a control board that is configured to take input from the rectified output of the permanent magnet generator.

The intermediate system may comprise a hydraulic pump 33, primed from a hydraulic fluid tank 36, and fed through a feed hose 35 to a source manifold 311. The manifold may provide a controlled flow bypass between the feed hose 35 and a return hose 37. The flow through this bypass may be controlled by a valve 39 opened and closed by an electric motor 310 connected to a control board 312. The control board 312 may include connections to monitor output voltage and current at the regulator 313, and may control the opening of the bypass valve 39 using negative feedback to maintain the output voltage and current at the desired, or required, level. A hydraulic motor 316 may be connected between the feed manifold 311 and the return manifold 38. As the control valve 39 is closed the bypass flow decreases which in turn increases the pressure on the inlet port of the hydraulic motor 316 providing a torque to maintain its angular velocity. By this means the power delivered to the generator, as torque at angular velocity, provides regulation of the generator output by responding to the electrical output of the generator. The hydraulic motor 316, may be any suitable hydraulic motor such as a Geroler® motor, which is a commercially available motor type which has rollers incorporated into an internal gear ring. The hydraulic pump 33 may be any suitable hydraulic pump such as an external gear pump. Based on the hull speed over which the system is to operate, the power output requirement at low speed, the turbine geometry and power output over the required hull speed range determined the capacities and capacity ratios between the pump 33 and motor 316 in conjunction with the mechanical gearing of the transmission link 315 between the motor 316 and the generator 314. Turbine geometry refers to the diameter of the turbine, the number of blades and the profile of the blades, with helix angle variation from root to tip in order to achieve required angular velocities for the hull speed range over which the system is to be deployed with minimum radial loss and determined stall angles and lift coefficients. In Figure 3 the intermediate system is implemented using flowing hydraulic fluid as coupling system from which controlled delivery of energy to the output shaft can be provided. Other suitable intermediate system implementations may be used, such as a magnetic coupling.

In the embodiment shown in Figure 3, the turbine 31 is provided with a spinner 32 for streamlining the shape and design of the hydro-generator so as to minimise the static drag. The turbine shaft may be passed through a water tight seal on the mounting leg 317 to the hydraulic pump 33. In Figure 3, the mounting leg may be fixed to a transom of the marine vessel, in a similar manner to a conventional outboard motor for a marine vessel.

Alternatively, the turbine shaft may be passed through the hull with the remainder of the system components inside the marine vessel, or the turbine and pump assembly may be mounted on the hull or keel of the marine vessel under the water line with the feed hoses to the pump 34 and 35 passing through the hull.

A hydraulic fluid tank reservoir 36, may be fixed to the top of the mounting leg 317 from which the hydraulic fluid can be provided to the system through hose 34 and returned from the system through hose 37. The feed hose 35 and return hose 37 can be passed through the deck and hull bulkhead into the marine vessel, with the remainder of the system components inside the hull space of the marine vessel.

The output from the hydraulic motor 316 may drive a pulley coupling 315 to the permanent magnet alternator 314. This provides a 3 phase AC output to the rectifier 313. The rectifier provides voltage and current sense points connected to the control board 312. The control board is an electric motor controller with programmable response to provide the proportional, integral and differential components of the feedback gain driving the rate and direction of the revolution of the motor turning the needle valve.

Figure 4 is in general a diagram showing the turbine being mounted within casings and fitted to a transom of the marine vessel, e.g., a sailing vessel. The mounting enables the turbine to be immersed or withdrawn from the fluid, e.g., water while the vessel is underway.

The turbine assembly with a spinner 41 may be fitted directly to a shaft of an exterior gear hydraulic pump 42. Exterior gear pumps are relatively low cost widely available devices, but other hydraulic pump types, such as gerotor or piston types may alternatively be implemented. When the pump is driven by the turbine turning, fluid is pushed along the hose 43 to an external coupling 44. The external coupling 44 may be connected to a flexible hydraulic hose that may be connected through the marine vessel shell to the generator. The hydraulic fluid returning from the generator inside the marine vessel may be connected to the return external fitting 45. The exterior gear hydraulic pump 42 may be mounted inside a casing 47. A top plate of this casing may be welded to an elliptical tube 49, which may form a mounting leg. The bottom plate of the casing 48, may be designed to accommodate a sump filter 46, and may be fitted with a drain plug that can be periodically removed when the assembly is withdrawn from the water to drain off any contaminants, such as water from condensation that may have collected. At the top of the elliptical tube 49 and above the water line is a top casing 410. The top casing 410 may provide one or more of the through connections for the hydraulic pipes, an atmospheric vent that maintains the internal pressure of the casings to close to atmospheric pressure, and mechanical fixtures for the brackets that mount the assembled unit to the transom. In ocean going deployments the atmospheric vent may be mounted within a dorado box to protect it from periodic immersion in the fluid. A form of transom mounting is 411, but other mechanical arrangements that allow the operator to insert and withdraw the unit from the water are possible.

One feature of this assembly shown in Figure 4 is that no electrical connections or equipment are present or required in this transom mounted part of the system. Another feature of this assembly shown in Figure 4 is that the casings can be fabricated from materials that provide mechanical strength, resistance to salt water corrosion, and resistance to the hydraulic fluid contained within the space enclosed by the casings. An example of such a material is, but is not limited to, sand cast 316 stainless steel.

Another feature of this assembly shown in Figure 4 is that the hydraulic fluid is contained within the casings a part of which is immersed below the water line. Therefore, an advantage of this assembly shown in Figure 4 is that heat generated by viscous drag and mechanical friction may be transferred to the hydraulic fluid which can then subsequently be conducted through the casing walls into the water. This advantageously enables a narrower temperature range over which the hydraulic system operates in comparison with an air cooled assembly.

A feature of this assembly shown in Figure 4 is the ability to use common off the shelf components for the hydraulics. This is realised by the use of an additional casing 412 that functions as a bell housing to provide a coupling between the standard input shaft of the hydraulic pump 42 and the shaft of the turbine assembly 41. This coupling may include a bearing support unit between the pump shaft and the turbine shaft. The shaft on which the turbine is mounted is formed from material resistant to salt water, for example 316 stainless steel, whereas the input shaft of the hydraulic pump may be conventional carbon steel. The cavity within this casing 412 may be air filled, with the shafts entering either side rotating within shaft seals to exclude oil from the main casing 47 or water from outside the assembly flowing in.

Figure 5 in general shows a packaged generator according to one or more embodiments where the packaged generator may be fitted to or inside a marine vessel, such as a sailing boat, and connected to a transom mounted component by a pair of hydraulic hoses.

The hydraulic fluid flows into the generator through an inlet port 50, and returns to the transom mount turbine and pump assembly through an outlet port 51. The inlet line may be split, or divided, into at least one parallel path wherein one path feeds an inlet of the motor 52, such as a gerotor motor, and a further path feeds an input port of a pressure compensated flow regulator valve 515. The pressure compensated flow regulator 515 may be connected in series with a non-compensated flow regulator 514 which combines with the flow from the motor 52 to exit at a hydraulic outlet port 51, and returning the fluid to the transom mounted assembly. The output shaft of the motor 52, may be provided with a motor pulley wheel 53 which is operatively connected to an input shaft pulley wheel 54 by a transmission belt. An input shaft connected to the input shaft pulley wheel 54 may be connected to a Permanent Magnet Generator (PMG) 513.

Gearing can be achieved by selecting a ratio between the circumferences of the two pulley wheels, that is the motor pulley wheel 53 and the input shaft pulley wheel 54.

The turbine speed range of rotation may be set by the design of the blades in conjunction with the operating hull speed range of the vessel on which the generator will be deployed. The turbine can therefore be designed to provide usable power output at the minimum water speed while the hydraulic circuit, valves, motor and pump are designed to contain the flow rates at maximum hull speeds with acceptable viscous, mechanical and volumetric loss. The usable power minimum required at minimum hull speed determines the turbine diameter.

Hydraulic gearing can be achieved by choosing a ratio of a displacement volume of a pump connected to the turbine to a displacement volume of the motor 52. When the displacement of the pump and the motor are equal, one revolution of the pump will correspond to one revolution of the motor multiplied by the volumetric efficiency total for the two devices. When the turbine characteristics have been determined for the chosen marine vessel's range of hull speed, the gearing needed to achieve the speed of rotation range required by the magnetic design of the PMG 513 is achieved through a combination of hydraulic and transmission gearing. The flow rate of the fluid through the generator varies with the speed of rotation of the turbine. However the inlet flow 50 may be split with a first portion flowing through the motor 52 causing it to rotate to drive the PMG 513. For a given inlet flow rate of hydraulic fluid, the speed of rotation of the motor 52 and PMG 513 may be determined based at least in part on the split ratio controlled by the two flow regulating valves, being the pressure compensated flow regulator 515 and the non-pressure compensated flow regulator 514. The non-pressure compensated flow regulator 514 can be placed in series with the pressure compensated flow regulator 515 to provide a minimum flow rate calibration point set at manufacture and assembly. When the pressure compensated flow regulator 515 is fully open, the non-pressure compensated flow regulator 514 may be set to ensure the motor turns at a sufficiently high speed to provide a detectable output from the PMG 513 when the turbine is rotating just below its minimum specified usable output speed. An electrical subsystem 59 can measure the speed of rotation of the PMG 513 using, for example, the frequency of its AC output which, combined with the position of the pressure compensated flow regulator 515 valve opening determines a speed that the turbine is rotating at and the amount of power available for delivery to the marine vessel. This has the advantage of not requiring any electrical sensors outside the vessel on the transom mounted assembly.

When the turbine is unable to provide sufficient power for transfer to the marine vessel load, the electrical subsystem 59 containing a controller, alters an operational mode of the system to a standby state. The system output is held at battery voltage, but if the generator potential is less than this, no current will flow from the generator into the vessel. The controller, 59, may also use the presence of the AC waveform from generator to detect the speed at which the generator is turning compared with the position of the flow regulator valve. This may be detected directly using threshold crossing and frequency measurement, or indirectly by tapping off to a parallel internal rectifier feeding a high resistance with DC. The DC level into the high resistance, with no current flowing into the vessel, provides an indication of the electrical potential of the PMG. The controller may vary the position of the flow regulator valve to establish whether there is sufficient power available at the turbine to transfer into the vessel and if not it may place the system into standby mode. In standby mode the controller minimises its power consumption so not to become a drain on the vessel's batteries.

Whenever the controller of the electrical subsystem 59 senses that the turbine has sufficient power available for transfer to the marine vessel, it alters the operational mode of the system to a generating state. This can be achieved by incrementally closing the pressure compensated flow regulation valve 515. The pressure compensated flow regulator 515 is a widely available hydraulic component where this type of valve commonly includes between 5 and 6 turns from fully open to fully closed, where fully closed completely throttles the flow through the valve thereby directing all of the flow from the turbine to the motor 52. The rotation of the valve can be controlled, for example, by using a worm drive 58. A worm gear may be fitted to a shaft coupled to a valve actuation shaft and engaged to the worm drive 58 fitted to a shaft driven by an electric motor 55. The electric motor may be, for example, a brushed DC motor that can be driven clockwise or counter clockwise according to the polarity of the electrical supply to the electric motor 55 and at speeds determined by the voltage level of the supply to the electric motor 55. This arrangement allows the electrical subsystem to control the direction and speed at which the pressure compensated flow regulation valve 515 is opened and closed. In addition to the worm gear, a pulley wheel for a timing belt may be fitted to the top of the shaft connected to the pressure compensated flow regulation valve 515. The timing belt may be coupled to a second pulley wheel to form a transmission link 57.

The second pulley wheel connected to the timing belt may be fixed to a spindle of a 10 turn potentiometer 56. A timing belt may be used to advantageously ensure no slippage is possible so the potentiometer output voltage is a precise analogue signal corresponding to the pressure compensated flow regulation valve's 515 rotational position. The output from the potentiometer 511 provides an input to the electrical subsystem 59, and the output from the electrical subsystem 59 operatively drives, or controls, the pressure compensated flow regulation valve 515 to a required position via a connection 510.

The electrical subsystem 59 may be powered by the marine vessel's battery connected to the input/output 516. In the event of the marine vessel's battery level dropping sufficiently, or the battery bank having catastrophically failed or been removed, then the valve 515 can alternatively be closed by manual rotation of the worm drive 58 while the turbine is immersed. This causes fluid to be diverted through the motor increasing the speed of rotation and the output voltage level delivered to the electrical subsystem input/output 516.

When the output voltage level becomes greater than that required by the internal control electronics of the electrical subsystem 59, the control system will take over and maintain an electrical output capable of powering the marine vessel's internal electrical systems, or a proportion of them based at least in part on the available power sourced from the turbine.

A further advantage of one or more embodiments of the present invention therefore is its ability to provide a virtual battery function when the batteries are severely depleted, faulty or absent when the marine vessel is under voyage within the operating range of the turbine. The electrical subsystem 59 may further provide means to convert the AC 3 phase output from the PMG 513 to DC voltage in order to power the marine vessel and maintain battery charge levels. In addition it contains the control electronics and provides an external interface 517 to other devices, control busses and the user. This external interface 517 may include one or more of the following, electrically analogue components, electrically digital components, human machine visual with selection buttons, control inputs, Controller Area Network (CAN) bus, National Marine Electronics Association (NMEA) connections/interfaces, Bluetooth, and/or Wifi.

As discussed hereinabove, the pressure compensated flow regulator 515 may control the hydraulic fluid flow through the motor 52. When the PMG 513 is loaded, the torque applied to the shaft may increase to maintain the speed of rotation constant. The speed that the PMG 513 rotates at may be related to the output voltage level supplied to the marine vessel. When a device in the vessel is switched on, the load increases and a requisite increase in torque must be applied to maintain the rotational speed of the PMG 513 and maintain a substantially constant output voltage. The pressure compensated flow regulation valve 515 control achieves this by preventing an increase in flow through the bypass. Thus the hydraulic fluid flow from the pump continues to be split according to the pressure compensated regulation valve 515 setting between the two paths. The result is an increase in pressure in the feed line which provides the torque delivery to the motor 52. This advantageously provides a means by which torque is automatically delivered to the shaft of the PMG 513 through the motor 52 in response to the load demand to maintain a constant PMG 513 speed of rotation. However, with increased load maintaining a substantially constant PMG 513 rotational speed may be insufficient to maintain an accurate output voltage level. This is because increasing the load incurs magnetic losses within the PMG 513 that must be compensated by an increase in the speed of rotation of the PMG 513. Therefore the control system within the electrical subsystem 59 responds to a drop in output voltage due to the increase of load by incrementally closing the valve of the pressure compensated flow regulator 515, thereby decreasing the flow through the pressure compensated flow regulator 515 and increasing the flow through the motor 52. Similarly, the flow is decreased if a device inside the marine vessel is switched off to give a decrease in load. Fluctuations in hydraulic fluid flow rate caused by variations in the rate of rotation of the turbine are not compensated for by the pressure compensated flow regulator 515 in the bypass circuit, but are passed to the motor 52 and manifest as rotational speed variations. These are detected by the control system and clamped to the required peak values of current and voltage.

Figure 6 in general shows an electrical subsystem of the arrangements shown in Figures 4 and 5. The electrical subsystem may include one or more of electrical power conditioning, regulation and/or drag management.

The power delivery part of electrical subsystem may be a 3 phase rectifier 61, which is a commercially available packaged diode array. The main output DC+ line is fused with a circuit breaker 63 and the return current is passed through a calibrated shunt 62. The calibrated shunt 62 may be a commercially available component that has a temperature stable linear voltage drop proportional to the current passing through it. In this embodiment the current shunt is 100A, lOOmV max output and the circuit breaker is rated at 80A DC. The control system of the electrical subsystem may be based on a microcontroller 69 providing a number of analogue and digital inputs and outputs. These devices are commercially available with example manufacturers Barth®, Arduino® and Raspberry PI®. In the arrangement shown in Figure 6, the microcontroller is Barth STG®.

Inputs 1, 2 and 3 are analogue inputs with a permitted range of 0 to Vcc. A count input of the microcontroller 69 counts electrical pulses over programmable periods to provide a frequency value. The electrical pulse high is between 0 and Vcc with internally programmable hysteresis. Outputs 1 and 2 are digital 0 to Vcc and the Pulse-Code Modulation (PCM) output is a stream of pulses encoded to provide an equivalent average voltage from the ratio of a mark area to a space area each period. The PCM output is similarly from 0 to VCC.

An external control interface may be used for programming the microcontroller 69 and/or for serial bus connectivity to user applications for configuring the generator operational modes and observing output levels, alarms and events. The microcontroller 69 may be supplied with 9V Vcc using a voltage regulator device 64. This 9V supply may be supplied from the DC rectified output of the PMG and/or the marine vessels battery line when the circuit breaker 63 is closed. Otherwise the 9V supply may be supplied directly from the DC rectified output of the PMG. Two phases of the PMG output may be connected to the input of a comparator 68. The comparator 68 is a commonly used device in electronics that provides a two state output, high and low (Vcc and GND) in response to a voltage on the input terminals. If the voltage on the + pin is above the - pin the output is high and is if the + pin is below the - pin the output is low. Other devices, for example with programmable or fixed hysteresis, may be alternatively used. The comparator 68 switches from high to low then low to high as the input sine wave from the two phases of the PMG output cross over polarity. This provides the frequency counting input of the microcontroller 69 with a means of measuring the rotational speed of the PMG, which is directly related to the rotational speed of the motor driving it and the associated rate of flow of the fluid passing through the motor.

Input 3 of the microcontroller 69 may be connected to the output voltage terminal of the 10 turn potentiometer coupled to the shaft of the pressure compensated flow regulator valve. The voltage on Input 3 provides a means by which the microcontroller 69 can measure, or determine, the split ratio of hydraulic fluid flow between the bypass path to the pressure compensated regulation valve and the path which passes through the motor to drive it. The combination of the speed at which the motor is rotating and the split ratio indicated by the pressure compensated flow regulator valve position provides a means for the microcontroller 69 to derive instantaneous power capacity of the turbine.

In one example, the method of derivation is by a look-up table for the specific turbine geometry deployed, wherein the microcontroller is provided with a look-up table for the particular turbine used. Each turbine geometry supported by the controller software can use a separate look up table. The turbine used can be programmed into the controller by several means including, provisioned by the user, at manufacture, or by reading a code from the transom mounted part of the system. The look-up table is provided with the measured speed of rotation and the available instantaneous power from the turbine is given by, or identified from, the closest valve opening level at that speed. The instantaneous power values have been empirically calibrated for each turbine design based on speed testing and powertransfer efficiency measurements during development of the turbine. The calibration values for the look-up table of a given turbine may then be loaded into a permanent memory of the microcontroller as part of its control software load. Therefore, the software load containing the turbine calibration tables may be switched or replaced to enable use of different turbines suited to different marine vessels. The microcontroller may therefore use instantaneous measurements of hydraulic fluid flow to determine instantaneous power capacity of the turbine in order to ensure that the delivered electrical power output to the marine vessel remains within a Betz limit of the given turbine therefore advantageously ensuring it will not stall.

Output power may be calculated by the microcontroller 69 though reading an output voltage from input 1 and an output current from input 2. Output voltage is provided through a gain unit 67. This gain unit 67 matches the working range of the generator output, 0 to 14.2V in this 12V nominal example, to the permitted range of the microcontroller input 0 to 9V and ensures that in the event of another system, such as solar energy source, increasing the marine vessels electrical line level to greater than 14.2V, this does not damage the microcontroller 69. There are a number of ways in which the gain unit 67 can be implemented, for example, by using a non-inverting operational amplifier that will saturate to Vcc on overvoltage.

Output current may be measured, for example, by using an instrumentation amplifier 66. This is a readily available integrated circuit that provides very high common mode rejection and a high differential gain of 100. The calibrated shunt 62 provides a voltage drop proportional to the current flowing through it, which in this example, is rated at 100A and lOOmV. Therefore, the output range of the instrumentation amplifier 66 may be 0 to 10V, but it will saturate at Vcc. However the saturation point will not be reached in arrangement of Figure 6 as the circuit breaker 63 will trip at currents of 80A and above, which gives a maximum input range of 0 to 8V to the microcontroller 69. Other calibrated shunts of 74mV output at 100A or 80A may alternatively be used and are widely available.

The output of the microcontroller 69 may set the speed and direction of rotation of the electric motor coupled to the pressure compensated flow regulatorthrough the worm drive assembly. Motor speed control is achieved by using a standard H bridge integrated circuit 611. This device has Transistor-Transistor Logic (TTL) with 3 inputs. Two inputs provide the direction control, clockwise or anti clockwise, and the remaining input is enable. The enable pin provides a means by which the drive current through the DC motor can be switched with a pulse width modulated signal that controls the speed at which it rotates. When the other pins are in 10 or 01 states, the motor rotates in one direction or the other, while if the other pins are in 00 or 11 state the motor does not rotate. The TTL supply is derived from the 9V line through voltage regulator 65 which provide the TTL power input to the H bridge Integrated Circuit (IC) and also to the level shifting circuit 610 converting the 9V Vcc outputs from the microcontroller to TTL levels. The H bridge voltage line for the motor drive is taken from the main output of the PMG/marine vessel's power, nominally 12V in this example to provide the motor with a full range of power and torque to operate the control valve.

The control system may be implemented in software, hardware or any combination thereof. A person skilled in the art of control theory and the programming language(s) supported by the chosen microcontroller would be able to implement the control system according to one or more embodiments of the present invention, as hereafter described. The control system may be programmed with Vmax, the highest permitted output voltage for the generator, and Imax the highest permitted current, which in this example are 14.2V and 80A respectively.

The control system may sample the output voltage, the output current, the pressure compensated flow regulation valve position and the PMG speed. The interval between each sample taken may be determined based at least in part on the control loop characteristics, which in turn may be determined by the turbine, marine vessel use and type and range of operating conditions specified. In addition to the current sampled information from the system, the controller may be provided with externally provisioned value of maximum output current, maximum output voltage and maximum inducted drag factor. Where these are not provided for the controller from an external sources it will use default values provisioned at manufacture resulting in low output low drag operation. The following operating modes are defined:

1. Current limited, where the user specifies a maximum current permitted. The generator control will close the pressure compensated flow regulation valve raising the output voltage and current until the user defined current limit is reached provided the system is operating at less than the maximum voltage and induced drag factor. This control mode will deliver current less than or up to the user defined current limit. The choice of current limit has a different effect on drag when at low hull speed in comparison with high hull speed. At low hull speed the induced drag is greater than at high hull speed. If the current supplied by the generator exceeds the demands of the marine vessel's systems, excess current charges the marine vessels batteries. When Vmax is reached the marine vessels batteries are charged.

2. Voltage Limited, where the generator will close the pressure compensated flow regulation valve until the maximum voltage is reached, providing the induced drag factor is not exceeded. This control mode extracts the maximum available power from the turbine during the time it is operated, thereby extracting the maximum possible energy from the environment. At very low battery levels, or very high demand from the marine vessels electrical systems, the current draw in this mode is limited by reaching the induced drag ratio limit. At high hull speeds this can provide very high current output with high hull speeds providing a means to rapidly recharge batteries during periods of fast sailing.

3. Induced drag ratio limited. The induced drag ratio is given by the power delivered divided by the power available from the turbine and relates to the induced drag on the turbine. This control mode is implemented by the control system closing the pressure compensated flow regulation valve until the product of the voltage and current delivered, transferred back through the intermediate system to provide extracted power from the turbine, reaches the selected maximum induced drag ratio limit (maximum 1). This control mode sets the permitted drag induced by the generation system to the same limit across all hull speeds. The actual power transferable increases with the hull speed, but the proportion of this transferred power to the power capacity of the turbine is constant. This mode allows a passage under drag control, where the output from the system is maximised at constant drag across the vessel's speed range.

The variable coupling between the turbine output shaft and the generator provides a means by which power is controllably transferred between the turbine and the electrical generator. The power capacity of the turbine, determined by the turbine geometry and the hull speed, is converted to internal potential in the intermediate coupling, then converted to extracted power through controlled release of extracted power as torque and speed of rotation of the generator shaft coupled to its output.

The intermediate coupling can be provided by a closed hydraulic circuit from which flow can be controllably diverted to power the output shaft. The input shaft, driven by the turbine, can be directly connected to a hydraulic pump causing the internal fluid to flow around the internal hydraulic circuit. Other embodiments providing flexibly controllable power linkages between the input and output shafts are possible including, but not limited to, electromagnetic coupling. The turbine power capacity, in this embodiment, is converted to potential through driving a flow of oil around the internal circuit. The intermediate coupling can be designed to absorb the full range of power and speed of rotation of the turbine corresponding to the range of hull speed expected from the vessel. The control system, receiving a signal indicative of the flow rate of the fluid over the turbine, wherein the turbine rotates due to the relative motion of the fluid caused by the vessels motion through the fluid, sets the position of a pressure compensated flow regulating valve that causes a portion of the fluid rotating internally to pass through a parallel path causing a hydraulic motor connected to the output shaft of the intermediate transfer coupling to rotate. The output shaft may be connected to a permanent magnet generator that converts the torque at the speed of rotation to electrical power consumed by the vessel. In embodiments the controller may receive a signal indicative of the position of the pressure compensated flow control valve to determine what proportion of the fluid flow around the closed internal transfer system is being diverted to provide the power extracted by the vessel. The instantaneous power extracted by the vessel may be determined by the current draw at the electrical potential, measured in volts, delivered to the vessel. The instantaneous extracted electrical power is the product of the current in amps and the potential in volts. In embodiments the controller may determine the instantaneous power capacity of the turbine by reference to data tables relating the power capacity of the turbine to the flow rate of fluid over it set by the vessels speed. In embodiments the controller may also determine the instantaneous power capacity of the turbine by receiving a signal indicating the pressure compensated flow regular valve position, the extracted electrical power, the transfer function of the intermediate coupling system, and reference to data tables relating to the power capacity of the turbine for extracted power at pressure compensated flow regulator valve settings. The transfer function of the intermediate coupling between the turbine and the generator is a mathematical function that translates the power taken by the vessel in electrical output to power extracted from the turbine. In embodiments this may be a simple coefficient or a more complex polynomial for control of turbine power capacity variations caused by a vessel moving through a fluid imposing surge, yaw and roll instantaneous modifications to the mean hull speed.

The controller may determine the instantaneous extracted power of at the turbine and compare this with a maximum permitted extracted power from the turbine. Where the extracted power is more or less than the permitted maximum extracted power, the controller may increase or decrease the flow through the pressure compensated flow regulator to bring the extracted power to the maximum permitted. The value of the maximum permitted extracted power can be determined from the maximum permitted induced drag factor multiplied by the instantaneous turbine power capacity. In embodiments, the maximum induced drag factor is provided to the controller by external actors such as, manufacturer, system operator, or algorithmically derived from, but not limited to, battery charge levels, vessels operating conditions, passage plan, weather forecasts or any combination of external vessel systems, vessel operational and environmental conditions.

The controller, operating within the maximum permitted instantaneous extracted power from the turbine, may deliver electrical output to the vessel by altering the position of the pressure regulated flow controller to increase or decrease the flow diverted to the motor of the intermediate system causing it to increase or decrease in speed. This causes an increase or decrease in generator shaft speed which in turn increases or decreases the potential of the delivered electrical energy as measured in volts. The controller, operating within the maximum permitted instantaneous extracted power from the turbine, may carry out this shaft speed control to a limit of either maximum permitted output voltage, maximum permitted output current, or the combination as maximum permitted output power. The maximum permitted voltage, current or combination power values may be provided to the controller from external actors such as, but not limited to, the vessels electrical system specifications, the specifications of the generator and rectifier, the operator, the state of charge and ratings of the vessels battery bank etc.

The controlled intermediate system connecting the turbine shaft to the generator shaft may deliver torque at angular velocity to the shaft of the generator from ONm, when the shaft is not turning, to a maximum equal to the maximum current, voltage potential and power absorption capacity of the vessels electrical system and battery bank. The controlled intermediate system, connecting the turbine shaft to the generator shaft may deliver ON m torque to the output shaft of the generator up to maximum power capacity of the turbine.

Embodiments of the present invention advantageously overcomes or mitigates the limitations and drawbacks of the conventional hydro-generator systems through the use of controlled transfer of power through an intermediate system containing potential energy converted from the kinetic energy provided by the turbine. In general, when power consumption of the vessel is less than power capacity of the turbine, the excess power is left as potential in the intermediate system rather than converted to electrical potential and regulated through energy dumping. This allows the turbine to have sufficient area to provide useful power delivery to the vessel at low speed without incurring a prohibitive drag penalty through power dumping at high speed. The embodiments provide useful power to the vessel over a wide range of hull speeds, and provides very high power capacity at high hull speeds, through the provision of drag controlled power transfer through the intermediate coupling. Further, the control method of the embodiments may provide the user with operational modes that allow tailoring of the generation to the vessels operating circumstances. An example of this is to use a low current or low induced drag factor mode of generation to slowly charge and maintain the vessel's battery banks over a long passage at low drag. Another example of this is to use a high current or high induced drag factor mode of generation for a short fast passage to anchorage, affording as much charge as possible before anchoring,

In the foregoing embodiments and examples, features described in relation to one embodiment and/or examples may be combined, in any manner, with features of a different embodiment and/or examples in order to provide a more efficient and effective hydrogenerator system. Note that, the above description is for illustration only and other embodiments, examples and variations may be envisaged without departing from the scope of the invention as defined by the appended claims.