Abstract
An energy recovery system 100 for a marine vessel 200 is herein disclosed comprising at least one water turbine 101, 102 with vertical axis 105, 106 respectively arranged aft and off center, that is either port side or starboard side, with respect to a rotational axis 211 of a respective propeller but at a distance from the propeller and from the rotational axis of the propeller such as to be at least partially in a wake range 21 of the propeller in order to recover at least part of the dissipated rotational power. A vessel 200 comprising at least one energy recovery system 100 and a method for recovering at least part of the energy dissipated by the marine vessel are herein also disclosed.
Claims
1. An energy recovery system for a marine vessel, the marine vessel comprising at least one marine propeller configured to transform rotational power into linear thrust by acting upon water in order to move the vessel, while at least part of the rotational power is dissipated in the formation of an accelerated vortical water flow in a wake of the propeller, wherein the energy recovery system comprises at least one water turbine with vertical axis rotatably fixed to a vessel hull and respectively arranged aft and off center, that is either port side or starboard side, with respect to a rotational axis of a respective propeller but at a distance from the propeller and from the rotational axis of the propeller such as to be at least partially in a wake range of the propeller in order to recover at least part of the dissipated rotational power from the accelerated vortical water flow.
2. The energy recovery system of claim 1 wherein the vertical axis of the at least one water turbine is at a distance from the rotational axis of the respective propeller that is about the same as a radius of the propeller.
3. The energy recovery system of claim 1 wherein the at least one water turbine is arranged in proximity and either port side or starboard side of a respective rudder, the rudder being arranged aft and center aligned with respect to the respective propeller, wherein the rotational axis of the at least one water turbine is at a distance from a vertical steering axis of the rudder that enables rudder deflection without interference by the at least one water turbine while enabling the at least one water turbine to be hit by tip vortices of the propeller wake before partial flow disruption by the rudder.
4. The energy recovery system according to claim 1 wherein the at least one water turbine has a rotor with a height that is about the same or less of a diameter (Dp) of the respective propeller and with a center horizontally aligned with the rotational axis of the respective propeller.
5. The energy recovery system according to claim 1 wherein the at least one water turbine is a helical water turbine.
6. The energy recovery system according to claim 5 wherein the at least one water turbine comprises blades twisted in one direction if the at least one water turbine is arranged port side with respect to the axis of rotation of the respective propeller and blades twisted in the opposite direction if the at least one water turbine is arranged starboard side with respect to the axis of rotation of the respective propeller, and wherein the direction of rotation of the at least one water turbine is respectively inverted as effect of the water flow.
7. The energy recovery system according to claim 1 comprising at least one generator functionally coupled to an upper shaft of the at least one water turbine, wherein the at least one generator is arranged inside the vessel hull.
8. The energy recovery system according to claim 1 wherein the at least one water turbine comprises a bottom shaft rotationally fixed to a sole piece.
9. The energy recovery system according to claim 8 wherein the sole piece of the at least one water turbine is in common with a respective rudder.
10. A marine vessel comprising at least one energy recovery system according to claim 1.
11. The marine vessel of claim 10 comprising at least one electric motor to power the at least one propeller respectively.
12. The marine vessel according to claim 10 comprising a port side propeller and a starboard side propeller and at least one port side energy recovery system and at least one starboard side energy recovery system, wherein the at least one port side energy recovery system comprises a port side water turbine with respect to the port side propeller and the at least one starboard side energy recovery system comprises a starboard side water turbine with respect to the starboard side propeller, or the at least one port side energy recovery system comprises a starboard side water turbine with respect to the port side propeller and the at least one starboard side energy recovery system comprises a port side water turbine with respect to the starboard side propeller, or the at least one port side energy recovery system comprises a port side water turbine and a starboard side water turbine with respect to the port side propeller (210) and the at least one starboard side energy recovery system comprises a port side water turbine and a starboard side water turbine with respect to the starboard side propeller.
13. The marine vessel according to claim 11 further comprising a rechargeable battery pack as electric power supply for the at least one electric motor and at least one main renewable energy source for recharging the battery pack in addition to the at least one energy recovery system.
14. (canceled)
15. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 shows a hydro-generator known in the prior art fastened on the transom of a vessel.
[0041] FIG. 2 shows a similar type of hydro-generator as in [FIG. 1], also known in the prior art, designed to be fixed under the hull of a vessel.
[0042] FIG. 3 shows a typical installation of the hydro-generator of [FIG. 1], as known in the prior art.
[0043] FIG. 4 shows another prior art hydro-generator installed just behind a propulsion propeller.
[0044] FIG. 5 shows schematically characteristics of a wake of a marine propeller and a new energy recovery system according to the present disclosure and its arrangement with respect to the marine propeller and its wake, seen from the top.
[0045] FIG. 6 shows schematically the same energy recovery system of [FIG. 5] and its arrangement with respect to the marine propeller and its wake, seen from the side.
[0046] FIG. 7 shows schematically a perspective view of a water turbine and its arrangement with respect to a marine propeller and its wake, according to an embodiment of the present disclosure.
[0047] FIG. 8 shows schematically a variant of the embodiment of [FIG. 7] comprising two water turbines.
[0048] FIG. 9 shows schematically a top view of a water turbine and its arrangement with respect to a marine propeller and a rudder, according to an embodiment of the present disclosure.
[0049] FIG. 10 shows schematically a variant of the embodiment of [FIG. 9].
[0050] FIG. 11 shows schematically yet another variant of the embodiments of [FIG. 9] and [FIG. 10].
[0051] FIG. 12 shows schematically a side view of an energy recovery system and its arrangement with respect to a marine vessel, according to an embodiment, as well as a method of recovering energy.
[0052] FIG. 13 shows schematically a partial top view of the same embodiment of [FIG. 12].
[0053] FIG. 14 shows schematically some water flow characteristics around water turbines of the present disclosure in absence of propeller wake.
[0054] FIG. 15 shows schematically another example of water turbine type that could be employed.
[0055] FIG. 16 shows schematically a marine vessel comprising an energy recovering system according to an embodiment.
[0056] FIG. 17 shows schematically a variant of the embodiment of [FIG. 16].
[0057] FIG. 18 shows schematically yet another variant of the embodiment of [FIG. 16] and [FIG. 17].
[0058] Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements whereas other elements may have been left out or represented in a reduced number in order to enhance clarity and improve understanding of the embodiments of the present disclosure.
DETAILED DESCRIPTION
[0059] [FIG. 1] shows a hydro-generator 1, known in the art, fastened via a lifting bracket 2 on the transom 11 of a marine vessel 10. The hydro-generator 1 comprises a submerged leg 3 ending with a torpedo-like housing 4 comprising a propeller shaft and a generator coupled to the propeller shaft (not shown). The propeller shaft is connected to a propeller 5 and has a horizontal axis of rotation 6 parallel to the longitudinal axis of the vessel 10.
[0060] [FIG. 2] shows a hydro-generator 1 similar to the hydro-generator 1 of [FIG. 1], and also known in the art, designed to be fixed under the hull 12 of a vessel, with power connection 7 through the hull 12. The hydro-generator 1 also comprises a submerged shortened leg 3 ending with a torpedo-like housing 4 comprising a propeller shaft and a generator coupled to the propeller shaft (not shown), and a propeller 5 with a horizontal axis of rotation 6 parallel to the longitudinal axis of the vessel.
[0061] [FIG. 3] shows a typical installation of the hydro-generator 1 of [FIG. 1], as known in the art. In particular, two hydro-generators 1 of the type shown in [FIG. 1], are installed at the transom 11 of a vessel 10 such that the respective propellers 5 are at a depth and lateral position with respect to the transom 11 such that they are outside of the wake of rudders 13, of the wake of the hull 12 itself and especially out of the wake of the vessel propeller 14, particularly when this is used to propel the vessel 10. This is because the performance of such a hydro-generator 1 depends on the quality of the water flow, which should be possibly free from any turbulence. The type of hydro-generator 1 shown in [FIG. 2] is typically placed under the hull centrally with respect to the hull 12 but forward with respect to the vessel propeller 14 for the same reason (not shown).
[0062] [FIG. 4] shows another type of hydro-generator 1 known in the prior art, e.g. as disclosed in CN107676214A1. The hydro-generator 1 is partly integrated into the rudder 13 of a marine vessel 10 with the hydro-generator propeller 5 placed just behind (aft) and facing the vessel propeller 14, center aligned with each other and with respective axes of rotation 6, 14 in line with each other. With such arrangement it is possible to recover at least part of the dissipated energy by using the tip vortices generated by the propulsion propeller 14 to rotate the hydro-generator propeller 5. This concept has however a series of disadvantages already mentioned in the background session.
[0063] [FIG. 5] and [FIG. 6] taken together show schematically some characteristics of a wake 21 of a marine propeller 210 and a new energy recovery system 100 according to the present disclosure and its arrangement with respect to the marine propeller 210 and its wake 21, seen from the top and from the side respectively. In particular, [FIG. 5] shows a cross section of the wake 21 in a xy plane passing through the center of the propeller 210, where x is the axial direction and y is the tangential direction, whereas [FIG. 6] shows an orthogonal cross section of the wake 21 in a xz plane passing through the center of the propeller 210, where x is the axial direction and z is the radial direction, the propeller 210 having an axis of rotation 211 parallel to the axial direction x. The velocity of the propeller wake 21 comprises components along the axial x, tangential y, and radial z directions, resulting in an accelerated vortical water flow past the propeller 210 due to dissipated rotational power by the propeller 210. The wake 21 can be divided in two major zones called respectively zone of flow establishment (ZFE) closer to the propeller 210 and zone of established flow (ZEF) further from the propeller 210, past the ZFE. Studies in the literature report that the extent of ZFE can be approximately up to x/Dp=2.63 downstream of a propeller wake, where x denotes the longitudinal distance from the propeller along the axial direction x, and Dp denotes the diameter of the propeller 210. The axial component of the wake velocity V.sub.x, is the major contributor to the total flow velocity in the wake range, that is within the slip boundaries 21 of the wake 21. Within the ZFE, the axial velocity V.sub.x distribution comprises two peaked ridges, having declining velocity towards the axis of rotation 211, due to the hub 212 of the propeller 210, and towards the slip boundaries 21 of the wake 21, and highest velocity in between V.sub.x-max. As the wake propagates in the axial direction x, the peaks gradually migrate towards the axis of rotation 211 until they merge into one in the ZEF, where the highest velocity V.sub.x-max is at the axis of rotation 211 of the propeller 210. The water flow velocity, within the slip boundaries 21 of the wake 21, relative to a moving vessel under propeller propulsion and relative to any water turbine moving with the vessel, includes the axial wake velocity V.sub.x and the water flow velocity due to the useful conversion of the propeller rotation power into linear thrust, as the vessel moves, that is the same as the vessel velocity but in opposite direction. Thus, for a moving marine vessel, under propeller propulsion, V.sub.x is the difference in axial water flow velocity between the inside of the slip boundaries 21 of the wake 21 and the outside of the slip boundaries 21 of the wake 21, where the water flow velocity relative to the moving vessel is a result of the linear thrust only. The energy recovery system 100 comprises at least one water turbine 101, 102 with vertical axis 105, 106 (parallel to the z direction), rotatably fixed to a vessel hull (not shown in [FIG. 5] and [FIG. 6]) and respectively arranged aft and off center, that is either port side or starboard side, with respect to the rotational axis 211 of the propeller 210 but at a distance from the propeller 210 and from the rotational axis 211 of the propeller 210 such as to be at least partially in a wake range 21 of the propeller 210, and more particularly at least partially in the zone of flow establishment (ZFE), possibly where the axial velocity is maximum V.sub.x-max tangential to the water turbine rotor 103, 104, in order to recover as much as possible of the dissipated rotational power. In particular, [FIG. 5] shows two water turbines 101, 102 from the top arranged aft and off center, respectively port side 101 and starboard side 102, with respect to the rotational axis 211 of the propeller 210, with about half of their respective rotors 103, 104 in the ZFE of the wake 21, that is with their respective vertical axes 105, 106 at a distance from the rotational axis 211 of the propeller 210 that is about the same as the radius (Dp/2) of the propeller.
[0064] As can be seen from the side view in [FIG. 6], the at least one water turbine 101 (the starboard side water turbine 102 being hidden behind the portside water turbine 101 and hence not visible in [FIG. 6]) has a rotor 103 with a height that is about the same (in this case) or less of the diameter Dp of the propeller 210 and has a center 107 horizontally aligned with the rotational axis 211 of the propeller 210.
[0065] [FIG. 7] shows schematically a perspective view of a water turbine 101 with vertical axis 105 and its arrangement with respect to a marine propeller 210 and its wake 21, portside with respect to the axis of rotation 211 of the propeller 210. The propeller 210 is in this example right-handed, that is it generates a forward linear thrust when it rotates clockwise. The wake 21 is represented here schematically as a three-dimensional vortical flow including tip vortices 21 resulting from the clockwise rotational motion of the propeller 210 and including velocity components in the axial x, tangential y and radial z directions.
[0066] [FIG. 8] shows schematically a variant of the embodiment of [FIG. 7] comprising two water turbines 101, 102, with vertical axes 105, 106, respectively portside 101 and starboard side 102 with respect to the axis of rotation 211 of the propeller 210, like in the embodiment of [FIG. 5] and [FIG. 6].
[0067] The water turbines 101, 102 of [FIG. 7] and [FIG. 8] are helical water turbines, and in particular of the Gorlov type. In particular, the portside water turbine 101 comprises blades 109 twisted in one direction whereas the starboard side water turbine 102 comprises blades 108 twisted in the opposite direction. The respective direction of twist of the blades 108, 109 depends primarily on the propeller walk, right-handed in this case, and it could have been inverted in case the propeller 210 was left-handed. It is also to be noted that the directions of rotation of the portside water turbine 101 and of the starboard side water turbine 102 are respectively inverted, as effect of the water flow 21, 21 and their respective arrangement and design with respect to the water flow 21, 21.
[0068] [FIG. 9] shows schematically a top view of a water turbine 101 with vertical axis 105 and its arrangement with respect to a marine propeller 210 and a rudder 220, that is port side with respect to the rotational axis 211 of the propeller 210 and with respect to the rudder 220, the rudder 220 being arranged aft and center aligned with respect to the propeller 210. The water turbine 101, the propeller 210 and the wake 21 are the same as in [FIG. 7]-8, seen from the top (schematically).
[0069] [FIG. 10] shows schematically a variant of the embodiment of [FIG. 9], with the difference that instead of the water turbine 101 on the port side, a water turbine 102, like the water turbine of [FIG. 8], is arranged on the starboard side, with respect to the rotational axis 211 of the propeller 210 and with respect to the rudder 220.
[0070] [FIG. 11] shows schematically yet another variant of the embodiments of [FIG. 9] and [FIG. 10] with both the water turbine 101 and the water turbine 102 respectively arranged on the port side and the starboard side, with respect to the rotational axis 211 of the propeller 210 and with respect to the rudder 220. In particular, the rotational axes 105, 106 of the water turbines 101, 102 respectively are at a distance from a vertical steering axis 221 of the rudder 220 that enables rudder deflection without interference by the water turbines 101, 102 while enabling the water turbines to be hit by tip vortices 21 of the propeller wake 21 before partial flow disruption by the rudder 220.
[0071] [FIG. 12] and [FIG. 13] taken together show schematically a side view and a partial top view respectively of an energy recovery system 100 and its arrangement with respect to a marine vessel 200, according to an embodiment. The energy recovery system 100 comprises two water turbines 101, 102 with respective vertical axis 105, 106 respectively arranged on the port side and the starboard side, with respect to the rotational axis 211 of a vessel propeller 210 and steering axis 221 of a rudder 220, like in the embodiment of [FIG. 11]. The energy recovery system 100 further comprises one or two generators 120 functionally coupled to the upper shafts 111, 112 of the water turbines 101, 102, where the at least one generator 120 is arranged inside the vessel hull 201, an option that is enabled by having water turbines with vertical axis. The generator 120 may be connected to an inverter 121 before the generated electrical current is returned to a battery 240 as recovered energy. The water turbines 101, 102 each comprise also a bottom shaft 113 rotationally fixed to a sole piece 230 for increased stability. In particular, the sole piece 230 is in common with the rudder 220, for convenience. Still in connection with [FIG. 12] and [FIG. 13], a method of recovering at least part of dissipated rotational power from an accelerated vortical water flow in a wake 21 of a marine propeller 210 configured to transform rotational power into linear thrust by acting upon water in order to move a marine vessel 200 is herein also disclosed. The method comprises rotatably fixing to a hull 201 of the vessel 200 at least one water turbine 101, 102 with vertical axis 105, 106, at a position that is aft and off center, that is either port side or starboard side, with respect to a rotational axis 211 of the propeller 210 but at a distance from the propeller 210 and from the rotational axis 211 of the propeller 210 such as to be at least partially in a wake range 21 of the propeller 210. The illustrated method further comprises rotationally fixing a bottom shaft 113 of the at least one water turbine 101, 102 to a sole piece 230, the sole piece 230 being in common with the rudder 220.
[0072] [FIG. 14] shows schematically some water flow characteristics around water turbines 101, 102 of the present disclosure also in absence of propeller wake, when e.g. a vessel is propelled, at least temporarily, by other means other than the propeller, e.g. by wind in case of a sailing vessel. In particular, the proximity to the rudder 220 can have the advantage to create a Venturi duct between the at least one water turbine 101, 102 and the rudder 220, while also taking advantage of the lift generated by the rudder shape, thereby causing the velocity of the water flow between the at least one water turbine 101, 102 and the rudder 220 to be higher than on the external side of the at least one water turbine 101, 102, even when not using the propeller 210, and even higher when using the propeller 210, thus further increasing the directional torque and hence the power efficiency.
[0073] [FIG. 15] shows schematically another example of water turbine type with vertical axis and lift-based design that could be employed, and in particular a H-Darrieus water turbine 122. Of course, like for the helical water turbine, the size of the rotor, and the number and shape of the hydrofoil blades may be suitably adapted according to vessel and propeller type and e.g. typical cruising speed.
[0074] [FIG. 16] shows schematically a marine vessel 200 and in particular a catamaran with a port side hull 201 and a starboard side hull 202, comprising a port side electric motor 215 and a starboard side electric motor 216, respectively connected to a port side propeller 210 and to a starboard side propeller 214, a rechargeable battery pack 240 as electric power supply for the electric motors 215, 216 and a photovoltaic system 260 as main renewable energy source for recharging the battery pack 240. The marine vessel 200 further comprises a port side rudder 220 and a starboard side rudder 224 located aft of and center aligned with the respective propellers 210, 214. In particular, the marine vessel 200 comprises a port side energy recovery system 100 and a starboard side energy recovery system 100 according to any of the disclosed embodiments, where the at least one port side energy recovery system 100 comprises a port side water turbine 101 with respect to the port side propeller 210 and the starboard side energy recovery system 100 comprises a starboard side water turbine 102 with respect to the starboard side propeller 214, thus symmetrically arranged with respect to the vessel 200.
[0075] [FIG. 17] shows schematically the same marine vessel 200 of [FIG. 16], with the difference that the port side energy recovery system 100 comprises a starboard side water turbine 102 with respect to the port side propeller 210 and the starboard side energy recovery system 100 comprises a port side water turbine 101 with respect to the starboard side propeller 214, thus still symmetrically arranged with respect to the vessel 200.
[0076] [FIG. 18] shows schematically the same marine vessel 200 of [FIGS. 16]-17, with the difference that the port side energy recovery system 100 comprises a port side water turbine 101 and a starboard side water turbine 102 with respect to the port side propeller 210 and the starboard side energy recovery system 100 comprises a port side water turbine 101 and a starboard side water turbine 102 with respect to the starboard side propeller 214.
[0077] With reference to all embodiments of [FIGS. 16]-18, the energy recovery systems 100, 100 and respective water turbines (101, 102, 101, 102) may be identical to each other with the exception eventually of the direction of twist of the water turbine blades depending on the arrangement of the water turbine either port side or starboard side of the respective propeller (210, 214) and on the walk of the propeller (210, 214) that may be both right-handed, or both left-handed, or one left-handed and one right-handed respectively.
[0078] In the preceding specification, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present teaching. In other instances, well-known materials, parts or methods have not been described in detail in order to avoid obscuring the present disclosure.
[0079] Particularly, modifications and variations of the disclosed embodiments are certainly possible in light of the above description. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically devised in the above examples.
[0080] Reference throughout the preceding specification to one embodiment, an embodiment, one example or an example, means that a particular feature, structure or characteristic described in connection with the embodiment or example is included in at least one embodiment. Thus, appearances of the phrases in one embodiment, in an embodiment, one example or an example, in various places throughout this specification are not necessarily all referring to the same embodiment or example.
[0081] Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and/or sub-combinations in one or more embodiments or examples.
