Platform for generating electricity from flowing fluid using generally prolate turbine

A platform-like device for generating electricity from moving fluids has two has at least two fluid turbines coupled to one another through a frame. The fluid turbines are adapted to rotate in opposite directions. The fluid turbines also provide buoyancy for the platform so that the platform is self supporting in the water. The fluid turbines preferably have helicoid flights (screw-like threads) mounted to generally prolate casings. The fluid turbines preferably connect to electric generators through belt, chain-drive, or other transmission systems. The platform may additional support a wind turbine.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

BACKGROUND

The generation of electricity from water today predominantly uses impoundments, such as dams.

To convert water currents into electricity without impoundments, in-stream energy conversion devices are placed in a flowing stream. According to the Electric Power Research Institute, such in-stream electricity generation without using impoundments remains a largely untapped potential. See, e.g., “North American Ocean Energy Status,” Electric Power Research Institute, March 2007. This report states that the world's first marine renewable energy system of significant size to be installed in a genuinely offshore location was the Marine Current Turbine (MCT) 300 kw experimental SeaFlow unit installed off the coast of Devon, UK in May 2003. The MCT SeaFlow unit used a rotating, axial-flow turbine using hydrodynamic, generally planar blades as working members. (The term “working member” here refers to a member having a surface that functions to react with a working fluid, such as water, such that movement of a working fluid causes movement of the working member.) The report discusses other in-stream projects that use axial-flow turbines with generally planar blades. The Verdant Power 5.5 axial flow turbines were installed in the East River of New York beginning in December 2006. The Canadian Race Rocks British Columbia Tidal Project delivered electricity for the first time in December 2006.

SUMMARY

An object of some embodiments of the invention is to provide an improved, in-stream platform for generating electricity from fluid flows, especially relatively shallow river and tidal flows. Other objects of some embodiments of the invention are to provide:(a) self-buoyant platforms for generating electricity from fluid flows;(b) platforms for generating electricity from fluid flows with low impact on the marine wildlife and the marine environment;(c) platforms for generating electricity from fluid flows subject to icing;(d) portable platforms for generating electricity from fluid flows;(e) improved apparatus for generating electricity at low cost; and(f) scalable arrangements of apparatus for generating electricity; and(e) improved apparatus for generating electricity from the combination of water flow and air flow.

These and other objects may be achieved by providing a platform that includes pairs of hydro turbines that use a generally helicoid working member, similar to screw threads, to convert a stream flow into rotational motion of a generally prolate carrier. (By way of non-limiting example, a football could be considered as having a prolate shape.) Helicoid working members on the exterior of such carriers tend to (a) reject debris, (b) avoid catching or otherwise harming marine life, and (c) have improved properties for continued operation in conditions that cause surface icing. The generally prolate shape provides buoyancy through water displacement to support electrical generators and other equipment loaded onto the platform. The generally prolate shape can accelerate fluid flow around its periphery and provide an increased radial moment and increased torque about its central axis when compared to comparably-sized working members on a circular cylinder.

The hydro turbine can generate electricity when flowing fluid impinges on the helicoid working members and causes the working members to rotate. The rotating working member couples to a drive system, which then transfers the rotational energy to at least one electric generator. The turbines counter rotate so that net torques on the platform at least partially (and preferably totally) cancel. For each of discussion, embodiments of the invention are described herein with respect to electricity generated from water flow, although electricity generated from any fluid flow is contemplated as well.

Additionally, a wind turbine can be used in combination with the hydro turbines. The wind turbine is securely positioned upon a housing of the platform, where the wind turbine uses multiple blades to convert the kinetic energy of the wind into rotational energy. The combination of the hydro turbines and a wind turbine provides multiple, possibly uncorrelated sources of energy conversion, and which yields a greater net energy output with lower variability than two sources alone. Multiple platforms may be anchored in groups in tidal, river, or other streams, while still have a low environmental impact.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a top view of an exemplary platform10for generating electricity from flowing fluid. The platform10is illustrated as attached at one end to a mooring, such as by way of a buoy20. For purposes of description, the end of the platform10shown attached to the buoy20may be referred to as the “forward” end, while the opposite side may be referred to as the “aft” end. As viewed from the aft end looking forward, the left side of the platform10may be referred to as the “port” side, while the right side may be referred to as the “starboard” side.

The platform10includes a frame having a port longitudinal side member26running forward and aft along the port side of platform10and a starboard longitudinal side member28running forward and aft along the starboard side of platform10. Additional frame members (discussed further below) hold the side members26,28in preferably generally parallel, spaced apart alignment. The port side member26holds a port-side, preferably generally-prolate hydro turbine12in a position running forward and aft along the port side of platform10. The starboard longitudinal side member28holds a starboard-side, generally-prolate hydro turbine14in a position running forward and aft along the starboard side of platform10.

Preferred hydro turbines12,14have helicoid working members (similar to screw threads)15,17coiling around the exterior of water-tight, generally-prolate casings16,18. The casings16,18of the turbines12,14are generally prolate, that is, generally symmetrical about a central axis, wider in the middle, and narrower at the ends. While generally prolate casings are desired, the degree of curvature may vary, and the casings need not be a mathematically perfect prolate shape. The turbines12,14preferably have sufficient displacement to be positively buoyant and to hold the platform10at or above the surface of the water. It is preferred that the turbines12,14provide sufficient buoyancy to support the frame and generators while holding the housing at or above the water line. The turbines12,14may be fully submerged or partially submerged with no less than one third of their diameters in the water. If additional structures are provided that are fully or partially submerged, or that otherwise offset the weight of the craft (such as by overhead cable), it is preferred that they provide less buoyancy than the combined buoyancy of the turbines12,14together, and even more preferred that they provide less buoyancy than a single turbine12,14individually. In each of the example above, the turbines provide the substantial majority of buoyancy. The turbines12and14may include one or more internal ballast bladders or compartments (not shown) with access ports to adjust total buoyancy as well as to balance forward-aft buoyancy and port-port buoyancy. Alternately, buoyancy may be adjusted with ballast on the frame.

The port longitudinal side member26supports a forward, port-side generator32toward the forward end of the member26, while the starboard longitudinal side member28supports a forward, side-side generator34toward the forward end of the member28. Each longitudinal side member26,28supports an aft generator33,35toward the aft ends of the members. A transmission system, such as chains or belts (not shown inFIG. 1), couples the hydro turbines12,14to electric generators32,33,34,35as discussed more fully below. A housing22coupled to the frame provides environmental protection for control, power conditioning and other equipment.

While the embodiment ofFIG. 1illustrates four generators at the forward and aft ends of platform10, differing numbers of generators and/or locations may be used. For example, each of the longitudinal side members26,28may support a single generator placed more centrally along the longitudinal side members to balance other loads on the platform. Alternately, the platform may have a single, centrally-placed generator. Ballast may be added to balance the platform. The embodiments herein are not limited to any specific number of generators or placement of generators.

The frame is adapted to attach to a single mooring buoy20, preferably through lines attached at two points along a front crossbar19. The buoy20in turn may attach through a chain to a bottom anchorage to form a “slack” mooring. With such a mooring, the platform may swing around the anchorage, which allows the platform to continue to operate in reversible stream flows, such as a tidal flow. Alternately, the platform may be moored to an overhead cable or other above-water structure or to a fixed pylon driven into the bottom. When the platform10is moored securely, water flow impinging on the helicoid working members15,17causes the working members15,17to rotate. Rotation of the working members in turn causes rotation of the rotors of electric generators32,33,34,35and generation of electricity. The electricity may be transmitted to shore through underwater cable or overhead cable, depending on the nature of the mooring for a particular site. Alternately, electricity can be consumed on the platform itself, such as for purifying water or generating hydrogen fuel.

FIG. 2is a starboard-side view of the platform10and mooring buoy20which illustrates an exemplary housing22, starboard hydro turbine14, and starboard generators34,35. The embodiment ofFIG. 2shows a single working member17on starboard turbine14, though a different number of working members may be used. For example, in an alternate embodiment (not shown) a turbine may include two flights interleaved like double-start screw threads.FIG. 2also illustrates an exemplary placement of elements of drive systems for the forward and aft generators34,35. In this embodiment, a forward starboard belt or chain31acouples the forward starboard generator34to the forward end of starboard turbine14, while an aft starboard belt or chain31bcouples the aft starboard generator35to the aft end of starboard turbine14. This view also illustrates top struts29aof the frame, which will be discussed further below in connection withFIG. 5.

FIG. 3is a forward-end view of platform10which illustrates an exemplary placing of housing22, starboard and port hydro turbines12,14, forward starboard and port generators32,34, forward starboard and port drive belts or chains30a,31a, and elements of the frame, including mooring cross bar19and top struts29a,29b. From this view can be seen that the helicoid working members15,17preferably turn in opposite directions, such that any lateral forces on turbines12and14at least partially (and preferably substantially entirely) offset each other to maintain the position of platform10. This view also illustrates top struts29aand bottom struts29bof the frame, which will be discussed further below in connection withFIG. 5.FIG. 3does not show a mooring buoy20secured to the crossbar19. However those skilled in the art will appreciate that a buoy or other anchoring mechanism may be used to moor or securely position the platform10.

FIG. 4is a perspective view of platform10which further illustrates an exemplary placing of housing22, port and starboard hydro turbines12,14, forward starboard and port generators32,34, aft port generator33, forward part and starboard drive belts or chains30a,31a, and elements of the frame, especially forward cross bar19. From this view also can be seen that the helicoid working members15,17turn in opposite directions. This view does not show a mooring buoy20secured to the crossbar19. However those skilled in the art will appreciate that a buoy or other anchoring mechanism may be used to moor or securely position the platform10.

FIG. 5is a perspective view of the frame24. The frame24includes port and starboard longitudinal members26,28as previously discussed. A forward crossbar41runs generally perpendicular to the longitudinal members26,28and connects to the longitudinal members26,28in their forward halves. An aft crossbar42runs generally perpendicular to the longitudinal members26,28and connects to the longitudinal members26,28in their aft halves. The longitudinal members26,28and crossbars41,42thus form a generally planar, horizontal square with portions of the longitudinal members26,28extending forward and aft beyond the crossbars41,42. From vertices of the square, or close thereto, four struts29aconverge at a vertex above the plane of the square, while four additional struts29bconverge at a vertex below the plane of the square, thus forming sides of an octahedron. The location of the vertices, if projected onto the plane of the square, would both lie in the center. The vertices may optionally be connected by a vertical pole (not shown). The struts29a,29bof the octahedron provides stiffness against twisting and sheer of the longitudinal members26,28. Additional and/or alternative bracing may be provided for frame strength and/or stiffness.

An additional forward crossbar19runs generally perpendicular to the longitudinal members26,28and connects to the longitudinal members26,28near the forward ends of the members. This additional forward crossbar19provides secure and convenient attachment points for a mooring.

FIG. 6is a perspective view of drive system components for a platform for generating electricity from a flowing fluid. WhileFIG. 6illustrates only a portion of forward starboard turbine14and generator34it should be understood that in this embodiment a similar arrangement will be found for the forward port generator32, and similar arrangements may be found for aft starboard and port generators33,35.

The starboard turbine14of this embodiment includes a helicoid working member17coupled in a one-to-one rotational relationship to the corresponding casing18. That is, a single rotation of a working member17causes a single rotation of the corresponding casing18in the same direction of rotation. The working member17may mount directly and fixedly to the exterior of the casing18. The starboard turbine14is rotatably mounted to a bearing (not shown) that is located within a cap38and coupled to the starboard longitudinal member28. The cap38preferably has an outer profile that smooths flow to the starboard turbine14(and at the trailing edges of turbines, smooths flow away from the turbines). It also protects the bearing from debris strikes. A transmission element31a, which may be a belt or chain, couples the turbine14to a shaft52through a pulley51, or a pulley may be affixed directly to the exterior of the casing18near its end most point51. The shaft51in turn drives the rotor of forward starboard generator34. The shaft52couples through a bearing53to the starboard longitudinal member28.

As moving liquid (e.g., flowing water) impinges on the helicoid working member17, it causes rotation of the helicoid working member17and casing18about the bearing (located within cap38). The rotation of the turbine14engages the belt or chain31a, which transmits mechanical power through the pulley51and shaft52to the generator34. The pulley diameter may be selected to cause the shaft52to rotate at a different rate than the turbine14. That is, the pulley may cause the shaft52to rotate at a higher or lower RPM than the turbine14.

The center line of the hydro turbine14may be beneath the water surface, therefore the bearing should be submersible and selected for prolonged, underwater operation. The cap38and forward end of the longitudinal member28may also be underwater or at the water surface and preferably will be made ruggedly to deflect debris and act as a shield for the bearing.

FIG. 7is a view of a platform60having a combined wind turbine and hydro turbines. The platform60includes a frame71, a port hydro turbine62, and a starboard hydro turbine63similar to ones described above in connection withFIGS. 1-6. Each turbine62,63has a helicoid working member64,65preferably coupled in one-to-one rotational relationship with a corresponding casing66,67. A housing70provides environmental protection for control, power conditioning, and other equipment.

A wind turbine61is positioned upon the housing70. In one embodiment, the wind turbine61is a horizontal axis wind turbine having multiple blades74, and more particularly may be a wind turbine as disclosed in copending U.S. patent application Ser. No. 61/202,189 filed Feb. 4, 2009 and entitled “Folding Blade Turbine.” Other wind turbines may be used.

FIGS. 8aand8bare schematic diagrams of preferred power conditioning circuitry for a platform for generating electricity from a flowing fluid.FIG. 8ais a schematic for a platform having two generators, such as a single port-side generator81aand a single starboard-side generator81b. Each generator81a,81bproduces alternating current (AC) electricity having a frequency and voltage that may vary according to the rotation rate of the turbines (not shown) and the electrical load on the generator circuit. Rectifiers82a,82bconvert the AC electricity into direct current (DC) electricity at a DC working voltage used internally to the platform. An optional battery83and/or other storage elements (e.g., capacitors) provide(s) combined storage for electricity produced by the two generators. An inverter84converts the combined DC electricity into AC electricity having a regulated frequency appropriate for a customer and having an AC working voltage used internally to the platform. A transformer85provides electrical isolation between the platform and a transmission circuit86. The transformer85may also increase the voltage of the AC electricity from the AC working voltage to a voltage appropriate for transmission to a customer.

The circuitry ofFIG. 8acan be adapted for additional generators by adding additional rectifiers.FIG. 8bis a schematic for a platform having four generators81a,81b,81c,81dfor fluid turbines and a fifth generator81efor a wind turbine. Additional rectifiers82c,82d,82econvert AC electricity into DC electricity at the DC working voltage. The battery83, inverter84and transformer85perform the same functions as inFIG. 8a, except that their ratings may be increased, such as by increasing the storage capacity of the battery83and the current capacity of the inverter84and transformer85. Additional circuitry may be provided, such as fuses, switches, monitoring equipment, etc.

Where a platform has both water and wind turbines, electrical power generation from the different resources will be non-correlated to some degree. This may result in reduced net variation in power output of the platform when compared to wind or water turbine generation alone. This reduced variation means the battery storage capacity may be less than would be required for separate wind and water installations.

The embodiments described above are intended to be illustrative but not limiting. Various modifications may be made without departing from the scope of the invention. The breadth and scope of the invention should not be limited by the description above, but should be defined only in accordance with the following claims and their equivalents.