Patent Description:
<CIT> describes a reversible turbine-pump system adapted for use with well liquid that is displaceable within a vertical shaft. The system includes a removable manifold that is fixed to the top of the shaft in operation.

Generally, it provides reversible pump-turbine located in a vertical shaft from which it is removable and further comprising a removable manifold fixed to the top of the shaft during operation wherein water flow to and from the reversible pump-turbine is through coaxial penstocks positioned in the shaft above the pump-turbine;
and wherein said pump-turbine comprises:.

The present invention establishes the required plant cavitation coefficient by positioning reversible pump-turbines with motor-generators, generally well below tailwater level in a generally vertical bore hole. Reversible pump-turbines with motor-generators will be referred to herein simply as "pump-turbines" or as "machines" The term "bore hole", rather than "shaft", is used herein to avoid confusion with the rotating shaft of the pump-turbine located therein.

Conventional pumped storage facilities position the runner well below tailwater elevation to suppress cavitation while keeping unit power and specific speed high. The critical cavitation coefficient for reversible pump-turbines is higher than it is for either turbines or pumps because the hydraulic profiles are a compromise between pumping and generating and are optimized for neither. Positioning of the runner below tailwater has heretofore required a deep and expensive excavation regardless of machine size and rating. The expense of excavation and underground construction has been cost prohibitive for small installations, of less than <NUM> MW, for example. Sites suitable for large installations are limited by geology, geography, competing land uses, and adequate transmission lines. Many suitable smaller scale sites exist, but existing reversible pump-turbines, even if scaled down in size and rating, still require excavation and construction costs that are prohibitive.

The proposed configuration utilizes a simple and inexpensive bore hole of perhaps <NUM> to <NUM> meters in diameter to position a high specific output reversible pump-turbine sufficiently below tailwater elevation to suppress cavitation. Such bore holes are routinely drilled as a commodity construction service for reasonable prices. A steel liner and conduits for hoisting water, electrical and control cables, for example, may be grouted in place within the bore hole. Pump-turbines adapted to this type of installation may be configured as single stage machines or may be configured as multi-stage machines utilizing specially configured "diffuser bowls" similar in function to those used on multi-stage submersible pumps. These pump-turbines would not normally use conventional scroll cases. As such, stages of these pump-turbines may be stackable to allow standard hydraulic designs to be used over a wide range of head conditions. The use of standard pump-turbine stages is further facilitated by the fact that the required plant cavitation coefficient can be achieved by simply establishing the required vertical bore hole depth. Compared to conventional underground powerhouse pump-turbine installations, there is a less frequent need to design and manufacture site specific machinery and there is no need carry the penstock nor tailrace conduit to extraordinary depths, which would be cost prohibitive in conjunction with small pumped hydro installations at most locations. The use of standard components results in increased quantities of like parts at reduced cost. Reduced costs in turn enable a greater number of projects to be built with increased part quantities.

Water flow to and from the reversible pump-turbine is through coaxial penstocks positioned in the shaft above the pump-turbine assembly. The associated motor-generator may be submersible and in certain preferred embodiments located below the pump-turbine(s). Locating the motor-generator below the pump turbines allows for a larger diameter, and therefore more economical, motor-generator for a given bore hole size. Allocating substantially all of the bore hole cross sectional area to water conveyance (up and down), rather than to space for the motor-generator, allows for the maximum power rating for a given diameter of bore hole.

The generator may alternatively be located outside of the water passageways and connected to the runner with a shaft. Such an arrangement may be cheaper than providing an underground powerhouse large enough to incorporate a scroll case, while allowing the use of a readily available air-cooled generator.

In a preferred embodiment, a removable manifold may be used to connect the inner pipe to tailwater and connect the outer pipe to the penstock leading to headwater. It is generally more efficient to connect the smaller diameter pump inlet/turbine outlet with the smaller of the coaxial pipes while connecting the larger pump outlet/turbine inlet with the larger of the two coaxial pipes. Alternative embodiments of this invention may utilize another arrangement as may be the case when multiple pump turbines might be installed, on a bulkhead, for example, in a common bore hole. The removable manifold may include an integral pneumatically controlled pressure relief valve. This integral pressure relief valve will itself reduce civil works costs by eliminating the need for a surge shaft and by reducing penstock surge pressure and penstock cost. Additionally, or alternatively, an air cushion may be left under the cover of the bore hole. Removal of the manifold allows removal of the machinery from the borehole. Dedicated hoisting equipment will facilitate installation, service, and maintenance without the need for confined space work. A water pressure actuated piston attached to the bottom of the eversible pump turbine may be used for raising and lowering. A spacer between the piston and the machine may be used to allow the machine to be raised entirely clear of the borehole.

Variable speed operation is facilitated by the ready availability of power control electronics developed for the wind industry. As in the case of wind turbine power converters, full power converters may be used in conjunction with permanent magnet motor generators and partial power converters may be used in conjunction with (generally larger) doubly fed induction generators.

The bore hole in which the reversible pump-turbine is installed may include provision for delivery of pressurized water to the bottom of the shaft, through a conduit separate from the main bore hole to hydraulically hoist the equipment for maintenance and repair and to controllably lower the equipment into operating position. The electrical power connection is preferably configured to automatically engage when the machine is lowered and to automatically disengage when the machine is raised. Such a connector may use conventional "wet mate" marine electrical connector technology or may be use a combination of compressed gas, insulating oil and inflatable seals, for example, to establish robust electrical connections isolated from ground potential.

The bore hole in which the equipment is located may terminate at the upper portal, the lower portal or at any convenient intermediate location. In the case of installation in conjunction with an existing pipeline, the vertical shaft may be located according to desired pressure profiles resulting from operation, load rejection, and other considerations. The shaft cover may incorporate a pressure relief valve and may be used to cap off a surge shaft containing air.

Multiple machines may be installed in a single shaft, on a common bulkhead, for example. The reversible pump turbines in accordance with the present invention may be used in conjunction with Pelton turbines, for example to facilitate generation at low power levels if required. The reversible pump turbines may be used in conjunction with off-stream seasonal storage reservoirs, where their primary purpose may be to raise water to the storage reservoir during high flow periods and to return water while recovering energy when stored water is required downstream.

In accordance with certain embodiments of this invention, gas pressure balanced pressure relief valves may be used to limit overpressure from water hammer.

An elbow with actuatable seals may be used in order to connect the draft tube to the tail race during operation. Inflatable seals may be used to seal the elbow in its operating position while allowing it to move freely during hoisting and lowering operations. Inflatable seals or supports may also be used to fix the machine into position during operation and to release it to allow it to be raised for maintenance.

In accordance with a further aspect of the invention a reversible pump turbine runner or pump impeller is provided that imparts to the flow an upward velocity component. This upward velocity component allows the flow to proceed directly up through the diffuser or a guide vane - diffuser combination in the case of a reversible pump-turbine, or directly to a diffuser (stator) stage in the case of a multi-stage pump, while maximizing the ratio of impeller tip diameter to maximum water passageway diameter. In the case of the present invention this ratio may be <NUM>. This maximizes the head per stage and allows a greater head to be achieved with a single stage machine. <FIG> illustrate the flow in the meridional plane as well as the X - shaped appearance of the impeller blades when viewed toward the trailing edge.

Referring to <FIG>,<FIG>, a conventional pumped storage plant with a reversible pump-turbine is shown. There are several notably expensive features in such a conventional installation. These include:.

Referring to <FIG> and <FIG>, a reversible pump-turbine installation in accordance with the present invention is shown. No underground powerhouse is required. Instead, a vertical borehole or shaft <NUM> allows the pump-turbine and motor-generator assembly <NUM> to be installed, removed for maintenance as needed, and reinstalled, while providing the desired low height-of-setting of thee unit below tailwater. The height of setting must be sufficiently low that the plant cavitation coefficient (plant sigma) is greater than the critical cavitation coefficient (critical sigma), the cavitation coefficient being defined as the ratio of absolute pressure at the low-pressure side of the runner divided by the vapor pressure of water at the temperature of the water. Shaft <NUM> connects submersible motor-generator <NUM> to pump-turbine stages <NUM>, <NUM>, <NUM>, and <NUM>. Vertical tailwater conduit <NUM> connects to diffuser <NUM> above the point of entry of penstock <NUM>. Pressure relief valve <NUM> is preferably mounted to removable manifold <NUM>. Removable manifold <NUM> bolts down to foundation <NUM> and connects to tailrace conduit <NUM> at flange 15a. Tailrace conduit <NUM> leads to the lower reservoir not shown. It should be noted that the number of stages may be adjusted according to head, height of setting, speed, installation rating and other factors. Penstock <NUM> connects to upper reservoir <NUM>. Tailrace conduit <NUM> connects to the lower reservoir <NUM>. Water flows through outer annulus <NUM> of borehole <NUM> toward the upper reservoir <NUM> as a pump and towards the pump turbine <NUM>.

It should be noted that the removable portion may be further divided into conveniently separable subassemblies <NUM>, <NUM>, <NUM> and <NUM>. For example, the manifold <NUM> might be lifted off first, the vertical portion of the tailrace conduit <NUM> might be lifted next, and the pump-turbine stages <NUM>, <NUM>, <NUM>, and <NUM> might be lifted last along with the motor-generator <NUM>. In the case of a motor generator on top, the stator might be left in place while the rotor, shaft, and balance of the assembly might be lifted out last.

Referring to <FIG>, a cross section of a pressure relief valve suitable of use in conjunction with the present invention is shown in its opened and closed positions respectively. Diffuser <NUM> is connected to ribs <NUM>. Ribs <NUM>, ring <NUM>, and ring <NUM> together radially support bladder <NUM> on its inner diameter surface when its inflation pressure is greater than the pressure in shaft <NUM>. Inflatable bladder <NUM> is supported from below by flange <NUM> and on its OD by enclosure <NUM>. The air pressure in bladder <NUM> may be precisely adjusted to just stop leakage from shaft <NUM> into manifold <NUM> (at tailwater pressure).

Referring to <FIG> and <FIG> a sectional elevation of a pump-turbine in accordance with the present invention is shown. Runner <NUM> is designed around a toroidal flow path wherein water reverses direction by approximately <NUM> degrees in the meridional plane. Wicket gates <NUM> make up an axial flow distributor. Turbine diffuser <NUM> recovers turbine runner exit energy. Stay vanes <NUM> provide mechanical support to the distributor hub <NUM>, turbine diffuser <NUM> as well as wicket gate servo system <NUM>. Generator <NUM> is preferably located below the turbine. Hoisting piston <NUM> may be used to raise and lower, using water pressure, the entire pump-turbine assembly with connected draft tube segments, pressure relief valve and elbow. Hoisting piston <NUM> may incorporate upper seal ring <NUM> and lower seal ring <NUM> to maintain a seal while passing across the tailrace connection.

Hollow shaft <NUM> may be used as a heat pipe evaporator in conjunction with the runner <NUM> serving as a condenser. Electrical connector <NUM> engages electrical receptacle assembly <NUM> when the machine is lowered. Shifting rings <NUM> and <NUM> provide torque to actuate wicket gates <NUM>.

Borehole <NUM> is associated with rock face <NUM>, grout <NUM> and steel liner <NUM>.

Shaft seal assembly <NUM> keeps the generator enclosure dry.

Piston assembly <NUM> supports generator <NUM> and pump-turbine <NUM> during raising and lowering. Valve <NUM> may be used to shut off water from penstock <NUM>. Tailrace conduit <NUM> connects to tailwater. Cover assembly <NUM> is removable.

Referring to <FIG>, valve <NUM> may be used to fill vertical shaft <NUM> during hydraulic raising and lowering of pump-turbine-motor-generator assembly <NUM> with attached pipe, elbow, and pressure relief assemblies <NUM>, Lower portal <NUM> serves to launch TBM during construction phase and serves as pumping inlet works. Headworks <NUM> serves as upper portal during construction and as service platform during maintenance. Crane <NUM> may be used to disassemble draft tube segments, elbow assembly and pressure relief valve from pump-turbine for maintenance.

Referring to <FIG> an elbow assembly <NUM> is shown. Inflatable seal <NUM> seals the upper end. Inflatable seal <NUM> closes the lower end. Elbow <NUM> directs flow to the tailrace conduit. Spool <NUM> travels with the pump-turbine during maintenance moves.

Referring to <FIG> an installation is shown wherein the machine shaft <NUM> is located under the headworks <NUM>.

Referring to <FIG>, the machine shaft <NUM> is located below the tailrace portal <NUM>.

Referring to <FIG>, machine shaft <NUM> is located at a location between the headworks <NUM> and tailrace portal <NUM>.

Referring to <FIG>, machine shaft <NUM> provides a connection to pressurized reservoir <NUM> as well as to tailrace tunnel <NUM>.

Referring to <FIG> a pressurized water reservoir <NUM> is shown in conjunction with a pressurized air column <NUM>. Pump or pump/turbine <NUM> may be in accordance with this invention or may be conventional. Air <NUM> may be fed to a gas turbine generator set <NUM>.

Referring to <FIG>, spray cooling of the air being compressed may be used to provide isothermal air compression.

<FIG>, <FIG>, <FIG>, and <FIG> depict one of many possible construction sequences.

Referring to <FIG>, a combined seal and PRV <NUM> positioned in machine shaft <NUM> is shown in conjunction with elbow <NUM> and tailrace conduit <NUM>. Machine shaft liner <NUM> is shown.

Referring to <FIG>, another embodiment is shown wherein inflatable seal <NUM> may also serve as a pressure relief valve.

Referring to <FIG> another embodiment is shown with vanes <NUM> in elbow <NUM>.

Referring to <FIG> a runner for a pump or reversible pump turbine is shown wherein flow is directed along a smooth sinusoidal path within the meridional plane. Blades (vanes) impart circumferential acceleration vector and acceleration vectors within meridional plan to guide water through water passageway. Blade sequences may be normal to vector sum. The larger impellar is more efficient and provides higher head per stage. lmpellars may be best made by 3D printing.

Referring to <FIG>, various pressure relief valve configurations are shown.

Referring to <FIG> splitter vanes are used.

Referring to <FIG>, multiple pump turbines are shown sharing a common penstock <NUM> and tailrace conduit <NUM>.

Referring to <FIG>, multiple submersible pump-turbines 62a-62f, installed together in the same machine shaft <NUM> are shown.

<FIG> show pump-turbines configured for installation on a bulkhead in a common machine shaft.

Referring to <FIG>, a medium/high voltage permanent-magnet motor/generator <NUM> and battery storage array <NUM> are connected to a utility grid <NUM> via a single cascade multilevel power converter. The power converter comprises a phase-shifting input transformer <NUM>, power cells incorporating a regenerative-capable front-end <NUM>, isolated DC buses <NUM>, and load-side inverters <NUM>. Each power cell DC bus is connected to a battery bank <NUM> via a disconnect switch <NUM>.

The individual DC bus <NUM> voltages are actively managed during operation to charge or discharge the battery banks <NUM> independently of power consumption or generation by the motor/generator <NUM>.

Referring to <FIG>, a low-voltage permanent-magnet motor/generator <NUM> and battery storage array <NUM> are connected to a utility grid <NUM> via a single two-level power converter. The power converter comprises an active front-end with line-side reactor <NUM>, an intermediate DC bus <NUM>, and a motor-side two-level inverter <NUM>. The power converter is connected to the grid through a disconnect <NUM> and step-up transformer <NUM>. The power converter DC bus <NUM> is attached to a battery array <NUM> through a disconnect switch <NUM>. The DC bus <NUM> voltage is actively managed during operation to charge or discharge the battery array <NUM> independently of power consumption or generation by the motor/generator <NUM>.

Referring to <FIG>, a permanent-magnet motor/generator <NUM> and battery storage array <NUM> are connected to a utility grid <NUM> using parallel and independent power converters. The converters may be connected using individual disconnects <NUM> incorporating protective functions. The motor/generator <NUM> is connected using a regenerative AC/AC power converter <NUM>. The battery array <NUM> is connected through DC bus disconnect(s) <NUM> to a grid-tie inverter <NUM>. A step-up transformer <NUM> increases inverter <NUM> output to grid voltage. Optionally, a disconnect <NUM> is placed between transformer <NUM> and the battery inverter <NUM>.

Referring to <FIG>, a medium/high voltage doubly-fed induction machine <NUM> and battery storage array <NUM> are connected to a utility grid <NUM>. The rotor windings of the electric machine are connected to a cascade multi-level AC/AC drive with connected battery storage as described in <FIG>. The stator windings of the electric machine are connected to the grid through a disconnect <NUM>.

Referring to <FIG>, a medium/high voltage doubly-fed induction machine <NUM> and battery storage array <NUM> are connected to a utility grid <NUM>. The rotor windings of the electric machine are connected to a low-voltage two-level AC/AC drive with connected battery storage as described in <FIG>. The stator windings of the electric machine are connected to the grid through a disconnect <NUM>.

Referring to <FIG>, a medium/high voltage doubly-fed induction machine <NUM> and battery storage array <NUM> are connected to a utility grid <NUM>. The rotor windings of the electric machine are connected to regenerative AC/AC drive <NUM>. The stator windings of the electric machine are connected to the grid through a disconnect <NUM>. The battery storage array is connected to a separate and independent DC/AC inverter <NUM> as described in <FIG>. Referring to <FIG>, multiple medium/high voltage permanent-magnet motor/generators <NUM> are connected to a utility grid <NUM> in an arrangement that allows either direct synchronous connection using direct on-line contactors <NUM> in conjunction with forward/reverse selecting contactors <NUM>/<NUM>, which are interlocked to prevent simultaneous closure. Regenerative power converters <NUM> can be used to bring the electric machines up to synchronous speed in either the pumping or generating mode, or to operate at variable other-than-synchronous speeds. Phase- shift input transformers <NUM> connect the active front-end of the converters <NUM> to the grid via disconnects <NUM>. A matrix of disconnects <NUM> allows any of the electric machines to be operated or started using any of the power converters.

The discussion included in this application is intended to serve as a basic description. The reader should be aware that the specific discussion may not explicitly describe all embodiments possible; many alternatives are implicit. It also may not fully explain the generic nature of the invention and may not explicitly show how each feature or element falling within the claims. Where the invention is described in device-oriented terminology, each element of the device implicitly performs a function. Apparatus claims may not only be included for the device described, but also method or process claims may be included to address the functions the invention and each element performs. Neither the description nor the terminology is intended to limit the scope of the claims included in this patent application.

Particularly, it should be understood that as the disclosure relates to elements of the invention, the words for each element may be expressed by equivalent apparatus terms or method terms-even if only the function or result is the same. As but one example, it should be understood that all actions may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Regarding this last aspect, as but one example, the disclosure of a "means for actuating" or an "actuator" should be understood to encompass disclosure of the act of "actuating "--whether explicitly discussed or not-and, conversely, were there effectively disclosure of the act of "actuating", such a disclosure should be understood to encompass disclosure of an "actuator" and even a "means for actuating". Such changes and alternative terms are to be understood to be explicitly included in the description.

A list of possibly useful reference materials is included on the next page.

Claim 1:
A reversible pump-turbine (<NUM>) adapted to be located in a vertical shaft (<NUM>) from which it is removable and further comprising a removable manifold (<NUM>) fixed to the top of the shaft during operation wherein water flow to and from the reversible pump-turbine is through coaxial penstocks adapted to be positioned in the shaft (<NUM>) above the pump-turbine; and wherein said pump-turbine (<NUM>) comprises:
an impeller with a toroidal flow path through approximately <NUM> degrees in the meridional plane;
a diffuser-guide vane combination into which the impeller discharges; and
a tailrace connection (<NUM>).