GB2467200A

GB2467200A - Series connected underwater turbines

Info

Publication number: GB2467200A
Application number: GB0919132A
Authority: GB
Inventors: James O'donnell
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-11-02
Filing date: 2009-11-02
Publication date: 2010-07-28
Anticipated expiration: 2029-11-02
Also published as: GB0919132D0; GB2467200B

Abstract

A system of submerged turbine driven hydraulic pumps 1 are positioned on a river bed and connected by a network of submerged pipes 2, 57, 58 to drive a hydroelectric turbine / generator 8, 60 which may be mounted at the river bank. The pumps may be connected hydraulically in series to provide a high pressure low flow supply, which may reduce frictional losses in the pipes. The turbines may have a duct / shroud (figures 4-6) and the base may comprise a container with sloping streamlined sides that can be filled with ballast to position the turbines firmly on the river bed. The system allows standard turbine / pump units to be manufactured, and simple installation at different sites.

Description

Submerged Impeller Driven Pump Hydroelectric Power Generation System Hydroelectric power generation offers an immense opportunity as a viable alternative to a number of low carbon emission electrical power generation systems. However current hydroelectric power schemes often involve significant environmental impact to water courses and water systems in areas of natural beauty. Hydroelectric systems commonly involve damming water ways or significant tunnelling into lakes in elevated mountainous locations entailing significant environmental impact and capital expenditure. A major disadvantage of the main forms of hydroelectric power generation scheme is that they are bespoke and entail significant capital cost as a result. Even the smallest of hydroelectric power schemes, usually a run of river type method will involve diversion of water flow to a civil engineering construction e.g. a sluice to channel water to the turbine. The invention described here is mainly applicable to fast flowing river systems while providing minimal installed capital cost and low environmental impact. The other advantage that this invention presents is that it is constructed in modular form and can be installed with minimal capital expenditure and eliminates the requirement for a bespoke designed installation.

The invention described here presents a very simple modular system that can be applied to any location involving a fast flowing river of sufficient depth to allow the submerged modular impeller driven pump units to operate. The submerged impeller driven modular pump units offer a significant advantage in that they can be manufactured relatively cheaply on a mass scale and be installed at a site location for low capital expenditure and minimal environmental impact during the installation phase. A small hydroelectric generator unit and ancillary buildings housing switchgear and transformers does need to be built at the site. However the compact nature of this system allows this to be built in a manner that can be blended in to the surrounding environment with minimal visual impact as practically all of the hydroelectric turbine fluid power generation system is contained below water level. All electrical power transmission and generator cabling connection is installed on dry land (e.g. a river bank) and therefore hazards associated with electrocution of fish and other water users through leakage of current or cable damage in the water is avoided. Further environmental impact reduction measures employed by this system are that the hydroelectric power unit water flow is within a self contained submerged loop connecting the submerged impeller driven pump units. Therefore no turbidity is created in the river by a hydroelectric power generation turbine discharge. The only interaction with the flow of water in the environment is between the impellers and water flow around the submerged nacelles, structures and piping. However these submerged items even collectively do not present a significant restriction to the water flow in the river system and thereby this limits environmental damage. The design of this system also lends itself very well to the use of non corrodible materials and particularly in the encasement of concrete items used as ballast and integrity of the main support structure.

The invention will now be described by the following figures: Figure 1. Overview of a typical installation at a river location.

Figure 2. Simple line drawing schematic of multiple submerged impeller driven pump system.

Figure 3. Illustration of theoretical overlaid pump and system curves for multiple submerged impeller driven pump system.

Figure 4. Cross section of typical submerged impeller driven pump system.

Figure 5. Illustration of typical submerged impeller driven pump system.

Figure 6. Section illustrating base section construction of submerged impeller driven pump system.

Figure 7. Layout of a submerged multiple submerged impeller driven pump hydroelectric system Figure 8. Typical schematic of a reaction type turbine for use on multiple submerged impeller driven pump hydroelectric power generation system.

Figure 9. Illustration of a layout where multiple submerged impeller driven pump units are connected in parallel configuration.

Figure 10. Illustrative flow pattern around submerged impeller driven pump system.

By reference to figure 1 each submerged impeller driven pump unit 1 is connected in series to another unit via an interconnecting pipe 2. The pipe 2 can be constructed from a number of materials, the preferred material type being a plastic made with an armour coating similar to those on offer by a number of manufacturers who specialise in subsea flow line installations. However rigid metallic pipe could also be used but is not the favoured approach for a number of reasons, mainly corrosion and cost, for the purposes of description of this invention materials will not be referenced directly. For a given number of submerged impeller driven pump units 1 the first stage takes its suction 3 from the discharge of the hydroelectric turbine 4 via the main suction flow line 58 and discharges 5 to the suction of the next unit and so on to the final impeller driven pump unit. The discharge 6 of the final impeller driven submerged pump unit feeds into the intake 7 of the power generation turbine 8 via a mina discharge flow line 57. Therefore the system operates in a closed loop with energy input to the pumps via the interaction of the impellers 9 and the water flow that rotates them to drive the pump 20 contained within the nacelle 11 via a gear box 18. Figure 2 illustrates the concept in terms of a schematic illustrating five submerged impeller driven pump units 1 in a closed loop, the overlaid curves illustrated in figure 3 are to be read in conjunction with figure 2. Each flow line 2, 57, 58 has a frictional pressure loss generated by fluid flow through the line 2, 57, 58. This pressure loss is illustrated as LPf in the following equations with n being the number of submerged impeller driven pump units. Each individual submerged impeller driven pump unit 1 generates a pressure increase LPunit n. The difference in the summation of pump pressure increases and pressure losses is equal to the available pressure to the hydroelectric power generation turbine 8.

Pressure Across Turbine Sum of submerged impeller driven pump lift pressures -Sum of head and frictional losses in connecting piping system P1 -PD E=1 LPunit n - tPf n + 1 Power = (P1 -PD) . r1 -Q flelec Fluid to electrical power conversion efficiency (%) Q = Fluid volumetric flowrate within pump/generator loop (m3/s) P Power turbine intake pressure (N/rn2) PD= Power turbine discharge pressure (N/rn2) P= Pressure increase across submerged impeller driven pump unit (N/rn2) IWfn= Pressure losses due to pipe internal friction and elevation head (N/rn2) n = Number of submerged impeller driven pump units When referring to figure 3 in conjunction with figure 2 the concept is illustrated where multiple centrifugal pumps operating in series can lift the head available to a power generation turbine to significant levels. Figure 3 illustrates the concept for a five pump series system as illustrated in the schematic in figure 2. In figure 3 the system curve 40 a, b, c, d, e illustrates the losses in the discharge piping system for a given pump, the point at where it originates on the V axis 45 (pump generated head in metres) of the plot is where its suction versus discharge elevation head lies on the plot. The overlaid curves on figure 3 represent how the submerged impeller driven pump unit 1 pump curves 41 a, b, c, d, e in series for a five centrifugal pump units connected in series would behave. For given operating conditions the pump head curve 41 and system curve 40 intersect at the duty point 42. The system curves 40 originate at 43 a, b, c, d, e for each point on the head axis 45.Note that pump units when installed in series elevate the pressure across the whole system additively resulting in a much higher pressure available for a given flow to the hydroelectric turbine 8 than if a single submerged impeller driven pump unit 1 had been used.

It is also possible using the system as illustrated in figure 9 to connect the submerged impeller driven pump unit in parallel, in this case the pump head generated is low and equal to that from a single centrifugal pump 20 contained within the submerged impeller driven pump unit 1 and the flow is rnaximised. This system although it generates a low head will allow a larger flow of fluid in the pump and piping network and utilisation of a different type of turbine 8. However for the purposes of describing the invention the connected flow circuit referred to will be connected in series. Other alternative configurations can involve dispensing with the pipe 57 between the discharge of the hydroelectric power turbine 8 and the suction of the first submerged impeller driven pump 1 in the network. This may offer marginally improved power output in open loop configuration. However the discharge of the power turbine tail race 37 may cause significant scouring on a riverbed or riverbank adjacent to its discharge point. An additional issue with the open loop configuration is that the intake 21 of the first stage pump 20 would need to have some form of solids removal as suspended solids would be likely to be present and ingress to the system via the pump suction in the form of organic and inorganic material would be highly likely. Hence a closed system offers a number of reliability advantages mainly associated by isolating the hydroelectric power fluid from the environment.

Referring to figure 1 a number of modular impeller driven pump units 1 are submerged in a river and the impeller units 9 are driven by the flow of water in the river. With reference to figure 4 the submerged impeller driven pump unit consists of a number of main features: the impeller 9 and its ducting 10, the nacelle 11 housing the centrifugal pump 20 and drive components, the base 28 and the sub assembly 26 retaining the nacelle 11 and impeller 9 and duct 10. The impeller 9 is connected to a common shaft 14 that is supported by a sealed bearing 15 leading to a primary coupling 16 and then a secondary coupling 17 to the gearbox 18. The gear box 18 increases the speed of the pump shaft by the impeller speed multiplied by the gear ratio to drive the pump shaft 19 and intake and discharge fluid via the pump 20. The nacelle housing 11 is of streamlined shape to avoid propagation of wake from the impeller and limit the efficiency of downstream units as illustrated in figure 10. The pump 20 intake 21 is at the rear of the nacelle 11 via an opening 22 at that point. The centrifugal pump 20 discharges via 23 through another opening 24 in the nacelle 11. The pump 20 intake 21 is connected to a suction line 25 either from the discharge of a previous submerged impeller driven pump unit or from the discharge line 57 from the power generation hydroelectric turbine 8. The nacelle 11 can either be sealed or allowed to operate in flooded mode. It is essential that the sealed components are: the common shaft bearing 15, gear box 18, centrifugal pump 20 internal bearings via pump 20 internal seals. Proprietary equipment for marine environments can be used for all of these applications and no particular manufacturer is required to be recommended and a number of component designs offered in the market place are suitable. The nacelle 11 and main rotational components contained within sit on a sub assembly 26; the sub assembly 26 supporting the nacelle 11 is made up of 2 separate sub assemblies. Sub assembly26 connects to another sub assembly 27 that is part of the base 28 structure. The sub assemblies 26, 27 can be mated in a number of ways, either by a mechanical locking device using male and female components or by bolting 29 in a diver assisted operation as illustrated in figure 5.

A key feature of the base structure 28 is that it is of sufficient inertia, not to be moved by the flow of the water body that the power is being extracted from and that it does not generate adverse flow patterns itself. Therefore the base structure 28 is of sloping design on all of the facings to allow minimum resistance to the flow from the streamlined nature of the base structure 28 and the nacelle 11 is illustrated in figure 10. The base structure 28 is made up of three main components: an outer casing 30, a concrete/cement fill 31, the lower sub assembly 27 immobilised in the concrete/cement fill 31. The outer casing 30 is made up of a top half 30 b and bottom half 30 a to allow installation of the impeller driven pump unit lower sub assembly27. Concrete is a key component in allowing the submerged impeller driven pump unit to remain static against the flowing stream without the need for using piles to fix the submerged impeller drive pump unit 1 to a river bed. Concrete/cement used in an unconfined manner in a fast flowing stream would eventually break down due to erosion. Therefore the base structure casing 30 also acts as the environmental barrier against degradation of the ballast material, concrete/cement fill 31. The relatively low profile of the base structure 28 to the stream flow as illustrated in figure 10.

To minimise environmental impact during installation it is essential that the procedures reflect the sensitivity of the installed location and the hazards associated with installing submerged equipment in a fast flowing river environment. The installation procedures would be specific to the conditions where the unit was installed, i.e. for a wide relatively shallow river close to the estuary the use of construction vessels would be necessary and for example the base structure 28 could be taken to location along with the nacellell and top sub assemble 26 and lower sub assembly 27 pre-mated and lifted and lowered in to location in one operation, similarly multiple units already connected up by flexible piping 2, 57, 58 could also be lowered in to position. For illustrative purposes in figure 6 the base structure 28 upper casing 30 b has shown fill hole 32 and vent post 33, where fluid concrete would be introduced via the fill hole 32 and air discharged via the vent hole 33. This concrete filling operation could take place on site with appropriate hosing and valves in the fill system to minimise environmental impact.

As described the series connection of the submerged impeller driven pump units allows a substantial increase in pressure across the network and use of high pressure drop reaction type turbines 34 as illustrated in figure 8. To allow the installation and operation of a reaction type turbine 34 to drive a generator 60 a series connection of the submerged impeller driven pump units 1 as illustrated in figure 7 would be required. To allow a network of submerged impeller driven pump units to operate a number of ballasting weights 51 would need to be used on the interconnecting flow lines 2 and the main hydroelectric turbine 8 discharge flow line 58 and hydroelectric turbine 8 suction flow lines 57.

The ballasting weights 51 would be used to absorb hydraulic loads induced by flow transients within the piping or external forces applied during periods of extreme river flow. As mentioned previously flow induced transients are an undesirable effect in using this method of hydroelectric power generation in particular in the closed loop configuration described. A key part of avoiding flow induced transients and centrifugal pump 20 damage is to avoid cavitation and ensure the closed loop system has flow lines 2, 57, 58 completely filled with water or water plus additives. To achieve a complete fill of the closed loop system 2, 57, 58 it is essential that the fill of the system is completed via a valve line up that allows all air to be vented off and displaced through a high point in the system. To achieve complete system fill water is introduced with the following valve line up by reference to figure 8, the main isolation valve 52 is in the closed position prior to initiating the fill up of the system and fluid is introduced via the inlet fill valve 62 and air is vented of through the vent valve 61 until water is seen to flow continuously from this point indicating that the whole system is completely filled and that no air pockets that could propagate cavitation are trapped within the system. Once the system fill is confirmed the main isolation valve 52 is opened and the vent valve 61 and fill valve 62 are then closed and the system is available to operate.

As previously referred to this description of the invention refers to a series configuration to describe how the power to a hydroelectric turbine 8 and generator 60 can be increased by increasing pressure across a number of submerged impeller driven pump units 1 connected in series configuration. As illustrated in figure 9 a parallel configuration of submerged impeller driven pump units 1 can be constructed and this ensures that instead of additive head/pressure from each submerged impeller driven pump unit 1, flow is increased with each submerged impeller driven pump unit 1 operating at similar suction and discharge pressures.

As illustrated in figure 10 a key feature of this invention is the ability to absorb energy from a flowing river while being hydrodynamically streamlined as illustrated by the streamlines 46 around the nacelle 11 and base structure 28.

Claims

Claims 1. A hydroelectric power generation system where submerged impeller driven pump Units generate fluid movement collectively in a system using interconnecting pipes between the pumps to drive a hydroelectric power generation turbine unit with the individual submerged impeller driven pump units attached to dedicated base structures incorporating ballast material.
2. As defined in claim 1 a submerged impeller driven pump unit with a ducted impeller system connected via a gear box and coupling mechanism driving a pump enclosed within a hydrodynamically streamlined nacelle.
3. As referenced in claim 1 multiple submerged impeller driven pump units connected between pump suction and discharges via a piping system in a submerged loop that supplies driving fluid pressure to a hydroelectric power generation turbine to generate electrical power.
4. As defined in claim 1 a submerged impeller driven pump unit mounted on a sloped face base structure that acts as cladding for a ballast material to prevent movement of submerged impeller driven pumping unit by water flow it is extracting energy from.
5. As referred to in claim 1 submerged impeller driven pumping unit lower sub structure incorporated in the base structure and encased in ballast material within the base structure.
6. As defined in claim 1 multiple submerged impeller driven pump units connected via piping that is primed via a system of isolation, fill and vent valves to expel air pockets within the interconnecting piping system ensuring that piping is completely liquid filled to eliminate pump cavitation. iAmendments to the claims have been filed as follows 1. A hydroelectric power generation system where a plurality of submerged ducted impeller driven centrifugal pump units connected in series with each other within a closed loop generate fluid movement collectively in a closed fluid filled system using interconnecting pipes between the pumps suction and discharges to drive a hydroelectric power generation turbine unit connected within the same loop as the submerged impeller driven pump units.2. A hydroelectric power generation system as defined in claim 1 where a submerged impeller driven pump unit employing a ducted impeller system connected via a gear box and coupling mechanism driving a centrifugal pump enclosed within a hydrodynamically streamlined nacelle that incorporates ports for pump suction inlet and discharge outlet pipes.3. A hydroelectric power generation system as defined in claim I where multiple submerged impeller driven centrifugal pump units connected between adjacent pump suction and discharges via a piping system in a submerged loop in series with each other that supplies elevated driving fluid pressure to a reaction type hydroelectric power generation turbine to generate electrical power.4. A hydroelectric power generation system as defined in claim 1 where multiple submerged impeller driven pump units incorporate within each unit a single centrifugal pump driven by a dedicated ducted impeller coupled to it via a gearbox.5. A hydroelectric power generation system as defined in claim 1 where a plurality of submerged impeller driven pump units connected in a closed loop to a hydroelectric power generation system whereby all electrical power transmission and generator cabling connection is installed on dry land. * S S * a. a a a _. .S L