GB2471699A - Electrical generation by multiple turbines - Google Patents

Electrical generation by multiple turbines Download PDF

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Publication number
GB2471699A
GB2471699A GB0911918A GB0911918A GB2471699A GB 2471699 A GB2471699 A GB 2471699A GB 0911918 A GB0911918 A GB 0911918A GB 0911918 A GB0911918 A GB 0911918A GB 2471699 A GB2471699 A GB 2471699A
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GB
United Kingdom
Prior art keywords
turbines
turbine
turbine system
generator
speed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0911918A
Other versions
GB0911918D0 (en
Inventor
Charles Pollock
Helen Pollock
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technelec Ltd
Original Assignee
Technelec Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Technelec Ltd filed Critical Technelec Ltd
Priority to GB0911918A priority Critical patent/GB2471699A/en
Publication of GB0911918D0 publication Critical patent/GB0911918D0/en
Publication of GB2471699A publication Critical patent/GB2471699A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B17/00—Other machines or engines
    • F03B17/06—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head"
    • F03B17/061—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head" with rotation axis substantially in flow direction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/02—Wind motors with rotation axis substantially parallel to the air flow entering the rotor  having a plurality of rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2210/00—Working fluid
    • F05B2210/16—Air or water being indistinctly used as working fluid, i.e. the machine can work equally with air or water without any modification
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/40—Use of a multiplicity of similar components
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/50—Kinematic linkage, i.e. transmission of position
    • F05B2260/505—Kinematic linkage, i.e. transmission of position using chains and sprockets; using toothed belts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Wind Motors (AREA)

Abstract

A wind or water powered turbine system uses two or more turbines which each have a diameter smaller than a single turbine sweeping the same equivalent area. The rotational speed of each turbine of the turbine system is therefore higher than a single turbine of equivalent power, so the total volume of electrical generators will be smaller, assuming they are directly driven. Each of the turbines can be mounted within a duct and the ducts can be arranged around a central point. The turbines may be arranged around a single generator, and may be coupled to the generator shaft via a belt or chain drive 103. Two or more turbines may be electrically or mechanically connected in series at low speeds and in parallel at high speeds.

Description

Electrical Generation The present invention relates to an electrical generator driven by two or more turbines, powered by a fluid. The invention is particularly suitable for wind or water powered generators.
The design and power output of wind powered or water powered turbines is limited by several factors: (i) The swept area multiplied by the velocity of the fluid entering the turbine determines the mass flow rate and therefore controls the kinetic energy input to the system. The larger the swept area the larger the kinetic energy which can be converted to electrical energy.
(ii) The tip speed ratio is the ratio of the tip of the turbine blade speed to the incident velocity of the incoming fluid. If the blade speed is too high the efficiency of the turbine reduces because the turbulence of each blade impacts the performance of the subsequent blade passing the same point. For a wind powered turbine the optimum tip speed ratio is known to be -f-, where n is the number of blades. n
Therefore as the power output of a turbine increases, its diameter increases, and its rotational velocity must decrease in order to maintain an optimum tip speed ratio for a given wind speed.
This creates a significant problem for the design of an electrical generator since lower shaft speeds require a higher torque to generate the same electrical power. Typically the size of an electrical machine is determined by its torque rating and so electrical generators directly driven by large wind turbines become very large. This increases the cost of the system and more particularly increases the weight of the system. In a wind powered application the weight of the turbine and generator has to be supported at the top of a tower, thus increasing the strength requirement of the tower.
It is therefore common for larger wind turbines to use a torque converter or gear system to take the lower speed of the turbine up to a higher speed to drive the generator. The geared system adds additional weight and cost. Furthermore, the additional losses and lower reliability of geared systems are undesirable.
It is the object of this invention to provide a system for wind or water powered generation, which improves the power to weight power capability of the system by using two or more turbines each of a diameter which is less than the diameter of a single turbine sweeping the same equivalent area such that the rotational speed of each of the smaller turbines is higher. Since the rotational speed of each turbine of the turbine system is higher than a single turbine of equivalent total power, the total volume of the electrical generators employed in a turbine system according to the invention will be smaller.
In a further aspect of the invention, each of the two or more turbines are mounted within a duct and the ducts are arranged around a central point to create a single structure with the equivalent or greater power rating of a single turbine of similar size.
In a further aspect of the invention the two or more turbines are arranged around a single generator, each turbine coupled to the central generator shaft via a belt or chain drive. The belt drive from each turbine may be used to further increase the rotational speed of the generator thus offering further reductions in the weight and volume of the electrical generator without the complexity of a mechanical gearbox.
The invention will now be described with the aid of the following diagrams in which Figure 1 shows comparative sizes of multiple turbines which have the same swept area as a single turbine; Figure 2 shows one embodiment of the invention with six turbines arranged around a central point; Figure 3 shows a further embodiment of the invention with a single generator at the central point coupled to each turbine with a belt drive arrangement.
Figure 1(a) shows a single turbine which could be used for wind or tidal generation systems. The turbine is shown mounted inside a duct though this is not always necessary. If the single turbine in Figure 1(a) has radius lm then the swept area of the turbine is calculated as it m2.
Figure 1(b) shows two turbines of radius 0.707 m which together have the same swept area as the single turbine in Figure 1(a).
Figure 1(c) shows four turbines of radius 0.5 m which together have the same swept area as the single turbine in Figure 1(a).
Table 1 shows the optimum rotational velocity of each of the turbines in Figure 1 based on a tip speed ratio which gives maximum efficiency. For a wind powered turbine the optimum tip speed 42r ratio is known to be -, where n is the number of blades. Since each of the turbines in Figure 1 is n illustrated with three blades the optimum tip speed ratio is -i. The values in Table 1 are all calculated with a wind speed of lOm/s.
Optimum Roational Velocity with three turbine blades for a wind speed of 10 mIs Area of Each Total Swept Area Optimum Rotational Turbines Radius Turbine m2 m2 velocity (rpm) 1 1.00 3.14 3 400 2 0.71 1.57 3 566 3 0.58 1.05 3 693 4 0.50 0.79 3 800 0.45 0.63 3 894 6 0.41 0.52 3 980
Table 1
From Table 1 it can be seen that using 4 turbines as in Figure 1(c) results in a turbine system in which each of the turbines rotate at twice the rotational angular velocity compared to a single turbine.
Since each of the 4 turbines has half the diameter of the equivalent single turbine the total size of the turbine system is similar. However, the doubling of the rotational velocity creates a benefit for the design of the electrical generators. If each smaller turbine is to deliver 25% of the power of the single larger turbine and is running at 800 r/min instead of 400 r/min the torque output of each turbine shaft is only 12.5% of the torque output of a single turbine delivering the same power. A directly driven generator mounted on each of the 4 turbines would be 12.5% of the size of an equivalent generator on a single turbine. The total volume of electrical generator equipment would therefore be 50% of that of a single turbine directly driving a single generator. If individual electrical generators are mounted on each turbine the output can be DC which can be easily combined in series or in parallel to a single dc supply to feed a single DC to AC inverter for grid connection or electrical supply or a battery charging system. The advantage of multiple smaller generators is that the series and or parallel connections of the DC output of the generators can be electronically switched depending on wind speed to provide a more common voltage output. This overcomes a major problem of prior art directly driven generators employing permanent magnet machines. In such machines the output voltage rises linearly with speed making resulting in small voltages at low wind speeds and potentially damaging voltages at high speeds.
The benefit of a turbine system according to the first aspect invention is that a system of multiple turbines with the same swept area as a single larger turbine according to the prior art provides the following: (i) A reduction in the torque delivered through the shaft of each turbine by a factor which is greater than the number of smaller turbines used in the turbine system; (ii) A reduction in the total volume and mass of generator components to deliver the same equivalent power without requiring the use of a gearbox.
(iii) Potential to series and/or parallel connect the outputs of multiple generators depending on wind speed to produce a more constant voltage to wind speed characteristic. The switching of the output connections can be achieved electronically or mechanically to have at least two in series at low speed and at least two in parallel at high speeds.
A second aspect of the invention is illustrated by Figure 2(a). For illustration this shows the turbine system made up of 6 smaller turbines, each of smaller radius than a single larger turbine. The six turbines are arranged around a central point. Each of the turbines is mounted in a duct. The effect of the duct has been well documented. It eliminates the radial flow of fluid off the ends of the turbine blades and maintains a more linear flow of fluid through the turbine. Each duct can be further enhanced by the addition of a diffuser to create a diffuser augmented turbine. The diffuser is an increasing diameter of the duct at the exit side. The increasing diameter reduces the pressure in the exit fluid and therefore draws more fluid in through the duct entrance. The increased fluid flow through a ducted turbine can increase the power conversion relative to an open sided turbine.
In the structure of Figure 2(a) the central area is blanked off with a shaped nose cone which helps to direct fluid from the central area into the ducts of the multiple turbines.
Figure 2(b) shows a 3D view of this aspect of the invention more clearly showing the nose cone deflecting the incoming fluid stream into the ducts of the turbine system. An example of a possible supporting structure for the ducts is illustrated in Figure 2(b). The turbine blades have not been shown for clarity.
A further aspect of the invention is shown in Figure 3. A single electrical generator 100 is positioned within the central area between the multiple turbines. The torque output from each of the turbines arranged around the central area can be delivered to the shaft of the electrical generator via belt drives or chain drives. One such belt drive 103 is illustrated in Figure 3. A drive pulley 101 would be mounted on the shaft of each turbine and would drive through a slot in the walls of the duct to a follower pulley 102 on the generator shaft. An additional belt drive would be used for each turbine with a suitable axial offset to clear other drive belts. For higher torque transmission without slipping it is possible to use a toothed belt and toothed pulleys.
If the driver pulley is larger than the follower pulley there will be a speed ratio between the turbine shafts and the generator shaft, resulting in a further increase in the generator speed relative to the turbine speed. In this way the size of the generator can be further increased. In the example illustrated in Figure 3 a ratio of 3:1 in the radius of the driver 101 to follower 102 gives a generator speed which is three times the turbine speed. In this example with six turbines, the speed of the generator in a wind speed of 10 m/s will now be 2940 r/min. This results in a very compact generator thus ensuring the complete assembly can be lightweight and easy to install. The strength rating of a supporting tower is therefore greatly reduced. In this example the volume of the generator would be only 13.6% of the volume of the equivalent generator directly driven from a
single prior art turbine with the same swept area.
Additionally because each turbine is transmitting one sixth of the power at 2.45 times the speed the torque on each turbine has been reduced by a factor of 14.7. This means that each turbine can be made from significantly lighter and cheaper materials compared to a single turbine rated to deliver the same total power. It can therefore be seen that a turbine system according to the invention can be manufactured at a very competitive price.
As a further modification and simplification to Figure 3 a single belt can be used to pass around the outer faces of two or more drive pulleys and deliver the combined power of two or more turbines to the generator in a single belt. Since the lap angle of the belt on each pulley is reduced by this arrangement the belt tension would need to be increased to avoid slippage. Alternatively the belt and pulleys can have teeth.
The arrangement of the turbines at evenly disposed radial positions is useful in this arrangement as the side load on the generator shaft is balanced by the pull of all the turbines. Implementation of the invention does not however require the generator to be centrally positioned or the turbines to be equally spaced.
The invention is applicable to all fluid powered generation, though is particularly suited to wind powered generators or water powered generators. It is particularly suited to smaller wind powered generators in domestic and light industrial applications, where a lightweight and low cost unit will encourage its use and make installation easier.

Claims (13)

  1. C'aims 1. A turbine system for fluid powered generation, comprising two or more turbines, the outputs of which can be coupled together mechanically or electrically to create a single electrical output, wherein the diameter of each of the two or more turbines is lower than the diameter of a single turbine of equivalent power rating such that the rotational speed of each of the smaller turbines is higher than a single turbine of equivalent power rating.
  2. 2. A turbine system according to Claim 1 wherein each of the two or more turbines drives an electrical generator and the outputs of each generator are connected together to supply a single electrical output stage.
  3. 3. A turbine system according to Claim 2 wherein the connections between the outputs of the two or more electrical generators can be reconfigured electronically or mechanically to have at least two in series at low speed and at least two in parallel at high speeds.
  4. 4. A turbine system according to Claim 1 in which two or more turbines are arranged around a central area, the central area containing an electrical generator, wherein the mechanical power output from each of the two or more turbines is delivered to the generator shaft using one or more belt or chain drive systems.
  5. 5. A turbine system according to Claim 4 in which the drive pulleys on each turbine are larger than the follower pulley or pulleys on the generator shaft such that the generator speed is higher than the speed of each of the turbines.
  6. 6. A turbine system according to Claim 2 or Claim 4 wherein there are three turbines.
  7. 7. A turbine system according to Claim 2 or Claim 4 wherein there are four turbines.
  8. 8. A turbine system according to Claim 2 or Claim 4 wherein there are five turbines.
  9. 9. A turbine system according to Claim 2 or Claim 4 wherein there are six turbines.
  10. 10. A turbine system according to Claim 2 or Claim 4 wherein there are six or more turbines.
  11. 11. A turbine system according to any preceding Claim wherein each of the turbines is mounted within a duct, the ducts then arranged together to create a single structure.
  12. 12. A turbine system according to any preceding Claim which is used as a wind powered generator.
  13. 13. A turbine system according to any preceding Claim 1-11 which is used as a water powered generator.
GB0911918A 2009-07-09 2009-07-09 Electrical generation by multiple turbines Withdrawn GB2471699A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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GB2471699A true GB2471699A (en) 2011-01-12

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012023866A1 (en) * 2010-08-20 2012-02-23 Pedro Saavedra Pacheco Marine wind turbine with extendable blades
WO2013164005A1 (en) * 2012-05-04 2013-11-07 Ferme Jean-Marc Quadruple francis turbine generator

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1087102A (en) * 1978-02-07 1980-10-07 Motohiro Yamada Windmill structure
FR2795140A1 (en) * 1999-06-17 2000-12-22 Herve Majastre Hydro-electric power generating station includes cylinder with internal helix, rotating as water flows through
DE20201215U1 (en) * 2002-01-18 2002-06-20 Dohm, Rudolf, 13156 Berlin Flow acceleration system for wind and water power plants
US20030170123A1 (en) * 2002-03-07 2003-09-11 William E. Heronemus Vertical array wind turbine
US20030168864A1 (en) * 2002-03-08 2003-09-11 William Heronemus Offshore wind turbine
EP1467093A1 (en) * 2001-07-11 2004-10-13 Hydra Tidal Energy Technology AS Generator for water current turbine with counter-rotating rotors.
JP2005023893A (en) * 2003-06-30 2005-01-27 Systec:Kk Turning force assembled type wind power generating device
EP1550807A1 (en) * 2003-12-30 2005-07-06 Rudolf Dohm Method and apparatus of accelerating the fluid flow in a wind or water driven energy converter
US20060171798A1 (en) * 2003-10-23 2006-08-03 Ocean Wind Technology, Llc Power generation assemblies, and apparatus for use therewith
DE202007010872U1 (en) * 2007-08-03 2007-10-11 Dressel, Stephan Wind turbine
US20090072543A1 (en) * 2007-09-18 2009-03-19 Oa Furniture Co., Ltd. Wind Power System

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1087102A (en) * 1978-02-07 1980-10-07 Motohiro Yamada Windmill structure
FR2795140A1 (en) * 1999-06-17 2000-12-22 Herve Majastre Hydro-electric power generating station includes cylinder with internal helix, rotating as water flows through
EP1467093A1 (en) * 2001-07-11 2004-10-13 Hydra Tidal Energy Technology AS Generator for water current turbine with counter-rotating rotors.
DE20201215U1 (en) * 2002-01-18 2002-06-20 Dohm, Rudolf, 13156 Berlin Flow acceleration system for wind and water power plants
US20030170123A1 (en) * 2002-03-07 2003-09-11 William E. Heronemus Vertical array wind turbine
US20030168864A1 (en) * 2002-03-08 2003-09-11 William Heronemus Offshore wind turbine
JP2005023893A (en) * 2003-06-30 2005-01-27 Systec:Kk Turning force assembled type wind power generating device
US20060171798A1 (en) * 2003-10-23 2006-08-03 Ocean Wind Technology, Llc Power generation assemblies, and apparatus for use therewith
EP1550807A1 (en) * 2003-12-30 2005-07-06 Rudolf Dohm Method and apparatus of accelerating the fluid flow in a wind or water driven energy converter
DE202007010872U1 (en) * 2007-08-03 2007-10-11 Dressel, Stephan Wind turbine
US20090072543A1 (en) * 2007-09-18 2009-03-19 Oa Furniture Co., Ltd. Wind Power System

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012023866A1 (en) * 2010-08-20 2012-02-23 Pedro Saavedra Pacheco Marine wind turbine with extendable blades
WO2013164005A1 (en) * 2012-05-04 2013-11-07 Ferme Jean-Marc Quadruple francis turbine generator

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