FI20205269A1 - Method and apparatus for Darrieus wind turbine with adjustable geometry - Google Patents
Method and apparatus for Darrieus wind turbine with adjustable geometry Download PDFInfo
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- FI20205269A1 FI20205269A1 FI20205269A FI20205269A FI20205269A1 FI 20205269 A1 FI20205269 A1 FI 20205269A1 FI 20205269 A FI20205269 A FI 20205269A FI 20205269 A FI20205269 A FI 20205269A FI 20205269 A1 FI20205269 A1 FI 20205269A1
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- turbine
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- wind turbine
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- 238000000034 method Methods 0.000 title description 2
- 230000008878 coupling Effects 0.000 claims abstract 2
- 238000010168 coupling process Methods 0.000 claims abstract 2
- 238000005859 coupling reaction Methods 0.000 claims abstract 2
- 230000007246 mechanism Effects 0.000 claims description 7
- 230000000694 effects Effects 0.000 claims description 5
- 238000005457 optimization Methods 0.000 claims 1
- 239000002184 metal Substances 0.000 abstract description 4
- 238000013461 design Methods 0.000 abstract description 3
- 239000002131 composite material Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 abstract description 2
- 239000004020 conductor Substances 0.000 abstract 2
- 229920000049 Carbon (fiber) Polymers 0.000 abstract 1
- 239000004917 carbon fiber Substances 0.000 abstract 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
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- 238000013459 approach Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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- 239000011150 reinforced concrete Substances 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
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- 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
- F03D7/00—Controlling wind motors
- F03D7/06—Controlling wind motors the wind motors having rotation axis substantially perpendicular to the air flow entering the rotor
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- 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
- F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor
- F03D3/06—Rotors
- F03D3/062—Rotors characterised by their construction elements
- F03D3/064—Fixing wind engaging parts to rest of rotor
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- 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
- F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor
- F03D3/06—Rotors
- F03D3/062—Rotors characterised by their construction elements
- F03D3/066—Rotors characterised by their construction elements the wind engaging parts being movable relative to the rotor
- F03D3/067—Cyclic movements
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- 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
- Y02E10/74—Wind turbines with rotation axis perpendicular to the wind direction
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- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Wind Motors (AREA)
Abstract
This invention relates to a Darrieus wind turbine with “free” airfoil blades attached to the rotating turbine structure only at or close to their lower ends, the means of attachment affording the adjustment of the opening angle of the blades with respect to the axis of the turbine, where • the simultaneous, uniform adjustment of the distance of all said blades (20) from the axis of said turbine is coupled with the simultaneous, uniform adjustment of the opening angle of all said blades (20) with respect to the axis of said turbine, an example of said coupling being a quadrangle linkage (30), and said adjustment is also coupled with the cyclical adjustment of the geometry and/or angle of attack of each said blade (20) during each rotation of the turbine, and • said blades (20) can be placed against the central mast (50) of the turbine in the case of severe weather, and • as said central mast (50) acts as a lightning conductor, no metal conductors or metal parts are needed in said blades (20) which, if made from materials such as carbon fiber composite, cause much less radar and EM interference than propeller turbines of the known art. This invention opens the way to a much lighter design of the turbine and its supporting structures such as lattice girder tripods.
Description
Method and apparatus for Darrieus wind turbine with adjustable geometry The typical solution in wind energy is a horizontal axis, three-bladed propeller turbine described in US6752595 and US6940185 and the references mentioned therein.
As the drawbacks of this technology have become apparent, a discussion has arisen in the technical literature about a coming transition to vertical-axis turbines (1). First, current turbines must withstand the worst possible storms in their operating geometry.
The forces encountered in heavy storms reguire strong structures: for example, the rotor and blades of the Enercon-126 turbine (2) with a maximum output of 7,5 MW have a mass of 384 tons.
The total mass of this turbine including its reinforced concrete foundation is ca. 6,000 tons, yielding a power-to-mass ratio of only 1,25 W per kg.
The basic reason for this “mass catastrophe” is that the output of a wind turbine tends to be proportional to the square of its dimensions while its mass tends to grow as the cube of its dimensions.
This requires a new approach in wind turbine technology.
Second, propeller turbines have to be turned to face the direction of the prevailing wind.
Elaborate and costly mechanisms are needed to turn these hundreds of tons of mass; in turbulent winds it is impossible to continuously follow the changes of wind direction and much energy is lost.
Third, the generator housing of the Enercon turbine has a diameter of 12 m and is located at a height of 135 m.
Together with a propeller 126 m in diameter this structure is visible over distances of tens of kilometers.
To this visual impact must be added the radar and S general EM interference caused by the metal in the rotating propeller. 3 © Fourth, the speed of the blade tips of propeller turbines cannot be increased at will because = of the rapidly increasing noise generated.
The noise is produced as the vortex formed + 30 behind the blade tip is reflected from the massive tower of the turbine each time a tip 3 passes close to the tower; this, together with the aerodynamic losses that increase rapidly N with the tip speed, limit the latter to ca. 80 m/s.
This limits the maximum rotational speed N of the turbine; in the case of Enercon-126 the maximum speed is as low as 11,7 rev/min.
The torgue needed to transmit 7.5 MW at 11,7 rev/min is 37 million newton-m, which reguires massive mechanical structures and generators of enormous size and mass.
These difficulties are directing the attention to vertical-axis wind turbines. Early such turbines and some current ones utilize the so-called “scoop and drag” phenomenon, where the drag force exerted by the wind on the turbine is not directed at the axis of the turbine, but deviates from it forming a momentum that rotates the turbine. An example of this is the Savonius rotor (GB244414), whose later developments are described in Ref. 4. In these turbines the peripheral velocity of the rotor is close to the wind velocity. From this follows their low efficiency and low specific power (i.e., their power per unit area of their active surface); several attempts, e.g., US7008171, have not resulted in substantial improvements. Better efficiency and specific power can be attained with narrow airfoil blades that move around a vertical axis at a velocity substantially higher than the wind velocity, as presented by Darrieus in US1835018 already in 1931. The majority of Darrieus wind turbines have either curved blades attached at both ends to a vertical axis, or rigid vertical blades attached to a rotating frame, as described in US5503525. The velocity of wind tends to increase with altitude above the earth’s surface. By setting the blades of a vertical-axis turbine at a positive opening angle with respect to the axis of the turbine, the peripheral velocity of a blade rotating at a given rate also increases with increasing height. This enables the whole blade to operate close to the optimum ratio of its peripheral speed to that of the medium (cf. (3)). This is approached in US4168439, where blades set at an opening angle of 45° with respect to the vertical axis of the turbine are attached to a rotating horizontal ring. The N blades are mounted on bearings on the ring to enable control of their pitch angle with > respect to the air flow meeting them. An analogous solution where blades are also set at a o fixed opening angle is presented in US4355956.
E In GB2175350 are presented several arrangements where the blades of a vertical-axis e turbine are articulated onto the axis of the turbine to enable adjustment of the opening S angle of the cone of motion of the blades. The blades have shrouds to carry the central N forces arising from their rotation. Similar solutions are presented in US5584655 and JP2003222069.
US8272840 and US8496433 describe Darrieus wind turbines where vertical airfoil blades are articulated to supporting arms to enable the changing of their angle of attack.
This is used to maintain a nearly constant speed of rotation of the turbine under varying wind conditions.
The possibility of uniformly changing the distance of all blades from the rotation axis and thus enabling the turbine to operate at higher rotation speeds in strong winds is not mentioned.
The visual and radar impact of the turbine remain unimproved in these inventions.
US8322989 presents a vertical-axis wind turbine where “vanes” can be moved closer or farther from the central axis of the turbine.
Although not a Darrieus turbine, this invention is noteworthy because it presents the idea of moving the active surfaces against a central mast in the case of severe weather.
US 2010/ 0172759 Al presents a large number of wind turbines with retractable blades; the one shown in Fig. 27 of the said application is reproduced in Fig. 1. According to the application the figure is “an example of a flexible blade wind turbine with airfoil that mounts on a pole 100. The airfoil blades 101 are made of a flexible material so that they will flex in the wind and yet be operational at even high wind speeds.
The blades have pegs 102 at the bottom which sit a in a holder 103 that is connected to a central rotating shaft 104 that powers the generator.
Alternatively, the rigid holder may be replaced by a spring mechanism that could allow the blades collapse all the way down to the pole.” Independent Claim 1 of the said application claims protection for “An energy generating wind turbine comprising a plurality of airfoil shaped blades and a central rotating shaft in which said blades are retractable to a smaller sweep diameter and the degree of retraction N is determined by the position of a floating hub on said central shaft of said wind turbine; 3 wherein said blades are connected to said floating hub by support arms.” © = Independent Claim 9 of the said application claims protection for “An energy generating * 30 wind turbine comprising a plurality of airfoil shaped blades connected to support arms e connected by pivot joints to fixed hubs on a central rotating shaft in which said blades are S retractable to a smaller sweep diameter and the degree of retraction is determined by N mechanical means that effect the angle of said support arms.” The Figure, its description and the Claims guoted above fail to describe how the proposed “retractions”, “collapse” and “angle of said support arms” are to be realized in practice.
Moreover, the important matter of a synthesis of these suggestions into a functioning wind turbine is not discussed. The objective of the present invention is to fill this gap with specific mechanisms described below in the Embodiments and the appended Claims. The above ideas are here integrated into a mechanism where the simultaneous, uniform adjusting of both the opening angle and the operating radius of the turbine blades is combined with the cyclical adjustment of the pitch angle and the airfoil shape of individual turbine blades during each revolution of the turbine.
This invention opens the way for “smart” wind turbines that use a processor to continuously optimize their geometry in varying wind conditions and protect themselves against severe weather. These turbines also concentrate the approaching air flow to enhance their power production.
The variable-geometry mechanism is illustrated in Fig. 2, where Fig. 2a shows the blade (20), blade support (30) and the rotating base of the turbine (10) in the “light wind” position. In moderate winds (Fig. 2b) the blade support (30) is raised to a vertical position while the opening angle on the blade is simultaneously reduced. In strong winds (Fig. 2c) the blade is raised to a nearly vertical position and brought still closer to the axis of the turbine. In the case of dangerous storms (Fig. 2d) the blade (20) is pressed against the central mast (50) of the turbine. The extension of the principle of variable geometry into the airfoil blades is described in Embodiment 2 and the appended Claim 6.
S ™ In stronger winds the rotation speed of the turbine is increased while the blades are 2 brought closer to the turbine axis. In addition to increased energy production, this reduces = the size and mass of the directly coupled generator. In addition, by removing the + 30 reguirement that the turbine be able to withstand the strongest storms in its operating e geometry, this invention opens the way to much lighter design of turbines and their S supporting structures, such as lattice girder tripods.
N Turbines of the present art generally contain metal in their blades for structural strength, lightning protection or the need to heat them for their deicing. The composite blades of the present turbine will flex as they rotate and special coatings can be used on them to enable them to shed any ice formed. These metal-free blades will cause only minimal radar or general EM interference and will have a naked-eye visibility of only a few km. This invention is described in the following Embodiments and the appended Claims with 5 reference to the accompanying drawings. Fig. 1 shows the prior art as described in in US 2010/0172759 Al; Fig.2 shows schematically the variable-geometry system of the present invention. Fig. 3 shows an Embodiment of the system employing a quadrangle blade support mechanism. Fig. 4 shows blade extensions 22 placed below blade bearings 21. Fig. 5 shows a schematic cross section of an airfoil blade. Embodiment 1 An embodiment of the adjustable-geometry feature of the present invention is shown schematically in Fig. 3a. The turbine consists of a rotating central platform 10 on which beams AC and BD supporting the lower ends of blades 20 are attached with bearings. These linkages are a variation of a parallelogram linkage (Fig.3b) where the opening angle of blade 20 would remain zero while its distance from the axis is varied. In Fig. 3a members CD are longer than members AB. These quadrangles couple the opening angle of the blade to its distance from the axis of the turbine, allowing a simultaneous adjustment of these two degrees of freedom with hydraulic or mechanical actuators 40 placed between the linkages. In Fig. 3a the ratio of the two short sides of the N linkages is 3:2, causing the opening angle of the blades to change from ca. 30? in the “light > wind” position shown to ca. - 19 in the “storm” position where blades 20 are pressed o against central mast 50.
E The directly coupled generator is attached to the rotating platform 10 and placed in e housing 15 attached to tripod 13. As the turbine torgue transmitted to the tripod structure S will become guite large during wind gusts or electrical shorts, the tripod is eguipped with N guy cables that connect the top of each leg to the base of the leg behind; assuming counter-clockwise rotation one such cable 99 is shown in Fig. 3a.
The pitch angle of each blade 20 attached to bearings 21 is cyclically adjusted during each rotation of the turbine. Together with the continuous adjustment of the turbine geometry, its speed of rotation and its blade geometry described in Embodiment 2, this affords the building of “smart” wind turbines that continuously maximize their energy production and also protect themselves from violent storms with the help of suitable wind and other sensors. The energy production of a turbine of given size can be increased by equipping its blades 20 with extensions 22 below bearings 21 and modifying actuators 40 to accommodate the extensions (Fig. 4).
The Betz effect (3), the tendency of the airflow to pass around a wind turbine, limits the efficiency of one-propeller turbines to a theoretical maximum of 59,3 %. Higher efficiency can in principle be attained in vertical-axis turbines because some of the airflow bypassing the upwind blades can be deflected into the downwind ones. This is done with external “concentration” structures in US 2010/ 0303618 Al; in the present invention this effect is produced with a cyclical blade pitch function that causes the bypass airflow to be deflected into the cone formed by the rotating blades of the turbine. The present Darrieus turbine may be compared with the “scoop and drag” turbine described in US7766601 where the independently moved blades are attached to the turbine structure at both ends. Embodiment 2 Fig. 5 shows schematically a cross section of a turbine blade divided longitudinally into N two sections to enable a continuous adjustment of the blade curvature during the operation > of the turbine. The main part 100 of the blade is reinforced with box beam 101 and is 2 connected with hinge 102 to separately adjustable tail part 103 reinforced with box beam = 104. Actuators similar to those used in airplane technology, e.g., US9663221 B2, can be + 30 used. o 3 N References:
1. Review of Savonius wind turbine design and performance, M.Zemamou,* A. Toumi? 3 Energy Procedia Volume 141, December 2017, Pages 383-388.
2. See www.enercon.de.
3. K. D. Jones, C. M. Dohring, and M. F. Platzer. "Experimental and Computational Investigation of the Knoller-Betz Effect", AIAA Journal, Vol. 36, No. 7 (1998), pp. 1240-
1246.
4. B. Sgrensen, Renewable Energy, Second Ed., Academic Press, Fig. 4.75.
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Claims (6)
1. A Darrieus wind turbine comprising a plurality of airfoil blades (20) connected to support arms connected by pivot joints to fixed hubs on a central rotating shaft in which said blades are retractable to a smaller sweep diameter and the degree of retraction is determined by mechanical means that effect the angle of said support arms, characterized in that e the simultaneous, uniform adjustment of the distance of all said blades (20) from the axis of said turbine is coupled with the simultaneous, uniform adjustment of the opening angle of all said blades (20) with respect to the axis of said turbine, and the Darrieus wind turbine further comprises means for the cyclical adjustment of the geometry and/or pitch angle of each said blade (20) during each rotation of the turbine, and that said coupling is effected by two quadrangle linkages (30) between the blade bearings (21) and the central platform (10), and a mechanical and/or electrical connection of said linkages with the mechanism that changes the geometry of said blades (20).
2. Darrieus wind turbine according to Claim 1, characterized in that said quadrangle linkages comprise upper short members (C-D) that are longer than the opposite short members (A-B).
3. Darrieus wind turbine according to Claim 1 or 2, characterized in that said turbine is provided with means for placing the blades (20) of said turbine against a mast S (50) in the case of severe weather. 8 © 4. Darrieus wind turbine according to any Claim 1 — 3, characterized in that said = turbine is equipped with means of attaching said blades (20) onto a mast (50) in the a > 30 case of severe weather.
S N 5. Darrieus wind turbine according to any Claim 1 — 4, characterized in that said N turbine is eguipped with a processor that receives information about the condition of the turbine, wind speed and direction and other variables to afford a continuous optimization of the geometry of the turbine as well as that of the individual blades,
the blade pitch functions, and the rotation speed of the turbine, and also to convert the turbine into a “severe weather” condition when necessary.
6. Darrieus wind turbine according to any Claim 1 — 5, characterized in that said turbine comprises blade extensions (22) attached to each blade (20) below blade bearings (21). o
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Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20205269A FI20205269A1 (en) | 2020-03-16 | 2020-03-16 | Method and apparatus for Darrieus wind turbine with adjustable geometry |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20205269A FI20205269A1 (en) | 2020-03-16 | 2020-03-16 | Method and apparatus for Darrieus wind turbine with adjustable geometry |
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| Publication Number | Publication Date |
|---|---|
| FI20205269A1 true FI20205269A1 (en) | 2021-09-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| FI20205269A FI20205269A1 (en) | 2020-03-16 | 2020-03-16 | Method and apparatus for Darrieus wind turbine with adjustable geometry |
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| FI (1) | FI20205269A1 (en) |
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