Diffuser-augmented vertical axis wind turbine

Abstract

A diffuser-augmented vertical-axis wind turbine (VAWT) assembly (100) for pole-mounted applications is disclosed. The assembly includes a rotor with blades (106) and hub (112) rotating about a vertical axis (300) within a casing (102) that defines a lower air inlet and an upper air outlet. A louvre grille diffuser (104) positioned over the outlet includes tilted slats (302) forming grille apertures (206) for air discharge. The diffuser is located in close proximity to the blades, with the apertures spaced less than a fraction of the rotor radius above them, creating a reduced-pressure region that accelerates airflow and increases power output. Photovoltaic panels (204) mounted on the slats enable combined wind and solar generation with minimal airflow obstruction. The casing may include upper and lower portions and a lip overlapping blade tips to reduce bypass airflow. The assembly may be pole-mounted and integrated into a street lamp.

Description

[0001] DIFFUSER-AUGMENTED VERTICAL AXIS WIND TURBINE

[0002] The present invention relates to vertical axis wind turbine (VAWTs), for example VAWTs that are pole-mounted with integrated solar panels.

[0003] Background

[0004] Pole-mounted equipment is used for applications in security, communication, lighting and environmental sensing. Pole-mounted equipment includes cameras, radio transceivers and network hubs, lights and sensors. Such equipment requires power to operate and this is typically provided by a connection to the electrical power grid at the base of the pole.

[0005] It is desirable to have less reliance on grid energy by generating renewable energy on the pole. This allows operation in remote or temporary locations away from the grid.

[0006] A vertical axis wind turbine is well suited for mounting on a pole as it can be turned by wind coming from any direction. It does not need moving parts to point the rotor into the wind. However, careful consideration has to be given to the airflow around the turbine so that it efficiently generates energy from the wind, which when blowing in a horizontal direction is perpendicular to the vertical turbine axis.

[0007] Conventional diffusers, also referred to as shrouds, are aerodynamic structures commonly used in turbomachinery for aircraft engines and have been used for applications in wind energy technology. Their primary function is to enhance wind turbine performance by accelerating airflow through a funnel-shaped structure, thereby increasing power output. By optimizing air mass flow, such diffusers contribute to improved turbine efficiency by raising the rotor's rotational speed (RPM) while reducing its starting torque. Additionally, they facilitate more stable turbine operation across a broader range of wind speeds, including low-wind conditions and turbulent environments, by providing enhanced extraction power.Such diffusers are suitable for horizontal axis wind turbines (HAWTs) where the wind direction is primarily along horizontal axes.

[0008] However, conventional diffusers are less useful for VAWTs, where the horizontal wind direction is perpendicular to the vertical turbine axis.

[0009] To achieve less reliance on grid energy, another solution to generate energy on the pole is to use solar panels mounted on the pole.

[0010] A problem arises when combining solar panels on the pole with the pole-mounted wind turbines. There is a competition for space on the top of the pole for both the wind turbine and the solar panels.

[0011] To combine pole-mounted wind and solar generation, the solar panels may be kept away from the wind turbine and its airflow exit (such as being at a higher level) so as not to interfere with the airflow through the turbine and out of its exit.

[0012] A problem with this approach is that the housing and solar panel supports are large and heavy and the airflow into and out of the turbine is not optimal.

[0013] Alternatively, to combine pole-mounted wind and solar generation, the solar panels have to be made with reduced area and distributed in a way that they do not interfere with the airflow (such as in a ring around the turbine on its casing).

[0014] Summary of invention

[0015] It is desirable to provide a vertical axis wind turbine assembly that overcomes at least some of the above mentioned problems.

[0016] According to a first aspect of the present invention, there is provided a vertical-axis wind turbine assembly comprising:

[0017] - a rotor comprising turbine blades and hub, the rotor having a vertical axis of rotation;- a casing surrounding the rotor in a horizontal plane providing a lower air inlet below the rotor and an upper air outlet above the rotor;

[0018] - a louvre grille diffuser having tilted slats and grille apertures between the slats,

[0019] wherein the louvre grille diffuser is arranged to enclose the upper air outlet of the casing such that the grille apertures act as the upper air outlet from the rotor.

[0020] Preferably, the grille apertures act as the upper air outlet for all air expelled from the rotor.

[0021] Preferably, the grille apertures act as the upper air outlet for more than 90% of air expelled from the rotor.

[0022] Preferably, the grille apertures act as the upper air outlet for more than 80% of air expelled from the rotor.

[0023] Preferably, the vertical distance of the louvre apertures from the blades is less than an eighth of the rotor’s radius.

[0024] Preferably, the vertical distance of the louvre apertures from the blades is less than a quarter of the rotor’s radius.

[0025] Preferably, the vertical distance of the louvre apertures from the blades is less than a third of the rotor’s radius.

[0026] Preferably, the assembly further comprises solar panels mounted on the slats.

[0027] According to a second aspect of the present invention, there is provided a polemounted vertical-axis wind turbine assembly comprising the vertical-axis wind turbine assembly of the first aspect and further comprising a pole and a mount configured to mount the casing on the pole.According to a third aspect of the present invention, there is provided a street lamp comprising the pole-mounted vertical-axis wind turbine assembly of the second aspect and one or more light mounted on the assembly.

[0028] Brief description of drawings

[0029] Figure 1 illustrates a VAWT according to an embodiment of the present invention mounted atop a pole.

[0030] Figures 2A and 2B illustrate respectively orthographic views from above and below a diffuser-augmented VAWT in accordance with an embodiment of the present invention.

[0031] Figure 3 illustrates in schematic form the components of the diffuser-augmented VAWT in accordance with the present invention in an exploded orthographic view.

[0032] Figure 4 illustrates a plan view of the underside of a diffuser-augmented VAWT and cross sections through it in accordance with an embodiment of the present invention.

[0033] Description of embodiments

[0034] Under normal conditions placing any obstacles above or covering the direct airflow path of a small vertical axis wind turbine acts as a damper and reduce the speed of the turbine and in some instances it will not rotate at all.

[0035] In embodiments, this is overcome by creating a cover with slats and apertures in the direction of turbine airflow that acts as an air accelerator, in combination the with curvature of the enclosure that holds the turbine to enhance the overall aerodynamics. The slats and apertures create low pressure that accelerates air through the turbine to generate power more efficiently. This provides further enhanced extraction power.

[0036] Embodiments of the present invention include a diffuser-augmented VAWT with the diffuser being a louvre grille above and covering the turbine blades, with slats thathave photovoltaic (PV) panels mounted on them. In between the slats of the louvre grille apertures in the shape of slots act as vents at the outlet of the wind turbine. A casing extends around the turbine blades and contains the air that drives the turbine. The wind passes up through the turbine and out through the louvre grille diffuser. Curvature of the casing provides additional internal space and improved airflow to turbine.

[0037] This has the advantage that the whole top surface of the assembly can be used for photovoltaic cell coverage, while at the same time allowing the cells to be tilted towards the sun, which is typically in the south when one is in the northern hemisphere. The slats holding the photovoltaic cells and the interleaved apertures act as a diffuser. They create turbulence, which lowers the pressure and accelerates air flow at the outlet of the turbine. The inventor has found that this arrangement increases the efficiency of the turbine so that it can produce useful power output at lower wind speeds. This has been verified in experiments with and without the louvre grille diffuser in place.

[0038] With reference to Figure 1, diffuser-augmented VAWT assembly 100 is shown mounted on a pole 114. This is suitable for a street lamp. The casing 102 surrounds the turbine blades 106 and hub 112. On top of the casing 102, a louvre grille diffuser 104 is just visible from this viewpoint. The casing 102 is mounted on the pole by struts 110. If the assembly is used for lighting, then LED (light emitting diode) lights can be mounted on the lighting mounts 108. Thus the vertical-axis wind turbine assembly has a rotor comprising turbine blades 106 and hub 112, the rotor having a vertical axis of rotation 300 (with reference to Figure 3). The casing 102 surrounds the rotor in a horizontal plane providing a lower air inlet below the rotor and an upper air outlet above the rotor. The louvre grille diffuser has tilted slats and grille apertures between the slats. The louvre grille diffuser 104 is arranged to enclose the upper air outlet of the casing such that the grille apertures act as the upper air outlet from the rotor.

[0039] The grille apertures act as the upper air outlet for preferably more than 80% of air expelled from the rotor, more preferably 90% and most preferably all of air expelled from the rotor.The vertical distance of the louvre apertures from the blades is preferably less than a half, more preferably less than a third and most preferably less than a quarter and even more preferably less that one eighth of the rotor’s radius from the axis to the rotor tip. In an example, the vertical distance of the louvre apertures from the blades is 30mm + / - 5mm, with a rotor radius of 250mm.

[0040] Figures 2a and 2b show the diffuser-augmented VAWT assembly 100.

[0041] With reference to Figure 2a, the upper casing 202 is shown. PV cells 204 mounted on the slats of the louvre grille 104.Through the apertures 206 in the louvre grille 104, the blades 106 can be seen.

[0042] With reference to Figure 2b in a view from underneath the assembly, the lower casing 208 surrounds the turbine blades 106 that are mounted on the hub 112. A shaft is shown centred in and descending from the hub 112. The hub may contain the generator and the shaft is a conduit for wiring, or the shaft may rotate and be connected to a generator in order to extract power from the wind turbine.

[0043] Features shown in a figure with reference numerals the same as shown in earlier Figures represent the same features and the earlier description of those features is applicable.

[0044] With reference to Figure 3, an exploded view of components of the diffuser-augmented VAWT assembly 100 are shown. At the top, the louvre grille 104 has slats 302 and apertures 206. The turbine hub 112 has 6 blades 106 mounted on it. The casing 102 is made in two parts in this assembly. An upper casing 202 and a lower casing 208.

[0045] With reference to Figure 4a, a plan view looking up from underneath the diffuser-augmented VAWT assembly 100 is shown. The lower casing 208 is shown surrounding the turbine blades 106. The dashed lines represent two cross sections. B-B and C-C. These cross sections are shown in Figures 4b and 4c respectively.With reference to Figure 4b, in the cross section B-B with reference to 4a, it can be seen that the casing 102 has a lip 402 moulded into the lower casing 208 and / or upper casing 202. The turbine blades 106 extend radially outward from the hub 112 to overlap the lip 402 so that the end of the blade 404 overlaps the lip 402. This obstructs air from going around the outside of the circle traced by the end of the blades 106. In an example, the hole diameter in the plane of 500mm diameter rotor blades is 513mm and the underside of blade tip to the lip surface is 8mm at the overlap.

[0046] With reference to Figure 4c, in the cross section C-C with reference to 4a, the aperture 206 can be seen in the cross section through the louvre grille 104.

[0047] The reason the aperture is not shown in Figure 4b is there is a central reinforcing post 406 to support the centre point of each slat. The centre post 406 can be seen in Figure 4b. The higher part of each slat is supported at each end by another post 408 as seen in Figure 4b.

[0048] In a wind tunnel test, without the louvre grille diffuser fitted to the assembly, 5m / s airflow yields 5V and 10m / s yields 8V. The voltage is too low for power output.

[0049] However, with the louvre grille diffuser 5m / s airflow yields 9.5V and 10m / s yields 12.45V. At 10m / s the voltage was sufficient to provide 3 to 5 W of power.

[0050] These wind tunnel results show the advantage of the louvre grille diffuser in providing improved efficiency of power generation.

[0051] In use, a power generator using embodiments of the present invention is the core of a Smart Hub, producing energy that is stored in batteries, harnessing renewable energy and reducing the reliance on grid energy, that can also produce backup power in the case of power blackouts.

[0052] Traditional external lighting in the UK is grid connected and consumes a large amount of energy. Embodiments enable a cost-effective alternative that uses less reliance on grid energy, with technology that reduces the carbon footprint. It uses reusable energy with compact, lightweight and efficient technology, powered byhybrid wind and solar. It is remotely manageable and has an eye pleasing structure, because it is compact. Being lightweight because the solar panels are closely integrated with the rotor casing, it is easier to install. The smaller casing uses less material and is therefore lower cost.

[0053] The improved generating efficiency gives the ability to offer a modular platform with more electrically powered modules, providing multiple solutions that can be adapted to customer needs. The Smart Hub may comprise a power generating module using an embodiment of the present invention, and has options to add several modules including advanced communications (wireless, 4G, 5G, satellite), security (HD CCTV with Al), intelligent sensors (monitoring and analytics) and programmable lighting. This is managed by software for management and control of the Smart Hub covering all aspects of data management, alert and reporting.

[0054] The customer benefits include energy savings, operational efficiency and integration of environmental monitoring, traffic analysis, security protection of people assets and the environment, and lighting optimisation. This is all enabled by the increase in efficiency provided by embodiments.

[0055] This increase in efficiency means that embodiments can be mounted on 4-6m high street poles to provide off-grid lighting with LEDs at 5 LUX running at 1-3W power consumption, generated from by the sun and wind alone.

Claims

Claims1. A vertical-axis wind turbine assembly comprising:- a rotor comprising turbine blades and hub, the rotor having a vertical axis of rotation;- a casing surrounding the rotor in a horizontal plane providing a lower air inlet below the rotor and an upper air outlet above the rotor;- a louvre grille diffuser having tilted slats and grille apertures between the slats,wherein the louvre grille diffuser is arranged to enclose the upper air outlet of the casing such that the grille apertures act as the upper air outlet from the rotor.

2. The assembly of claim 1 , wherein the grille apertures act as the upper air outlet for all air expelled from the rotor.

3. The assembly of claim 1 or claim 2, wherein the grille apertures act as the upper air outlet for more than 90% of air expelled from the rotor.

4. The assembly of any preceding claim, wherein the grille apertures act as the upper air outlet for more than 80% of air expelled from the rotor.

5. The assembly of any preceding claim, wherein the vertical distance of the louvre apertures from the blades is less than an eighth of the rotor’s radius.

6. The assembly of any preceding claim, wherein the vertical distance of the louvre apertures from the blades is less than a quarter of the rotor’s radius.

7. The assembly of any preceding claim, wherein the vertical distance of the louvre apertures from the blades is less than a third of the rotor’s radius.

8. The assembly of any preceding claim, further comprising solar panels mounted on the slats.

9. The assembly of any preceding claim, further comprising a pole and a mount configured to mount the casing on the pole.

10. A street lamp comprising the vertical-axis wind turbine assembly of claim 9 and one or more light mounted on the assembly.

Images