GB2502979A

GB2502979A - Wind turbine with outer stationary vanes surrounding inner vanes

Info

Publication number: GB2502979A
Application number: GB1210287.7A
Authority: GB
Inventors: Jonathan Harry Warrilow
Original assignee: ENGINEERING INNOVATION CONSULTANCY Ltd
Current assignee: ENGINEERING INNOVATION CONSULTANCY Ltd
Priority date: 2012-06-11
Filing date: 2012-06-11
Publication date: 2013-12-18
Also published as: GB201210287D0

Abstract

A wind turbine comprising multiple inner vanes 21, 22, 23 rotating about a central axis and a second set of outer stationary vanes 24, 25, 26 surrounding the inner vanes to obscure them from view. Preferably the outer vanes provide a narrowing passage, to increase the speed of the air entering the turbine, and the inner vanes are concave shaped to create an aerofoil effect. The fixed outer vane structure may also deflect air from the oncoming blades of the inner turbine and create a low pressure zone in the air behind the turbine. These two aspects combined with the aerofoil section of the inner turbine vanes also make the device more efficient that known vertical axis wind turbines.

Description

WIND TURBINE

Field of the Invention

This invention relates to a wind turbine design for harnessing wind energy and turning it into useful mechanical power from which mechanical loads or electrici-ty generating devices can be driven.

Background to the Invention

Wind turbines (both horizontal and vertical axis) are proving to be a valuable source of power generation and come in many styles. Vertical axis wind tur- bines are less efficient than those of horizontal axis in clean (non turbulent) air-flow. However they are more efficient than horizontal axis ones in turbulent air such as in built up areas where the presence of buildings causes disruption to the airflow Large wind turbines can be used on an industrial scale for large scale power generation both on and off shore. Medium sized units can be seen on industrial estates for small power generation and very small ones can be seen on private properties and yachts for what is known as micro' power generation. One of the big concerns with the use of wind turbines for domestic electricity generation in populated areas is their visual impact and indeed any device that is moving in- herently catches the eye' and draws the observer to it's presence. The move-ment of many wind turbines on the roofs of houses would undoubtedly raise concern and objection from neighbours.

This invention seeks to overcome the inherent inefficiencies of vertical axis wind turbines and thus improve performance whilst also overcoming the visual con-cern of wind turbines by making them far more discreet and hence acceptable for domestic use.

Prior Art

Vertical axis wind turbines come in a variety of styles.

Fig 1 shows the most basic style more often used for advertising than power generation. This consists of a curved rotating panel (1) whose wind resistance is greater on one side than the other. The resultant difference in force about the vertical axis causes the rotation. This panels sits on a rotating shaft (2) and fixed base (3).

Fig 2 shows a basic configuration of vertical axis wind turbine using a plurality of concave blades' (4) mounted at set distances around the circumference of a circle. In the centre of the circle are axles (7) and bearings (8) about which the unit rotates. Rotation occurs due to the difference in wind resistance on the concave face (5) compared to the convex face (6) on the opposite side of the axis of rotation.

Fig 3 shows a unit they may be found on industrial or retail premises for local small scale power generation. These use a combination of aerofoil effect and varying areas presented to the wind to cause rotation of the whole blade struc-ture (9) about a fixed column (10).

All of the above existing technologies expose the viewer to the sight of a rotat-ing object and suffer inefficiency as the drag of the blades moving into the wind acts against the positive force of the blades moving downwind and actually slows the turbine down to less than the wind speed.

Fig 4 shows a design published in US Patent No 4,142,822 which similarly guides the air into the rotating turbine (11) with fixed outer plates (12) but fo-cuses on the inner turbine blade shape and indeed relies upon the outer blades set at only a very small tangential angle, thus not obscuring the inner turbine from view-the main feature of the invention claimed herein.

The invention herein described is a new design that hides rotating parts from view whilst still maintaining but significantly enhancing the fundamental perfor-mance benefits of the US Patent.

Summary of the Invention

According to the present invention, there is provided a vertical axis wind turbine around which are a series of fixed outer blades mounted in a rotary pattern. A preferred embodiment of the invention will now be described by way of example by reference to Figures 5, 6 and 7.

Figure 5 shows the outside view of the turbine.

Figure 6 shows the outside view with the outer top plate and inner top plate par-tially removed for clarity.

Figure 7 shows a plan view directly from above (with the inner and outer top plates removed entirely for clarity).

Referring to Figure 5, the device consists of a number of fixed outer blades (13) which do not rotate and form part of the structure that supports the top plate (14) and bottom plate (15). These in turn provide the mounting points of bear- ings (16) which support a shaft (17) which is free to rotate by virtue of the bear-ings.

Referring now to Figure 6. Inside the outer structure of items 13, 14 and 15 sits a conventional vertical axis wind turbine (similar to as shown in figure 2). This comprises of an inner bottom plate (18) and inner top plate (19). Secured be- tween these are a plurality of concave blades (20) which are mounted in a rota-ry pattern at equal angles and distance from the shaft (11). The inner bottom plate (18) and inner top plate (19) are secured to the shaft (17) by one of many conventional means (keyways, splined shaft, grub screw, shrink fit etc).

The invention works by air entering the device from any direction. For the pur-poses of illustration we shall refer to figure 7 and consider airflow entering from the bottom of the illustration.

Air enters the unit through the windward facing apertures between the fixed outer blades (13). It is directed onto the concave blades exerting a pressure and resultant force on the inner blades 21, 22, 23. The outer blades 24, 25, 26 act to shield the blades on the other side of the turbine from the wind. This results in deflection of the air from hitting the rotating blades heading into the wind (those on the left hand side of figure 7) meaning that there is a strong differential in forces between the blades on opposite sides of the axle (17) and rotation of the inner turbine occurs. Because of the wind deflecting action of outer blades 24, 25, 26 the resultant force causing the rotation is much greater than that seen in a conventional vertical axis wind turbine (figure 2) and hence more force is transmitted to the shaft (17) and an increase in mechanical power output is seen.

Efficiency is further enhanced by two more important features of the preferred embodiment of the invention. Firstly, as the air passes through the apertures between the fixed guides, it sees a diminishing gap. To maintain air flow vol- ume, the air speed increases as it passes through this decreasing gap. The ve- locity of the air hitting the concave inner blades is hence faster than the prevail-ing wind speed hitting the turbine assembly.

Secondly, because of the almost enclosed nature of the fixed outer guide struc- ture, there is created a zone of low pressure air at the rear of the structure. Fig- ure 8 shows a representation of the air pressures and predominant air flow with-in the turbine.

The high pressure zone is at the front on the face (zone A) where the wind hits the turbine. As the wind enters the turbine it moves the concave blades and im-parts some of its energy to the blades. Air pressure is consequently lower in the centre of the turbine (zone B) after losing some of its energy to the blades. The very presence of the fixed outer structure causes a low pressure zone behind it (zone C). As the air passes from the centre of the turbine (zone B) and exits at the rear to the low pressure area (zone C) it passes over the concave inner blades. These have an aerofoil effect as the path around the front of the blade is longer than the path around the rear. The concave blade itself is hence sucked forward by the airflow providing an additional rotary force applied to the shaft (17).

It will be appreciated that the specific shape of both the inner and outer blades can be somewhat different to those shown in the preferred embodiment without detracting from the claimed invention. For example the outer blades could be simply straight or curved in a slightly different way. Also it will be appreciated that the number of inner and outer blades can change, and the whole turbine could be layed on its side (or indeed any angle) whilst not detracting from the principles and novelties of the embodiment described herein.