GB2413829A

GB2413829A - Wind operated turbine.

Info

Publication number: GB2413829A
Application number: GB0410160A
Authority: GB
Inventors: Andrew Douglas John Buckingham
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-07
Filing date: 2004-05-07
Publication date: 2005-11-09
Also published as: GB0410160D0

Abstract

A wind operated turbine has a rotor 1 with an axis (11, Fig1) carrying turbine rotor blades 10 located within a casing. The casing forms a duct with an air inlet 3 and an air outlet 4, the rotor blades 10 forming with the duct a blade impingement region with the duct having a sectional area that reduces towards the blade impingement region to form a throat interface between an inner duct surface and the tips of the blades to produce a Venturi effect on the blades of the rotor. The turbine may be mounted on rooves, eaves and corners of buildings for electrical power generation in urban areas.

Description

24 1 3829

WIND OPERATED TURBINE

This invention relates to a turbine and more particularly to a prismatic rotor wind turbine for mounting on buildings and structures in urban areas for producing electrical energy, for example, or for acting as a fluid pump such as a water pump.

The energy available from the wind is, by nature, diffuse and it is normally necessary to construct 'farms' of very large wind turbines spread over a wide area of land to gather enough electrical energy to make it worthwhile to feed the National Grid (in the U.K.). Wind farms have a significant effect on the remote areas in which they are situated, particularly as regards visual impact and noise, and they suffer from relatively high capital and maintenance costs per unit of electricity generated. Even though wind speeds and directions are not constant, large wind turbines must normally be constrained to rotate at a substantially constant speed to allow their alternators to be matched to the National Grid for frequency and phase and to avoid the machines being damaged or destroyed by self-induced vibrations.

It is precisely because wind energy is diffuse and variable with time and geography that harvesting it would be better done using many turbines situated across the country rather than limited to a few sites remote from centres of population. Furthermore, to limit conductance losses, the generation of electricity from wind power would be better done close to the point of use, i.e. within or adjacent to urban areas. Placing conventional large wind turbines in such areas would be inefficient, uneconomic and environmentally unacceptable, whereas large numbers of small wind turbines could be more effective if it were possible to mount them onto existing buildings or use specially built structures that are designed to occupy little land. In particular, one of the reasons why conventional wind turbines designed to operate at constant speed will not function satisfactorily in built-up, hilly and wooded areas is the 'boundary layer effect' that occurs near the ground. Here, the average wind speed is lower than at greater heights whilst the flow of air around and over man-made and natural obstacles tends to be non-steady, characterized by gusting, sudden changes in wind direction, swirling eddies and even reversed flow.

The angular shapes of typical man-made obstacles such as buildings tend to cause air to accelerate around their corners and over their rooves. Any wind turbine designed to work in urban areas would need to be able to exploit variability of wind speed rather than suffer from it.

According to the present invention, there is provided a wind operated turbine comprising a rotor having an axis carrying turbine blades located within a casing, the casing forming a duct including an air inlet on one side and an air outlet on another side of the rotor axis, the blades forming with the duct a blade impingement region with the duct having a sectional area that reduces towards the blade impingement region to form a throat interface between the inner duct surface and the tips of the blades, thereby to cause air upstream of the rotor blades to be accelerated and increased in pressure thereby to provide a relatively increased drive effort on the turbine.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Fig. l is a diagrammatic front view looking into an inlet of a wind turbine, Fig. 2 is a diagrammatic end view of the turbine shown in Fig. l, Fig. 3 is a diagrammatic sectional view of the turbine and shows it in a possible position of mounting adjacent the lower end of a roof of a building, Fig. 4 is a longitudinal sectional view taken along the line A-A of Fig. 5, Fig. 5 is an end view of the turbine with a cowling end removed, Fig. 6 is a diagrammatic sectional view taken along the line B-B of Fig. 4 and shows a left-hand rotor half, and Fig. 7 is a similar view taken along line B-B in Fig. 4 but showing a stator of the turbine.

The present wind turbine is intended to be suitable for use in urban areas in order specifically to harvest energy from the wind in such urban areas.

The arrangement of the turbine could be as shown generally in Figs. l and 2. It would be possible (and desirable) for a series of such turbines to be mounted side-by-side. The turbines would be fixed along the eaves or at the roof apex of a domestic house, for example, or at the corners or roof tops of public buildings.

Fig. 3 shows the turbine located at the eaves of a house, with its main body slightly below the roof line R and with its driving axis extending substantially parallel to that roof line R. Size constraints would limit these turbines to have a power generation capacity of, say 50W each on a gusty day but a typical 3-bedroom, semi-detached property could easily be fitted out with six turbines, both front and back, along its eaves, representing some 300W of generation capacity, even assuming only half are working efficiently at any one time.

Although such urban turbines would be designed in the first instance to retrofit to existing buildings and structures, it is hoped that eventually they could be incorporated into the cladding of new buildings from the outset.

Figs. 4 to 7 show various sectional views of the urban turbine, as it may be designed for low cost and high reliability. The general arrangement of the device would be as follows.

The turbine basically consists of a prismatic rotor 1 separately assembled as an integral unit and located within an aerodynamically designed, two-piece outer casing 2. An upper part 2A of the casing 2 is composed of an air inlet 3 and an air outlet duct 4.

A key feature which will be noted is the creation of a 'throat' in a region within the ducting that is substantially coincident with the section of maximum blade impingement (see especially Figs. 2, 3 and 5) of the rotor l and which, due to the judicious choice of inlet and outlet flow areas, causes the entering air to be accelerated and increased in pressure with respect to the surrounding air. In other words, a Venturi effect is produced. The air flow through the turbine is as shown by i0 the arrows in the inlet and outlet ducts 3,4 of Fig. 3.

This Venturi effect allows the turbine to spin at a proportionally greater speed and generate more power than a conventionally bladed turbine occupying the same volume.

A grille 5 is located within the inlet duct 3 to help keep debris (such as leaves) and birds out of the rotating assembly. A lower part of the casing 2B supports the rotor assembly and encloses the returning blades. It would sensibly be provided with a drain to allow rainwater to escape. The two parts 2A and 2B of the casing are preferably bolted together using integral flanges at each end of the turbine, which would also serve to lock a tubular shaft 6 against rotation. The tubular shaft 6 forms the central axis of the turbine about which the rotor l rotates.

For volume production, both casing parts 2A, 2B are preferably manufactured from one-piece mouldings of a W - stabilised plastics material, such as UPVC. The use of plastics for the casing 2 would also help attenuate mechanical noise broadcast by the turbine rotor l and minimise the transmission of vibration to the supporting structure. For lower volume larger turbines and prototypes, sheet metal fabrication with soundproof cladding may be preferable on economic grounds.

The rotor drum is preferably constructed in two s halves 7,8, these being joined at the centre using a flanged joint 9. Each rotor half 7,8 is made in the shape of a drum with a set of curved blades 10 sensibly spacedapart around the external circumference of the drum.

Normally, each blade 10 would extend substantially the entire length of the rotor half 7,8 respectively. A typical convenient number of blades would be eight but more or fewer may be chosen. The blades 10 may run strictly axially along each rotor half 7,8, or be arranged on an angle, or as a spiralling curved helix. Each rotor half 7,8 may have its blades 10 set at the same angle with respect to the axis of the rotor (indicated by reference numeral 11) or running on an identical helix, so that the blades appear to run continuously through the central flanged joint 9, or they may be set at opposite angles, so as to create a 'chevron' effect. The blades 10 of each rotor half 7, 8 need not be aligned at the central joint but rather be angularly offset.

For reasons of environmental ruggedness, low rotational inertia and cost for volume production, each half rotor would be preferably manufactured as a lightweight one-piece plastics moulding, having its blades integral with the drum. The use of plastics for the rotor and blades would also be expected to minimise noise created by air/solid surface interaction at the turbine rotor. However, other methods may be preferable for prototyping and low volume production, such as aluminium fabrication.

The rotor 1 would preferably rotate around the fixed tubular shaft 6 on a pair of standard rolling element bearings 12 of known design, these being located within housings moulded into each end of the rotor 1. The shaft 6 is preferably of tubular construction.

Electrical power is preferably generated by using a pancake' or 'disc' type alternator 13 (Fig. 4) of generally known design, for example, of a brush-less, lO permanent magnet type. The alternator 13 preferably consists of two discs 13A, 13B, each supporting a ring of permanent magnets, surrounding a wound stator 14 (Fig. 7) that is firmly fixed to the static shaft 6. Wires from each of the stator coils are firstly collected at a local terminal within the rotor drum and thereafter the power wires 15 would run along the centre of the tubular shaft 6 out to a terminal box (not shown) on the outside of turbine casing 2. The two magnet holding discs 13A, 13B are accurately diametrically located within each rotor half 7, 8 and fixed by clamping them between the rotor half flanges 9.

Using the method of construction proposed, the magnets and rotor of the alternator are effectively protected against the ambient environment, especially rain and dust ingress, both of which tend to be associated with wind impingement. However, it is envisaged that it may be required to use a prismatic rotor or rotors that do not contain an integral alternator. Rather, a single large such 'passive' rotor or a chain of connected smaller ones could be used to drive a single, exterior alternator of known design via a coupling and separate shaft.

Whether integral to the rotor l or mounted separately, the alternator could be replaced by a DC electrical generator. However, the brushes of such generators represent a greater friction power loss and tend to wear out and need to be replaced. Instead of driving an alternator or generator, the turbine(s) could also be arranged to drive a fluid pump, such as a water pump.

It will be appreciated that the present turbine is specifically intended for harvesting energy from the wind in urban areas and its low inertia, fundamentally balanced, prismatic rotor l is designed to operate at unsteady speeds and allows the turbine to accelerate rapidly to extract power from gusts. It is also substantially completely enclosed, apart from the inlet and outlet ducts, of course, so as to limit noise emission to its surroundings and make it sufficiently unobtrusive to mount onto, or build into, domestic, commercial or public buildings.

Claims

1. A wind operated turbine comprising a rotor having an axis carrying turbine blades located within a casing, the casing forming a duct including an air inlet on one side and an air outlet on another side of the rotor axis, the blades forming with the duct a blade impingement region with the duct having a sectional area that reduces towards the blade impingement region to form a throat lo interface between the inner duct surface and the tips of the blades, thereby to cause air upstream of the rotor blades to be accelerated and increased in pressure thereby to provide a relatively increased drive effort on the turbine.

2. A turbine according to claim 1, wherein the casing is constructed to provide a Venturi effect at the blade impingement region.

3. A turbine according to claim 1 or 2, wherein the air duct on the downstream side of the blade impingement region has a sectional area that increases from the throat.

4. A turbine according to claim 1, 2 or 3, wherein the rotor is substantially completely enclosed within the casing.

5. A turbine according to any one of the preceding claims, wherein the casing is fitted with a grille to avoid ingress of birds, debris and the like.

6. A turbine according to any one of the preceding claims, wherein the rotor is of prismatic shape.

7. A turbine according to claim 6, wherein the rotor is in the form of a cylinder with the turbine blades of the rotor being located around its circumference and running axially along its length.

8. A turbine according to claim 7, wherein the turbine blades are mounted so as to run at an angle with respect to the longitudinal axis of the rotor.

lo

9. A turbine according to claim 7, wherein the turbine blades are mounted as a helical spiral with respect to the longitudinal axis of the rotor.

10. A turbine according to any one of the preceding claims, wherein the rotor comprises two halves joined at a flanged joint.

11. A turbine according to claim 10, wherein the turbine blades of the rotor run at different angles on opposing halves of the rotor.

12. A turbine according to claim 7, wherein the turbine blades of the rotor are offset in an angular sense on opposing halves of the rotor.

13. A turbine according to any one of the preceding claims and comprising an AC alternator for the generation of electricity.

14. A turbine according to claim 13, wherein the alternator is enclosed entirely within the rotor.

15. A turbine according to claim 13 or 14, wherein the alternator is of a brush-less, permanent magnet type. l

16. A turbine according to claim 15 as appendant to claim 10, wherein the alternator comprises a magnetic disc or discs located between flanges of the two rotor halves and surrounding a wound stator fixed to a static shaft around which the rotor rotates.

17. A turbine according to any one of claims 1 to 12 and comprising a DC generator for the generation of electricity by the turbine.

18. A turbine according to claim 17, wherein the DC generator is entirely enclosed within the rotor.

19. A turbine according to any one of claims 1 to 12, and including a pump for the movement of a fluid.

20. A turbine according to any one of the preceding claims, wherein the casing has means for mounting the casing on a building or other urban structure.

21. A turbine according to claim 20, wherein the pump is entirely enclosed within the rotor.

22. A wind operated turbine, substantially as hereinbefore described with reference to the accompanying drawings.

23. A plurality of wind operated turbines according to any one of the preceding claims, said turbines being mechanically coupled together to drive a separate alternator, generator or fluid pump.

24. A building or other urban structure having a turbine or a plurality or turbines according to any one of the preceding claims mounted thereon or therein.