AU6562801A - Improvements to solar heat engines and industrial chimneys - Google Patents

Description

Page 1 of6 INVENTOR: NORMAN LOUAT TITLE: IMPROVEMENTS TO SOLAR HEAT ENGINES AND INDUSTRIAL CHIMNEYS BACKGROUND OF THE INVENTION Field of Invention The title of this invention is "Improvements to Solar Heat Engines and Industrial Chimneys". The present invention relates generally to the field of industrial chimneys and of solar energy power generators. More specifically, the present invention is related to collecting and guiding air heated by the burning of fuel or through the action of sunlight. In the case of solar heating this can result in a flow suitable to drive a power-generating turbine. In this connection this invention has particular application in providing a power source in sunny areas and as a large-scale air exchange system to provide community-wide cooling and cleaning. In reference to industrial chimneys it allows the creation of the draught normally achieved through the use of tall towers without the use of a tower as such.

Discussion of Prior Art Using solar heated air to induce an updraft is known in the art in various configurations as illustrated by US patents: 4,118,636; 4,224,528; 4,275,309; 5,096,467; 4,388,533; 4,414,477; 5,734,202.

Typically a surface, capable of absorbing heat, collects energy from impinging sunlight.

A clear glass or plastic material usually encloses the heat-collecting surface to help trap the heat.

The transparent material additionally may have an opening which allows heated air to escape from the greenhouse structure and other openings to allow ambient air to be drawn into the *greenhouse structure. More particularly, as air is heated within the greenhouse structure, it becomes less dense than the surrounding air and rises through any outlet in the transparent Smaterial. Air in the surrounding environment is drawn into the greenhouse structure to replace the air which escapes.

One notable observation is that the height to which the rising air climbs controls how much air escapes and enters the greenhouse structure.

Finally, some type of wind-driven turbine is introduced in the flowing air to drive an electric generator.

Such devices, as described in the prior art, have at least two shortcomings: they typically involve only linear air movement within the greenhouse and they require a physical, chimney-like structure to contain any resulting updraft.

A few prior devices mention thermally inducing vortex-like, or rotational, air flow rather than simple linear flow; but appear to do so only within an attached physical chimney. Vortex-like Page 2 of 6 airflow simply means a column of flowing air which has tangential components of velocity of magnitude comparable with those of the upward motion. The importance of achieving a vortex-like flow relates to the effect such flow has on the height of the generated updraft. The purpose of a chimney or smokestack is to prevent the inward flow of ambient air into the column of hot air rising from the chimney, thus allowing the updraft to flow unimpeded. To achieve a higher up-draft, a higher chimney is required. However, manufacturing costs and engineering complexity increase as the height of a physical chimney increases. Due to the centrifugal forces associated with rotation, a vortex-like flow obviates the need for a chimney because it inhibits the mixing of the rising air with ambient air. The patents of Lucier, 4,275,309, and Valentin, 4,452,046, contemplate rotational air flow but still envisage a tall, physical chimney-like structure. They differ from the present invention which uses a specific vortex flow instead of a physical chimney to isolate the resulting rising air. The absence of a physical chimney decreases both the engineering complexity and manufacturing costs associated with solar-powered wind generators. Whatever the precise merits, features and advantages of the above cited references, none of them achieve or fulfills the purposes of the present invention. Accordingly, an object of this aspect of the present invention is to provide a solar-powered air flow generator which is simple to build and inexpensive to manufacture.

Another object of the present invention is to provide means of deflection of air flow within the structure so as to result in a rotational component. Still another object of the present invention is to provide an appropriately shaped and positioned aperture within a solar powered air-flow S: generator which will allow escaping, heated air to flow upwards in a vortex-like manner and, optionally, drive a turbine.

Still another object of the present invention is to provide a solar- powered air-flow generator which removes local, heated air in a spiraling updraft and replace it through a flow of downward moving cooler, cleaner air.

A further object of the present invention is to provide a solar powered air-flow generator which inhibits the mixing of ambient air with the produced up-draft by imparting a vortex-like flow on the escaping air rather than using a physical chimney. The virtual chimney created by the vortex-like flow supports updrafts which exceed those supported by feasible physical chimneys.

A further object of this invention is to provide essentially the same air-flow pattern when the source of heat is the burning of some fuel rather than from solar radiation These and other objects are achieved following the lines indicated in the detailed description that follows.

SUMMARY O F THE INVENTION Problems and disadvantages associated with the prior art are addressed and overcome by the present invention. Deflections within the present solar-powered air-flow generator cause the solar-heated air within the entire structure to move in a rotational manner. Consequent on the principle of the conservation of angular momentum, air which escapes the structure with rotation as component of its velocity, retains that rotation at all levels. This movement allows it to rise in the atmosphere without mixing with the environment; without a physical chimney.

This result is true independent of the source of heat which raises the temperature of the Page 3 of 6 air and so reduces its density. In the case of solar heating it would seem from the ensuing discussion that cheap power can be obtained by the use of a process which encapsulates the essentials of the world's weather cycle. The weather cycle represents one of the largest engines operating on this planet. In the weather cycle, as in any heat engine, there is both a source and a sink for heat. Mechanical work is done when the heat is transported between source and sink.

In the weather cycle, heat is supplied, mainly at the earth's surface, by radiation from the sun.

This heat is converted into mechanical work through convective air currents which transport the heat to the upper levels of the atmosphere, where it is radiated to the heat sink provided by outer space.

The primary task of the following discus is an examination of the properties of a model system.

This system involves three essential elements: a heat collector, a central orifice in the heat collector containing a turbine which drives an electric generator and finally, an air column which forms an extension of the central tower. In turn, the conclusions of this examination are detailed below.

The heat collector will take the form of a large, rather flat truncated cone, circular in plan, highest near its center and consist of light transparent sheets fixed in position through the action of a sufficiently rigid skeleton. It should be realized at the outset that commercially significant power is measured in hundreds of megawatts and that, since the sun provides about 1 kilowatt per square meter, we should envisage collectors whose radii, are conveniently measured in S: kilometers. (A circular collector of 1 kilometre radius would provide an energy input of- 3 X 10 9 watts Air entering at the periphery, in particular, with a component of tangential velocity imposed by the presence of vanes, will absorb heat from the sun and flow inwards toward a central orifice. Conservation of angular momentum will result in an increase in tangential velocity with decreasing radial distance.

oo oi 0* oo oo a Page 4 of 6 The next item is the central orifice. This will have circular cross-section and enclose an axially disposed turbine which will be caused to rotate by the ascending air. The material circumscribing the orifice has only to support itself and the turbine and to be capable of preventing radial air flow. The final item is the air column. Calculation shows that if the efficiency of the engine is to be such as to allow the off-take of significant power, the height of the column must be such as to be conveniently measured in kilometers. In principle, as in the familiar smokestack, such a column can be provided by a solid structure. In practice, the cost associated with such an approach would be prohibitive. To recognize how this difficulty can be surmounted it is helpful to understand the role of a smoke-stack.

In a smoke-stack or industrial chimney, the pressure, at the same height, of the air moving inside is lower than that of the still air outside by an amount which increases steadily with distance from the top of the stack. Thus, the wall of the stack acts as a barrier, that is to say, it provides a force which acts to prevent the inward flow of air. Were the wall not there, inward flow and the resultant mixing would continue until the pressure differential and the attendant upward motion of the air were essentially extinguished. Crucial to the operation of the engine is the fact that the barrier to this inward flow need not be material but can be provided through the centripetal forces associated with rotation Indeed, calculation shows that inward motion can be suppressed by imparting tangential components of air velocity whose maximum is comparable in magnitude to the speed of the upward motion in the column. An interesting outcome of these calculations is the prediction of the existence of a central region in which there is no motion. This is gratifying in view of the observation of well known "eye" in a hurricane and the recent observation using Doppler radar of S similar phenomena in tornadoes. It should be remembered that these natural phenomena depend on the same properties of the rotational air column as those invoked in respect of the proposed heat engine.

The phenomena identified above differ from those of conventional heat engine only in the "fuels" involved. In the two cases cited above, as well as in the sea spout, energy is stored in the heat of vaporization of water and liberated when the vapour condenses, resulting in a rise in the temperature of the air. In the case of the engine, as in that of the so-called dust-devil, this temperature is raised by the direct action of the sun. In all three cases, energy is transported from ground level to the upper reaches of the atmosphere.

Since air is transported upwards there must be a compensating flow in the reverse direction.

Characteristically, this air is cleaner and cooler than that which it replaces. The reduction in temperature can be significant. Its magnitude should approach the temperature increase engendered by local (atmospherically unstable) heating at ground level. Its impact is familiar to all who have experienced the cool breezes which often precede thunderstorms.

It is apparent that the operation of this engine would be environmentally friendly. Again, since fuel employed is free the only apparent ongoing costs are those associated with Page 5 of 6 maintenance. This would suggest that this approach would lead to the production of power at significantly smaller costs than those of more conventional methods.

The essentials of the engine considered here are of course independent of the source of heat Claims 1. The solar heat collector would embody the usual principle of a greenhouse. The translucent structure would be circular in plan about a structurally robust central tower of height, h, above a nominally planar, light- absorbing base, such that, for example, the product of h and the radius is a constant. Air is heated within the structure by the action of the sun and is allowed to escape through an aperture at the top of the tower. The height of the tower is sufficient only to contain a windmill or windmills and the associated eclectic generator or generators and air deflecting vanes. The translucent material, glass, plastic sheeting etc. is enclosed on upper and lower surfaces by a loadbearing, mainly, translucent material, such as heavy-duty steel wire mesh. The whole is fixed in place by a structure of sufficient rigidity. The implied strength is necessary to resist the action of the forces developed consequent on the reduced pressure within the enclosure and or by external winds. These forces could tend to cause implosion or explosion or lateral displacement of the structure.

2. The apparatus as in claim 1 in which the escaping air is caused to have rotational components of velocity through the action of two sets of vanes located at two radii approximating that of the central tower. The outer set being at a radius rather greater than that of the tower and having a height necessary to span the distance between the structure and the base and having lengths in the directions parallel to the base sufficient to ensure uniform flow of the air. Because angular momentum is conserved, the radial velocity at radii smaller than that of these vanes is naturally such that its product with radius from the centre is a constant. In the interests of efficiency, a second set of vanes located at a particular radius, less than that of the tower and above the first set with a pitch such that, as a result of their presence, the component of radial velocity beyond them is proportional to the radius. Consequent on the action of these two sets of vanes, the flow in air at all heights above the tower is divided into two zones; in the outer, the variation of radial velocity is that of a vortex, in the inner; it is that of a solid. The vertical component of velocity in nominally the same in both zones.

3. The apparatus as in claims 1 and 2 in which the pitches of the vanes are adjusted through an electronic feedback mechanism so as to maximize the energy output that will vary with the height of the sun and the amount of cloud and other variables.

4. The apparatus as in claims 1,2, and 3 and in which the central tower may contain a windmill coupled to an electric generator. In an alternative configuration the windmill and generator may be omitted and the apparatus used simply as giant air conditioner as a consequence of its ability to produce an upward current of sufficient force to penetrate any inversion layer which may be present

Claims (4)

1. The solar heat collector would embody the usual principle of a greenhouse. The translucent structure would be circular in plan about a structurally robust central tower of height, h, above a nominally planar, light- absorbing base, such that, for example, the product of h and the radius is a constant. Air is heated within the structure by the action of the sun and is allowed to escape through an aperture at the top of the tower. The height of the tower is sufficient only to contain a windmill or windmills and the associated eclectic generator or generators and air deflecting vanes. The translucent material, glass, plastic sheeting etc. is enclosed on upper and lower surfaces by a load- bearing, mainly, translucent material, such as heavy-duty steel wire mesh. The whole is fixed in place by a structure of sufficient rigidity. The implied strength is necessary to resist the action of the forces developed consequent on the reduced pressure within the enclosure and or by external winds. These forces could tend to cause implosion or explosion or lateral displacement of the structure.

2. The apparatus as in claim 1 in which the escaping air is caused to have rotational components of velocity through the action of two sets of vanes located at two radii approximating that of the central tower. The outer set being at a radius rather greater than that of the tower and having a height necessary to span the distance between the structure and the base and having lengths in the directions parallel to the base sufficient to ensure uniform flow of the air. Because angular momentum is conserved, the radial velocity at radii smaller than that of these vanes is naturally such that its product with radius from the centre is a constant. In the interests of efficiency, a second set of vanes located at a particular radius, r, less than that of the tower and above the first set with a pitch such that, as a result of their presence, the component of radial velocity beyond them is proportional to the radius. Consequent on the action of these two sets of vanes, the flow in air at all heights above the tower is divided into two zones; in the outer, the variation of radial velocity is that of a vortex, in the inner; it is that of a solid. The vertical component of velocity in nominally the same in both zones. *o 4

3. The apparatus as in claims 1 and 2 in which the pitches of the vanes are adjusted through an electronic feedback mechanism so as to maximize the energy output that will vary with the height of the sun and the amount of cloud and other variables.

4. The apparatus as in claims 1,2, and 3 and in which the central tower may contain a windmill coupled to an electric generator. In an alternative configuration the windmill and generator may be omitted and the apparatus used simply as giant air conditioner as a consequence of its ability to produce an upward current of sufficient force to penetrate any inversion layer which may be present Page 6 of 6 The apparatus as in claims 1,2,3 and 4 save that the source of heat is an apparatus for the burning of fuel and the means of extracting power may be omitted. In this case, the provision of a rotational component of velocity acts to allow the generation of draughts which would otherwise require tall chimneys. Also in this case the site of combustion would be located below the tower and would take the form of, for example, a circular grate. Referring to the schematic diagram. Air flowing through fire in the grate would by virtue of a solid barrier to its motion be forced to divert first to a horizontal direction and then to a vertical direction in a annular space whose radius would exceed that of the grate. Vertical flow in this annular space would again be interrupted by the presence of a solid horizontal barrier and channeled to a horizontal flow directed towards the axis of the tower. This flow would then be modified by the presence of vanes so that on passing the end of vanes at some radius rv, measured from the axis of the tower, the initially radial flow will have acquired a tangential component of velocity of magnitude comparable with that of the initial radial flow. At some radius r i r v the flow would enter the interior of the tower and change direction again becoming a vertical flow with a rotational component of magnitude demanded by the principal of the conservation of angular momentum. The heated air would exit the tower and form a stable rotating column which has little tendency to mix with the surrounding air o.oo* oo* ooo. *o a.