GB2473450A

GB2473450A - Balloon having inner and outer gas compartments

Info

Publication number: GB2473450A
Application number: GB0915791A
Authority: GB
Inventors: Saeed Osman
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-09-09
Filing date: 2009-09-09
Publication date: 2011-03-16
Also published as: GB0915791D0

Abstract

A balloon for supporting a load 5 in the air comprises a primary compartment 4 for receiving a first gas and one or more secondary compartments 3, for receiving a second gas. The secondary compartments are contained within the primary compartment and supported away from the wall 1 of the primary compartment by support means 20 such that when the compartments are filled with gas the first gas completely surrounds the secondary compartment(s). The supports may be made from fibre-reinforced polymer, carbon fibre-reinforced polymer or aluminium. Surfaces of the primary and secondary compartments may be coated with a non-stick material such as PTFE. The balloon may be used to suspend a wind turbine.

Description

BALLOON

FIELD OF THE INVENTION

This invention relates to balloons, airships and the like for supporting loads in the air.

BACKGROUND OF THE INVENTION

It is well known to use balloons for buoyantly supporting a load of some type in the air. Such balloons are also known as lighter than air aircraft, or airships, and work on the principle that a gas having a lower density than the surrounding air will experience an up-thrust, allowing the envelope containing the gas to become airborne. The term "balloon" will be used throughout the following description, but this term is taken to mean any container that achieves buoyancy in the air by containing a gas.

Known balloon or airship designs typically use low density gases such as hydrogen or helium, sealed in an envelope, to provide lift. Hydrogen provides a number of advantages over helium. Hydrogen is less dense, providing a greater lifting force per unit volume; is cheaper to produce and is more abundant. However, a major disadvantage is that hydrogen, when mixed with oxygen, is highly combustible. Exposure to a spark or flame will result in an explosive reaction and is clearly undesirable for any load carrying aircraft, since such an explosion would result in the load falling to the ground. Helium, being inert at standard temperatures, will not undergo such explosive reactions.

To overcome this safety issue previous designs have simply incorporated helium and suffered with the disadvantages associated therewith. Alternatively, US patent application No. US2005/0224638 describes an airship that utilises hydrogen as the main lifting gas, but mixes a quenching gas with the hydrogen which has a fire extinguishing action. Such an arrangement is undesirable because typical quench gases are denser than air and therefore detract from the buoyancy force of the hydrogen. Furthermore, typical quench gases are harmful to the environment and would escape in the event of puncture of the gas envelope.

The present inventor has appreciated that there is a need for a lighter than air aircraft that retains the benefits of using hydrogen as the lifting gas but does not suffer from the safety issues mentioned above.

SUMMARY OF THE INVENTION

The invention is defined in the appended independent claims. Preferred features of the invention are listed in the accompanying subclaims.

An embodiment of the invention provides a balloon for supporting a load in the air, the balloon comprising a primary compartment for receiving a first gas and one or more secondary compartments, for receiving a second gas. The secondary compartments are contained within the primary compartment and supported away from the wall of the primary compartment by support means such that when the compartments are filled with gas the first gas completely surrounds the secondary compartment(s).

Preferably the first gas is inert (e.g. helium), while the second gas has a density lower than that of air, but may also be reactive/volatile/explosive when exposed to the air and particularly to oxygen (e.g. hydrogen). The helium gas acts as a barrier between the hydrogen contained in the inner compartment and the oxygen present in the atmosphere outside the balloon.

The support means may comprise a plurality of struts, each attached at one end to the wall of a secondary compartment and at the other end to either the wall of the primary compartment or the wall of a different secondary compartment. The support means have one or more holes therein, to enhance strength, and are preferrably comprised of fibre-reinforced polymer (FRP), carbon fibre-reinforced polymer (CFRP) or aluminium.

Alternatively, or in addition to struts, the support means may include one or more resilient members, such as a spring.

Embodiments of the invention may have an exhaust for venting gas into the atmosphere, the exhaust being individually connected to each gas compartment. Further, a store may be provided for a quenching gas, used to prevent reactions by the gases used in the balloon, the store being connected to the exhaust. Each secondary compartment may also have an inlet to receive a quenching gas.

Temperature sensors and/or pressure sensors and/or oxygen sensors may also be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Several embodiments of the invention will now be described in detail with reference to the accompanying figures in which: Figure 1 shows the main components of an embodiment of the present invention from front-on; Figure 2 shows an alternative embodiment of the invention incorporating multiple inner compartments; Figure 3A shows an example of a support structures used to hold the inner compartment(s) with respect to the outer compartment; Figure 3B shows a further example of a support structure used to hold the inner compartment(s) with respect to the outer compartment; Figure 4A shows a side view of a further embodiment of the invention; Figure 4B shows a front-on view of the embodiment of Figure 4A; Figure 4C shows a top down view of the embodiment of Figures 4A and 4B; Figure 5 shows a further embodiment of the invention; Figures 6A and 66 show various possible arrangements for the inner compartments; Figures 7A and 7B show a further embodiment of the invention; Figure 8 shows a schematic diagram of an exhaust arrangement.

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DETAILED DESCRIPTION

Figure 1 shows a side view schematic drawing of a balloon, used to support a load 5, according to an embodiment of the current invention. The balloon comprises an outer wall 1 formed of a gas impermeable material and an inner wall 2 also formed from a gas impermeable material. The inner waIl 2 defines inner compartment 3. In addition, an outer compartment 4 is defined between outer wall I and inner wall 2. The inner compartment is kept in position by support means (not shown) attached to the inner wall and the outer wall such that a spacing is maintained between the outer wall I and the inner wall 2 at all positions. In use, inner compartment 3 and the outer compartment 4 are filled with gas such that the inner compartment 3 is completely surrounded by the gas contained in outer compartment 4. The gas used in the inner compartment is chosen to be buoyant, to provide the main lifting force to suspend the balloon in the air. The gas used in the outer compartment is chosen to be inert so as to inhibit combustion, but is also preferably lighter than air. Optionally the inner compartment is filled with hydrogen and the outer compartment is filled with helium.

The helium gas acts as a barrier between the hydrogen contained in the inner compartment and the oxygen present in the atmosphere outside the balloon. Therefore, in the event that an ignition source punctures the outer wall of the balloon, any flame or combustion will be extinguished upon contact with the helium. Even if the inner container is subsequently pierced, leaking hydrogen and helium into the atmosphere, the ignition source will have been extinguished and so the hydrogen will not ignite upon mixing with atmospheric oxygen.

In the event that both the inner and outer containers are pierced and the gaseous contents are vented into the atmosphere it is preferable to prevent subsequent ignition of the hydrogen by a further ignition source. Ignition of hydrogen is prevented when helium is present at concentrations of 12% or greater (meaning that in a mixture of hydrogen and helium, 12 atoms of helium are present for every 88 hydrogen molecules -i.e. a ratio of 3 helium atoms to 22 hydrogen molecules). Therefore, it is preferable for the helium contained in the balloon to occupy at least 12% of the total volume of the balloon available for hydrogen and helium. Even more preferably, helium represents 15% or greater of the volume of the balloon. In this way, should the hydrogen and helium mix either inside the balloon or outside in the atmosphere, ignition of the hydrogen when exposed to oxygen will not immediately occur, allowing time for the hydrogen to dissipate to safe levels. It is also

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possible to provide a mixture of the first gas (i.e. the helium) with a quench gas in the primary compartment to reduce the effects of the second gas (i.e. the hydrogen).

Figure 2 is a schematic drawing of a further embodiment of the invention using the same reference numerals as Figure 1. Rather than having a single inner compartment for the hydrogen gas, a plurality of inner compartments 3 are provided. As with the previous embodiment, each inner compartment 3 may be kept in position by support means (not shown) attached to the walls 2 of the inner compartments 3 and the wall I which defines the outer compartment 4. In use, each inner compartment 3 is surrounded in its entirety by helium gas. Any number of compartments may be used. The advantage of using many compartments is to minimise the risk of contamination by gas leakage in the event of a puncture of one of the compartments. Also, in the event that it becomes necessary to lower the balloon, it is possible to vent the hydrogen from one or more of the compartments rather than having to vent from a single large container, allowing for a more controlled descent of the balloon. Furthermore, keeping the hydrogen in several separate compartments improves safety since it is unlikely that all the compartments will be punctured in the event of a projectile hitting the balloon.

In all embodiments, it is preferable that the outer wall 1 of the balloon and the inner walls 2 making up the one or more compartments are comprised of a light weight, high strength material, such as fibre-reinforced plastic (FRP) (also known as a fibre-reinforced polymer) or more preferably, carbon fibre-reinforced polymer (CFRP) compound. FRPs are composite materials made of a polymer matrix reinforced with fibres. Typically fibres of fibreglass, carbon or aramid are used in conjunction with polymers such as epoxy, vinylester or a polyester thermosetting plastic. It is also possible to use glass reinforced polymer (GRP), also known as glass reinforced plastic, or a similar material. Such materials can be manufactured as a series of panels and held together in the desired shape using one or more methods such as riveting or adhesive tape. Furthermore, heat shrink treatment could be used to improve the adhesion between panels.

It is possible to coat the inner or outer walls with a non-stick material such as polytetrafluoroethylene (PTFE). On the outer side of the outer wall, which is in contact with the atmosphere, this serves to reduce aerodynamic drag. On the inner side of the outer wall, or on either side of the inner walls, such a coating prevents the adsorption of gas molecules, or contaminants, on the surface of the wall, which can result in weakening of the balloon structures. Use of helium gas in the outer compartment also further helps to avoid adsorption of gas because it is a good conductor of heat. This allows natural convection currents to be set up within the compartments, keeping the gas circulating.

The support means preferably comprises a reinforcing frame, used to hold the inner compartment(s) with respect to the outer compartment, which takes into account weight-versus-rigidity and also allows the gas in the outer compartment to flow through the entire compartment freely. Figure 3A shows an example of such a support structure. A series of supports, or struts, 20 are employed. Each strut is comprised of a main support body having a plurality of holes formed therein. The holes reduce the amount of material required for the support, whilst improving strength and also allowing gas to circulate.

Preferrably the holes are circular or oval in shape.

These struts are connected at one end to an inner compartment wall 2 and at the other end to either the outer compartment wall I or to another inner compartment wall. In this way, when the balloon compartments are inflated with gas, each inner compartment is retained in a position spaced from both the outer wall and the other inner compartments.

As a result, each inner compartment is entirely surrounded by the helium gas contained in the outer compartment. The support structure, comprised of this series of struts, is preferably rigid but may have a degree of yield, or give, allowing the structure to flex by around 3%-10% and preferably 5%-8%. This flexibility can be achieved, for example, by using FRP or CFRP as the material for the struts, although it is also possible to use other materials such as aluminium. One preferred option is to use aluminium coated with polymer and machine shaped for reinforcement of the frame with passages for the gas to flow through.

Figure 3B shows further support means which may be used as an alternative to, or in addition to the support means illustrated in Figure 3A. Figure 3B shows the same features as Figure 1 but with the addition of resilient members 30 extending between the outer compartment wall and the inner compartment wall. The resilient members, which are preferrably springs or similar, support the inner compartment wall whilst providing a degree of flexibility or suspension to allow the inner comparment to move relative to the outer compartment in high turbulence or as a result of an impact. Furthermore, the resilient members can be arranged to support the inner compartment away from the outer compartment wall even when uninflated (i.e. when the compartments are not filled with the respective gases). Whilst Figure 3B shows only a single inner compartment supported by two resilient members, it will be appreciated that more members, or more inner compartments, can be provided with each compartment supported by its own set of resilient members. Furthermore, the resilient members can be placed at any point around the outer/inner compartments and not just in the positions indicated in the figure, In the simplest case, a single resilient member could be used, extending from the top of the outer compartment wall. Other types of support means are possible, for example it would be possible to provide magnets of opposite polarities on both the outer compartment and inner compartment to retain the inner compartment in place by magnetic force. A plurality of individual magnets could be distributed over the inner and outer surfaces, or coatings of magnetic materials could be used.

Figures 4A and 4B show a preferred embodiment of a balloon arrangement having a specific shape. Again, common reference numerals with previous figures are used.

These figures show a general load 5 and it will be appreciated that any type of appropriate load may be supported.

Figure 4A shows a side view from which it can be seen that the balloon is approximately in the shape of an aerofoil, tapering towards the front end 6, which faces into the wind, and the rear end 7 which is positioned downwind. The degree of tapering is greater towards the front end, with a gentler tapering towards the rear end, This shape provides an aerodynamic arrangement allowing the balloon to remain stable in high wind conditions, such as those found at altitudes between 800m and 10km. Furthermore, optional fins 41 may be provided at the rear of the balloon on the top, bottom or sides (not *shown) of the balloon in any embodiment.

Figure 4B shows a view from the front of the balloon of Figure 4A (with the optional fins 41 not shown). Three inner compartments are provided. This view demonstrates how the inner compartments may be different sizes so as to fit into an overall aerodynamic shape. The mid section on the top side of the balloon extends, or bulges, out further than the side lobes, allowing a larger central inner compartment. The curvature results in enhanced air-flow over the balloon and improves the aerodynamics of the shape. Figure 4C shows a top down view of the balloon as viewed from above to show how the tapering towards the front and rear also applies to the sides of the balloon.

A further embodiment is shown in Figure 5. This embodiment shares the same features as the embodiment described in relation to Figures 4A and 4B, but has a greater

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width along the axis marked "Y". This allows for a greater number of inner gas compartments, in this case five, to be incorporated along this width.

Figures 6A and 6B show plan views of an outer compartment containing a plurality of inner compartments. These figures show how different distributions and numbers of inner compartments can be used. Figure 6A shows a symmetrical distribution about the longitudinal axis X. Each inner compartment (or inner balloon) is formed in an extended rod/cylindrical type shape, extending along the length of the outer compartment in the direction of the axis X. Figure 6B shows an alternative, non symmetrical arrangement, which may incorporate inner compartments of varying different shapes and sizes, although symmetrical arrangements based upon either half of Figure 6B (along the X axis) may also be used. Spherical inner compartments may be used in conjunction with elongated inner compartments. The elongated inner compartments may extend along the entirety of the length of the outer compartment, or only partially along the length. The precise arrangement of inner compartments is dependent upon the weight and volume of the payload. The figures show arrangements having a central inner compartment having a greater volume than the surrounding inner compartments. Such an arrangement advantageously provides better weight distribution to better support the payload, and to reduce fatigue on the overall structure.

The underside of the balloon preferably comprises a hull 8 of reinforced polymer or a similar material. Glass reinforced polymer (GRP), also known as glass reinforced plastic, or FRP may be used. The wall of the outer compartment may be comprised either entirely of flexible FRP or CFRP derivative, with a portion being attached to the rigid hull.

Alternatively the wall of the outer compartment may be formed from the flexible portion and the rigid hull together, with the flexible portion being attached to the hull by one of the methods described above in relation to the panels making up the outer balloon structure.

The reinforced hull allows for a rigid support structure having good aerodynamic properties since the balloon can be shaped as an aerofoil. As can be seen from Figures 4A -4C, the ballon has a highly curved leading edge, which would face into the wind, and a trailing edge with a lesser degree of curvature to the leading edge. By making the hull more rigid than the upper portion the balloon can be shaped with a greater curvature on the the upper side and a lower curvature on the hull side (the under side), this asymmetry between the top and bottom sides is known as camber. The resulting aerofoil design directs air over and under the structure, being shaped so that air flows faster over the top than under the bottom, acting like a wing to sustain/enhance/supplement lift from the balloon. The span of the "wing" is preferrably large, having a similar dimension to the length of the balloon. The balloon aerofoil shape described above can be applied to any balloon for supporting a load, and not just a balloon with the specific internal structure described herein.

Figures 7A and 7B show a further embodiment of the invention, providing a cross sectional view and a plan view respectively. As can be seen from the figures, a central load 71 is supported beneath the central region of a doughnut or ring shaped balloon. As with previous embodiments, the balloon itself comprises an outer compartment 72 and one or more inner compartments 74 defined by an outer wall and one or more inner walls respectively. As with previous embodiments, the inner compartments are filled with a gas, preferably hydrogen, and are surrounded by the gas contained in the outer compartment, which is preferably helium. The main difference with previous embodiments is that, in this instance, the outer compartment is doughnut shaped, extending circumferentially around the load. The inner compartments may be doughnut shaped also, but it is also possible to use other shapes as described previously. A plurality of supports 73 are provided around the inner perimeter of the outer compartment to support the load. As described above, the cross section of the ring shaped balloon may be aerofoil shaped, having greater curvature on the top than the bottom and greater curvature on the outer edge than the inner edge.

As described above, this can be applied to any ring shaped balloon and not just one with the specific internal structure described herein.

In any embodiment, one or more tethers are optionally provided to prevent the apparatus from floating away. The tethers may be connected to the load or directly to the balloon. Whilst only one tether is necessary, it is preferable to use more. In particular, at least three tethers are preferred to ensure stability of the apparatus when airborne.

Preferably three tethers are attached, or clamped using clamping means, at clamping points on the load. The tethers are connected at their other ends to anchor points, which may be on the ground, on a platform at sea, on a ship, or on the sea bed. The tethers may be made from metallic wire and preferably steel wire. The wire can be further reinforced with a compound polymer to enhance strength, performance and safety.

In order to supply gas to fill the inner and outer gas compartments, a gas inlet system is required. This may simply be a set of gas hoses connected to the compartments at one end and being connectable to a gas supply at the other. The hoses extend from the balloon to the ground, possibly along the tethers, where they are connected to a supply of gas. Such a system can be used with any balloon structure, and not just the type described herein.

It may become necessary to vent gas from the balloon. This could be to lower the balloon to perform maintenance on the ground, or to vent gas in an emergency. To this end, an exhaust may be provided on the balloon. Preferably the exhaust is located at the rear of the balloon 7, although where the balloon is ring or doughnut shaped the exhaust may be placed on an outer section of the hull or alternatively on the upper side of the hull away from the payload. Each gas compartment is connected to the exhaust by connection means such as a gas hose. Gas may be selectively vented from a given compartment, be it the outer compartment or, more likely, the one or more inner compartments. Preferably the exhaust comprises an isolation, non-return valve to allow gas to escape and prevent oxygen from the atmosphere entering the compartments. A schematic of the valve arrangement is shown in Figure 8. Each gas compartment may have its own non-return valve 10 positioned between the compartment and the main exhaust. Preferably a store for containing a neutralising gas is included, with a valve 11 positioned between the store and the main exhaust. A master valve 12 may optionally be positioned along the main exhaust, preferably before the connection between the main exhaust and the store for neutralising gas.

The neutralising gas, or quenching gas, is an additional safety feature and is injected into the exhausted gas to prevent combustion. For example, it may be necessary to vent hydrogen from the inner compartments in the event of a fire, or during a lightning storm. It could be possible for the hydrogen gas to be ignited as it passes into the atmosphere from the exhaust. By injecting a neutralising gas into the hydrogen stream, combustion is inhibited as the hydrogen mixes with oxygen from the atmosphere because hydrogen concentration is greatly reduced by the presence of the neutralising gas. The neutralising gas could be any non-reactive, inert, gas and particularly preferred neutralising gases are carbon dioxide or helium. The neutralising gas may be stored in compressed form in tanks. At high altitudes, where the concentration of oxygen in the atmosphere is lower and wind speeds are higher, there may be no need for the neutralising gas to be used. Therefore, the system may be arranged to only introduce the neutralising gas at a certain altitude in response to an output from an altimeter.

It may also be required to inject neutralising gas directly into the respective gas compartments under emergency circumstances such as when oxygen is detected in one or more hydrogen compartments (as described below). This can be achieved by providing an inlet to each inner compartment to allow neutralising gas to be injected into the balloons.

Although a dedicated inlet can be provided for the neutralising gas, preferably the inlet hoses are used aswell, or instead, to inject neutralising gas. This could be accomplished by providing a two way valve on the inlet tube.

A number of sensors can be provided on the balloon structure. In particular, temperature and pressure sensors and oxygen sensors can be positioned within each compartment. The temperature and pressure sensors allow the operator to determine whether there is a problem with the balloon that may require maintenance. The oxygen sensor is another safety feature, since if the inner compartment is contaminated with oxygen, action will be necessary, for example venting the hydrogen or injecting a neutralising gas. The balloon could be caused to undertake these actions, in relation to a single inner compartment or any number of them, when the sensors detect a concentration of oxygen above a predetermined level.

The data accrued by the sensors will need to be transmitted to the ground, and this can be achieved by using wireless communication, fibre-optics along the tether lines or any number of alternatives as known in the art.

A number of features are described in relation to exhausts for gases, and neutralising gases. It will be appreciated that such features could be implemented with any balloon type and not just a balloon having a structure as described herein.

The current invention finds particular utility in supporting wind turbines in the air.

However, the invention could also be used as a cellular tower replacement, and observation tower, a meteorological station, a localised tn-axis reference point (as an alternative to GPS), a mobile generator, a broadcasting tower, fire fighting apparatus, rain inducing technology or as a transportation device.

Claims

CLAIMS1. A balloon for supporting a toad in the air comprising: a primary compartment for receiving a first gas; and one or more secondary compartments, for receiving a second gas, contained within the primary compartment and supported away from the wall of the primary compartment by support means such that when the compartments are filled with gas the first gas surrounds the secondary compartment(s).
2. A balloon according to claim 1 wherein the support means comprise a plurality of struts each attached at one end to the wall of a secondary compartment and at the other end to either the wall of the primary compartment or the wall of a different secondary compartment.
3. A balloon according to claim 1 or 2 wherein the support means have one or more holes therein.
4. A balloon according to claim 1, 2 or 3 wherein the support means are comprised of fibre-reinforced polymer (FRP), carbon fibre-reinforced polymer (CFRP) or aluminium.
5. A balloon according to any preceding claim wherein the support means includes one or more resilient members, such as a spring.
6. A balloon according to any preceding claim wherein surfaces of the primary and/or the secondary compartments are comprised of FRP, CFRP or glass reinforced polymer (GRP).
7. A balloon according to any preceding claim wherein the surfaces of the primary and/or secondary compartments are coated with a non-stick material such as polytetrafluoroethylene (PTFE).
8. A balloon according to any preceding claim further comprising a rigid hull.
9. A balloon according to claim 8 wherein the rigid hull is comprised of GRP or FRP.
10. A balloon according to any preceding claim having an exhaust for venting gas into the atmosphere, the exhaust being individually connected to each gas compartment.
11. A balloon according to claim 10 further comprising a store for a quenching gas, the store being connected to the exhaust.
12. A balloon according to any preceding claim, wherein each secondary compartment has an inlet to receive a quenching gas.
13. A balloon according to claim 11 or 12 wherein the quenching gases are one of carbon dioxide or helium.
14. A balloon according to any preceding claim having one or more temperature sensors and/or pressure sensors.
15. A balloon according to any preceding claim having one or more oxygen sensors to monitor the concentration of oxygen in the gas compartments.
16. A balloon according to any preceding claim wherein the primary compartment is filled with the first gas and the secondary compartment is filled with the second gas.
17. A balloon according to claim 16 wherein the first gas is inert.
18. A balloon according to claim 16 or 17 wherein the second gas has a lower density than air.
19. A balloon according to claim 16, 17 or 18 wherein the first gas is helium.
20. A balloon according to any of claims 16 to 19 wherein the first gas also includes a quench gas.
21. A balloon according to any of claims 16 to 20 wherein the second gas is hydrogen.
22. A balloon according to any preceding claim wherein the load is a wind generator such as a wind turbine.
23. A wind generator comprising a balloon according to any preceding claim, a plurality of blades mounted on a rotor and an associated electrical generator, the rotor and generator being supported by the balloon.