GB2565068A

GB2565068A - Energy harvesting fluid storage apparatus

Info

Publication number: GB2565068A
Application number: GB1712237.5A
Authority: GB
Inventors: Haden Colin; Rhodes Andy; Spratley Jonathan
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2017-07-31
Filing date: 2017-07-31
Publication date: 2019-02-06
Also published as: GB201712237D0

Abstract

A fluid storage apparatus (100) comprises a storage vessel (10) for storing compressed fluids and a digital valve assembly (40) for controlling the flow of fluid to or from the storage vessel (10). The digital valve assembly (40) comprises an energy storage device (41), such as a capacitor and battery, and an energy harvesting device (60, 70, 100) for generating energy from heat. The storage vessel (10) and/or the digital valve assembly (40) define a temperature-conducting surface on which the energy harvesting device (60, 70, 200) is mounted; and the energy harvesting device (60, 70, 200) generates electricity using the thermoelectric effect to charge the energy storage device (41). Particularly, but not exclusively, the electricity is generated during filling of the fluid storage apparatus. The vessel may be a gas cylinder and include a valve guard. An associated method is also provided.

Description

- 1 ENERGY HARVESTING FLUID STORAGE APPARATUS

FIELD OF THE INVENTION

The present invention relates to energy generation for a digital valve of a fluid storage apparatus for storing a compressible fluid (e.g., a gas cylinder). Electricity is generated from the difference between the temperature of the storage vessel and of the surrounding environment. Particularly, but not exclusively, the electricity is generated during filling of the fluid storage apparatus.

BACKGROUND ART

The use of storage vessels, typically referred to as cylinders, for storing and dispensing pressurised fluid is ubiquitous. Some notable examples include their use to store and dispense gases for medical purposes, for scientific research or for industrial applications. The cylinders may further be used to transport pressurised fluid between locations, either to be transferred to local storage for later use or to be extracted on demand from the cylinder at the point of use. Although reference is made to a “cylinder”, it will be understood that the invention is applicable broadly to all portable pressurised gas containers whether they are strictly in the form of a cylinder or not.

Such cylinders are used to supply gas or liquid for a range of applications including welding and cutting hoses and torches, gas packaging machines and laboratory equipment.

Such cylinders may include digital valves having components for the purposes of display or operation. For example, pressure in the cylinder can be monitored by a pressure gauge utilising an electronic display or electronic sensing elements, or electronic actuators may be incorporated in the valve mechanism. Other examples can be electronic communication devices (e.g. wireless devices) or location sensors (e.g. GPS). Thus, a power source must be provided to the cylinders to allow such electronic components to operate. Given that cylinders are normally portable and employed at locations remote from a power sources, the conventional means to supply power is to provide a battery connected to the cylinder. However, the use of batteries in this manner has disadvantages; conventional batteries are limited in their capacity, meaning that larger batteries are often required for higher power

-2densities. Further, conventional batteries have a limited lifespan and are typically very expensive. These problems are compounded by the nature of their use, where cylinders are often deployed at remote locations for extended periods of time, meaning the power that can be supplied by the battery will not be sufficient to provide a full range of operation over the time period required.

A solution to this problem would be to simply provide a connection to a local power source, such as an attachment to the mains. However, sometimes the location at which the cylinder may be used would not include a local power source. Furthermore, there are instances where use of a local power source would not be desirable, such as when combustible material is stored in the cylinder - if safety provisions are not adequate, a short-circuit and subsequent power surge could be dangerous.

There is thus a need to provide an alternative to simply replacing the batteries of such a device, and the inventors have developed a means to generate electrical power on the cylinder assembly so as to provide a power source without relying on connection to a local power source, which can be unavailable or dangerous, or relying on power stored in a battery, which can be expensive, impractical and/or unsuitable for purpose.

The present invention seeks to provide such a means for generation of electrical power, which provides various advantages over the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a fluid storage assembly for storing fluid defined by claim 1.

A digital valve assembly is a device for controlling the flow of fluid to or from a storage vessel. The digital valve assembly may include valving for this purpose, which valving may be manually actuatable and/or actuated by an electromagnetic actuator. The digital valve assembly includes an energy storage device for powering one or more components of the digital valve assembly, which may include: a display; a pressure sensor, a flow sensor, a temperature sensor, a GPS receiver, a tilt sensor, or other electronic sensing elements;

-3electromagnetic actuators; communication devices (e.g. wireless devices) or location sensors (e.g. GPS).

The inventors have discovered that the filling of a cylinder with pressurised fluid can produce significant enough changes in temperature that energy useful for charging the energy storage device of a digital valve assembly may be harvested from the difference between the temperature of the fluid cylinder and the ambient environment.

Moreover, it has been found that a solid state device, such as those taking advantage of the Seebeck effect, offers the most effective way of obtaining energy from that temperature difference.

Such devices can also be used to obtain energy from the cooling of the cylinder relative to the ambient environment when the cylinder is being used to supply compressed fluid to external equipment. However, it has been found that the best source of energy is the filling process.

Solid state devices, such as Seebeck generators, have polarity. That is, they have opposing “hot” and “cold” surfaces and generate energy only when the “hot” surface is hotter than the “cold” surface (not vice versa). In view of this, and the fact that filling rather than emptying provides the better opportunity to harvest energy, it is preferred for the solid state device to be positioned with its “hot side” against the fluid storage apparatus.

Moreover, filling is a much faster process than emptying. In the context of a digital valve assembly, it is typical to use a battery as an energy storage device. The inventors have discovered that the charging behaviour of a battery is less suitable than that of a capacitor for capturing the harvested energy obtained from the increased temperature of the fluid storage apparatus relative to the cooler ambient environment. Accordingly, in such embodiments a capacitor is preferred to a battery (or may supplement a battery).

LIST OF FIGURES

-4For a better understanding of the invention and to show how the same may be put into effect, reference is now made, by way of example only, to the accompanying drawings in which:

Figure 1 shows an embodiment of a fluid storage apparatus in accordance with the invention; and

Figure 2 shows an exemplary energy harvesting device.

DESCRIPTION

A fluid storage apparatus 100 can be seen in Figure 1.

The fluid storage apparatus 100 comprises: a storage vessel 10; a digital valve assembly 40; and an energy harvesting device.

The storage vessel is arranged to store compressed fluids, which may be delivered to the storage vessel 10 or released therefrom via the digital valve assembly 10. Typically, the storage vessel 10 will be a gas cylinder.

The storage vessel 10 comprises a wall 11. The wall 11 is preferably made of a thermally conductive material, such as a metal. An inside surface 14 of the wall 11 defines a cavity 15 in which fluid may be stored. The cavity 15 communicates with the digital valve assembly 40 via an opening 12.

The digital valve assembly 40 is mounted on the storage vessel 10 such that it can control the flow of fluid through the opening 12 of the storage vessel 10.

The digital valve assembly 40 comprises an energy storage device 41. Preferably, the energy storage device 41 comprises a capacitor. The energy storage device 41 may comprise a capacitor and a battery.

The digital valve assembly 40 comprises: a valve body 43; a valve member 42; and, optionally, an electromagnetic actuator 45.

-5The valve body 43 is a unitary component that is preferably formed of a conductive material such as metal. The valve body 43 includes a conduit 43c that extends between a first connector 43a and a second connector 43b. The valve member 42 extends into the conduit 43c and opens or closes or varies the opening degree of the conduit. The valve member 42 may be driven manually, or by the actuator 45. In this way, the valve member 42 can control a flow of fluid between the first and second connectors 43a, 43b.

The second connector 43b can engage with the opening 12 of the storage vessel 10, thus placing the conduit 43c in communication with the cavity 15. For example, the second connector 43b may have a thread arranged to engage with a complementary thread on the opening 12.

The first connector 43a can engage with a hose or an external device and may be sized and shaped accordingly. For example, the first connector 43a may have a threaded outer surface.

During filling of the storage vessel 10 with pressurised fluid, the temperature of the fluid increases and, as a result, the temperature of the storage vessel 10 also increases. In this way, an outside surface 13 of the wall 11 increases in temperature during the filling of the fluid storage vessel 10. Similarly, an outside surface 44 of the valve body 43, through which the compressed fluid is forced during the filling process, also increases in temperature.

Therefore, the outside surfaces 13 and 43, collectively or individually, define a temperatureconducting surface from which heat energy may be used to generate electricity. The phrase “temperature-conducting” in temperature-conducting surface is merely a label (like “first” or “second”, and is not intended to impart any particular material properties). It is, of course, preferable that the temperature-conducting surface will be formed of a material with good thermal conductance such as brass or steel.

At least one energy harvesting device 60, 70 for generating energy from heat is mounted on the temperature-conducting surface. For example, a first energy harvesting device 60

-6may be mounted on the outside surface 13 of the wall 11 and/or a second energy harvesting device 70 may be mounted on the outside surface 43 of the valve body 43.

The at least one energy harvesting device 60, 70 is preferably mounted on the temperature-conducting surface as closely as possible thereto to improve the conduction of heat. A thermally-conductive adhesive may be used for this purpose. Alternatively, or in addition, the at least one energy harvesting device 60, 70 may be mounted on the temperature-conducting surface via some other material layer.

The at least one energy harvesting device 60, 70 generates electricity using the thermoelectric effect, such as a solid state device. Most preferably, the energy harvesting device is a Seebeck generator.

A suitable solid state energy harvesting device 200 is shown in Figure 2.

The energy harvesting device 200 has a first side 210 and a second side 220 with a semiconductor layer 230 therebetween and at least two contacts 240, 242.

The semiconductor layer 230 is arranged such that when the temperature of the first side 210 exceeds the temperature of the second side 220, a potential difference is created across the two contacts 240, 242. In this way, the energy harvesting device 200 is arranged to generate electricity when the first side 210 is mounted on the temperatureconducting surface and the temperature-conducting surface has a greater temperature than the ambient environment.

As is common among Seebeck generators, the semiconductor layer 230 may not generate electricity when the temperature of the first side 210 is lower than the temperature of the second side 220. Accordingly, it is preferred for the purpose of capturing energy during filling of the cylinder that the first side 210 of the energy harvesting device 200 faces the temperature-conducting surface and the second side 220 faces away from the temperature-conducting surface.

-7For example, the semiconductor layer 230 may include a plurality of regions of P-type material and a plurality of regions of N-type material and a set of interconnections 231 therebetween.

Since such energy harvesting devices 200 are potentially fragile, in preferred embodiments, the digital valve assembly comprises a valve guard 48 for protecting the valve body 43, and the energy harvesting device 200 is located within the valve guard 48. As known in the field, the valve guard 48 is typically formed as a shield that extends around the majority of the valve body 43, with an aperture for allowing a user to access the valve body 43. Such a valve guard 48 could extend around a portion of the valve body 43 on which the energy harvesting device 200 is mounted.

As mentioned above, it is preferred that the energy harvesting device 60, 70, 200 is configured to generate energy during filling of the fluid storage apparatus 100. It has been found that this process raises the temperature of the fluid storage apparatus 100 too rapidly for a conventional battery to be charged efficiently. It is therefore preferred that the energy storage device 41 is, or includes, a capacitor. In this way, the energy harvesting device may directly charge the capacitor in an efficient way.

Optionally, the energy storage device 41 may also include a battery, and the capacitor could be used to charge the battery.

The above described fluid storage apparatus can be used in the following method steps: providing a fluid storage apparatus 100; filling the storage vessel 10 with pressurised fluid, whereby the temperature-conducting surface increases in temperature relative to the ambient environment; and harvesting energy from the temperature-conducting surface using an energy harvesting device 60, 70, 200.

Claims

1. Fluid storage apparatus (100) comprising:

a storage vessel (10) for storing compressed fluids;

a digital valve assembly (40) for controlling a flow of fluid to or from the storage vessel (10), the digital valve assembly (40) comprising an energy storage device (41); and an energy harvesting device (60, 70, 100) for generating energy from heat, wherein:

the storage vessel (10) and/or the digital valve assembly (40) define a temperatureconducting surface on which the energy harvesting device (60, 70, 200) is mounted; and the energy harvesting device (60, 70, 200) is arranged to generate electricity using the thermoelectric effect to charge the energy storage device (41).

2. The apparatus of claim 1, wherein the energy harvesting device (200) is a Seebeck generator.

3. The apparatus of any preceding claim, wherein the energy harvesting device (60, 70, 200) is arranged to generate electricity when the surface has a greater temperature than the ambient environment.

4. The apparatus of claim 3, wherein:

the energy harvesting device (200) is a solid state device having a first side (210) and a second side (220);

the energy harvesting device (200) is arranged to generate electricity when the temperature of the first side (210) is greater than the temperature of the second side (220) but not when the temperature of the first side (210) is less than the temperature of the second side (220); and the first side (210) of the energy harvesting device faces the temperatureconducting surface and the second side (220) faces away from the temperature-conducting surface.

5. The apparatus of any preceding claim, wherein the temperature-conducting surface includes an outside surface (13) of a wall (11) of the storage vessel (10), wherein the inside surface (14) of the wall (11) of the storage vessel (10) defines a cavity (15) for the storage of fluid.

6. The apparatus of any preceding claim, wherein:

the digital valve assembly (40) comprises a valve body (43) comprising first and second connectors (43a, 43b);

the digital valve assembly (40) comprises a valve member (42) for controlling a flow of fluid between the first and second connectors (43a, 43b);

the first connector (43a) is arranged for attachment to a hose or an external device; the second connector (43b) engages an opening (12) in the storage vessel (10) to place the valve body (43) in fluid communication therewith; and the temperature-conducting surface includes a surface (44) of the valve body (43).

7. The apparatus of claim 6, wherein the digital valve assembly (40) comprises a valve guard (48) for protecting the valve body (43), and the energy harvesting device (60, 70, 200) is located within the valve guard (48).

8. The apparatus of any preceding claim, wherein the energy storage device (60, 70, 200) is a capacitor and the energy harvesting device (60, 70, 200) directly charges the capacitor.

9. A method of charging a store of charge of a digital valve assembly, comprising the steps of:

providing a fluid storage apparatus (100) in accordance with any preceding claim; filling the storage vessel (10) with pressurised fluid, whereby the temperatureconducting surface increases in temperature relative to the ambient environment;

harvesting energy from the difference between the temperature of the temperatureconducting surface and the temperature of the ambient environment.