A power distribution system for powering refrigerated containers

Abstract

A wireless power distribution system for supplying electrical power to a stack of refrigerated cargo containers. The system comprising multiple elongate spaced-apart upright posts, one for each column

Description

Refrigerated cargo containers, commonly named reefers, are used to transport temperature sensitive cargo, such as for example, flowers, food and chemicals etc. Reefers comprise a refrigeration plant that requires connection to an external power supply to operate. The power connection is conventionally implemented by plugging a power cable of the reefer into a socket of an external power supply. When a reefer requires moving, e.g. loading onto or unloading off of a ship, truck or train, or within a port, the power cable requires manual disconnection and reconnection to a new power supply. To this end, each reefer comprises a power cable terminating in a plug for connection with a socket of an external power supply. Within a port, port operatives (dockers) undertake this role, which thus requires implementation of extensive safety access protocols to provide a safe working environment. To minimise the operational disruption this causes, multiple reefers are connected or disconnected in batches, meaning that some reefers may be without power for extended periods of time; this may lead to deterioration or spoiling of cargo. Figure 1 illustrates a conventional reefer access gantry structure 1 to provide manual access to a stack of reefers 2. In this example the structure 1 can accommodate stacks of reefers up to three high, and six wide. The gantry structure 1 comprises a multi-level walkway with steps 1A between each level. The structure carries electrical cables (not shown) that supplies electrical power from a power supply 3, typically three-phase, to sockets 4 on each level. An operator climbs the gantry 1 to gain access to the reefers and sockets 4 for the purpose of connecting and disconnecting power cables 5 of the reefers 2 into the sockets 4. It has been proposed in CN103887894, DE 102017107307, WO2014095016 and JP2011205780 to use wireless inductive charging to supply electrical power to a reefer. According to a first aspect of the invention there is provided a power distribution system for supplying power to a stack of refrigerated cargo containers of n containers high and m containers wide, the system comprising m elongate spaced-apart upright elements; each upright element separately carrying n wireless power transmission units, each for supplying electrical power wirelessly to a different cargo container of a single column of the stack. The invention provides a simpler and more economic solution to installing a wireless power distribution system for a stack of reefers, particularly for stacks of three or more high. Compared with the systems of CN103887894, DE102017107307, WO2014095016 and JP2011205780, the invention allows for less vertical posts per stack column of reefers and / or avoids the need for raised horizontal bracing, which complicates assembly and adds cost. Unlike the prior art systems, the elongate spaced-apart upright elements can be, if desired, unconnected to one another. The upright elements may be spaced apart by a lateral separation distance between 8 feet (2.438m) and 10 feet (3.048m) inclusive. The standard width of a reefer is 8 feet, (2.438m), which sets the minimum range value. Although the upright elements may be spaced apart by more than 10 feet (3.048m), this would, in most cases, unnecessarily enlarge the footprint of the stack. The upright elements may be permanently fixed into the ground, e.g. concreted in. Alternatively, each may be releasably supported on a separate base such as, for example, a pre-formed aperture in the ground. Alternatively, the base could itself be portable in which case the upright element need not be releasably supported to the base. One or more, or each upright element may be freestanding, i.e. not supported by guy wires or the like. The concept of a portable power distribution system is considered to have independent inventive merit, and thus according to a second aspect of the invention there is provided a power distribution system for supplying power to a vertical stack of refrigerated cargo containers, the system comprising a portable freestanding upright element carrying multiple wireless power transmission units spaced apart vertically along the freestanding upright element each for supplying electrical power wirelessly to a different cargo container of the stack. The system may comprise m of the portable freestanding upright elements arranged in a line, where m>l, for supplying power to a stack of refrigerated cargo containers of m containers wide and n containers high. The system allows for the rapid deployment of a reefer power distribution system to vary reefer storage capacity at a particular location. For example, at locations where there is no capacity, or to expand existing capacity without the need to install fixed infrastructure. For example, it may be used to expand capacity of existing reefer stations of stacks one or two reefers high, where there is an existing power supply, to three or more reefers high. Each upright element may be supported by a separate base means configured to support the upright element in a substantially vertical orientation. The upright element may be releasably detachable from its respective base. In one arrangement each base means comprises an aperture in the ground configured to receive and retain the upright element in a substantially vertical orientation. In certain variants, the base may itself be portable. Where so, the base may comprise apertures configured to receive tines of a fork-lift to allow the base to be lifted by the fork-lift. Although less preferred the base could be provided with wheels to enable the upright to be wheeled into position. The portable freestanding upright element may include electrical connectors remote to the wireless power transmission units to allow each wireless power transmission unit to be physically and electrically connected and disconnected to an external power source. Favourably the electrical connectors are located, when the system is in use, lower down relative to at least one or two (possibly all) of the wireless power transmission units to provide convenient access by an operative without need of a ladder, cherry picker, scissor lift or other climbing equipment. The invention will now be described by way of example with reference to the following Figures in which: Figure 1 is a perspective view of a stack of reefers and a prior art multi-level gantry structure carrying a power distribution system; Figure 2 is a perspective view of a stack of reefers and a power distribution system comprising a set of spaced apart upright members; Figure 3 is a variant power distribution system comprising lateral bracing between the uprights; Figure 4 is a perspective view of an upright with a variant structure; Figure 5 is a perspective view of a system allowing for temporary positioning of uprights, and Figure 6 is perspective view of a variant system for allowing temporary positioning of uprights; and Figure 7 is a perspective view of a portable upright structure including a portable base. Figure 2 illustrates a stack of reefers 10, e.g. as would be commonly found in a terminal yard of a marine port. In this example, the stack is three reefers high and six reefers wide, though this should not be taken as limiting Each reefer 10 comprises a refrigeration unit, not shown, to control the temperature within the reefer’s interior, and a wireless power receiving unit 11 configured to receive electrical power wirelessly by induction from a wireless power transmission unit 13 to power the refrigeration unit. The reefer 10 may also include power circuitry, which may form part of the wireless power receiving unit 11, configured to one or more of: transform, rectify, invert and convert (e.g. 1 to 3 phase) the electrical power received from the wireless power transmission unit to make it compatible to supply the refrigeration unit. This may be of particular value where the wireless power receiving unit 11 is retrofitted to the reefer 10. Also shown in Figure 2 is a power distribution system comprising a line of six vertical upright posts 12, one for each vertical column of reefers 10 of the stack. Each post 12 is set into the ground, e.g. concreted in, at a spacing of X from its nearest neighbour(s), where X is at least 8ft (2.4m) and favourably at most 10 ft (3.05m). Each post 12 carries three wireless power transmission units 13, one for each of the three reefers 10 per vertical column of the stack. The wireless power transmission units 13 are spaced apart vertically from one another to align with the height of the receiving power units 11 of the stacked reefers 10. A typical vertical spacing between wireless power transmission units 13 along each post 12 is approximately nine foot six inches (2.9m), corresponding to the height of a Hi-Cube reefer unit, which is now the most common form of reefer, and becoming more so over time. Through this arrangement, the series of posts 12 carries an array of wireless power transmission units 13, one for each reefer 10 of the stack; each transmission unit 13 lying face-to-face with a different receiving unit 11. The preferred spacing between a transmission unit 13 and its paired receiving unit (which typically corresponds also with the separation between the post 12 and the reefer 10) is around 40cm ± 10cm. The preferred lateral misalignment is no more than 5cm. A misalignment tolerance of <5cm in the relatively positioning of shipping containers within a stack is already common working practice to ensure their stability of the stack. The system further comprises an electrical power supply 14. Each wireless power transmission unit 13 is connected to the electrical power supply 14 via electrical leads 15 which run up the posts 12. The leads 15 may be carried within the posts 12, or secured externally to them. Typically, the electrical power supply 14 supplies a three-phase alternating current (ac). Thus, the power distribution system will typically need to include a power circuit to modify the output of the electrical power supply 14. The power circuit (not shown) may be provided at the electrical power supply 14, at each wireless power transmission unit 13, somewhere in between, or possibly spread across one or more of these positions. In operation, electrical power is transmitted wirelessly, through induction, from the transmitting units 13 to their respective receiving units 11 to power the refrigeration units of the reefers 10 of the stack. Each wireless power transmission unit 13 includes a control system including a sensor, e.g. an electro-magnetic sensor, configured to detect the presence of receiving unit 11 within a proximity of 40cm ± 10cm, and, in response, to regulate the power used by the wireless induction circuitry of the unit 13. This mechanism allows the power consumed by wireless power transmission unit 13 to be minimised when there is no reefer to power. The receiving unit 11 can include means to transmit power requirement information wirelessly to the wireless power transmission unit 13, e.g. using a very short-range RF protocol, and the control system configured, in response to receiving said information to regulate the power transmitted. This also serves to improve the overall electrical efficiency of the system, as the power supplied to the reefer can be cycled to match the time-varying power requirement of refrigeration unit - e.g. as the compressor and / or fans are switched on and off. Ideally, the posts 12 require no lateral supporting structure as this simplifies construction and maintenance. Nevertheless, there may be occasions where lateral supports are preferred. Figure 3 illustrates an example structure, which is substantially identical to that of Fig 2, with the addition of lateral supports between the posts 12, including horizonal struts 16 and diagonal wire ties 17. The posts 12 of the variants of Fig 2 or 3 may comprise solid or hollow section, such as an I-beam, H-beam or tube (of circular or other cross-sectional shape). Each post could be formed from multiple sections mounted one-atop the other. The posts 12 may taper so as to narrow towards their upper end. A suitable material for the construction of the posts is steel by virtue of its relatively low cost and high strength, though it will be appreciated there are a wide variety of other materials, metallic and non-metallic that could be suitable. An alternately construction of upright is illustrated in Fig 4, in which each upright of the line comprises a freestanding lattice tower 20. Each lattice tower 20 comprises at least three vertical members, in this example there are four, interconnected by a lattice frame work. This structure may be preferred for servicing columns of reefers that are five high or more. If the uprights are to be located in a single position permanently, they may be concreted into place. However, there may be occasions where it is desired to demount the uprights: e.g. to move them to a new location within a port where it is desired to expand the reefer stack size, or whether the space they are occupying is to be used for an alternative purpose. The following describes arrangements that provide flexibility in the number and / or positioning of uprights. Figure 5 illustrates a line of holes 30 set in one or more concrete slabs 31. Each hole 30 is set at a spacing of X from its nearest neighbour(s), where X is at least 8ft (2.4m) and favourably at most 10 ft (3.05m). Each hole 30 has a size and depth to receive an upright 12A and hold it substantially vertical. Each upright 12A (of which only lower portion shown in Fig 5) is provided with cables 15, one per wireless transmission unit, each terminating with an electrical connector 15A, e.g. a socket or plug, to electrically connect the wireless transmission units 13, carried on the upright 12A to corresponding electrical connectors 15B to make connection to the external power supply 14. When it is wished to install an upright, the upright, with transmission units 13 already mounted thereon, is manoeuvred to the hole and its bottom end lowered therein. The electrical connectors 15A 15B are mated. When it is wished to remove an upright, the connectors 15A 15B are disconnected before the upright is lifted out from the hole 30. Figure 6 illustrates a variant means of securing uprights 12A in place in which each upright 12A is mounted (e.g. fastened and / or welded) to a base plate 40 adapted to be fastened to the ground via bolts 20 (or equivalent fixings) to a holding down assembly 41 comprising threaded apertures 42. Each set of apertures 42 has a centre spacing from its nearest neighbouring of X, where X is at least 8ft (2.4m) and favourably at most 10 ft (3.05m). Figure 7 illustrates a base 50, e.g. taking the form of a plate, slab, block, or pallet-like structure, having a variant design that includes apertures 51 to receive tines of a forklift to facilitate transport of the upright. The base 50 includes through apertures 52 for fastening the base 50 to the ground by bolts 53, but may instead, or additionally, be weighed down by one or more weights (not shown) placed upon it. The upright 12A may be permanently fixed to the base 50, e.g. through welding, or may be releasably attached to the base by fasteners. The latter allows the base 50 and upright 12A to be separated from one another to facilitate transportation. Although less preferred, the base 50 unit may be provided with wheels to enable the base, with or without the upright, to be wheeled about. To aid connection and disconnection of the connectors 15A and 15B, the cables 15 extend down from the uppermost transmitting units in order that connectors 15B lie within two metres above of the ground when the uprights are vertical and in use. This is relevant to any of the embodiments described and illustrated in Figs 2-7. The above examples describe uprights configured to accommodate stacks of reefers up to three reefers high. The principle of the invention can be applied to stacks of any number high though the benefits of the system are greatest for stacks three or more reefers high. It will be appreciated that the width of the stack can be any number >1 though it is usually likely to be greater than one, dependant on the number of reefers expected to require power, and limited only by the space available at the location.

Claims

1. A power di stribution system for supplying power to a stack of refrigerated cargo containers of n containers high and m containers wide, the system comprising m elongate spaced-apart upright elements; each upright element separately carrying n wireless power transmission units, each for supplying electrical power wirelessly to a different cargo container of a single column of the stack.

2. A power distribution system according to claim 1 wherein the elongate spaced-apart uprights elements are unconnected to one another.

3. A power distribution system according to claim 2 wherein the upright elements are spaced apart by a separation distance between 8 feet (2.438m) and 10 feet (3.048m).

4. A power distribution system according to claim 1,2 or 3 wherein each elongate spaced-apart upright element is freestanding5. A power distribution system for supplying electrical power to a stack of refrigerated cargo containers, the system comprising a portable freestanding upright element carrying multiple wireless power transmission units spaced apart vertically along the freestanding upright element, each for supplying electrical power wirelessly to a different cargo container of the stack.

6. A power system according to claim 5 comprising a base that supports the upright element in a substantially vertical attitude.

7. A power system according to claim 6 wherein the base comprises apertures configured to receive tines of a fork-lift.

8. A power system according to any claim 5, 6 or 7 wherein the portable freestanding upright element includes an electrical connector comprising an electrical plug or socket, located remote to the wireless power transmission units to electrically connect the wireless units to an external power source.5 9. A method of installing a distribution system for supplying power to a stack ofrefrigerated cargo containers of n containers high and m containers wide, the method comprising installing m elongate spaced-apart elements in an upright orientation; each upright element separately carrying n wireless power transmission units, each for supplying electrical power wirelessly to a different10 cargo container of a single column of the stack.

10. A method according to claim 8 wherein each wireless power transmission unit is mounted to the upright before the upright is rendered vertical.15AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-1007 10 2515Claims20 1. A power distribution system for supplying power to a stack of refrigerated cargocontainers comprising m columns of containers n containers high, where m>l07 10 25, the system comprising m elongate spaced-apart upright elements; each upright element separately carrying n wireless power transmission units, each for supplying electrical power wirelessly to a different cargo container of a single column of the stack.5 2. A power distribution system according to claim 1 wherein the elongate spaced-apart uprights elements are unconnected to one another.

3. A power distribution system according to claim 2 wherein the upright elements are spaced apart by a separation distance between 8 feet (2.438m) and 10 feet (3.048m).10 4. A power distribution system according to claim 1,2 or 3 wherein each elongatespaced-apart upright element is freestanding.

5. A power distribution system for supplying electrical power to a stack of refrigerated cargo containers, the system comprising a portable freestanding upright element carrying multiple wireless power transmission units spaced 15 apart vertically along the freestanding upright element, each for supplyingelectrical power wirelessly to a different cargo container of the stack.

6. A power system according to claim 5 comprising a base that supports the upright element in a substantially vertical attitude.

7. A power system according to claim 6 wherein the base comprises apertures 20 configured to receive tines of a fork-lift.

8. A power system according to any claim 5, 6 or 7 wherein the portable freestanding upright element includes an electrical connector comprising an electrical plug or socket, located remote to the wireless power transmission units to electrically connect the wireless units to an external power source.

9. A method of installing a distribution system for supplying power to a stack of refrigerated cargo containers of n containers high and m containers wide, the method comprising installing m elongate spaced-apart elements in an upright orientation; each upright element separately carrying n wireless power5 transmission units, each for supplying electrical power wirelessly to a differentcargo container of a single column of the stack.

10. A method according to claim 8 wherein each wireless power transmission unit is mounted to the upright before the upright is rendered vertical.ioCM

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