The present invention relates to the field of energy supply systems. In particular, it relates to systems and methods for supplying energy (e.g. electricity and/or fuel) to various offshore users.

It is known to provide an offshore charging buoy for supplying electrical power from a wind farm to charge electrically-powered vessels. The buoy is tethered to the sea bed with mooring lines and connected via a cable to an electrical power supply from the wind farm. When a vessel requiring charging arrives at the buoy, it connects to the buoy via a cable from the buoy allowing electrical power to be transferred from the wind farm, via the buoy, to the vessel.

According to a first aspect, there is provided an offshore energy supply system comprising: an energy supply module for facilitating supply of energy from at least one energy supply to at least one user; at least one energy supply connection means for connecting the energy supply module to the at least one energy supply; and at least one user connection means for connecting the energy supply module to the at least one user, such that energy can be transferred from the at least one energy supply via the energy supply module to the at least one user; wherein at least one of the at least one energy supply is arranged to supply electrical energy and/or fuel (e.g. a gas or liquid fuel such as hydrocarbon(s), hydrogen, ammonia and/or methanol and the like), and the energy supply module is configured such that it can be located on a sea bed.

As such, an offshore energy supply system may be provided with an energy supply module which is locatable on a sea bed. For example, the energy supply module may have sufficient weight, density and/or buoyancy (or lack of buoyancy) such that it can rest on a sea bed, e.g. without floating or drifting off. In some cases, the energy supply module could comprise connection means for fixing the energy supply module to the sea bed.

The energy supply module is preferably watertight, i.e. such that it does not allow the ingress of water.

Compared to systems where such a module is provided at the sea surface (e.g. in a buoy), locating the energy supply module on the sea bed may provide various advantages.

For example, locating an energy supply module on the sea bed means that ocean surface space is not used, thereby providing a minimised or reduced risk of collisions with marine traffic (e.g. vessels) and/or improved survivability under extreme meteorological conditions.

Locating an energy supply module on the sea bed also means that, compared to locating it at the sea surface, it is less exposed to factors such as the marine environment, met-ocean conditions, and forces from waves, currents and wind, etc. As such, it may have a longer lifetime before requiring maintenance, repair or replacement, for example.

Such a system may also be easily scaled up (e.g. for increased electric power and/or fuel supply capacity) as, unlike systems where the energy supply module is provided in a buoy, there are no such constraints on its weight and/or volume. In addition, (due, for example, to the possibility of increased scale) such a system may allow implementation of fast(er) charging facilities, which typically require a larger energy management system with increased weight compared to non-fast charging facilities.

The possibility of increased scale may also mean that a system may be provided that can combine both electric power and fuel supply systems, and/or charge and/or or fuel multiple users concurrently.

A further advantage is that the system may cover a larger area (and thereby potentially charge/refuel a larger number of users) compared, for example, with systems in which an energy supply module is provided at the water surface, e.g. in a buoy. This is because (e.g. when the at least one user connection means is or comprises one or more cables or hoses) the at least one user connection means (or at least one/some of them) may extend diagonally/non-vertically (i.e. at an angle to the vertical) such that a plurality of user connection means may extend or “fan out” over an (a larger) area or region, e.g. of the water surface and/or in the water.

Furthermore, a single energy supply module may be used to facilitate providing both electrical energy and fuel.

According to a second aspect, there is provided an offshore energy supply system comprising: an energy supply module for facilitating supply of energy from at least one energy supply to at least one user; at least one energy supply connection means for connecting the energy supply module to the at least one energy supply; and at least one user connection means for connecting the energy supply module to the at least one user, such that energy can be transferred from the at least one energy supply via the energy supply module to the at least one user; wherein at least one of the at least one energy supply is/are arranged to supply fuel (e.g. crude oil, natural gas, and/or “new” fuels such as hydrogen, ammonia and/or methanol and the like).

As such, an offshore energy supply system may be provided which can supply fuel to a user, thereby facilitating the supply of fuel to users in an offshore environment.

In some cases, at least one of the at least one energy supply may be arranged to supply electrical energy. As such, the system may be able to supply both or either of fuel and electricity to a user (or to different users).

The energy supply module is preferably configured such that it can be located on a sea bed, e.g. as in the first aspect described above.

The following comments may apply to either or both of the first and second aspects.

The at least one user (to which energy is supplied) could be or comprise any system or device requiring energy (e.g. fuel and/or electricity) in an offshore location.

The offshore energy supply system may be permanently or temporarily connected or connectable to the at least one user (e.g. via the at least one user connection means). For example, the offshore energy supply system may be permanently connected or connectable to an offshore user such as a vessel, which requires charging and/or refuelling before moving to a different location. In contrast, users whose location is not required to change may be permanently connected or connectable to a (suitably nearby located) offshore energy supply system. Users that may be permanently connected or connectable to a (suitably nearby located) offshore energy supply system may include oil and gas production subsea structures, underwater remotely operated vehicle (ROV) docking stations, aquaculture farms, other blue industrial users (e.g. offshore mining), and other such offshore systems requiring power and/or fuel, for example.

The at least one user may be located at the water surface and/or under the water.

The at least one user could be or comprise one or more of an offshore vessel (e.g. a boat), a ROV, an offshore aquaculture user, and an offshore mining site, and the like.

The at least one user (e.g. a vessel such as a boat) could be a fully electrically powered user, a partly electrically powered user (e.g. a hybrid) or a fully fuel-powered user. An offshore energy supply system as described herein could supply all or a part of a user’s energy needs. This could be completely electricity, completely fuel, or a combination of the two. For example, if an offshore user can be at least partly powered by electricity, using an offshore energy supply system as described herein to supply it with electricity can reduce that user’s fuel consumption. This may then lead to a reduction in emissions from that user.

In an example, one non-electric vessel without battery systems will stop at one offshore energy supply system (offshore power supply site) for one hour. In this example, the vessel requires a power of 2 MWh. If the vessel receives an offshore power supply from the offshore energy supply system of 1 MWh, it only needs to use fuel to generate 1 MWh. If the vessel receives an offshore power supply from the offshore energy supply system of 2 MWh, it does not need to generate any power from power generation systems on the vessel. In this case, there is no electric charging since there are no battery systems on the vessel.

In contrast, if the vessel is a full or hybrid electric vessel, there will be battery systems on board the vessel. In this case, the offshore energy supply system can be used to cover its power needs at one offshore site for one hour and to provide the electric power to charge the battery systems on the vessel.

As such, the offshore energy supply system may avoid the need for a vessel to deviate (e.g. significantly) from its course for bunkering / power supply at a port as such repowering and/or recharging can be provided offshore by an offshore energy supply system as described herein. Such an arrangement may thereby save power and/or time as it may avoid the need for a vessel to travel longer distances for repowering/refuelling.

The energy supply module (which may in some cases also/alternatively be referred to as a base template) is arranged to facilitate supply of energy from at least one energy supply to at least one user.

For example, the energy supply module may comprise one or more connectors for connection to the at least one energy supply connection means and/or to the at least one user connection means. Preferably, such connectors are suitable for use underwater. Preferably, the energy supply module is configured that that it can connect (e.g. directly or indirectly) the at least one energy supply connection means to the at least one user connection means, e.g. such that they are in electrical and/or fluid connection with each other. The energy supply module may comprise one or more controllers and/or processors for controlling (e.g. starting, stopping, and/or regulating) the supply of energy from the at least one energy supply via the energy supply module to the at least one user. For example, the one or more controllers and/or processors could be configured to manage any gaps in (electricity and/or fuel) supply, for example between different sources, preferably based on the required power supply and/or charging needs of a user.

The energy supply system preferably comprises an energy management system for controlling (e.g. starting, stopping, and/or regulating) the supply of (e.g. electrical) energy from the at least one energy supply to the at least one user. The energy supply module preferably comprises the energy management system. For example, the energy management system may correspond to or comprise the one or more controllers and/or processors described above.

The energy management system may be configured to control or regulate the current and/or voltage of the electrical energy supply. This could depend on the supply needs of a user to be charged. For example, the energy management system could reduce the voltage from a high voltage to a lower voltage and/or convert the supply from AC to DC, suitable for a user to be charged.

In some cases, the energy management system may be configured such that it is able to provide “fast” charging of a user. Fast charging may be charging at several C (current density) rate (e.g. 5C) compared to a standard rate C. Fast charging is often challenging and the energy management system may need further components in order to be able to provide such fast charging of a user. For example, (e.g. additional) electrical energy storage means (e.g. one or more batteries or larger capacity of batteries) may be provided in the energy management system for facilitating fast charging.

The energy management system may comprise one or more batteries for storing electrical energy. Such one or more batteries may be particularly useful for the provision of fast charging, as described above. However, one or more batteries may also be useful even when fast charging is not provided.

The energy supply system may comprise a fuel management system (FMS) for controlling (e.g. starting, stopping, and/or regulating) the supply of fuel from the at least one energy supply to the at least one user. For example, some fuel types such as hydrogen may require compression and/or cooling (e.g. by the FMS) in order to be supplied to a user. As such, a FMS may comprise one or more compressors and/or coolers for compressing and/or cooling the fuel supply. A FMS may additionally or alternatively comprise one or more pumps for pumping the fuel to a user. In some cases, e.g. when the fuel is ammonia, only pumps but no compressors/coolers may be required.

At least one of the at least one energy supply connection means may be connected to an electrical energy supply and/or to a fuel supply.

The electrical energy supply could be or comprise one or more wind turbines, wind farms, wave power generators, tidal power generators, nuclear power plants (e.g. a subsea or underwater nuclear power plant), geothermal power generator, or any other kind of electrical energy supply (or a transformer station connected to such an electrical energy supply). In many cases, such power supplies may be located at the sea bed which can make it convenient for connecting them to a seabed energy supply module.

The fuel supply could be or comprise a hydrocarbon, hydrogen, ammonia and/or methanol supply, production facility (e.g. via a pipeline) and/or storage tank or the like. In some cases, fuel such as hydrogen, ammonia and/or methanol may be produced using electricity from a/the electrical energy supply, e.g. a same electrical energy supply that is also supplying electrical energy to the system.

As such, “green” or “clean” energy may be supplied to a user which may be powered or fuelled by such energy offshore.

Preferably, the at least one energy supply connection means and/or the at least one user connection means are suitable for use underwater, e.g. in a subsea environment.

In some embodiments, the at least one energy supply connection means and/or the at least one user connection means comprises a cable and/or hose or other conduit for transmitting electrical energy and/or fuel.

Preferably, the at least one energy supply connection means and/or the at least one user connection means are flexible (non-rigid) such that they can bend or flex in the water.

In some embodiments, the at least one user connection means comprises a subsea shuttle or transportation means. The subsea shuttle or transportation means is preferably suitable for transferring electrical energy (e.g. in one or more batteries or battery packs) and/or fuel to the one or more users. The subsea shuttle or transportation means could comprise a remotely operated vehicle, for example. In such cases, the energy supply module may be arranged to charge one or more batteries or battery packs such that it/they may then be transported by the subsea shuttle or transportation means to a user. The subsea shuttle or transportation means may also be arranged to (first) transport one or more batteries or battery packs from a user to the energy supply module for charging.

Alternatively or additionally, the energy supply module may be arranged to supply fuel into one or more fuel carriers (containers) such that it/they may then be transported by the subsea shuttle or transportation means to a user. The subsea shuttle or transportation means may also be arranged to (first) transport one or more fuel carriers (containers) from a user to the energy supply module for supplying with fuel (i.e. filling at least partially with fuel).

The at least one user connection means may be suitable for connecting to a user at a seabed and/or in sea water and/or at sea surface level.

The at least one energy supply connection means and/or the at least one user connection means may comprise one or more connectors (e.g. at one or both ends thereof) suitable for connecting the at least one energy supply connection means and/or the at least one user connection means to a user and/or the energy supply module, e.g. in an underwater environment. For example, a Blue Logic subsea connector may be provided at an end of each at least one user connection means for connecting the at least one user connection means to a user(s).

In some cases, a connector may be configured to provide a physical connection to the user to which they are facilitating the supply of energy. Such a physical connection would be preferred if fuel is being supplied, for example. However, in other cases, a connector may provide a remote or distanced connection, for example if electrical energy is to be supplied to a user by induction. In that case, the connector may “connect” to the user by induction and with a spacing (e.g. around 1 m) between the connector and the user.

As discussed above, the energy supply module is preferably actually located on the sea bed.

In some cases, the energy supply module may be or comprise an existing subsea template on a seabed, such as an existing seabed subsea template for supplying crude oil (e.g. connected to a crude oil supply). In such cases, such an existing template may be adapted or added to such that it can also supply electrical energy and/or other fuels to users (e.g. as described herein). The other fuels could, for example, comprise a gas or liquid fuel such as hydrocarbon(s), hydrogen, ammonia and/or methanol and the like.

The energy supply system preferably comprises a plurality of user connection means for connecting the energy supply module to a plurality of users. As such, the energy supply system may be able to (configured to) supply energy to a plurality of users (e.g. 2, 3, 4, 5 or 6 or more users), e.g. simultaneously.

The energy supply system preferably comprises a plurality of energy supply connection means for connection to a plurality of energy supplies. As such, the energy supply system may be able to connect to (be connected to) a plurality of energy supplies, e.g. simultaneously. The plurality of energy supplies could be the same kinds of energy supplies or they could comprise more than one kind of energy supply (e.g. electricity and fuel(s)).

In some embodiments, for example in deep-water locations where the water is more than around e.g. 30-60 m deep, at least one or each of the at least one user connection means is/are connected to a buoyancy element. The 30-60 m depth range may vary depending on factors such as met-ocean conditions and marine/vessel traffic in the area. For example, in some cases, at least one or each of the at least one user connection means may be connected to a buoyancy element (even) in locations where the water is shallower than the 30-60 m depth range mentioned above. In other cases, even if the water is (slightly) deeper than around 30-60 m, a buoyancy element may not be used or needed.

Use of such a buoyancy element as described above may help to facilitate connection of the at least one or each of the at least one user connection means to a user(s) and/or provide support to the user connection means to which it is connected.

Preferably, the buoyancy element(s) is/are connected to the at least one user connection means such that the/each buoyancy element is located beneath the sea surface, preferably at a depth of around 20-40 m beneath the sea surface. This can help to avoid collision with any vessels or other objects on the sea surface. The suggested depth of the/each buoyancy element of around 20-40 m may depend, for example, on the vessel types, their travelling speeds and/or the met- ocean conditions (including tides in rivers and near port areas) in the area. In some cases, for example, the depth might be reduced to 10 m when there are only small vessel types (e.g. supply vessels with water depth: 3-5 m plus the recommended margin of 4 m) in the area. A buoyancy element may be provided for each (or at least some of the) user connection means. Different kinds of buoyancy elements (e.g. with different buoyancies) may be provided for different user connection means depending, for example, on the type of user connection means, e.g. the kind of energy (electricity or fuel) the user connection means is configured to convey, and/or the length or weight of the user connection means, for example.

In some cases, more than one buoyancy element may be provided for a given user connection means, for example if the user connection means is particularly long and/or heavy (e.g. in deeper water locations).

One or more mooring lines may be connected to a buoyancy element. Such mooring lines may help to keep the buoyancy element, and hence user connection means to which the buoyancy element is connect, in its/their desired position. The one or more mooring lines are preferably moorable/moored/connectable/connected to the sea bed.

In some embodiments, a user connection means comprises a first part and a second part, wherein the first part of the user connection means connects (or extends from) the energy supply module to a buoyancy element, and the second part of the user connection means connects (or extends from) the buoyancy element to a user. The first and second parts of the user connection means may have the same or different flexibilities and/or buoyancies. For example, the second part of the user connection means may be more flexible than the first part.

In some embodiments, a user connection means may comprise a single first part connecting (or extending from) the energy supply module to a buoyancy element, and a plurality of second parts (e.g. branching off from the first part) for connecting (or extending from) the buoyancy element to a plurality of (separate) users. This can facilitate the supply of energy to multiple users simultaneously.

In some embodiments, a first user connection means may supply fuel to a user and a second user connection means may supply electricity to the same user simultaneously.

In some embodiments, the offshore energy supply system comprises one or more ROVs, wherein the/each ROV is preferably configured to facilitate connecting (or disconnecting) at least one of the at least one user connection means to (from) a user or users. As such, the/each ROV is preferably suitable for use underwater. The/each ROV is preferably controllable remotely. The/each ROV may be configured to facilitate connecting (or disconnecting) at least one of the at least one user connection means to (from) a user or users automatically. For example, the/each ROV may comprise a receiver for receiving a signal (directly or indirectly) from a user (e.g. an approaching user), the signal indicating that the user is approaching and requiring refuelling or recharging. The signal would preferably indicate what kind of energy supply (e.g. electricity and/or what fuel) the user requires. On receipt of such a signal, the/each ROV is preferably configured to facilitate connection of at least one user connection means to the user (e.g. to a connection point on the user), for example by use of a positioning system such as GPS.

Preferably, the approaching user does not send its signal directly to an ROV but sends it to the energy supply module, which then sends that signal (or a further signal based on or comprising that signal) on to an ROV. If more than one ROV is provided in the system, the energy supply module may send the signal to a particular ROV.

An ROV may be an Eelume ROV, for example.

Preferably, an ROV may be controllable over a range of over 4 km, possibly over 10 km, for example.

When not in use, the ROV may be stored or secured at the energy supply module, for example.

In some embodiments, a catcher (catching means) may be provided to facilitate connecting (or disconnecting) at least one of the at least one user connection means to (from) a user or users. The catcher may be any means suitable for catching hold of the user connection means and bringing it to/from a user for connection/disconnection thereto/therefrom. A catcher may be attached to a crane (e.g. on a user such as a vessel), wherein the crane is arranged to move and control the position of the catcher.

The at least one energy supply connection means, the at least one user connection means, the at least one buoyancy element (if provided) and/or the energy supply module are preferably configured such that when the energy supply system is not in use, the at least one energy supply connection means and/or the at least one user connection means can be secured at, in and/or on the energy supply module. Such storing/securing of the at least one energy supply connection mean and/or the at least one user connection means may be facilitated by an ROV (such as the one described above), for example, and can help to ensure the secured/stored components do not interfere with any other operations in that area.

In order to facilitate such securing of the at least one energy supply connection means, the at least one user connection means and/or the at least one buoyancy element (if provided) in and/or on the energy supply module, one or more retraction means (e.g. one or more windable reels or cogs) may be provided at the energy supply module for retracting or winding in the at least one energy supply connection means, the at least one user connection means and/or the at least one buoyancy element (if provided).

Retracting the at least one energy supply connection means, the at least one user connection means and/or the at least one buoyancy element when not in use can help to minimise degradation of these components over time, thereby reducing any potential maintenance required and increasing their usable lifetime.

According to a further aspect, there is provided a method of installing an offshore energy supply system, where the offshore energy supply system is according to either of the aspects described above (with any of the optional and/or preferred features). The method comprises: providing an energy supply module for facilitating supply of energy from at least one energy supply to at least one user; providing at least one energy supply connection means for connecting the energy supply module to the at least one energy supply; and providing at least one user connection means for connecting the energy supply module to the at least one user, such that energy can be transferred from the at least one energy supply via the energy supply module to the at least one user.

According to a further aspect, there is provided a method of supplying energy to at least one user, the method comprising using an offshore energy supply system to supply energy from the at least one energy supply to the at least one user. The offshore energy supply system is preferably according to either of the first or second aspects described above (with any of the optional and/or preferred features).

Thus, a system and method may be provided for providing preferably clean or green energy to users in an offshore environment. With the construction of offshore green energy sources, such as wind farms and hydrogen production facilities, new green energy sources are available in offshore locations. Such energy sources may be used to supply energy to users that can run on such energy (e.g. electrical energy and/or “green” fuels such as hydrogen) in offshore locations. This may have a significant impact in providing reliable, green and affordable energy supplies for offshore use.

Preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawing, in which:

Fig. 1 is a schematic diagram of an offshore energy supply system supplying electrical energy to a vessel;

Fig. 2 is a schematic diagram of an offshore energy supply system supplying electrical energy to a vessel in shallower water that that of Fig. 1 ;

Fig. 3 is a schematic diagram of an offshore energy supply system supplying electrical energy to one vessel and fuel to another vessel; and

Fig. 4 is a schematic diagram of an offshore energy supply system supplying electrical energy to a two vessels and fuel to a third vessel in shallower water that that of Fig. 1.

As illustrated schematically in Fig. 1, an energy supply system 1 comprises a base template 2 with an electrical energy management system (EEMS) 3 and a fuel management system (FMS) 12. The electrical energy management system 3 is connected to electrical supply cable(s) 8. The FMS12 is connected to a fuel storage tanker 13 and/or a fuel pipeline 14. The fuel storage tanker 13 could store crude oil, for example, or another hydrocarbon fuel. The fuel pipeline 14 could supply hydrogen or ammonia, for example, from a hydrogen or ammonia supply.

The base template 2 is located on the sea bed 9.

The electrical supply cable(s) 8 are connected to an offshore energygenerating structure (not shown) such as a wind turbine, wind farm, or hydrogen production facility. The cable(s) 8 allows energy to be supplied from the offshore energy-generating structure to the base template 2. In some embodiments, two or more cables 8 are provided to supply electricity to the base template 2.

The EEMS 3 controls the supply of electrical energy from the offshore energy-generating structure via the base template 2 to a vessel 7A, which can be powered at least partially by electricity, at the sea surface 10. The EEMS 3 can control the current and/or voltage of the electrical supply to match the requirements of the vessel 7A. The EEMS 3 can also manage supply gaps between one or more power sources (of an offshore energy-generating structure), such as a transformer station or a wind turbine or wind farm, and the required power supply or charging needs of a vessel 7A. A transformer station may receive power from a wind turbine or wind farm, for example. A cable 4 is provided to connect the base template 2 to the vessel 7A, and via which electrical energy can be supplied from the offshore energy generating structure via the base template 2 to the vessel 7A.

In the example shown in Fig. 1 , this is a “deep-water” location, where the water is more than 30-60 m deep. As such, a buoyancy element 5 is connected to the cable 4 to facilitate its connection to the vessel 7A. The buoyancy element 5 is connected to the cable 4 in a location such that the buoyancy element 5 is a depth D beneath the sea surface 10, where the depth D is around 20-40 m. As discussed above, locating the buoyancy element 5 at such a depth D beneath the sea surface 10 can help to minimise the risk of the buoyancy element 5 colliding with vessels on or passing over the sea surface 10, for example.

In some embodiments, multiple cables 4 are provided so that the base template 2 can be connected to and provide electrical energy to multiple vessels concurrently.

The cable 4 is formed of two parts. A first part 4A connects the base template 2 to the buoyancy element 5. A second part 4B connects the buoyancy element 5 to the vessel 7A. The first and second parts 4A and 4B can have different flexibilities and/or buoyancies. For example, the second part 4B may be more flexible that the first part 4A and/or have a lower buoyancy.

The cable 4 is connected to the vessel 7A via a connector 11.

A pick-up system such as an ROV 6 is provided to facilitate connecting the cable(s) 4 to the vessel(s) 7A. In some cases, the ROV 6 is an Eelume ROV. The pick-up ROV 6 may be able to operate over an area or region with a radius of 4 km or more, for example.

In other cases, the cable(s) 4 may be connected to the vessel(s) 7A with a catcher (e.g. using a crane on the vessel to pick up the cable(s) 4 and bring the cable(s) 4 to the vessel(s) 7A for connection thereto).

In other cases, the cable(s) 4 may not be needed and a subsea shuttle may be used to transport a charged battery or battery pack, for example, from the base template 2 to a vessel. A subsea shuttle may also be used to (previously) transport one or more batteries of battery packs from a vessel to the base template 2 for charging.

In the example shown in Fig. 1 , the cable(s) 4 are connected to the vessel(s) 7A. The cable(s) 4 are connected to the vessel(s) 7A with a suitable subsea connector, such as a standard universal connector, e.g. a Blue Logic subsea connector.

When the system 1 is not in operation (i.e. no vessels are being supplied with energy), the whole system (e.g. including the cable(s) 4, buoyancy element 5 and ROV 6) can be kept securely within or on the base template 2, thereby ensuring that these components do not interfere with any other operations in that area. For example, one or more coil devices (not shown) may be provided to wind in/out the cable 4 and buoyancy element 5 (or any other cables and/or buoyancy elements provided.

In some cases, mooring lines are provided to moor the buoyancy element 5 to the sea bed 9.

Fig. 2 is a schematic diagram of an offshore energy supply system T supplying electrical energy to a vessel in shallower water that that of Fig. 1. Many components of Fig. 2 are the same as those shown in Fig. 1 and have the same reference signs. These will therefore not be described again.

In Fig. 2, the water depth D’ is less than around 30-60 m. As such, a buoyancy element 5 is not required and a single continuous cable 4’ connects the base template 2 to the vessel 7A to supply it with electrical energy via the EEMS 3. In this case, the built-in or inherent buoyancy of the cable 4’ is sufficient to support its own weight in the water.

Fig. 3 is a schematic diagram of the offshore energy supply system 1 supplying electrical energy to one vessel 7A and fuel to another vessel 7B. Many components of Fig. 3 are the same as those shown in Fig. 1 and have the same reference signs. These will therefore not be described again.

In Fig. 3, as well as supplying electrical energy to the vessel 7A, the system 1 is also supplying fuel via a fuel supply cable 15 to a second vessel 7B, which can be powered by fuel. Like the cable 4, the cable 15 is formed of a first part 15A and a second part 15B. The first part 15A connects the base template 2 to a buoyancy element 5A. The second part 15B connects the buoyancy element 5A to the vessel 7B. The first and second parts 15A and 15B can have different flexibilities and/or buoyancies. For example, the second part 15B may be more flexible that the first part 5A and/or have a lower buoyancy.

The cable 15 is connected to the vessel 7B via a connector 16. As above, the ROV 6 can facilitate connection of the cable 15 to the vessel 7B. The FMS12 controls the supply of fuel to the vessel 7B. The FMS12 comprises different components to control the supply of different kinds of fuel. For example, a first part of the FMS12 might comprise a pump for facilitating and controlling the supply of crude oil to the vessel 7B. Another part of the FMS12 might comprise a compressor and/or cooler for facilitating and controlling the supply of hydrogen to the vessel 7B. A further part of the FMS 12 might be configured to facilitate and control the supply of ammonia to the vessel 7B.

Fig. 4 is a schematic diagram of the offshore energy supply system T supplying electrical energy to a two vessels 7A and 7C and fuel to a third vessel 7B. Many components of Fig. 4 are the same as those shown in Fig. 1 and have the same reference signs. These will therefore not be described again. Similar to in Fig. 2, the water is depth D’ is less than around 30-60 m. As such, a buoyancy element 5 or 5A is not required and single continuous cables 4’, 4” and 15’ connects the base template 2 to the vessels 7A, 7B, 7C to supply them with electrical energy or fuel. In this case, the built-in or inherent buoyancies of the cables 4’, 4” and 15’ are sufficient to support their own weight in the water.