IT201900008367A1 - A NATURAL GAS LIQUEFACTION SYSTEM - Google Patents

Description

"A NATURAL GAS LIQUEFACTION SYSTEM"

DESCRIPTION

TECHNICAL FIELD

The present disclosure relates to natural gas liquefaction technology. More specifically, novel systems and methods for efficiently liquefying a hydrocarbon feed stream, such as a natural gas feed stream, are disclosed herein.

ANTERIOR ART

[0002] Natural gas is a mixture of hydrocarbons in a gaseous state. Natural gas predominantly comprises methane and may contain a portion of other heavier gaseous components. It is useful to liquefy natural gas for a variety of reasons and mainly for storage and transportation purposes. Liquefied natural gas (also referred to by the acronym LNG) occupies a much smaller volume and can therefore be transported for example by LNG vessels. Liquefied natural gas is not only easier to transport due to the smaller volume it occupies, it is also safer.

Many methods for liquefying natural gas have been developed in recent decades. In principle, after a purification pre-treatment, the natural gas is processed through a plurality of refrigeration stages using heat exchangers to progressively reduce the temperature of the gas until it liquefies. Regardless of the type of liquefaction technology used, the refrigeration and liquefaction process is relatively energy-intensive. Compressors or compressor trains are required to process cryogenic fluids, i.e. refrigerant fluids, which are used to remove heat from the natural gas stream until liquefaction.

Refrigerant compressors are usually driven by gas turbine engines, steam turbines or electric motors and require large amounts of power. Some of the same natural gas that needs to be refrigerated and liquefied is generally used as the main source of energy to drive refrigerant compressors, for example to generate steam to drive a steam turbine, or combustion gas to run an engine. gas turbine, which in turn directly drive one or more compressors or refrigerant compressor trains, or are used to drive electric generators. The electrical energy thus generated is used to drive electric motors, which drive compressors or refrigerant compressor trains. Using electric generators to produce electrical energy from mechanical energy and electric motors to convert electrical energy into mechanical energy to drive refrigerant compressors avoids the need to run variable speed steam or gas turbines to adapt the rotation speed to the demands of variable flow from the refrigerant compressors. The electric generator actuator can rotate at a constant speed thus maximizing the efficiency of the actuator, while a variable speed electric motor can in turn drive the refrigerant compressor at variable speed, depending on the refrigerant flow requirements.

[0005] Electric power for the electric motor that drives a train of LNG compressors is generated by one or more electric generators, as there is usually no suitable electricity network available in the locality where the LNG plant is located.

[0006] Possible configurations of LNG systems and related compressor trains are described in WO 2018/206102.

A common feature of the LNG systems described above is that an important portion of natural gas is used to generate the mechanical power required to drive the compressor trains and to increase the volumetric enthalpy content of the natural gas flow through liquefaction. This has a negative impact on the liquefaction rate of the gas, as part of the gas is used to generate mechanical power to drive the compressors. Furthermore, the consumption of fossil fuel to run the liquefaction process also has a negative environmental impact, as it generates carbon dioxide.

It would therefore be desirable to provide an LNG system that reduces energy consumption and negative environmental impact. The environmental effect can also give rise to an increase in costs or taxes due under applicable legislation or standard requirements.

SUMMARY

According to one aspect, an integrated natural gas liquefaction system is described here, comprising an energy conversion system adapted to convert energy from a renewable energy source into energy that can be used to liquefy natural gas through at least one circuit refrigerant adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor. The energy conversion system may comprise an energy collector to collect energy from the renewable energy source.

[0010] Specifically, herein described embodiments of an integrated natural gas liquefaction system (in short "integrated LNG system") comprises at least one refrigerant circuit adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor. The integrated natural gas liquefaction system also includes an energy collector, capable of collecting energy from at least one renewable energy source. A mechanical power generator of the integrated natural gas liquefaction system is adapted to convert energy supplied by the energy collector into mechanical power. The mechanical power generator can be powered directly or indirectly by energy from the energy collector. For example the energy from the energy collector can be converted and / or stored for later use by the mechanical power generator.

The mechanical power generator is mechanically coupled to the refrigerant compressor. Energy from the renewable energy source is thus harnessed by the integrated LNG system to drive at least one refrigerant compressor, thereby reducing or eliminating the need to burn natural gas, or other fossil fuel, to drive the refrigerant compressor.

As will be clear from embodiments of the integrated natural gas liquefaction system described below, the energy collected by the energy collector can be temporarily stored. The energy collected can be converted into one or more different types of energy, for example according to the nature of the renewable energy source used, the nature of the energy collector, the way of storing energy. In embodiments described herein, the energy collected from the renewable energy source can be converted, for example, into electrical energy, potential energy, chemical energy, thermal energy (heat), kinetic energy or combinations thereof.

[0013] In the sense used here, an energy collector of the integrated LNG system is any aggregate of machinery capable of producing useful energy, such as electrical, mechanical or chemical energy, using a renewable energy source, such as solar energy, tidal energy , wind energy, geothermal energy and the like.

[0014] The energy collector may comprise, inter alia, a concentrating solar power plant, a solar photovoltaic plant, a wind power plant, a hydroelectric plant, a tidal or wave energy conversion plant, a geothermal system, or combinations thereof. Energy collected from the renewable energy source by means of the energy collector can be made available as electrical power to drive one or more compressors of one or more compressor trains of the LNG system by means of one or more electric motors, which convert the energy electrical into mechanical energy. For example, solar or wind energy can be converted into electrical energy, which is subsequently converted into mechanical energy by an electric motor to drive a compressor or compressor train.

In other embodiments, energy collected by means of the energy collector from the renewable energy source can be used to produce hydrogen via electrolysis. Hydrogen can then be used, for example, to power an internal combustion engine, such as a gas turbine engine, to produce mechanical power and drive a compressor or a train of compressors adapted to process one or more refrigerants of the integrated LNG system.

In other embodiments, energy collected by means of the energy collector from the renewable energy source can be made available as thermal energy (heat). Heat can be converted into mechanical power to drive a refrigerant compressor. The conversion can be done through a thermodynamic cycle, for example a Rankine cycle using a steam turbine, or a Bryton cycle, using a gas turbine.

In other embodiments, the mechanical power is converted into electrical energy, which can be converted into mechanical energy or chemical energy, for example into hydrogen, which is subsequently used to power an internal combustion engine, such as a turbine engine gas, to generate mechanical power and drive the refrigerant compressor.

[0018] Further characteristics and embodiments of the invention are described in greater detail below, with reference to the attached drawings, and are set out in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] A better appreciation of the embodiments of the invention and its many advantages can be obtained from the detailed description that follows with reference to the attached drawings, in which:

Fig.1 illustrates a simplified schematic representation of a plant according to the present description in an embodiment; there

Fig.2 illustrates a simplified schematic representation of a plant according to the present description in a further embodiment; there

Fig.3 illustrates a schematic and simplified representation of a plant according to the present description in a further embodiment; the

Figures 4A, 4B, 4C and 4D summarize different embodiments of energy storage devices suitable for use in an LNG system according to the present description; the

Figs 5, 6, 7, 8 and 9 illustrate diagrams of integrated LNG systems using concentrated solar energy, in one embodiment; there

Fig.10 illustrates an LNG system that uses renewable energy sources to produce hydrogen as fuel for a gas turbine engine; and the

Fig. 11 illustrates a further LNG system using renewable energy sources to produce hydrogen as a combustion for fuel cells.

DETAILED DESCRIPTION

A new and useful integrated natural gas liquefaction system has been developed. In order to increase the efficiency of the natural gas liquefaction system, energy from a renewable energy source contributes at least in part to the operation of one or more refrigerant compressors. Using energy from a renewable energy source reduces the consumption of natural gas, or other high-value non-renewable energy sources to operate the refrigerant compressor actuators.

Since renewable energy sources may not be available to provide the full amount of power required, or may provide more than the power required to drive refrigerant compressors, according to embodiments described herein measures are taken to accumulate or store a excess energy fed by the renewable energy source for use when insufficient power is supplied from the renewable energy source. In some embodiments, excess electrical energy generated by converting renewable energy can be exported to an electrical grid.

[0022] In order to ensure that the LNG system can operate even in the event of a power failure from the renewable energy source and / or from an energy storage system, auxiliary energy systems can be provided to operate the compressor. coolant, if so required. In some embodiments, the auxiliary drive system may comprise a gas turbine engine disposed on the same shaft line as the refrigerant compressor train.

[0023] Coming now to the drawings, Fig.1 illustrates a diagram of a first embodiment of an integrated natural gas liquefaction system (here briefly also referred to as the LNG system), globally labeled 1. As mentioned above, it is A variety of liquefaction technologies have been developed that can be used to liquefy natural gas. The structure and operation of the liquefaction system cycles are not relevant in the context of this disclosure. What is relevant is that, in general terms, a natural gas liquefaction system comprises one or more compressors or compressor trains, which process one or more refrigerant fluids that are subject to cyclic thermodynamic transformations. Mechanical power drives one or more refrigerant compressors. The refrigerant fluid at the delivery of the compressor (s) is cooled and expanded to reach low temperatures. The expanded refrigerant removes heat from the natural gas stream by heat exchange with it. The heated refrigerant gas is re-compressed by the refrigerant compressor (s).

The present disclosure concerns an efficient way of using renewable energy sources for the operation of one or more refrigerant compressors in an integrated LNG system.

[0025] In the diagram of Fig.1, as well as in the remaining figures, the core of the thermodynamic cycle of the LNG system, which processes one or more refrigerant fluids, comprises at least one refrigerant circuit 3. The refrigerant circuit 3 comprises at least one refrigerant compressor. In the diagram of Fig.1, the compressor 5 is representative of one or more compressors or compressor trains for processing one or more refrigerant fluids. The refrigerant circuit also comprises a chiller 7, an expander 9 and a heat exchanger 11. The refrigerant fed by the refrigerant compressor 5 is cooled in the chiller 7, for example by heat exchange with air, water or another refrigerant of a other refrigerant circuit. The compressed and cooled refrigerant is expanded in the expander 9 to reach a sufficiently low temperature, so that heat with it can be removed from the natural gas (NG) stream fed by a conduit 12 and flowing through the heat exchanger 11. Al Liquefied natural gas (LNG) is obtained from the outlet side of the heat exchanger 11, which is collected in an LNG tank 15.

Those skilled in the art of LNG systems will understand that the refrigerant circuit 3 is used only as a schematic representation of a generic refrigeration system comprising one or more refrigerant circuits. The structure and operation of the refrigerant circuit per se is not particularly relevant. In embodiments described here, an important aspect is that the refrigeration system comprises at least one refrigerant compressor and one motor for the refrigerant compressor, and that at least some of the power to drive the refrigerant compressor is provided by the renewable energy source. .

[0027] In practice, the refrigerant circuit 3, which is shown only schematically in Fig.1, as well as in the remaining figures, can be configured according to any of many refrigeration systems and cycles, or parts thereof, such as, for example, but without limitation:

- a single mixed refrigerant cycle, marketed under the PRICO® brand;

- a single mixed refrigerant cycle, marketed by Linde under the LIMUM® brand;

- a triple cycle mixed cascade refrigerant system, marketed by Linde under the MFC® (Mixed Fluid Cascade) brand;

- a CASCADE® system by Conoco Phillips;

- a Shell Double Mixed Refrigerant (DMR) system;

- an APCI® system of mixed refrigerant / propane;

- an AP-X® system.

Construction details and operation of the exemplary refrigeration systems mentioned above are known and will not be described in this context.

The refrigerant compressor 5, which schematically represents one or more compressor trains for one or more refrigerants, is driven by a first actuator. In fact, in the case of several refrigerant compressors, one or more compressors can be grouped to form one or more compressor trains, each driven by at least one respective actuator. In the embodiment schematically illustrated in Fig.1, an actuator 17 is mechanically coupled to the refrigerant compressor 5. In general terms, the actuator is a mechanical power generator, which generates mechanical power to rotate the refrigerant compressor (s) 5.

[0030] By way of example, the actuator 17 can comprise an electric motor. The electric motor is powered by electrical energy from an electrical energy source, for example from an electrical network 19 which forms part of the LNG 1 system.

[0031] The electrical energy is supplied to the network 19 directly or indirectly by an energy collector 20, which collects energy from a renewable energy source. In the embodiment of Fig.1, the renewable energy source is solar radiation, which is converted into electricity by a photovoltaic field 21 including a plurality of photovoltaic panels 23 electrically coupled to the grid 19 through the inverter unit 25. L The inverter unit 25 can comprise a single inverter or a plurality of inverters. In the following, the inverter unit 25 will be referred to simply as "inverter", but this is not to be understood in a limiting sense. The energy collector 20 therefore comprises the photovoltaic panels 23 and the inverter 25. A frequency variator 27 can be positioned between the inverter 25 and the electric motor 17. In the diagram of Fig. 1 the inverter 25 is connected to the frequency converter 27 via the network 19.

[0032] The electric motor 17 can rotate at a rotation speed which differs from the frequency of the alternating current supplied by the inverter 25 and which can be non-constant, in order to adapt the rotation speed of the refrigerant compressor 5 to the operating conditions of the thermodynamic circuit 3. For example, if a lower refrigerant flow rate is required, the refrigerant compressor 5 can be operated at a lower speed.

It should be noted that the amount of energy provided by the renewable energy source may be sufficient to drive all the compressors of the LNG system 1. However, in some embodiments, the renewable energy source can only be used to supply energy to one or a few refrigerant compressors, or only part of the energy required to drive a compressor or train of compressors. For example, if two compressors or compressor trains using two separate actuators are provided in the LNG 1 system, one of said actuators can be operated according to the current art, while the other can be a mechanical power generator directly or indirectly powered by energy from the energy collector. In some embodiments, a portion of the renewable energy collected by the energy collector 20 may also be used to power other system services if necessary or desirable.

[0034] The energy collector 20 can provide sufficient power to drive the compressor 5, i.e. all the compressors of the LNG system 1, or some of them, for example if more than one actuator is provided and if only one or some of them are powered by energy from the renewable energy source.

[0035] If the power required by the compressor 5 is lower than the total power generated by the inverter 25, the excess energy can be stored in an energy storage system 29. The latter can include one or more devices of energy storage, some of which will be described later. In general, the energy storage system 29 can comprise one or more storage devices suitable for this use, selected from the available storage devices.

[0036] In the event of a power failure, i.e. if the power supplied by the renewable energy source via the energy collector 20 is insufficient to drive the refrigerant compressor 5, or some of the refrigerant compressors of the system 1, energy can be used accumulated in the energy storage system 29.

If the energy available from the energy storage system 29 is insufficient, or if for any reason it is preferred not to exploit the stored energy, an auxiliary mechanical actuator can be provided to directly or indirectly operate the refrigerant compressor (s). For example, the auxiliary mechanical actuator can be coupled directly to the refrigerant compressor 5 and drive the refrigerant compressor 5 with mechanical power generated by the auxiliary mechanical actuator. Hybrid operating conditions can also be envisaged, in which the compressor or train of compressors is driven by power generated by the auxiliary mechanical actuator and by power supplied by the energy storage system 29.

In some embodiments, the auxiliary mechanical actuator can drive an electrical generator, which converts mechanical power into electrical power. The electrical power generated by the electrical generator driven by the auxiliary mechanical actuator can be used to power an electrical motor mechanically coupled to the refrigerant compressor 5. Mechanical power generated by the electrical generator driven by the auxiliary mechanical actuator can be made available through the distribution network electrical energy 19 and can be added to the electrical energy obtained from the renewable energy source through the energy collector 20.

In the embodiment of Fig.1 an auxiliary mechanical actuator 31 comprises a gas turbine engine 31, mechanically coupled to an electric generator 33. The gas turbine engine 31 may comprise a compressor section 31.1, a section of combustor 31.2 and an expander or turbine section 31.3. The gas turbine engine 31 can be powered by natural gas NG from conduit 12.

[0040] The LNG system 1 described above and schematically shown in Fig.1 can operate in different modes according to the amount of energy available from the renewable energy source and collected by the energy collector 20, and according to the amount of power required for drive the refrigerant compressor 5. As noted above, if the energy collector 20 provides more energy than is required to drive the refrigerant compressor 5, excess energy can be stored in the energy storage system 29.

If insufficient power is available or if power is not available from the energy collector 20, energy from the energy storage system 29 can be used to drive the refrigerant compressor 5. For example, energy from the energy storage system 29 can also be used for short periods of time, during which the renewable energy source provides insufficient energy. If power is not available from the renewable energy source or insufficient power is available and the shortage cannot be compensated for by energy from the energy storage system 29, the auxiliary mechanical actuator 31 is used. The gas turbine engine 31 is turned on and used to generate electrical energy through the electrical generator 33. The electrical energy thus generated is converted into mechanical energy by the electric motor 17 to drive the refrigerant compressor 5.

[0042] While in Fig.1 the energy collector 20 collects solar energy through photovoltaic panels 23, other renewable energy sources can come into play. By way of non-limiting example, Fig. 2 illustrates an LNG system, again indicated with 1 as a whole, which comprises an energy collector 20 comprising a wind farm, for converting wind energy into electrical energy. The wind farm is shown in 22. Wind turbines of the wind farm 22 are indicated with 24. The reference number 25 indicates a converter that can convert the electrical energy generated by the wind turbines into electrical energy suitable for powering the electricity distribution network 19 The remaining components of the integrated LNG system 1 in Fig.2 are the same as in Fig.1 and are marked with the same reference numbers. These components will not be described again.

[0043] The same integrated LNG system 1 can exploit different sources of renewable energy through various energy collectors. This is visually represented by way of example in Fig. 3, in which an integrated LNG system 1 comprises an energy collector 20 including a field 21 of photovoltaic panels 23 and a further energy collector 20 which includes a wind farm 22. Some components of the LNG system 1 in Fig.3 are the same as in Figs.1 and 2 and are marked with the same reference numbers used in Figs.1 and 2 and are not described again.

[0044] Inverters or converters 25 convert the electrical energy generated by the wind turbines 24 of the wind farm 22 and by the photovoltaic panels 23 of the photovoltaic field 21 into electrical energy at the correct frequency and phase for export to the grid 19. A system accumulator 29 collects excess energy that may be available from the energy collector 20.

[0045] While the remaining components of the integrated LNG system 1 of Fig.3 may be the same as shown in Figs.1 and 2, in the exemplary embodiment shown in Fig.3 a different mode of use of the mechanical power coming from the 'auxiliary mechanical actuator. The auxiliary mechanical actuator 31 comprises a gas turbine engine which can be mechanically coupled to the refrigerant compressor 5 through a shaft line 40 and a clutch 41. A second clutch 43 is disposed along the shaft line 42 which connects mechanically the electric motor 17 to the refrigerant compressor 5. When the electric power from the network 19 is insufficient to rotate the electric motor 17, the clutch 43 can be opened and the clutch 41 can be closed, so that mechanical power from the motor to gas turbine 31 can be used to directly drive the refrigerant compressor 5. Under some operating conditions, both clutches 43 and 41 can be engaged and mechanical power from the gas turbine engine 31 and the electric motor 17 can be used in combination to operate the refrigerant compressor 5.

[0046] The energy storage system 29 can comprise one or more different storage devices. Continuing to refer to Figs.1, 2 and 3, Fig.4A summarizes some options for the energy storage systems 29 to be used in an LNG system according to the present description.

[0047] An overview of energy storage technologies can be found in Xing Luo et al, “Overview of current development in electrical energy storage technologies and application potential in power system operation”, Applied Energy 137 (2015) 511-536, available at https://www.sciencedirect.com/science/article/pii/S0306261914010290.

According to some embodiments, the energy storage system 29 can comprise battery energy storage devices, flow battery energy storage devices, flywheel energy storage devices; super-capacitor energy storage devices, superconducting magnetic energy storage devices, or combinations thereof. In these devices, electrical energy is converted and stored into various forms of energy. For example batteries, including flow batteries, store energy in the form of chemical energy. Flywheel energy storage involves converting electrical energy into kinetic energy by rapidly rotating a flywheel, which is arranged in a low-pressure vessel to reduce friction and is supported by low-friction bearings, including a modulus of magnetic leavening, for example. Super-capacitor energy storage devices involve the accumulation of electrical charges between two conductive plates separated by a dielectric layer. The accumulation of super-conductive magnetic energy involves the accumulation of energy in the form of a current flow that flows in coils made of super-conductive material and kept at cryogenic temperature to achieve near zero resistance, thus reducing or substantially eliminating electrical losses. In Fig.4A the energy storage system 29 comprises a battery 51 and a rectifier 53, which electrically connects the battery to the network 19.

[0049] Continuing to refer to Figs.1, 2 and 3, a different energy storage system 29 is shown in Fig.4B. This exemplary embodiment comprises a cryogenic energy storage system such as a liquefied air storage system, also known as the LAES system. The energy storage system, marked 29 as a whole, may comprise an air compressor 55 driven by an electric motor 57, which is electrically coupled to the network 19. Excess electrical energy, made available by the energy collector 29, is used to drive the electric motor 57. The compressed air supplied by the air compressor 55 is cooled and liquefied and finally collected in a liquid air storage tank 59. More specifically, liquid air is obtained by compressing a stream of air by means of the 55 air compressor, cooling the compressed air flow in heat exchangers 58A, 58B and expanding the flow of cooled air into an expander or Joule-Thomson valve 60.

Liquid air is kept at a low temperature in the liquid air storage tank 59. When energy needs to be recovered from the cryogenic energy storage system 29, a cryogenic pump 62 feeds a flow of liquefied air through a heater 64 and the flow of pressurized and heated air is expanded in an expander 66 such as a turboexpander. Mechanical power generated by the turboexpander 66 drives an electric generator 68 and the electric power thus generated is fed to the network 19 to drive the refrigerant compressor 5 of the integrated LNG system 1.

[0051] Continuing to refer to Figs.1, 2 and 3, a hydraulic energy storage system 29 is shown in Fig.4C. The hydraulic energy storage system may comprise a lower water basin 70A and an upper water basin 70B. A conduit 72 connects the lower water basin 70A to the upper water basin 70B. A reversible turbine pump 74 arranged in the duct 72 is adapted to pump water from the lower basin 70A to the upper basin 70B and to be rotated by water flowing in the opposite direction, from the upper basin 70B to the lower basin 70A. An electric machine 76 is mechanically coupled to the reversible turbine pump 74. When the reversible turbine pump 74 operates in pumping mode, the electric machine 76 operates in motor mode and is powered by electrical energy from the network 19. The electrical energy is thus converted into mechanical energy by the electric machine 76 and into potential hydraulic energy by the turbine pump 74. When the reversible turbine pump 74 operates in turbine mode, the potential hydraulic energy is converted into mechanical energy by the turbine pump 74 and into energy from the electric machine 76 operating in generator mode.

In other embodiments, the hydraulic energy storage system may comprise separate pump and turbine, arranged in separate conduits, one for pumping water from the lower basin 70A to the upper basin 70B and the other for flowing water from the upper basin 70B to the lower basin 70A. A single electric machine, adapted to operate in an engine mode and in a generator can be provided and selectively coupled to the pump and turbine. Alternatively, a separate electric motor and a separate electric generator can be mechanically coupled to the pump and turbine, respectively.

Compressed air energy storage systems (CAES systems) can be used as an alternative energy storage system 29. Continuing to refer to Figs. 1, 2 and 3, an example of a CAES system is shown in Fig.4D and again marked 29. The CAES system comprises an air compressor 80, a cave 82 and / or an air reservoir 83 and a turbine 84. In the exemplary embodiment of Fig.4D the air compressor 80 and the turbine 84 are arranged on the same shaftline 86. An electric machine 87 arranged along the shaftline 86 can be connected selectively to the air compressor 80 through a first clutch 88A and to the turbine 84 through a second clutch 88B.

In energy storage mode the electric machine 87 operates in electric motor mode and converts electric energy available in the network 19 into mechanical energy, to drive the air compressor 80. Compressed air supplied by the air compressor 80 can be cooled in a heat exchanger 89 is stored in the cave 82 and / or in the pressurized air reservoir 83. The turbine 84 is inoperative and the clutch 88B can be disengaged.

In power supply mode the clutch 88A can be disengaged and the clutch 88B can be engaged to connect the electric machine 87 to the turbine 84. The electric machine 87 operates in generator mode. Compressed air previously stored in cave 82 and / or pressurized air reservoir 83 is fed into a combustor 92 where compressed air can be mixed with a fuel, for example natural gas from conduit 12. The combustion gas from combustor 92 is expanded into turbine 84 for generating mechanical power which is converted into electrical power by the electrical machine 87 operating in generator mode. Exhaust gas from the turbine 84 can be used to pre-heat the compressed air in a pre-heater 94 located upstream of the combustor 92. A frequency converter 90 can be connected between the electrical machine 87 and the electrical distribution network 19.

[0056] The energy storage systems 29 illustrated in Figs.4A, 4B, 4C, 4D are shown only by way of example. Those skilled in the art of energy storage will understand that other energy storage systems can be used, either alone or in various combinations, for the purpose of accumulating excess energy generated by the renewable energy source. The selection of energy storage technology can depend on several factors, including environmental conditions, the availability of natural or man-made water basins, air reservoirs or caves, etc.

The energy from the energy storage system 29 can be used to provide additional energy to cover a peak power demand by the refrigerant circuit 3, or to provide energy when no energy is available from the renewable energy source, for example during the night in the case of a solar photovoltaic system, or when the wind does not blow, in the case of a wind farm.

According to some embodiments, solar energy can be harnessed by means of a concentrating solar power plant and converted into thermal energy. Fig.5 illustrates an integrated LNG system 1 comprising a refrigerant circuit 3 adapted to circulate a refrigerant fluid therein. The refrigerant circuit 3 comprises a refrigerant compressor 5, a chiller 7, an expander 9 and a heat exchanger 11. The refrigerant fed by the refrigerant compressor 5 is cooled in the chiller 7 and expanded in the expander 9 to reach a sufficiently low temperature , so that with it heat can be removed from the natural gas (NG) flowing into the duct 12. On the outlet side of the heat exchanger 11, liquefied natural gas (LNG) is obtained, which is collected in the LNG tank 15. As above mentioned in connection with Fig. 1, the refrigerant circuit 3 and the respective refrigerant compressor 5 are used only as a visual representation for any type of refrigeration system, which may include one or more compressor trains and one or more refrigerant circuits according to any available LNG technologies.

In the embodiment of Fig.5 an energy collector, again indicated with 20, is provided for collecting solar energy. The energy collector 20 comprises a concentrating solar power plant 101. Concentrating solar power plants are known in the art and do not require detailed description. Only the main components of it will be mentioned here. In some embodiments, the concentrating solar power plant 101 may comprise a closed circuit adapted to circulate a heat transfer fluid, which transfers heat from the solar concentrators to a thermodynamic circuit, in which heat is partially converted into mechanical power. In the exemplary embodiment of Fig. 5, the concentrating solar power plant 101 comprises a solar concentrator 103. Several types of solar concentrators are known in the art and can be used in the concentrating solar power plant 101. In via merely by way of example, in Fig.5 the concentrator 103 comprises a plurality of heliostats, such as for example parabolic mirrors 103A. A closed heat transfer fluid circuit 105 transfers heat from the solar concentrators 103 to the thermodynamic circuit 107.

[0060] In the exemplary embodiment of Fig.5 the thermodynamic circuit is adapted to perform a regenerative Rankine cycle and comprises a steam turbine 109, which can comprise a high pressure turbine 109A and a low pressure turbine 109B. In this embodiment, therefore, the steam turbine 109 is a mechanical power generator, which generates mechanical power to drive the refrigerant compressor 5 of the refrigerant circuit 3 by exploiting renewable energy. In some embodiments, the process fluid processed through the steam turbine 109 may be water. In other embodiments, the process fluid may be an organic working fluid.

[0061] The process fluid circulating in the thermodynamic circuit 107 is heated, vaporized and superheated using heat from the closed circuit of heat transfer fluid 105, through a heater 111, a vaporizer 113 and superheater 115. Superheated steam is partially expanded in the high turbine pressure 109A, heated again in a regenerator 117 and further expanded in the low pressure turbine 109B. Expanded vapor is condensed in a condenser 119, pumped by a pump 121 again through the heating section of the circuit, comprising the heater 111, the vaporizer 113 and the superheater 115.

[0062] In some embodiments, the thermodynamic circuit 107 may comprise an auxiliary boiler, in which heat is regenerated for example by burning natural gas, when for example insufficient solar power is available. The boiler can be arranged to supply thermal energy to one or more sections of the closed steam circuit. In the diagram of Fig. 5 the boiler is shown at 123 and is configured to provide regeneration heat. More generally, the boiler can be used to supply additional thermal energy to the heater, the vaporizer and / or the superheater in the steam circuit, whenever no heat is supplied or insufficient heat is supplied from the concentrator 103.

In some embodiments, the steam turbine 109 and the refrigerant compressor 5 can be arranged on a common shaft line. A clutch 131 may be disposed along the shaft line between the steam turbine 109 and the refrigerant compressor 5.

[0064] In some embodiments, a machine, for example an electric motor / generator 133, can be electrically coupled to the steam turbine 109 and / or to the refrigerant compressor 5. In the diagram of Fig.5 an electric motor / generator 133 is arranged on the same shaft line as the refrigerant compressor 5 and the steam turbine 109 is mechanically coupled to it by means of a coupling 135. The motor / generator 133 is electrically coupled to the network 19.

[0065] The electrical network 19 can be functionally coupled to an energy storage system 29, as shown in Figs.1, 2, 3, not shown in Fig.5. In some embodiments, if the mechanical power generated by the steam turbine 109 exceeds the demand by the refrigerant compressor 5, excess power can be converted into electrical power by the electric motor / generator 133, which operates in generator mode, and stored in an energy storage system 29. Conversely, energy from the energy storage system 29 can be used if the heat available from the concentrating solar power plant 101 and / or the boiler 123 is insufficient.

In some embodiments, the integrated LNG system 1 of Fig. 5 may further comprise a gas turbine engine 31, similar to the gas turbine engine 31 of Figs. 1 and 2. The gas turbine engine 31 can be put into operation to operate the electric generator 33, connected to the electricity grid 19, if the energy from the concentrated solar power plant 101 and / or from the energy storage system 29 is insufficient and if the boiler 123, or if said boiler 123 supplies insufficient heat or if it is temporarily unavailable, for example. Mechanical power generated by the gas turbine engine 31 is converted into electrical energy by the electrical generator 33. The electrical energy is made available through the electrical network 19 to drive the electrical motor / generator 133 in motor mode and thereby drive the compressor. coolant 5, either by itself or in combination with the steam turbine 109.

In some embodiments the concentrating solar power plant 101 may also comprise a heat accumulator 102.

While in Fig.5 the concentrating solar power plant 101 uses linear solar concentrators, in other embodiments heliostats can be used which concentrate the solar energy on a receiver placed on top of a tower. The receiver can be part of a closed circuit, in which a heat transfer fluid circulates. The heat transfer fluid can transfer heat to a working fluid, which converts thermal energy into mechanical energy for example through a Rankine cycle.

In other embodiments concentrated solar power can be converted to mechanical power using a Bryton cycle. Concentrated solar power can heat a stream of compressed air, which is then expanded into a power turbine. The power turbine generates mechanical power to drive an electric generator. The power turbine can be mechanically coupled to an air compressor, for example an axial air compressor, which compresses air which is then heated by concentrated solar power. In other embodiments, the entire mechanical power generated by the power turbine can be converted into electrical energy and the air compressor can be driven by the electric motor. An auxiliary combustor can be provided to provide heat if solar energy is insufficient.

[0070] Fig.6 illustrates a schematic of an integrated LNG plant 1 comprising a refrigerant circuit again shown at 3, and an energy collector 20 which includes a concentrating solar power plant 101. The refrigerant circuit 3 can be configured as described above in relation to Figs.1 and 2, for example, and will not be described again.

[0071] In the embodiment of Fig.6, the concentrating solar power plant 101 comprises a tower 201, on the top of which a receiver 203 is installed. Heliostats 205 focus the solar radiation on the receiver 203, where a heat transfer fluid flows, e.g. molten salt. Receiver 203 forms a part of a closed heat transfer circuit 207.

In some embodiments, the closed heat transfer loop 207 may comprise a hot fluid reservoir 209 and a cold fluid reservoir 211. Hot heat transfer fluid from the receiver 203 is collected in the hot fluid reservoir 209, where energy solar energy can be stored in the form of thermal energy. Hot heat transfer fluid can circulate from the hot heat transfer fluid reservoir 209 through a steam generation system 213 and from there into the cold fluid reservoir 211, from which the spent heat transfer fluid flows back into the receiver 203.

The steam generation system 213 may comprise a superheater 215, an evaporator 217 and a preheater 219. Hot heat transfer fluid from the hot fluid reservoir flows sequentially through the superheater 215, the evaporator 217 and the preheater 219, in relation of heat exchange with a working fluid which circulates in a closed circuit 221 where the working fluid undergoes sequential thermodynamic transformations to convert heat into mechanical power. The working fluid circulating in the closed loop is preheated in the preheater 219, evaporated in the evaporator 217 and superheated in the superheater 215. The hot, pressurized working fluid expands sequentially in a high pressure steam turbine 223 and in a turbine at low pressure steam 225. The partially expanded working fluid from the high pressure steam turbine 223 can be regenerated in the regenerator 221 in heat exchange ratio with the heat transfer fluid, before being further expanded in the low pressure steam turbine 225.

The exhausted working fluid leaving the low pressure steam turbine 225 is condensed in a condenser 227, collected in a tank 229, from which the condensed working fluid is pumped by the pump 231 back into the steam generation system 213 .

In the exemplary embodiment of Fig.6, the mechanical power generated by the steam turbines 223 and 225 drives an electric generator 233, which is electrically connected to an electrical distribution network 19. The electric motor 17 of the refrigeration circuit 3 can be powered by electricity from the electrical distribution network 19.

[0076] In other embodiments, not shown, similarly to the embodiment of Fig.5, the steam turbines 223 and 225 can directly rotate the compressor 5 of the refrigerant circuit 3.

In some embodiments, an auxiliary gas turbine engine 31 may be provided to drive an electrical generator electrically connected to the electrical distribution network 19, similarly to the embodiment of Fig.2, to generate electrical power if not there is sufficient power generated by the generator 233.

In other embodiments, the auxiliary mechanical actuator may comprise a gas turbine engine, which can be mechanically coupled, for example through a clutch, to the refrigerant compressor 5, as shown in the embodiment of Fig. 3.

While in Figs. 5 and 6 solar energy is used in combination with a Rankine cycle to generate mechanical power to drive the refrigerant compressor 5, in other embodiments a different cycle can be used to convert heat into mechanical power, for example a Bryton cycle that uses a gas turbine engine. Fig.7 illustrates an integrated LNG system 1 which comprises a refrigerant circuit 3 which comprises the same components already described above and marked with the same reference numbers used in the previously mentioned figures. The integrated LNG system 1 further comprises an energy collector 20 adapted to collect solar energy. In the embodiment of Fig.7 the energy collector 20 comprises a concentrating solar power plant again indicated by 101, which comprises a tower 201 and a receiver 203 disposed at the upper end of the tower 201. Heliostats 205 focus the energy on the receiver 203, where a heat transfer fluid, for example a molten salt, flows. The receiver 203 forms part of a closed heat transfer circuit 207. In the embodiment of Fig. 7 the closed heat transfer circuit 207 comprises a hot fluid reservoir 209 and a cold fluid reservoir 211. Hot heat transfer fluid from receiver 203 is collected in the hot fluid reservoir 209, where solar energy is stored in the form of thermal energy. Hot heat transfer fluid can circulate from the hot fluid reservoir 209 through an air heater 251 and then into the cold fluid reservoir 211, from which the spent heat transfer fluid returns to the receiver 203.

[0080] In the air heater 251 thermal energy is transferred from the heat transfer fluid, which circulates in the closed circuit 207, to the compressed air fed by an air compressor 253. Hot compressed air is expanded in a turbine of power 255 and is discharged through a smokestack 257. The exhaust air can be used to preheat the compressed air supplied by the air compressor 253 in a preheat heat exchanger 258.

The power turbine 255 and the air compressor 253 are mechanically coupled via a shaft 259, so that the mechanical power which is generated by the expansion of the hot compressed air in the power turbine 255 is used to drive the air 253. The additional power generated by the power turbine 253, and which is not required to drive the air compressor 253, is available on the output shaft 261.

The power turbine 255, the air compressor 253, the shaft 259 and the air heater 251 form part of a gas turbine engine generally designated 265, where ambient air performs a Bryton cycle to convert heat, fed to the air by the heat transfer fluid circulating in the closed circuit 207, in mechanical power available on the output shaft 261.

[0083] In the embodiment of Fig.7 the output shaft 261 is mechanically coupled to the refrigerant compressor 5 of the refrigerant circuit 3, so that mechanical power made available by the gas turbine engine 263 directly drives the refrigerant compressor 5 In other embodiments, not shown, the output shaft 261 may be mechanically coupled to an electrical generator, which provides electrical power exported to an electrical distribution network 19. The electrical energy from the electrical energy distribution network 19. it can be used to power an electric motor, which converts the electric power into mechanical power to drive the refrigerant compressor 5, according to an arrangement similar to Fig.1.

To recover excess power made available on the output shaft 261, an electric generator 271 can be mechanically coupled to the output shaft 261 and electrically coupled to the electrical power distribution network 19.

If insufficient power is available from the energy collector 20, a combustor 263 can be provided, through which compressed air flows before being expanded into the power turbine 255. A fuel, for example natural gas diverted from the duct 12, can be mixed with the compressed air in the combustor 273 and the air / fuel mixture can be burned to generate high temperature compressed combustion gas, which is expanded in the power turbine 255.

In a modified embodiment of the system shown in Fig.7, air can be heated directly in the receiver 203 and the closed loop 207 can be omitted. A heat storage system can be provided to accumulate an excess of thermal energy, for example by using reservoirs of a heat storage medium.

Many alternative embodiments of the integrated LNG plant 1 comprising an energy collector 20 comprising a concentrating solar power plant can be thought of. Continuing to refer to Fig.1, Fig.8 illustrates a further embodiment of an integrated LNG system 1 which exploits mechanical power generated by a solar power plant at concentration 101. Elements and components equal or corresponding to those already described with reference to Fig. 5 are marked with the same reference numbers and will not be described again.

[0088] In the embodiment of Fig.8, the boiler 123 is omitted, but in other embodiments, not shown, the boiler 123 can also be provided.

In Fig.8 the electric motor / generator 133 can operate in a generator mode, if the mechanical power generated by the steam turbine 109 exceeds the power required to drive the refrigerant compressors 5. Electricity generated by the electric generator 133 can be used to produce hydrogen in a water electrolyser 141, which can be electrically connected to the network 19 through a rectifier 143. Hydrogen produced by the electrolyser 141 can be stored in a hydrogen storage tank 145 and can be used, when so required , as a fuel for powering a gas turbine engine 31 (see also Fig.1).

If required, a mixture of hydrogen from the hydrogen storage tank 145 and natural gas from the natural gas line 12 can be fed to the combustor 31.2 of the gas turbine engine 31. The gas turbine engine 31 can be made functioning to move the electric generator 33, which supplies electrical power to the network 19 to power the electric motor / generator 133 when it is operated in motor mode to drive the refrigerant compressor 5.

Thus, in the embodiment of Fig.8, solar power can be used to drive the refrigerant compressor 5 and also to generate electrical power if sufficient solar power is available. The electrical energy is converted into chemical energy through the production of hydrogen and stored in the hydrogen storage tank 145. The energy stored in chemical form can be used when solar power is not available, for the continuity of the operation of the refrigerant circuit 3.

Hydrogen can also be produced using a different concentrating solar power plant as described herein.

While in the embodiment of Fig.8 solar energy is primarily used to generate mechanical power and drive the refrigerant compressor 5 with it, in other embodiments solar energy, or energy from other renewable energy sources, it can be fully exploited to produce hydrogen. The latter can power a gas turbine engine to drive a refrigerant compressor 5 of the refrigerant circuit 3. In some embodiments, solar energy can be converted into chemical energy, stored in the form of hydrogen, by photocatalytic dissociation of water.

In other embodiments, hydrogen can be produced by electrolysis of water, in which case solar energy is converted into electrical energy either directly in a photovoltaic system or by using a concentrating solar power plant to generate mechanical power, which it is used to drive an electric generator.

In other embodiments, not shown, electrical power for the production of hydrogen can be provided by a wind farm.

[0096] Continuing to refer to Figs. 5 and 8, Fig. 9 illustrates a simplified embodiment of an integrated LNG system 1, which comprises an energy collector adapted to collect energy from a renewable energy source, using solar power concentrated to produce hydrogen. The integrated LNG system 1 of Fig. 9 comprises a concentrating solar power plant 101 as in the embodiments of Figs. 5 or 8. The main components of the concentrating solar power plant 101 are marked with the same reference numbers as in Figs. 5 and 8 and will not be described again. A different solar concentrating power plant can be used, for example as illustrated in Figs. 6 and 7.

In the embodiment of Fig.9 the steam turbine 109 generates mechanical power to drive an electrical generator 133, which converts mechanical energy into electrical energy fed to an electrolyser 141 to produce hydrogen by electrolysis. The hydrogen thus produced can be stored in a hydrogen storage tank 145 and used to power a gas turbine engine 31. The gas turbine engine 31 drives the refrigerant compressor 5 of the refrigerant circuit 3. If necessary or desired Natural gas from the conduit 12 can be used on its own or in admixture with the hydrogen from the hydrogen storage tank 145.

[0098] While in Fig.9 solar energy is collected via a concentrating solar power plant 101, in other embodiments, solar energy can be collected in different ways, for example by means of a field 21 of photovoltaic panels 23 ( Fig. 1), to produce electricity which is then used for the production of hydrogen by electrolysis. Other energy collectors to collect energy from renewable energy sources can be used to generate electricity for the electrolytic production of hydrogen, for example wind turbines in a wind farm 22.

[0099] Fig. 10 illustrates an integrated LNG system 1, in which the energy collector 20 for collecting energy from a renewable energy source (here again solar energy) comprises a field 21 of photovoltaic panels 23 and wind turbines 24 of a wind farm 22, to generate electricity fed through inverter 25 to the grid 19. The electricity generated in this way is used to produce hydrogen in an electrolyser 141. Hydrogen is collected in a hydrogen storage tank 145 to power a gas turbine 31. As mentioned above, natural gas can be mixed with hydrogen in the combustor 31.2 or used alone if insufficient hydrogen is available or hydrogen is not available from the tank 145. The gas turbine engine 31 drives the refrigerant compressor 5 of the refrigerant circuit 3.

[0100] Hydrogen produced by exploiting power from a renewable energy source can alternatively be used in fuel cells, suitable for generating electrical power. The electric power can in turn be used to drive an electric motor adapted to drive the refrigerant compressor or compressors 5 of the refrigerant circuit 3.

[0101] Fig. 11 illustrates a diagram of a further integrated LNG plant 1 comprising a refrigerant circuit 3 with one or more compressors schematically represented by compressors 5. The same reference numbers used in Fig. 11 are used to designate equal parts or equivalent to those already described in relation to Fig. 10. In the embodiment of Fig. 11 the electricity generated by an energy collector 20, adapted to collect energy from a renewable energy source, is used to produce hydrogen by electrolysis in an electrolyser 141. The hydrogen thus produced is collected in a hydrogen tank 145, from which hydrogen is fed to a fuel cell system 146. Chemical energy from the hydrogen stream is converted into electrical energy by the fuel cell system 146 and exported to an electrical grid 19 via inverter 148 or whatever other electrical energy conditioning device. The electrical energy 19 feeds an electric motor 152 mechanically coupled through a coupling 154 to the compressors 5 of the refrigerant circuit 3. A gas turbine engine 31 can be provided as an auxiliary actuator to drive the compressor 5 if there is no power available. on the electrical network 19.

[0102] In general, a method for liquefying natural gas in an integrated natural gas liquefaction system is described herein, in which at least one refrigerant circuit is integrated with an energy collector adapted to collect energy from a renewable energy source. The method comprises the step of generating power using energy collected from the energy collector and producing hydrogen using that power in a hydrogen production plant. The method also includes the step of generating power (mechanical or electrical, for example) by means of a power generator fed with said hydrogen.

While in the examples described above solar energy and wind energy are used to provide useful power to drive the refrigerant compressors, other renewable energy sources can be used. For example, tidal or wave power generation systems can be used, which convert tidal or sea wave energy into other forms of useful power, such as mechanical power or electrical power. The electrical or mechanical power generated by the renewable energy source can be used to drive compressors 5 of a refrigerant circuit 3 and excess power, if available, can be accumulated as described above. In some embodiments, electrical energy generated by a renewable energy source can be used for the production of hydrogen. Various tidal or wave power generation devices and related systems are described in "Intermittent wave energy generation system with hydraulic energy storage and pressure control for stable power output", Journal of marine Science and Technology, December 2018, vol. 23, n. 4, pp. 802-813; and T.J. Hammons, “Tidal Energy Technologies: Currents, Wave and offshore Wind Power in the United Kingdom, Europe and North America” available at http://cdn.intechweb.org/pdfs/9342.pdf. These systems and devices can be comprised in an energy collector adapted to collect energy from the respective renewable energy source.

In still further embodiments, the energy collector 20 of an integrated LNG system 1 may comprise a geothermal plant, in which geothermal heat can be used to generate mechanical power by mechanical drive or by electrical generation. In the first case, the mechanical power is used directly to drive the compressor or compressors 5 of the refrigerant circuit 3. In the second case, mechanical power can be converted into electrical power, which is then used to drive one or more refrigerant compressors 5 by means of an electric motor .

[0105] While the invention has been described in terms of various specific embodiments, it will be clear to those skilled in the art that many changes, modifications and omissions are possible, without departing from the scope and spirit of the claims. Furthermore, unless otherwise specified, the order or sequence of any process or method steps can be varied or reconfigured according to alternative embodiments.

[0106] Various embodiments of the invention are contained in one or more of the following clauses, which can be combined in any suitable way, unless otherwise indicated here:

Clause 1. An integrated natural gas liquefaction system comprising: at least one refrigerant circuit adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor; an energy collector, capable of collecting energy from at least one renewable energy source; And

a mechanical power generator adapted to convert energy supplied by the energy collector into mechanical power, in which said mechanical power generator is mechanically coupled to said refrigerant compressor.

Clause 2. The system of Clause 1, further comprising an energy storage system, adapted to store energy from the energy collector, and to supply energy to the mechanical power generator.

Clause 3. The system of Clause 2, where the energy storage system includes at least one of the following: a heat storage system; a compressed air energy storage system; a cryogenic energy storage system; an electrical energy storage system, including a battery arrangement, a super-capacitor arrangement, a liquid metal battery arrangement, a redox flow battery; a hydrogen tank.

Clause 4. The system of clause 1 or 2 or 3, further comprising an auxiliary mechanical actuator adapted to provide auxiliary mechanical power to directly or indirectly drive the refrigerant compressor when the power from the mechanical power generator is insufficient.

Clause 5. The system of Clause 4, wherein the auxiliary mechanical actuator comprises a gas turbine engine or an electric motor.

Clause 6. The system of clause 4 or 5, in which the auxiliary mechanical actuator is mechanically coupled to an electric generator, and in which the electric generator is electrically connected to an electric motor mechanically coupled to the refrigerant compressor.

Clause 7. The system of clause 4 or 5, in which the auxiliary mechanical actuator is mechanically coupled to the refrigerant compressor.

Clause 8. The system of any of the preceding clauses, wherein the mechanical power generator includes a steam turbine.

Clause 9. The system of clause 8, where the energy collector comprises at least one of the following: a photovoltaic field; a wind farm; a concentrating solar power plant; a hydroelectric plant.

Clause 10. The system of any of the preceding clauses, further comprising a hydrogen generator directly or indirectly powered by energy from the energy collector and a hydrogen storage tank adapted to accumulate said hydrogen; wherein the mechanical power generator comprises an internal combustion engine adapted to be fed with said hydrogen and to generate mechanical power with it.

Clause 11. The system of clause 10, wherein the hydrogen generator includes an electrolyser, and wherein said electrolyser is powered by electrical energy supplied by the energy collector.

Clause 12. A method of liquefying natural gas in an integrated natural gas liquefaction system comprising a refrigerant loop and an energy collector adapted to harvest energy from a renewable energy source; the method including the following steps:

collecting energy from the renewable energy source by means of said energy collector;

generate mechanical power from the collected energy;

operating at least one refrigerant compressor of the refrigerant circuit with said mechanical power; And

removing heat from a natural gas stream by means of said refrigerant.

Clause 13. The method of clause 12, further comprising the following steps:

storing at least part of the energy collected by the energy collector in an energy storage system; And

extracting energy from the energy storage system when energy is required to drive said refrigerant compressor.

Clause 14. The method of clause 12 or 13, further comprising the step of generating auxiliary mechanical power with an auxiliary mechanical actuator when the power from the renewable energy source is insufficient to drive said refrigerant compressor.

Clause 15. The method of clause 14, wherein the step of generating auxiliary mechanical power comprises the step of generating said auxiliary mechanical power by means of an internal combustion engine, preferably using said natural gas.

Clause 16. A method of liquefying natural gas in an integrated natural gas liquefaction system comprising a refrigerant circuit, comprising at least one refrigerant compressor and an energy collector adapted to collect energy from a renewable source source; the method including the following steps:

generate power from the energy collected by the energy collector from the renewable energy source and produce hydrogen with it; And

to operate a refrigerant compressor with power generated by said hydrogen.

Clause 17. The method of clause 16, wherein the step of operating the refrigerant compressor comprises the step of powering a gas turbine engine with said hydrogen and operating the refrigerant compressor with said gas turbine engine.

Clause 18. An integrated natural gas liquefaction system comprising:

an energy collector designed to collect energy from a renewable source;

a hydrogen production plant, capable of producing hydrogen using energy collected by the energy collector from the renewable energy source;

a power generator adapted to be fed with hydrogen produced by said hydrogen production plant; And

at least one refrigerant circuit adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor powered by said power generator.

Claims (18)

"A NATURAL GAS LIQUEFACTION SYSTEM" CLAIMS 1. An integrated natural gas liquefaction system comprising: at least one refrigerant circuit adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor; an energy collector, capable of collecting energy from at least one renewable energy source; And a mechanical power generator adapted to convert energy supplied by the energy collector into mechanical power, in which said mechanical power generator is mechanically coupled to said refrigerant compressor. The system of claim 1, further comprising an energy storage system, adapted to store energy from the energy collector, and to supply energy to the mechanical power generator. The system of claim 2, wherein the energy storage system comprises at least one of the following: a heat storage system; a compressed air energy storage system; a cryogenic energy storage system; an electrical energy storage system, including a battery arrangement, a super-capacitor arrangement, a liquid metal battery arrangement, a redox flow battery; a hydrogen tank. The system of claim 1 or 2 or 3, further comprising an auxiliary mechanical actuator adapted to provide auxiliary mechanical power to directly or indirectly drive the refrigerant compressor when the power from the mechanical power generator is insufficient. The system of claim 4, wherein the auxiliary mechanical actuator comprises a gas turbine engine or an electric motor. The system of claim 4 or 5, wherein the auxiliary mechanical actuator is mechanically coupled to an electric generator, and wherein the electric generator is electrically connected to an electric motor mechanically coupled to the refrigerant compressor. 7. The system of claim 4 or 5, in which the auxiliary mechanical actuator is mechanically coupled to the refrigerant compressor. The system of any one of the preceding claims, wherein the mechanical power generator comprises a steam turbine. The system of claim 8, wherein the energy collector comprises at least one of the following: a photovoltaic field; a wind farm; a concentrating solar power plant; a hydroelectric plant. 10. The system of any one of the preceding claims, further comprising a hydrogen generator directly or indirectly powered by energy from the energy collector and a hydrogen storage tank adapted to accumulate said hydrogen; wherein the mechanical power generator comprises an internal combustion engine adapted to be fed with said hydrogen and to generate mechanical power with it. 11. The system of claim 10, wherein the hydrogen generator comprises an electrolyser, and wherein said electrolyser is powered by electrical energy supplied by the energy collector. 12. A method of liquefying natural gas in an integrated natural gas liquefaction system comprising a refrigerant loop and an energy collector adapted to harvest energy from a renewable energy source; the method including the following steps: collecting energy from the renewable energy source by means of said energy collector; generate mechanical power from the collected energy; operating at least one refrigerant compressor of the refrigerant circuit with said mechanical power; And removing heat from a natural gas stream by means of said refrigerant. The method of claim 12, further comprising the following steps: storing at least part of the energy collected by the energy collector in an energy storage system; And extracting energy from the energy storage system when energy is required to drive said refrigerant compressor. The method of claim 12 or 13, further comprising the step of generating auxiliary mechanical power with an auxiliary mechanical actuator when the power from the renewable energy source is insufficient to drive said refrigerant compressor. The method of claim 14, wherein the step of generating auxiliary mechanical power comprises the step of generating said auxiliary mechanical power by means of an internal combustion engine, preferably using said natural gas. 16. A method of liquefying natural gas in an integrated natural gas liquefaction system comprising a refrigerant circuit, comprising at least one refrigerant compressor and an energy collector adapted to collect energy from a renewable source source; the method including the following steps: generate power from the energy collected by the energy collector from the renewable energy source and produce hydrogen with it; And to operate a refrigerant compressor with power generated by said hydrogen. The method of claim 16, wherein the step of operating the refrigerant compressor comprises the step of powering a gas turbine engine with said hydrogen and operating the refrigerant compressor with said gas turbine engine. 18. An integrated natural gas liquefaction system comprising: an energy collector capable of collecting energy from a renewable source source; a hydrogen production plant, capable of producing hydrogen using energy collected by the energy collector from the renewable energy source; a power generator adapted to be fed with hydrogen produced by said hydrogen production plant; And at least one refrigerant circuit adapted to circulate at least one refrigerant therein, wherein the refrigerant circuit comprises at least one refrigerant compressor powered by said power generator.