WO2010082228A2

WO2010082228A2 - A process and a system for energy generation utilising liquid and/or gas heat sources on board naval units

Info

Publication number: WO2010082228A2
Application number: PCT/IT2010/000011
Authority: WO
Inventors: Franco Finocchiaro
Original assignee: Franco Finocchiaro
Priority date: 2009-01-19
Filing date: 2010-01-18
Publication date: 2010-07-22
Also published as: ITMI20090039A1; WO2010082228A3

Abstract

A process and a system for energy generation aboard naval vessels utilising liquid and/or gaseous heat sources at temperatures ranging between 50 and 800 Celsius degrees deriving from the motor apparatus and/or from the same onboard auxiliary units comprise the following stages: a) indirect heat exchange between said gaseous heat sources and/or direct or indirect exchange with said liquid sources and one or more subsystems capable of generating energy through Rankine thermodynamic cycles where organic fluids ORC (Organic Rankine Cycles) circulate, b) production of mechanical energy by means of ORC subsystems, c) heat removing from the ORC devices to the external environment, d) onboard use of said mechanical energy and/or conversion of mechanical energy produced by the ORC turboexpanders into electric energy by means of electric generators, e) distribution of the electrical energy produced to the onboard electric loads and/or to electric propulsion motors.

Description

A PROCESS AND A SYSTEM FOR ENERGY GENERATION UTILISING LIQUID AND/OR GAS HEAT SOURCES ON BOARD NAVAL UNITS

DESCRIPTION TECHNICAL FIELD

The present invention relates to a process and a system for generating energy utilising liquid and/or gaseous heat sources on board naval vessels. BACKGROUND ART

With regard to naval applications, in the period between the years 1970-1980, the United States Navy has studied the implementation of Rankine cycles directly coupled to the propulsion system in order to increase its power. The system was not fully implemented because of difficulties due mainly to the use of high pressure circuits in naval units.

In order to increase the autonomy of naval units it is attractive to use cycles ORC (Organic Rankine Cycle) using organic fluids which do not present the risk of condensation in the turbine.

In the patent "METHOD AND APPARATUS FOR DECREASING MARINE VESSEL POWER PLANT EXHAUST TEMPERATURE - US 7121906 B2 (October 17, 2006) and in the patent application "RANKINE CYCLE DEVICE HAVING MULTIPLE TURBO-GENERATORS - US 2006/0112692 Al (June 1, 2006) methods and apparatuses for reducing the thermal profile emitted by the exhausts of naval units and the production of electrical power on board are described. The above mentioned patents describe the use of organic refrigerants circulating in ORC devices for energy production and claim the allocation of at least one evaporator of said ORC devices within the exhausts of the marine power plant providing exclusively a direct exchange of the sensible heat from the hottest combustion gaseous sources to the coldest organic refrigerant. With reference to the circulating organic fluids, "wet fluids" may be inadequate for ORC devices as they become saturated during their expansion in the turbine (threat of turbine damage). On the contrary, "dry fluids" do not reach the two-phase state at the end of the expansion. On the basis of the characteristics of the organic fluid selected and of the temperature level of the hot sources a limited superheating of the fluid may be preferred, since ORC are generally focused on the recovery of low grade heat power.

DISCLOSURE OF THE INVENTION

Surprisingly the present invention provides a system for generating mechanical and/or electrical energy by means of ORC circuits either for the propulsion of naval vessels or for its use on board.

The present invention addresses the growing demand in the naval field to arrange technical solutions which, being integrated with the onboard auxiliary and/or with either electrical or mechanical onboard propulsion systems, allow better autonomy, flexibility, reduced environmental impact and reduced maintenance.

The present invention permits to take advantage of onboard waste heat, having temperatures from 50 to 800 Celsius degrees and more preferably from 70 to 570

Celsius degrees. The required heat for rising the temperature and/or to evaporate and/or to superheat the organic working fluid of the ORC device, whenever the heat is derived from gaseous hot sources, it is displaced exclusively by means of indirect exchange via thermovector fluids circulating in closed loops; whenever the heat is derived from hot liquid sources, it is displaced by direct and/or indirect exchange.

Therefore, in order to recover and displace heat from onboard hot gas sources to the

ORC working fluid, at least one gas-economiser transferring heat to a thermovector fluid must be placed within said gas sources (e.g. exhaust gas from the vessel prime movers and/or from any other combustion auxiliary devices).

Moreover the present invention offers the advantage of not being limited by the use of commercially available refrigerants as working media, but may take advantage from all other possible organic fluids having thermochemical stability at the working conditions and being previously selected on the basis of their saturation temperature and according to the level of the temperature of heat sources, in order to maximise the waste heat capture.

As the properties of the working fluids affect the cycle efficiency, the fluids of the present invention may be selected among organic fluids not potentially harmful to human's health or to the naval vessel environment and having low environmental impact in terms of ozone depleting potential and greenhouse warming potential and/or having controllable explosion and fiammability characteristics. The object of the present invention consists in providing a process for energy generation on board naval units using liquid and/or gaseous heat sources, with temperatures between 50 and 800 Celsius degrees and, more preferably, between 70 and 570 Celsius degrees, deriving from the motor apparatus and/or from onboard auxiliaries and comprising the following steps: a) thermal exchange with organic fluid/s circulating in one or more onboard ORC devices, in order to heat said organic fluid/s, being said thermal exchange an indirect exchange with said gaseous sources and/or a direct/indirect exchange with said liquid sources; b) consequent vaporisation in a vaporiser/s of said circulating organic fluid/s and expansion of the produced vapour/s in turboexpander/s with production of mechanical energy; c) thermal exchange, in recuperator/s, between said expanded organic vapour/s and the same liquefied organic fluid/s exiting a condenser/s in which said vapour/s has/have been condensed, being said condenser/s placed downstream of both said turboexpander/s and of said recuperator/s, in order to rise the temperature of said liquefied fluid/s and to cool down said vapour/s; d) increasing the pressure of said liquefied fluid/s exiting said condenser/s and recycling back said liquefied fluid/s to said evaporator/s, by means of one or more pumping devices, closing therefore the thermodynamic cycle/s of said onboard ORC device/s; e) dissipation of the condensing heat of the organic fluid/s circulating in said ORC device/s by means of onboard or off-board cold sources; f) conversion of the mechanical energy produced by the turboexpander/s of the ORC device/s into electric energy by means of an electric generator/s and/or onboard use of said mechanical energy produced preferably in order to propel the naval unit.

Another object of the invention is to provide a system for onboard energy generation in naval units using liquid and/or gaseous sources, with temperatures between 50 and 800 Celsius degrees and more preferably between 70 and 570 Celsius degrees, deriving from the motor apparatus and/or from the onboard auxiliaries comprising: one or more apparatuses for indirect heat transfer from onboard hot gaseous sources to ORC device/s and/or one or more apparatus for direct/indirect heat transfer from onboard hot liquid sources to said ORC device/s; one or more ORC devices in which are circulating one or more organic fluids able to generate energy by means of Rankine thermodynamic cycles; one or more apparatuses for heat transfer from ORC device/s to inboard and/or off-board cold sources; one or more apparatuses for heat transfer from QRC device/s to inboard and/or off-board cold sources; one or more devices for monitoring/regulating the operating parameters of the ORC device/s, of the heat transfer apparatus/es from the hot onboard sources to said ORC device/s and from said ORC device/s to cold sources inside and/or outside the naval unit.

The system may include the possibility of using at least one electric generator coupled to the turboexpander of the ORC device, including at least one device to connect it to the electric network of naval vessel. In order to minimise maintenance and to eliminate wear, the turbogenerator can be equipped with active magnetic bearings, and it may, for example, consist of a single body, including an overhung impeller and a high frequency generator placed between the structures of two magnetic bearings, each consisting of an axial/radial system. The rotor shaft of the generator is kept suspended in levitation by the bearings without contact surfaces. The system may include power factor regulation equipment, voltage transformers, regulators and also a central to control ORC device/s for the start-up, operation and shutdown phases, and also a distribution central for electrical energy generated by ORC system, in order to distribute it among both propulsion electric motors and a wide variety of electrical loads. In the case of using electric motors for propulsion, they are generally equipped with cooling systems and devices suitable for static or dynamic adjustment of the number of revolutions in order to allow accurate adjustment throughout the full range of speeds, in both forward and backward march. It is also possible to provide systems for coupling/decoupling the electric motors and the axes of the propulsive apparatus.

In a different embodiment of the present invention the system may be integrated with the onboard auxiliaries by means of thermal and/or mechanical and/or electrical energy exchange with at least one or more apparatuses of the onboard auxiliary equipment, wherein said auxiliary equipment includes all sorts of onboard apparatuses or services assisting the navigation, the motor apparatus or the transport of persons and goods, such as, for example, the oil lubrication circuit, the thermal- oil circuit, the steam circuit, the heating fuel service, the inter-refrigeration units, the air conditioning, the cooling loops, the inert gases plant. Moreover the system according to the present invention, may use advantageously a single apparatus for indirect heat transfer, via a single thermovector fluid, in order to recover heat from a plurality of onboard hot sources, by transferring heat to one or more ORC devices of said system. Additionally, at least one heat rejection apparatus of the ORC device/s is integrated with the cooling system of the naval vessel and/or utilises directly refrigerants derived from the external environment such as water or air.

Finally, in another embodiment of the present invention, one or more ORC devices, or at least a section of said ORC device/s, is skid-mounted and engineered for minimising space, optimising maintenance and access so that its installation within the naval unit and/or its removing from it is facilitated.

BRIEF DESCRIPTION OF THE FIGURES

As a continuation of what has been previously described two possible exemplifying and not limiting schemes are reported in order to illustrate further aspects and embodiments of the invention. It is clear that further changes, modifications and different application embodiments of the present system can be implemented by skilled persons in the state of the art without departing from the scope of the invention or the accompanying claims.

Figure 1 illustrates a conceptual block diagram where the main stages and sections present in the system of invention are underlined.

Figure 2 shows a block diagram according to a typical and simplified variant of the system.

DETAILED DESCRIPTION OF INVENTION

In the block diagram of figure 1 the motor apparatus and the onboard auxiliaries generating heat are indicated in block 1. For example, one or more internal combustion engines and/or one or more gas turbines are connected to the propulsion axes of the naval vessel 3 by means of appropriate coupling/decoupling devices 2.

Alternatively, said internal combustion engines and/or gas turbines can provide exclusively mechanical energy to alternators with the aim of producing propulsion energy via electric motors opportunely connected to propellers. The motor apparatus and onboard auxiliaries 1 may include one or more boilers and/or diesel auxiliary equipment in order to operate the naval vessel or to heat fluids and goods or finally any combination of onboard equipment generating thermal and/or mechanical energy. The block X therefore includes both sources, whose energy capacity and thermal level are higher than other, and heat sources having a thermal level being lower than other but also exploitable through the system according to the present invention.

Waste heat from hot gaseous sources is indirectly supplied to the block 5 of ORC energy generation, by using a suitable organic or inorganic thermovector medium flowing in one or more primary heat transfer circuits 4. The energy generation block 5 may contain one or more organic cycles using one or more different working fluids, in order to maximise the heat recovery and the efficiency of the system. The thermovector medium, after transferring heat to a cold source or more of the ORC generator is recycled to a hot source or more. It may be convenient to dispose of one or more secondary heat transfer circuits, which are generally indicated in the block 6, in the case of simultaneous recovery from high thermal level sources and from sources having a temperature lower than the others. Among the possible lower enthalpy level sources it is possible to report the lubrication and cooling circuits of the internal combustion engines or of the gas turbines, which may supply, in the whole or in part, the thermal energy to the working fluid of the organic Rankine cycle, through heat exchangers arranged in series or parallel in such circuits. In this case the secondary heat transfer system from the hot sources to the cold sources of the organic cycle may not require an independent circuit but could be integrated with the aforementioned lubrication and engine cooling systems. A heat rejection block 7 includes onboard refrigeration equipment and may communicate directly with the external environment, from which it draws the cooling medium capable of dissipating the heat of rejection. Interconnected to said heat rejection block 7 are the motor apparatus and auxiliary 1, the block 5 for ORC generation and the block 6 of heat transfer units. A turboexpander present in the block 5 operating the organic cycle may be connected to an electric generator 8. The electrical energy eventually produced by the cycle, after being transformed in the block 9 to a proper voltage and, at the occurrence, power factor corrected, it is sent to the electricity network of the vessel (that is diagrammed in a line connecting block 10 and block 12 representing a device for regulating the number of revolutions of the electric motor) by means of an electric power central of interconnection and control 10 of the generation system. The electrical energy supplied to the network is withdrawn from the ORC generation block 5, in whole or in part, with the aim of operating one or more electric motors 11 coupled to the axis of propulsion by means of at least one appropriate coupling/decoupling device. Alternatively, the energy generated can be connected directly by a dedicated grid, after conversion to the appropriate voltage, to the electric propulsion and/or to electric loads. In both cases it is preferably present the device 12 for regulating the number of revolutions of the electric motor. Alternatively to what is described in the block diagram shown in figure 1, the mechanical energy produced by the turbogenerator of the Rankine cycle may be used without conversion to electrical energy, by connecting the shaft of the turbine for the expansion by means of a servo systems for coupling/decoupling the axis of propulsion and for adjusting the number of revolutions. In special implementations of the invention the above shown diagram may be limited only to the primary heat transfer circuit, without including the secondary circuit of heat removal from lower temperature sources, or using only thermal sources at lower level without adopting a heat extraction circuit from sources with higher temperature level. The simplified diagram of figure 2 illustrates a possible variant of the present invention. A stream of fuel 13 and air as a support of combustion air 14 feed the motor apparatus 15, which may include or not, further auxiliary equipment generating energy. From the propulsion system/auxiliaries a stream or more streams of high temperature exhausts exit. The exhausts release sensible heat to the thermovector stream of the heat transfer circuit by means of one or more indirect heat exchangers/recuperators 16. For example, said recuperator may be composed of single spiral tubes, or of removable tube bundle with floating plate, in order to compensate for the expansion of the tubes with respect to the mantle of the heat exchanger. The extractability of the bundle allows a smooth cleaning of the mantle side and of the tubes. In the tubes a relatively high speed of the thermovector fluid (over 0.6 m/s, preferably greater than 1 m/s) must be ensured in order to avoid the stagnation of the same fluid and localised overheating, which, in the case of using an organic fluid, may alter the properties causing the shortening of its life. The temperature of the flue gas may, if necessary, be controlled by means of turboblowers or turboaspirators designed to mix the high temperature stream with air or exhausted, or lower temperature mixtures.

A primary heat transfer circuit is preferably composed of at least two pumps 17, wherein at least one of which is in standby, while the second pump ensures the circulation of the fluid and provides the heat transfer from the source to a block of ORC turbogenerator. The primary heat transfer circuit is equipped with an expansion tank 18 for the thermovector fluid and with one or more feeding reservoirs 19 of the fluid. In a possible modification of the scheme, the primary heat transfer circuit of the thermovector fluid may be opportunely integrated with one or more auxiliary boilers in order to improve the flexibility and efficiency of the system. In the primary heat transfer circuit a three-way valve 20 may be successfully installed to divert the thermovector fluid to a heat rejection circuit 21 in the phases of start-up, shutdown of the generating system and/or of the motor apparatus 15 and onboard auxiliaries. During these operations, the stream previously cooled is fed to the primary heat transfer circuit, by-passing the block of ORC turbogenerator. Once these operations are completed, the aforementioned three-way valve 20 is switched again in order to feed the heat exchanger 22 of the circuit operating the Rankine cycle. The heat rejection circuit 21 previously mentioned is preferably integrated with the cooling system of the vessel and utilises refrigerants derived from the external environment, such as water or air 23, which, once heated, are released outside the naval vessel. The thermovector fluid circulating from the higher temperature sources releases sensible heat to the working fluid of the organic cycle, with the aim to vaporise the fluid and, if necessary, to superheat it. The working fluid is fed to the turboexpander during the normal operation of plant by means of a line 24 when a bypass line 25 is intercepted. The bypass line 25 can be opened, wholly or in part, during the operations of start up or shutdown. An inhibition device (not indicated) of the liquid phase drag to the blades of a turboexpander may be present upstream of the turboexpander 26. The vapour of organic fluid activates the turboexpander 26, which can be directly coupled to the electric generator 27 through a flexible coupling, generating electricity, or the turboexpander 26 may be connected to the propulsion axis of the vessel via a convenient coupling/decoupling system. The vapour discharged from turboexpander 26 flows through a regenerator 28, where the vapour preheats the organic fluid releasing sensible heat and thus improving the efficiency of the cycle. The use of a regenerator allows both a reduction of heat released in condensation, and a decrease of heat which is introduced in the cycle during the heating of the liquid, since that working fluid is evaporated from a higher temperature with respect to that exiting a condenser 29. The vapour is then fed to the condenser 29 where the vapour is cooled and liquefied by the passage of the refrigeration fluid coming from the heat disposal circuit 21. The liquefied organic fluid is then fed, through a pumping device 30, to the regenerator 28 and subsequently to the heat exchanger 22, thereby closing the cycle. Upstream of the pumping device an apparatus capable of preventing the passage of the vapour to the pumps may be present.

In a modification of the present invention, the organic fluid condenser of the block of ORC turbogenerator is not directly cooled by the refrigeration system of the naval vessel, but the organic fluid condenser releases heat to a second Rankine organic cycle, which generates an additional portion of energy and releases heat to the heat disposal system of the naval unit connected with the external environment. The exhausts of combustion, after transferring heat to the primary heat transfer circuit are fed to a discharge 31 , by using, if necessary, a proper turboblower or turboaspirator (not indicated).

In a variant of the system, the exhausts can exchange further heat with respect to what is released to the ORC turbogenerator by means of one or more heat exchangers or economiser, in order to heat suitable streams so to increase the energy efficiency. In the case of reaching gas temperatures that allow the formation of acidic condensates it is necessary to use special materials in the discharge ducts and in the indirect heat exchange recuperators.

The electric generator 27 is connected to a transformer 32, which is in turn connected to the electricity network of vessels and to the connection and control central of the onboard electric equipment 33. The propulsion electric motor 34 is then connected to the electric grid, via a transformer 35 and includes a system for regulating the number of revolutions 36. Finally, the electric motor 34 is coupled to the propulsion axis through a suitable coupling/decoupling device 37. EXAMPLE 1 A naval propelling apparatus includes a gas turbine being characterized by the following parameters, at standard ISO conditions (dry bulb temperature of 15 Celsius degrees, 60% relative humidity, 1013 mbar pressure):

Exhaust gas flow rate [kg/s] 67,8

Exhaust gas temperature [Celsius degrees] 530

Natural Gas flow rate [kg/h] 5000

LHV natural gas [kJ/kg] 44196

Thermal power input [kW] 61432,4

Electrical power [kW] 22080

Electrical efficiency [%] 36

The exhaust gases from such a unit enter the indirect exchange recuperator, where they release 17.7 thermal MW to a thermovector fluid cooling down to about 300 Celsius degrees. The thermovector fluid (1370 t/h) acquires sensible heat, heating itself up from 250 to 270 Celsius degrees, and is fed to a heat exchanger vaporizer, where it transfers heat to a liquid stream of isopentane at 150 Celsius degrees under pressure, raising its temperature to 240 Celsius degrees to vaporize it and the thermoconvector fluid transfers additional heat to superheat the liquid stream of isopentane, in order to use said isopentane in an energy production system utilizing an ORC. The thermovector fluid is cooled to about 250 Celsius degrees and it is relaunched, through a pumping device, to the flue gas indirect heat exchange recuperator. The produced isopentane vapour (147 t/h) are expanded (expansion ratio of about 10.6) in a high efficiency turbine (83%), producing about 4100 kW of brake power. The vapour expanded enters at 186 Celsius degrees a heat exchanger- regenerator, where it preheats the liquid stream of the working fluid up to 150 Celsius degrees, cooling itself to 85 Celsius degrees. The vapour stream enters a condenser, where it releases the latent heat to the refrigeration circuit of the vessel, cooling down to 40 Celsius degrees and condensing itself. In order to enhance the efficiency of the cycle, said organic fluid flows through a preheater where it receives, by direct or indirect heat exchange, a portion of low enthalpy additional heat (3.4 MW) from a cooling stream (86 Celsius degrees) deriving from the cooling system of the naval vessel, from jackets and from the lubrication of onboard diesel alternators, and increasing its temperature up to 70 Celsius degrees, while the cooling fluid is cooled down to 80 Celsius degrees. The Rankine cycle is closed by relaunching the organic fluid, through the pumping device, to the heat exchanger- regenerator previously mentioned. The shaft of the organic fluid expansion turbine is coupled to an electric generator through a flexible coupling. The connection to the medium voltage network of the naval vessel occurs after transforming to 6.6 kV. About 3990 kWe are produced (efficiency of the alternator at 0.974, with the radiant heat loss from the system being neglected). A portion of the electrical power available is used for the electrical loads of the Rankine circuit and for the heat transfer loop from the fumes of the gas turbine (about 280 kWe). The remaining portion is available for onboard services or for naval propulsion as, for example, the case of marine systems CODLAG (Combined Diesel-Electric and Gas) or CODAG (Combined Diesel and Gas), using electric transformers and electric propulsion motors, adopting synchronous static variable frequency actuators for adjusting the number of revolutions. Finally, the fumes of the gas turbine at 300 Celsius degrees, before being sent to the turboaspirator of the exhaust pipe, may release an additional portion of heat (8.5 MW) to service fluids, cooling themselves down to 180 Celsius degrees, in order to further raise the thermal efficiency of the naval vessel. EXAMPLE 2

The combustion exhausts at 400 Celsius degrees (45.4 kg/s) pass through an indirect heat exchange recuperator releasing 7.1 MW thermal to a thermo vector fluid and cooling themselves down to about 260 Celsius degrees. The circulating thermovector fluid (231 t/h) increases its temperature from about 200 to 250 Celsius degrees and it is fed to a heat exchanger evaporator of an Rankine device, where it releases heat to a pressurized liquid organic stream of octamethylcyclotetrasiloxane at 132 Celsius degrees, vaporizing it and raising the temperature of said stream to 240 Celsius degrees. The thermovector fluid, cooled down to about 200 Celsius degrees, is relaunched to said exhaust recuperator by the pumping system of the primary heat transfer circuit. The organic fluid vapours produced (131 t/h) are expanded from 2O x 10⁵ Pa to 0.6 x 10⁵ Pa in a turboexpander with magnetic bearings (efficiency = 80%), producing about 1220 kW brake. The expanded vapour enters, at 148 Celsius degrees, in a heat exchanger-regenerator, where it preheats the liquid stream of the working fluid up to 132 Celsius degrees, cooling itself to 100 Celsius degrees. The vapour stream enters a heat exchanger, where it condenses and cools down to 89 Celsius degrees. The heat of transition of phase (about 6 MW) is released in condenser to a water cooling loop, which water is heated from 40 to 80 Celsius degrees and can be used for onboard services. The Rankine cycle closes relaunching the organic fluid, through the pumping device, to the previously mentioned heat exchanger-regenerator. A portion of the electrical energy produced (130 kWe) is used for the electric loads of the ORC device and for the electric loads of the primary heat transfer circuit by flues of the gas turbine. The remaining portion of the electrical energy produced is available for the onboard services or for the naval propulsion via LCI (Load Commutated Inverter) driven synchronous electric motors.

Claims

1. A process for energy generation on board naval units using liquid and/or gaseous heat sources, with temperatures between 50 and 800 Celsius degrees and more preferably between 70 and 570 Celsius degrees, deriving from the motor apparatus and/or from onboard auxiliaries and comprising the following steps: a) thermal exchange of at least an organic fluid circulating in at least one onboard ORC device, in order to heat said organic fluid, being said thermal exchange an indirect exchange with said gaseous sources and/or a direct/indirect exchange with said liquid sources; b) consequent vaporisation in at least one vaporiser of said at least a circulating organic fluid and expansion of the produced organic vapour in at least one turboexpander with production of mechanical energy; c) thermal exchange in at least a recuperator between said expanded organic vapour and the same liquefied organic fluid exiting a condenser in which said vapour has been condensed, being said condenser placed downstream of both said turboexpander and recuperator, in order to rise the temperature of said liquefied fluid and to cool down said vapour; d) increasing the pressure of said liquefied fluid exiting said condenser and recycling back said liquefied fluid to said evaporator, by means of at least a pumping device, whereby closing the thermodynamic cycle of said onboard ORC device; e) dissipation of the condensing heat of the organic fluid circulating in said ORC device by means of onboard and/or off-board cold sources; f) conversion of the mechanical energy produced by the turboexpander of the ORC device into electric energy by means of an electric generator and onboard use of said mechanical energy produced preferably in order to propel the naval unit.

2. The process of claim 1, wherein additional heat from said onboard hot liquid and/or gaseous sources is transferred to preheat said circulating organic fluid before said vaporization and/or to superheat said produced vapour before said expansion.

3. The process of claim 1, wherein said electric energy produced by said electric generator is supplied, as a whole or partially, to the onboard electric loads by means of the onboard electric network and by a dedicated grid, preferably including, in said electric loads, electric motors and more preferably propulsion electric motors.

4. A system for energy generation on board naval units using liquid and/or gaseous sources, with temperatures between 50 and 800 Celsius degrees and more preferably between 70 and 570 Celsius degrees, deriving from the motor apparatus and/or from the onboard auxiliaries comprising: at least one apparatus for indirect heat transfer from onboard hot gaseous sources to at least one ORC device, and at least one apparatus for direct/indirect heat transfer from onboard hot liquid sources to said ORC device; at least one ORC device in which at least one organic fluid able to generate energy by means of Rankine thermodynamic cycles circulates; at least one turboexpanser for the expansion of the organic fluid; at least an organic fluid condenser able to condenser the organic fluid of said

ORC device; at least one apparatus for heat transfer from said ORC device to inboard and/or off-board cold sources; at least a heat rejection apparatus of said ORC device; at least one device for monitoring/regulating the operating parameters of said

ORC device, of said heat transfer apparatus from the hot onboard sources to said ORC device, and from said ORC device to inboard and/or off-board cold sources, i.e. inside and/or outside the naval unit.

5. The system of claim 4, wherein said ORC device uses at least one organic working fluid selected among organic fluids not potentially harmful to human's health or to the vessel environment, having controllable flammability and explosion characteristics and preferably having a low environmental impact in terms of ozone depleting potential and greenhouse warming potential.

6. The system of claim 4, wherein the organic fluid condenser of said ORC device is cooled by means of a second organic cycle Rankine, which generates an additional portion .of energy and releases heat to said inboard and/or off-board cold sources.

7. The system of claim 4, wherein the turboexpander of the ORC device uses active magnetic bearings in order to minimise maintenance and wear of the mechanical parts.

8. The system of claim 4, wherein at least one heat rejection apparatus of said ORC device is integrated with the cooling system of the naval vessel and utilises directly refrigerants derived from the external environment such as water or air.

9. The system of claim 4, wherein at least an ORC device, or at least in a portion thereof, is skid-mounted and engineered in order to minimise space so that maintenance and access is optimised and its installation within the naval unit and its removing therefrom is facilitated.

10. The system of claim 4, wherein a single apparatus for indirect heat transfer, via a single thermovector fluid, is used in order to recover heat from a plurality of onboard hot sources, by transferring heat to at least one ORC device.

11. The system of claim 4, wherein at least one electric generator coupled to said ORC turboexpander and at least one mechanical device coupled to said turboexpander are included, in order to use said mechanical energy produced and preferably used in order to propel the naval unit.

12. The system of claim 11, wherein at least one apparatus of said system exchanges energy with at least one apparatus of the onboard auxiliary equipment.

13. The system of claim 11, wherein at least one apparatus to interconnect, to transform, to dispatch, and/or power factor regulate the electric energy produced by the system is included.

14. The system of claim 12, wherein at least one control section for the repartition of the electric energy produced among electric loads of naval unit is included, by means of the onboard electric network and by a dedicated grid, including preferably in said electric loads electric motors and more preferably propulsion electric motors.