Patent Publication Number: US-2015075167-A1

Title: Electronic system and method of automating, controlling, and optimizing the operation of one or more energy storage units and a combined serial and parallel hybrid marine propulsion system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation application of U.S. patent application Ser. No. 13/340,107, filed on Dec. 29, 2011, which claims priority to U.S. Provisional Application Ser. No. 61/427,903, filed on Dec. 29, 2010 and U.S. patent application Ser. No. 13/340,107, filed on Dec. 29, 2011 is a Continuation-In-Part application of U.S. patent application Ser. No. 12/612,383, filed on Nov. 4, 2009, which claims priority to Canadian Patent Application No. 2,643,878, filed on Nov. 14, 2008, the entirety of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention generally relates to marine electric propulsion systems. Specifically, the invention relates to the definition, programming and parameterization of an electronic management computer to interface, integrate, optimize, automate and simplify the operation of a combination of serial and parallel marine hybrid electric propulsion systems. 
     BACKGROUND OF THE INVENTION 
     One of the novelties of the invention is to utilize automation to restrict the use of an ICE (Internal Combustion Engine) to when it can be operated at near optimum efficiency by combining electrical storage with a parallel and a serial marine hybrid electric propulsion system in a marine vessel. 
     To help understand marine hybrid propulsion, we may quickly define the different systems that we are going to refer to. Diesel electric may be defined as a system where a generator is required for propulsion and its electrical power output is directly connected to the propulsion electric motors. In a serial hybrid system, a large ESU (Energy Storage Unit) is placed between the generator and the loads; the energy storage unit is used as a buffer and also for electric only operation when low power is required. In a parallel hybrid system, the ICE is directly connected to the propulsion shaft through a clutch and reduction gear and it is furthermore connected to an electric motor/generator. 
     We can understand the inherent inefficiencies of strictly diesel electric propulsion systems. When the house loads are less than the propulsion loads or the installation does not require multiple generators, the multiple power conversions make this technology quite inefficient. The inefficiency of diesel electric is why newer installations tend to adopt either parallel or serial hybrid by making an energy storage unit part of the system. 
     On the other side of the spectrum, where in very high power requirements the ICE is being used past its most efficient area, the electric motor of the associated parallel hybrid system can also be utilized through the energy storage unit to assist in providing thrust, but for a limited time. Again, once the ESU reaches its low level, there is no solution but to reduce power. In certain weather conditions, reducing power is not desired, and could even be dangerous. Therefore, the problem with parallel hybrid is that it is inefficient at very high power or at low power when the batteries are depleted. 
     Like parallel hybrids, use of serial hybrids may also result in problem areas. For example, the problem here lies in that at normal continuous power, even though the engine is running at the most efficient area, the combined losses of generating and using would be more than 10% worse than a good parallel system operating in the same optimum range, even assuming that the ESU battery was 100% efficient. 
     Also, as far as house loads are involved, the use of an ESU being pulsed by an efficient ICE can reduce its operating time and greatly improve the efficiency of generating and maintaining large house loads. Current practice on most yachts is to use fixed speed AC (Alternative Current) generators designed for peak loads, the AC current produced is not directly compatible with an ESU that is DC (Direct Current) by nature, and these generators must run almost continuously when house loads are high, such as use of air conditioning. Another major consideration is electric power production, whether it is from a standalone generator, a motor/generator coupled to a parallel hybrid system, fuel cells, wind/water generator or solar panels. Fuel is still the best way (in terms of volume/weight) to store energy and until the price of fossil fuels increase dramatically, and as long as extended range navigation or some form of shore power independence is required, fuel will still be used. With this in mind, the best way to convert this fuel into electric (or propulsion) power is to use high efficiency variable speed diesel HVDC generators, as long as they are being used in their best RPM and torque window for the load. By cycling the generator into an ESU and providing variable house loads through HV high efficiency inverters, operational saving of up to 70% can be achieved on a yearly basis compared to old technology fixed speed AC generators. 
     In certain vessels where an old technology AC generators are already installed or the need for a low cost emergency backup power is needed, an existing AC fixed speed generator can still be used by redirecting its output to the HVDC shore power charging system of the vessel, thereby providing a power source for the HVDC systems. Such a system can also be balanced so as to load the AC generator to its best operating point thereby avoiding the issues of wrong loading conditions. 
     To solve these issues, the present invention includes a system and method for use of both parallel and serial hybrid technologies in combination with an ESU, in order to optimize the operation of a modem hybrid electric marine vessel. 
     SUMMARY OF THE INVENTION 
     This invention relates to the automation and optimization of a complex hybrid system for marine vessels where a hardware unit with three mode (OFF, AUTO and ON) as stated in Patent application WO 2010/054466 A1 from the same inventor, together with throttle position, is used as a power management interface between complex and dissimilar boat systems and the operator, so as to ease the operation, increase safety, reduce the workload, increase comfort and greatly improve fuel efficiency. This involves the use of control software to integrate, optimize and combine in a marine hybrid system, the operation of one or more variable speed HVDC generator(s), one or more (ESU) and a combination of one or more HVDC parallel hybrid and serial hybrid propulsion systems. To further optimize efficiency, heuristic algorithms based on fuel consumption versus kW produced at different loads and RPM are used. Once an energy storage unit is coupled to an electric motor and to an ICE, a complete 3D map is produced describing the efficiency of each device by measuring the actual kW produced for every gram of fuel at different RPM and torque over the whole power range for each of these devices. This information and the energy storage characteristics are then used by the software to determine which is the best device(s) to use, single or in combination, for the action to be performed. All of this based solely on simple thrust lever commands and one of the 3 modes (OFF, AUTO and ON) selected by the operator as described in WO 2010/054466. 
     While the limitations of diesel, electric only, diesel electric, serial hybrid and parallel hybrid are well known, each of those has strong points and each has its disadvantages. The present invention incorporates these disparate technologies and merges them into a unified computer controlled system, with the role of automatically optimizing these technologies in a transparent fashion for the vessel operator and thus drastically increasing their combined efficiencies in accordance with the punctual loads demanded. For example, low power maneuvering and movement up to hull speed for a limited time is accomplished purely under electric. In one embodiment, (See  FIG. 1 ) should the ESU get down to the lower limits, the generator automatically starts, and runs at peak efficiency to recharge the ESU and shuts down once the upper ESU limits is reached ( FIG. 5 ). Should the demands of propulsion increase to a point that is close to the peak efficiencies of the variable speed DC generator, the generator may start again ( FIG. 6 ), and provide power to all loads until the demands decrease. If power requirements for propulsion continue to increase, then the parallel engine(s) may start ( FIG. 7 ), synchronize, a clutch/transmission may connect it to its associated propeller and electric motor/generator ( FIG. 1 ), this electric motor/generator may change function from propulsion to generation and its power may then be used to power other electric propulsion motor(s) and loads. At this point the generator may shut down. In the final portion, should maximum power be required, the generator would be automatically restarted and combined to all loads to provide a mixture of parallel and serial hybrid power to all of the vessels loads, irrespective of their nature, in a completely transparent fashion for the vessel operator. It is worth mentioning that the operator has very little knowledge of all of this optimized switching, as the transitions in power demands are met by using the Energy Storage Unit and the electric motors. In this example, up to a momentary 100 kW/h of energy can be extracted from or pushed back into the ESU, to smooth out and optimize the transitions. 
     Propeller sizing is also important to consider in a mixed configuration. Electric motors have inherently very high torque even at very low rpm due to the nature of the technology. ICEs on the other hand have very low power at low rpm and thus the propellers are designed so that they do not stall the engine at low speed. This compromise is very costly in terms of efficiency. On the other hand of the spectrum, due to the logarithmic nature of drag increase with speed, ICE engines are normally sized for the maximum propeller loads and are therefore ill suited for low power utilization. Maximum propeller load is normally not the most fuel efficient area of utilization of an ICE either. By combining an electric motor and an ICE, the very low power setting can be accomplished by the electric motor allowing a propeller to be pitched and surfaced to the most efficient point of the ICE. It is also understood that at very high power, the ICE might not be able to achieve its top RPM because of the high pitch and surface of an optimized propeller, but there again the coupled electric motor can be of assistance in enabling the ICE to stay in its efficient area and still have the vessel achieve its expected performance ( FIG. 8 ). 
     In accordance with one embodiment of the present invention, the system includes a hybrid EMC (Energy Management Computer) system. The EMC includes a human actuable input device, the human actuable input device selecting one of a plurality of operating modes. An ESU (Energy Storage Unit) is further included, the ESU having a corresponding charge level. A generator is included, the generator selectively supplying at least one of house power, propulsion power and ESU recharge power based at least in part on the selected one of the plurality of operating modes. An electric motor is included, the electric motor operating in an electric generation mode to generate electric power and as motor in a propulsion mode to turn a propeller. A prime mover ICE (internal Combustion Engine) is included, the prime mover ICE is controlled to turn the propeller and to drive the electric motor to generate the electric power when the electric motor is in the electric generation mode. An EMC is included, the EMC having a processor controlling the operation of the prime mover internal combustion engine, the generator and the electric motor based at least in part on the selected operating mode, the ESU charge level, a house load demand and a propulsion demand. 
     In another embodiment, a method includes receiving a selected one of a plurality of operating modes. Using a generator to selectively supplying at least one of house power, propulsion power and ESU recharge power based at least in part on the selected one of the plurality of operating modes. Operating an electric motor in an electric generation mode to generate electric power and as motor in a propulsion mode to turn a propeller. Controlling the operation of a prime mover ICE, the generator and the electric motor based at least in part on the selected operating mode, the ESU charge level, a house load demand and a propulsion demand. The prime mover ICE being controllable to turn the propeller and to drive the electric motor to generate the electric power when the electric motor is in the electric generation mode. 
     In yet another embodiment, the system includes an ESU, a prime mover ICE, an electric motor, and a generator cooperating in both a serial and a parallel hybrid configuration to provide power to turn a propeller coupled to the marine vessel. An EMC controlling the ESU, the prime mover ICE, the electric motor, and the generator, the EMC automatically switching between providing power to the propeller in the serial configuration and the parallel hybrid configurations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a simplified schematic view of an embodiment of a combined serial and parallel hybrid system for a marine vessel constructed according to the principles of the present invention; 
         FIG. 2  is a detailed schematic view of the embodiment of the combined serial and parallel hybrid system shown in  FIG. 1 ; 
         FIG. 3  is a flow chart of an exemplary operation of an energy management computer for the combined serial and parallel hybrid system for shown in  FIG. 1  and constructed in accordance with the principles of the present invention. It shows the different inputs that affect its behavior and the devices that it controls; 
         FIG. 4  is a schematic of an exemplary operation of the energy management computer shown in  FIG. 3  controlling power production, power conversion and power consumption; 
         FIG. 5  is a flow chart showing an exemplary operation of an energy storage unit constructed in accordance with the principles of the present invention; 
         FIG. 6  is a flow chart showing an exemplary operation of a generator module constructed in accordance with the principles of the present invention; 
         FIG. 7  is a flow chart showing an exemplary operation of a propulsion system in a twin hybrid parallel squared configuration constructed in accordance with the principles of the present invention; and 
         FIG. 8  is an exemplary graph showing the area of optimized operation of electric motor/generator and internal combustion engine in a combined serial and parallel hybrid system typical of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     If petroleum based products are to be used, the most efficient way to provide propulsion is through an advanced common-rail diesel engine directly connected to a propeller via a proper gear reduction ratio and with a propeller sized and pitched to provide the right load. Regretfully, this is not often the case. 
     Fixed speed AC generators used for house loads have a very high operating cost for the power they provide. The best way to generate energy is through a state of the art common-rail variable speed diesel engine coupled to an advanced HVDC generator, whose energy is stored in a high voltage electric storage unit capable of accepting and releasing a large amount of power with very low losses. Variable daily power demands are met through an efficient HVAC inverter, this allows the generator to be run only at its best efficiency area and just a few minutes per day, if the energy storage unit is sized appropriately. 
     One of the advantages of using a state of the art HVDC permanent magnet motor/generators is the infinite possibilities of power extraction and generation, with the advanced of new high performance motor controllers (motor inverters), the most sophisticated devices may allow bi-directional power transfer and voltage up-scaling. This voltage up-scaling allows when in motor mode to keep the rated output of the motor even as the energy storage units depletes, and conversely may allow in generation mode to provide full voltage output back into the energy storage unit even at very low RPM. 
     Diesel electric propulsion is very inefficient by its nature (e.g. inherent losses in multiple power conversion). The operating benefits only start to show up on large vessels equipped with multiple generators and where house loads are sometimes higher than propulsion loads, (so the power has to be converted into electric anyway). 
     Parallel hybrid systems are normally recognized as the most efficient way to operate a marine vessel but the efficiency window is quite narrow. Serial hybrid are normally considered the most flexible, more expensive but less efficient than parallel hybrid in their narrow operating window. 
     Electric only operation is the most elegant, simple and economical, but until the energy storage issues are resolved, (cost and energy storage capacity), it may require recharging with a generator that uses petroleum products and/or with wind/water generators, solar panels or fuel cells. This rapidly increases the cost and complexity of this type of system. 
     Even if battery only electric propulsion is extremely efficient at low speed and for low speed maneuvering, a large part of the market still demands the capability to go at high speed (even if for limited time). Commercial, pleasure fishing and diving operators want to go at high speed to their temporary destination and revert to low speed for hours or days before coming back at high speed to offload their expensive and/or time sensitive cargo, so that they can do it all over again. 
     Therefore, a way to automate the combination of the current technologies and greatly increase efficiency at all speeds is needed. A transparent integration of the above can be achieved if proper automation is used, and it is possible in integrate all of these into a uniform and extremely efficient system. This invention is directed at such a system and its control and operation using state of the art components, electronics and logic. 
     The system of the present invention is programmed to operate efficiently in different modes for different situations, such as when at the dock and connected to shore power, or when at sea in OFF, AUTO or ON modes. 
     Now referring to  FIG. 1 , which shows an exemplary simplified embodiment of the combined serial and parallel hybrid system of the present invention referred to generally as “10.” Large lines represent bi-directional high voltage DC power flow. The narrow lines represent the data communications lines between the EMC  12  and the different devices it controls via a processor. In this embodiment, the helm station controls  14  are the mechanism by which the operator interfaces and monitors the operation of the EMC  12 . The helm station controls  14  (that can be duplicated in as many locations as required), is the interface that tells what may be the operating mode to function in (OFF, AUTO and ON) and how the EMC  12  is going to respond to the Throttles and Joystick inputs. 
     The OFF mode is described as the electric only mode, all low speed (up to hull speed for a limited time) maneuvering is done in pure electric mode where the EMC ( 12 ) has control of the (ESU) Energy Storage Unit  36  power, the two propellers  18 , 20  via their connected electric motors  22 ,  24  and the bow thruster  26 . Should low seed maneuvering be maintained for hours and the power selection is in OFF mode, a warning (both visual and audio) may be activated and load shedding may be initiated once the ESU  36  reaches a predetermined low limit, (normally 40% of capacity for AGMs and 20% for Lithium). A further example of automation programming in a low power OFF mode is if the yacht had been operating on the electric only mode (OFF), and wished to continue in electric only mode once the ESU  36  had reached the predetermined state to automatically switch to the generator  32 ,  34 . This could happen, for example, if entering a port where diesel operation is not desirable. The system would provide a warning of low power, and then the operator would choose an override function. This would allow the yacht to continue to function in electric only mode (OFF) by shutting down all non-essential power from the house loads, including AC power in use, all on-board lights with the exception of navigation lights and computer systems. 
     The AUTO mode is the normal operating mode of the system. In automatic mode, the low speed maneuvering is done as stated in the OFF mode with the exception that once the low ESU ( 36 ) level is approached, the generator ( 32 ,  34 ) is automatically started to recharge the battery. If the vessel, due to a combination of higher propulsion or house loads maintains a ESU ( 36 ) discharge rate over a stable period (of approximately 5 minutes) that is close to the window of optimum generator operation, the generator may start and, once the ESU ( 36 ) has reached its 95% level, the variable speed generator ( 32 ,  34 ) may slow down to accommodate the loads until these loads are reduced below its optimum operating window, at which time the generator ( 32 ,  34 ) may be shut down until required again. In this example, this mode may accommodate up to a total of 100 kW of combined power requirement (propulsion and house loads). 
     If propulsion load demands go above the optimum windows of the generator ( 32 ,  34 ) for an extended period but do not increase dramatically, then the EMC  12  may start the prime mover  28  and once warmed-up may synchronize the speed, close the clutch or engage the transmission to drive directly the propeller  20  and in turn generate power using its accompanied electric motor/generator  24 . Once accomplished and assuming that the power demands are less than 200 kW total (in this example), the generator ( 32 ,  34 ) may shut down. In this mode, the prime mover  28  provides up to 200 kW of power split between the two propellers, as some of the power extracted from the prime mover  28  through its attached motor/generator  24  may feed the house loads through the High Voltage Distribution Box  30  and the second propeller  18  through its connected electric motor  22 . This mode provides the highest level of efficiency has the prime mover  28  loads a closely matched to the optimum operating window by using the attached electric motor/generator  24  in combination. This also allows for effective propeller usage as the vessel in long range fuel saving mode never ends-up having a propeller  18  water-mill with its associated drags. Should total power demands exceed 200 kW, the EMC  12  may order a restart of the generator  32 ,  34  and by combining all power sources  28 ,  32  may allow up to a combined 400 kW of propulsion power. 
     It is worth noting that all these transitions are accomplished by the EMC  12  logic, with the primary goals of being the most efficient at using each of the different power producing/storing devices  28 ,  32  and  36  and of being completely transparent to the operators. It is also important to mention that these transitions are accomplished in a smooth power transfer method by using the energy stored in the electrical storage unit  36  as a buffer and the capability of electric motors to exceed the continuous rated power limits to complement or supplement variable thrust loads while the configuration is changing. 
     The ON mode is what may be considered an abnormal mode, it is a mode that overrides most energy saving modes and starts all available power units  28 ,  32 , a way to override the battery charging logic, and also a way to have instantaneous emergency power of up to 500 kW by combining the power of all engines, electric motors  18 ,  20  and the ESU  36 . The emergency mode is described in WO 2010/054466,  FIGS. 4 ,  5  and  6 . 
     In this example of a combined serial and parallel hybrid system, the ICE generator  32 ,  34  is 100 kW. The serial electric propulsion motor  22  is 200 kW. The parallel ICE  28  is 330 kW and its associated parallel electric motors/generator  24  is 100 kW. So in the electric only OFF mode, a total of 100 kW (50 kW per propeller) is available due to the limitations of available power from the ESU  36 . In serial hybrid electric AUTO state ( 36 + 32 ,  34 ), a total of 200 kW (100 kW per propeller) is available. In low power prime mover  28  AUTO state, a total power of 300 kW (150 kW per propeller) is available. In high power prime mover  28  AUTO state, by combining the generator  32 ,  34  and the prime mover  28  with its mechanically connected electric motor/generator  24  a total of 400 kW of power is available to both propellers  18 ,  20 . In ON mode state, a total power of up to 500 kW could be attained by the automatic combination of all power producing devices  28 ,  24 ,  32 ,  34  and  36  for a period of a few minutes. 
     Now referring to  FIG. 2 , which shows a more detailed description of a mixed parallel, serial and electric hybrid system in accordance with one embodiment of the present invention. All controls  14  are (sail by wire) computer generated and all data communication amongst the peripherals managed by the EMC  12  and is done through CanBus, J1939, NMEA 2000 and/or EtherCan to name a few. All power management communications from the EMC  12  and any of the multiple peripherals, (Motor controllers  38 ,  40  and  42 , User interfaces  14 , Battery management system  16 , HV switching  30 , Inverters  44 , Navigation information  46  and related equipment&#39;s is done through J1939, CanBus, NMEA 2000 and EtherCAN standard. All vessel operation passes through the Energy Management Computer  12 , this one has been programmed to store historical data and as such also allow limited access through the external communication link  48 , whether in the form of USB, Ethernet, Cellular, WiFi, Blue tooth or Satellite. This allows system monitoring, updating, alarms, status and certain functions to be performed remotely. 
     This exemplary embodiment has the following characteristics: A Parker MDL PLC is used as the EMC (Energy Management Computer) logic 12, a 35 kW/h 360 VDC ESU (Energy Storage Unit)  36  rated at 3C (105 kW of power and approximately 28 kWh of energy). A 100 kW continuous variable speed DC generator  32 ,  34 , a 200 kW/h electric drive motor  22  coupled to a propeller  18  and a parallel hybrid side  28 ,  50 ,  24  comprised of a 330 kW ICE (Internal Combustion Engine)  28  coupled to a clutch/transmission  50  and to a 100 kW electric motor/generator  24  attached to the propeller  20 . A variable speed Can bus controlled bow 8 kW thruster  26  can be added. With the use of a joystick  14  full electronic control in forward, reverse, lateral and rotation axis can be done and if a reference to position and heading  46  is provided, automatic position hold can be implemented at each navigation station in a transparent basis, making low speed maneuvering in wind or current very easy and efficient. External Communication  48  and Helm Controls  14  were extensively discussed in described in WO 2010/054466. In keeping with the energy saving nature of this invention, should Wind Generator  52  or Solar Panels  54  be present, a DC/DC Bidirectional Charger/Converter  56  may allow any excess power to be redirected to the ESU  36 . 
     The primary starting device for the Generator Engine  32  is the associated Electric Motor/Generator  34  through the ESU  36 , this allow for a much faster spin-up before fuel is allowed to flow thereby increasing efficiency and minimizing operation at low RPM. Should there be a fault with the ESU  36  or EMC  12 , the low voltage Starter  57  would be used for Generator  32  start instead. A lot of fuel is lost and pollution generated by starting and by low speed operation of a cold ICE. The inventor described an algorithm (in patent application WO 2010/054466 P29-32) that (in normal cases) starts the ICE  32  using its electric motor/generator  34 . The idea is to spin the ICE  32  to operating speed before providing fuel for operation; this allows almost immediate high efficiency, eliminates start-up smoke and losses in low speed operation. Shut down includes a short period of temperature stabilization at lower speed before the complete shut-down takes place. 
     Since some of the Low Voltage accessories  58  are considered essentials (Energy Management Computer  12 , for example), the limited size Low Voltage Energy Storage  60  would also get power from the Generator&#39;s Alternator  62  when this one is operating. The energy producing devices of this drawing  32 ,  28  are controlled by their own Engine Control Units  64 ,  66  and act as the communication interface (J1939) between them and the Energy Management Computer  12 . The same function is achieved by the Inverter Controller  38 ,  40  and  42 , their attached motor/generators and the EMC  12 . 
     When shore power is available, it is connected through a universal high voltage battery charger  68  able to operate within a large range of frequencies and voltage making it worldwide compatible. This charger is also fully insulated (meaning there is no electrical link between the boat and dock power). Since all boat DC loads  58  are provided from a small LVDC battery  60  powered by HVDC/L VDC converters  56  and higher voltage AC loads  70  are provided through high efficiency HVDC/AC inverters  44 , all powered from the ESU  36 , the shore power loads can be monitored and adjusted through the main EMC  12  so as not to exceed the available shore power, since all peak boat demands are met by the ESU  36 . Even a small 120V 10 Amps house plug is able to provide more than 25 kW of power per day, more than enough to run most small boats with intermittent high loads like water heaters, microwaves and other cooking appliances, as long as the peak loads are provided by a proper ESU  36  and its associated peripherals. 
     Another issue with advance automation is the (what if) scenarios: What happens if the EMC  12  device becomes unusable or if the ESU  36  becomes faulty? On large vessels, it is customary to have backup fail safe systems for the EMC  12 , and the ESU  36  because of its higher stored power is usually divided in two parts, so having one of the two units fail has little effects on the operation. But on smaller vessels, a backup was needed. In case of serial hybrid system, an emergency mode can be activated when the EMC  12  is not operational, thereby turning the system into a strictly diesel-electric, by-passing all logic, automation and ESU  36 , and having the propulsion respond directly to the attached generator. In the case of a parallel hybrid system, taking the EMC  12  offline allows the prime movers to be controlled directly by the related throttles, thereby bypassing the EMC  12  and controlling the engines directly. 
     Now referring to  FIG. 3 , which shows an example of hybrid system energy management logic by the EMC  12 . The simplified flow chart describes the different Inputs required by the EMC to do full system optimization and where is the logic Output going to. The EMC  12  continually monitors for status and demands changes from all the Inputs and coordinates the start/stop/demands to different outputs available in the vessel. Once propulsion has been activated in accordance with the operating mode (OFF, AUTO or ON), whether the input is from the joystick or the throttle(s), the system may activate the relevant output to move the vessel in accordance and transparently to the user. For example,  FIG. 4  shows that the EMC  12  controls power production, power conversion and power consumption. 
     Now referring to  FIG. 5 , which shows the logic of the management (programmed in the EMC  12 ) of the ESU  36 . Since propulsion always has priority, should low power storage limits be reached because of the selection of the mode (OFF) and the corresponding alarms be ignored, a load shedding algorithm would be enabled, some primary house loads would be maintained, but hot water heaters, air conditioning, normal power outlets would be shed in a progressive matter in order to maintain navigation, communication and propulsion for as long as possible. Should such an unusual power demand be put on the system, the EMC may record such action as it might affect manufacturer&#39;s warranty. In this embodiment, all energy storages units used in the system of the present invention (whether AGMs, Lithium or hyper-capacitors) have a minimum absorption and discharge rate of 3C (3 times their rated capacity), this means that a 33 kW/h battery bank can provide up to 100 kW of power in both charge and discharge actions. When Lithium batteries are cycled between 20% and 95% of charge, this mean that the effective energy that can be used and later replaced is in the order of 28 kWh. This power replacement is usually done in less than 30 minutes using a 100 kW HVDC generator, including the cool-off before shut down. A large and efficient battery bank and its associated management unit is of prime importance on any good hybrid application, especially on marine vessels where the propulsion loads are often replaced by fairly large and intermittent house loads. 
     In the case of house loads, since all house power is provided by the ESU  36  energy storage unit, any ICE used may be at optimum power (minimum fuel per kilowatt) to recharge the ESU  36  according to the charge window. The ESU  36  topping-up (100%) may be performed if propulsion loads demands that an ICE maintains operation or if the ON mode of operation is selected. This may be used to electrically synchronize and equalize the ESU through the BMU ( 16 ) up to full charge. This is also accomplished anytime the vessel is coupled to shore power. 
     In an exemplary operation of the ESU  36 , the ESU  36  may operate based on stored limits and actual parameters provided by the Battery Management System  16 , such as the state of charge (SoC) of the ESU  36 . For example, if the SoC of the ESU  36  is between approximately 11-20%, meaning the charge remaining in the battery is approximately between 11-20% of its fully charged state (Step  100 ) and the OFF, AUTO and ON state of the Helm Control  14  is in the OFF (Step  102 ) configuration then the EMC  12  may shed non-essential loads and generate an alarm (Step  104 ) to advise the operator of the impeding low battery system deactivation, if on the other hand, the Helm Control  14  was in the AUTO configuration (Step  102 ), then the automatic generator start function (Step  106 ) would start the generator and charge the ESU  36 . If the SoC was less than 10% (Step  108 ) and no operator action was performed to change the operating state from OFF to either AUTO or ON, then the EMC  12  would do an automatic system shutdown (Step  110 ) in order to protect the integrity of the system and allow a subsequent system re-start. If the SoC was not less than 20% and has not reached the upper limit then the EMC  12  considers the system to be in normal charge state, continue at charge voltage (Step  120 ) up to the 95% limit (Step  112 ) while monitoring the individual ESU  36  cellules voltages and temperatures provided by the BMS  16  and reducing charging Amperage as appropriate (Step  122 ). Now, for the third possibility, if SoC&gt;95% (Step  120 ) then the EMC  12  may reduce the bus voltage to float level (Step  114 ) and verify the status of the mode status (AUTO or ON) (Step  116 ), If AUTO (the normal mode of operation) was active then the generator would be stopped (Step  118 ), if on the other hand the ON mode was active, the generator would continue its load following operating state. By cycling the generator  32  into the ESU  36  and providing variable house loads  70  through HV high efficiency inverters  44 , operational saving of up to 70% can be achieved on a yearly basis compared to old technology fixed speed AC generators. 
     Continuing to refer to  FIG. 5 , in an exemplary embodiment where propulsion has priority over other system loads (Step  104 ), non-essential loads would be described but not limited to, hot water heaters, air conditioning, normal power outlets, stabilizers, non-essential lights in order to maintain navigation, communication and propulsion for as long as possible. Should such an unusual power demand be put on the system  10 , the EMC  12  may record such action as it might affect manufacturer&#39;s warranty. 
     Now referring to  FIG. 6 , which shows the logic of operation (programmed in the EMC  12 ) of the generator module, its relation to the helm station  14  (OFF, AUTO and ON) selection and the total vessel electrical loads (house and propulsion) as calculated by the EMC  12  and provided by the High Voltage Distribution and Safety Control Box  30 . This module may respond immediately to changes in the mode selection (OFF, AUTO and ON) and has priority over the SoC module detailed in  FIG. 5 . This loop may also enable the operator to toggle the state of the charging system from charge to discharge. One good example is if the system is in charge state (AUTO and generator operating) and the operator knows that he may reach destination within the time frame allowed by the energy remaining status of the ESU  36 , he might by momentarily selecting the OFF mode then switch back to AUTO mode put the system back in discharging state and make it to destination on electric only, where charging may be accomplished by shore power. The reverse is also true, if the operator may be reaching a destination where shore power may not be available and he wants to have a full ESU  36  upon arriving, should the system be in a partial discharge state (AUTO and generator not operating), by changing the status momentarily selecting the ON mode then switch back to AUTO mode, he would change the status of the generator module into charge state. Continue to refer to  FIG. 6 , this loop, (Generator Module) is also in charge of monitoring the total electrical loads provided by the High Voltage Box  30  to the EMC  12 . Since on initial system calibration on a vessel first commissioning, a generator efficiency map is built in the EMC  12 , it is also the role of this Generator Module to coordinate the operation of the generator according to the electrical loads of the system by verifying the elapse time, the amount of load and its location within the area of optimum efficiency of the generator. For example, if battery charging is not required yet, but the total system electrical loads are such that they fall within the optimum operating window of the generator, it then make sense to automatically start and operate the generator in a load following function, as the generator is already operating in its optimum operating window in accordance with the least amount of fuel per kW of power produced philosophy of this invention. By quickly following the logic diagram of  FIG. 6 , we see that if the generator is operating (Step  200 ) and the (OFF, AUTO and ON) mode is now in the OFF state (Step  202 ) then the generator should be stopped (Step  204 ). On the other hand if the mode is now in AUTO (Step  206 ) and the total systems loads are less than 20% of the generator most efficient point, then the generator should also be stopped (Step  204 ). The rest of the routine (Step  208 ) is where any load above the least efficient point may ask for a generator start (Step  210 ) and the standard load following with rpm (Step  212 ). 
     Now referring to  FIG. 7 , which shows the logic of operation of the propulsion system in a Twin Hybrid Parallel Squared configuration. It is important to emphasize at this point that since the electric motors  22  and  24  are always either powering or generating, having a single engine operating does not prevent dual propellers from providing propulsion thereby allowing a significant reduction in drag on twin propeller vessels. It is also important to mention that according to this invention, system loads are the total of propulsion and house loads and are what is used to determine the best system to use to generate power, ESU  36 , Generator(s)  32 ,  34  and/or Prime Mover(s)  28 , and not necessarily just the speed of the vessel. For example, in an exemplary operation of at least one prime mover  28 , the at least one prime mover  28  may have predetermined modes of operation based on whether the Helm Controls  14  is set to “OFF,” “AUTO,” or “ON,” modes. These modes of operation are referred to herein as the “twin hybrid parallel squared” module. In large vessels, when (for high continuous power requirements) there is demand for very high boat speed, a twin engine prime mover might be the most cost effective, but even in this case, having a powerful generator and a large ESU  36  is still advantageous. The operation is just a little more complex. As described herein, one can see an example of the logic that is used to control such a system. This Propulsion Module is involved on any configuration anytime that safety key in enabled (Step  300 ) on the helm control  14  and the bus voltage is of at least 240 volt thereby allowing propulsion. Should either of these two states not be satisfied, propulsion may not be allowed or may be stopped (Step  302 ). The next box (Step  304 ) relates to stored maximum propulsion power limits of the system in each of three different configurations, namely electric only where power is limited to 3C or three time the nominal energy stored in the ESU  36 , in this example approximately 100 kW, 3C plus generator  32  or single engine if operating in a multi-engine configuration and if all engines are operating the full power of all engines combined with the addition of the ESU  36  or the generator  32 ,  34  depending on the elapse time. Upon verification that the OFF, AUTO and ON in not in the ON position (Step  306 ), since the ON position override all logic, has all engines operating (Step  328 ) and goes on to load following (Step  310 ). The next verification is the elapse time of the new load change, if there was one (Step  308 ). This leads into the actual load checking according to the engines stored efficiency mapping (Step  312 ). Once the load is determined and according to an internal efficiency map of all power producing devices (EMC  12 ), a simple to follow logic may start/stop the different devices depending on total load requirements and on the status of the OFF, AUTO and ON modes. 
     If the system loads are substantially constant, then the EMC  12  may determine if the system loads are less than the prime mover efficiency point (optimum ICE efficiency) minus approximately 20% ( FIG. 8 ) or if the generator  32  is not operating (Step  312 ). If yes to either, then the EMC  12  may determine if the at least one prime mover  28  is operating (Step  314 ). If the at least one prime mover  28  is operating, the EMC  12  may shut down the at least one prime mover  28  (Step  316 ). In either of these two cases (Step  314 ) the system would revert to electric only operation, with or without the generator depending on the status of the ESU  36  following logic diagram  5 . If the system loads are not less than the prime mover efficiency point minus approximately 20% or if the generator  32  is operating, then the EMC  12  may determine if the propulsion loads are approximately within the 20% above or below the prime mover efficiency point and the operating mode is AUTO (Step  318 ). If yes to both, the EMC may determine if two or more prime movers  28  are operating (Step  320 ). If two prime movers  28  are operating, then the EMC  12  may shut down one of the two prime movers  28 , and in particular, the EMC  12  may shut down the prime mover  28  that has been for a longer period of time (Step  322 ) and allow the system  10  to continue to operate within its efficiency window (Step  310 ). If two prime movers  28  are not operating, the EMC  12  determines if one or no prime movers are operating (Step  324 ). If no prime movers  28  are operational, then the EMC  12  may start one of the prime movers  28 , and in particular, the prime mover  28  with less hours of operation (Step  326 ) and allow the system  10  to continue to operate within its efficiency window (Step  310 ). It should be also noted that in a multi-prime-mover vessel, the engine started is always the one with the least number of operating hours and the one stopped is always the one with the most operating hours, this simple logic maintains a nice balance of operating hours on the engines thereby simplifying maintenance. 
     Continuing to refer to  FIG. 7 , in AUTO mode if propulsion load demands marginally rise above the optimum efficiency of the generator  32  for an extended period of time, the EMC  12  may start the prime mover  28  and drive the first propeller  18  directly and in turn generate power using the first electric motor  22 . If power demands are less than 200 kW total, the generator  32  may shut down. In this embodiment, the prime mover  28  may provide up to 200 kW of power split between the first propeller  18  and the second propeller  20 . This mode provides the highest level of efficiency as the prime mover  28  loads closely matched the optimum operating window ( FIG. 8 ) by using the attached electric motor/generator combination. This also allows for effective propeller usage as the vessel never ends-up having a propeller water-mill with its associated drags. Should power demands exceed 200 kW, the EMC  12  may restart the generator  32  and combine all power sources to allow up to a combined 400 kW of propulsion power. 
     In another exemplary method of using at least two prime movers  28 , each prime mover  28  may have an associated cooling system including a closed loop (not shown) and a cooling fluid, for example, water, to prevent overheating of each prime mover  28 . In particular, both prime movers  28  may be in fluid communication with the same cooling loop (not shown) such that when one of the two prime movers  28  is idle or off, and the other prime mover  28  is operating, the idle or off prime mover  28  may be maintained an operative temperature which may decrease the warm-up time and thermal shock, and increase startup fuel efficiencies. 
     Furthermore, during startup of the prime mover internal combustion engine  28 , the energy storage unit provides power to spin the electric motor  24 , which further rotates the prime mover internal combustion engine  28  to an operating speed before fuel is provided to power the prime mover internal combustion engine  28 . Additionally, when the clutch  50  coupled to the prime mover internal combustion engine  28  is in a closed position the electric motor  24  recharges the ESU  36 , and wherein when the clutch  50  is in an open position, the electric motor  24  provides propulsion. Moreover, the energy management control unit  12  may synchronize the rotations per minute of the electric motor  24  and the rotations per minute of the prime mover internal combustion engine  28  such that clutch opening and closing can be done under optimum load and rpm thereby further increasing efficiencies. 
     Now referring to  FIG. 8 , which shows the area of utilization of the mixed propulsion (ICE and electric motor) in a parallel configuration. Usually in a well-designed parallel hybrid system, the electric motor is approximately 30% of the power of the ICE. Since electric motor have a much greater low speed torque than an ICE and ICE are extremely fuel inefficient at low power and low rpm, it is logical that the attached electric motor be the sole provider of propulsion when at low power. An electric motor that has approximately 30% of the power of an ICE also most likely has a higher low speed torque, so in a parallel system this allows for the elimination of the standard transmission and its mechanical losses, since the electric motor is able to handle the forward, neutral, reverse simply by logic. When, due to power requirements, the ICE is automatically started, the attached electric motor is then used as a generator when below the optimum ICE (Internal Combustion Engine) efficiency curve for a given rpm, with the aim to bring the efficiency of the ICE closer to the optimum 80-90% of load, always aiming for the lowest amount of fuel used per kilowatt produced. If power demands exceed the optimum ICE efficiency curve, then the attached electric motor is used to assist in propulsion with the aim of keeping the ICE at its best efficiency. This is accomplished at low power by using strictly electric for all maneuvering, reverse and forward up to hull speed for limited time and when en route, optimizing the operation by making sure that the propellers (in a multi propeller installation) have equal thrust so has to avoid any drag caused by asymmetrical power utilization. The same logic being used when one or more ICE is running whether in propulsion or generation to always optimize its operation, by using the attached electric motor/generator loads and the rpm to maintain (in normal operation) optimum efficiency. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.