Method of operating an internal combustion engine of a watercraft

Abstract

The disclosure relates to a method for operating an internal combustion engine of a watercraft, in particular on inland waters, in which (i) in an electrolysis unit for the production of hydrogen, water is split into hydrogen and oxygen, (ii) a carbon dioxide sorption unit extracts carbon dioxide from the ambient air, (iii) the hydrogen and the carbon dioxide are fed to a methanol synthesis unit for the production of methanol, and are synthesized therein to methanol, (iv) a photovoltaic unit absorbs solar energy and converts it into electrical energy. The electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit. The methanol produced is transported by means of a distributor system to at least one tank of the watercraft, and is fed from the tank as required to the internal combustion engine, and therein is combusted to generate mechanical energy.

Claims

1. A method for operating an internal combustion engine of a watercraft comprising: splitting water into hydrogen and oxygen in an electrolysis unit configured for production of the hydrogen; extracting carbon dioxide from ambient air at a carbon dioxide sorption unit; feeding the hydrogen and the carbon dioxide to a methanol synthesis unit, wherein the methanol synthesis unit synthesizes the hydrogen and the carbon dioxide into methanol; and converting absorbed solar energy at a photovoltaic unit into electrical energy, wherein the electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit, wherein the methanol is transported by a distribution system to a tank of the watercraft, and wherein the methanol is supplied from the tank as fuel for combustion to the internal combustion engine for generation of mechanical energy, wherein the internal combustion engine is part of a power unit of a hybrid electrically powered watercraft, and wherein the mechanical energy of the internal combustion engine is converted by the power unit into electrical drive energy for propulsion of the watercraft.

2. The method according to claim 1, wherein the internal combustion engine is a reciprocating piston engine configured to operate with a compression ratio of at least 14:1.

3. The method according to claim 2, further comprising: splitting part of the methanol into a synthesis gas including hydrogen and carbon monoxide at a splitting unit arranged in the watercraft; and feeding the synthesis gas into the reciprocating piston engine.

4. A method of producing methanol for use as fuel in an internal combustion engine of a watercraft comprising: splitting water into hydrogen and oxygen in an electrolysis unit configured for production of hydrogen; extracting carbon dioxide from ambient air at a carbon dioxide sorption unit; feeding the hydrogen and the carbon dioxide to a methanol synthesis unit, the methanol synthesis unit synthesizing the hydrogen and the carbon dioxide into methanol; and converting absorbed solar energy at a photovoltaic unit into electrical energy, wherein the electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit, wherein the internal combustion engine is part of a power unit of a hybrid electrically powered watercraft, and wherein the mechanical energy of the internal combustion engine is converted by the power unit into electrical drive energy for propulsion of the watercraft.

5. The method according to claim 4, further comprising: transporting the methanol by a distribution system to a tank of the watercraft; and feeding the methanol from the tank to the internal combustion engine configured to combust the methanol for generation of mechanical energy.

6. The method according to claim 4, wherein the water is desalinated in a seawater desalination unit and fed to the electrolysis unit, and wherein the seawater desalination unit is operated by the electrical energy generated in the photovoltaic unit.

7. Apparatus configured to operate an internal combustion engine of a watercraft comprising: an electrolysis unit configured to split water into hydrogen and oxygen for production of hydrogen; a carbon dioxide sorption unit configured to extract carbon dioxide from ambient air; a methanol synthesis unit configured for the production of methanol using the hydrogen and the carbon dioxide, wherein the methanol synthesis unit synthesizes the hydrogen and the carbon dioxide into the methanol; and a photovoltaic unit configured to convert absorbed solar energy into electrical energy, wherein the electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit, wherein the methanol is transported by a distribution system to a tank of the watercraft, and wherein the methanol is supplied from the tank as fuel for combustion to the internal combustion engine for generation of mechanical energy, wherein the water is desalinated in a seawater desalination unit and fed to the electrolysis unit, and wherein the seawater desalination unit is operated by the electrical energy generated in the photovoltaic unit.

8. The apparatus according to claim 7, wherein the internal combustion engine is part of a power unit of a hybrid electrically powered watercraft, and wherein the mechanical energy of the internal combustion engine is converted by the power unit into electrical drive energy for propulsion of the hybrid electrically powered watercraft.

9. The apparatus according to claim 7, wherein the internal combustion engine is a reciprocating piston engine configured to operate with a compression ratio of at least 14:1.

10. The apparatus according to claim 9, further comprising: a splitting unit arranged in the hybrid electrically powered watercraft, the splitting unit configured to split part of the methanol into a synthesis gas including hydrogen and carbon monoxide, and wherein the synthesis gas is fed into the reciprocating piston engine.

11. Apparatus configured to produce methanol for use as fuel in an internal combustion engine of a watercraft comprising: an electrolysis unit configured to split water into hydrogen and oxygen for production of hydrogen; a carbon dioxide sorption unit configured to extract carbon dioxide from ambient air; a methanol synthesis unit using a supply of the hydrogen and the carbon dioxide, wherein the methanol synthesis unit synthesizes the hydrogen and the carbon dioxide into methanol; and a photovoltaic unit configured to convert absorbed solar energy into electrical energy, wherein the electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit, wherein the internal combustion engine is part of a power unit of a hybrid electrically powered watercraft, and wherein the mechanical energy of the internal combustion engine is converted by the power unit into electrical drive energy for propulsion of the watercraft.

12. The apparatus according to claim 11, further comprising: a distribution system adapted to transport the methanol to a tank of the watercraft, wherein the methanol is fed from the tank as fuel for combustion to the internal combustion engine for generation of mechanical energy.

13. The apparatus according to claim 11, wherein the water is desalinated in a seawater desalination unit and fed to the electrolysis unit, and wherein the seawater desalination unit is operated by the electrical energy generated in the photovoltaic unit.

14. A method for operating an internal combustion engine of a watercraft comprising: splitting water into hydrogen and oxygen in an electrolysis unit configured for production of the hydrogen; extracting carbon dioxide from ambient air at a carbon dioxide sorption unit; feeding the hydrogen and the carbon dioxide to a methanol synthesis unit, wherein the methanol synthesis unit synthesizes the hydrogen and the carbon dioxide into methanol; and converting absorbed solar energy at a photovoltaic unit into electrical energy, wherein the electrolysis unit, the carbon dioxide sorption unit and the methanol synthesis unit are powered by the electrical energy generated in the photovoltaic unit, wherein the methanol is transported by a distribution system to a tank of the watercraft, and wherein the methanol is supplied from the tank as fuel for combustion to the internal combustion engine for generation of mechanical energy, wherein the water is desalinated in a seawater desalination unit and fed to the electrolysis unit, and wherein the seawater desalination unit is operated by the electrical energy generated in the photovoltaic unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail by means of examples of embodiment with reference to the attached schematic drawings that have further details.

(2) In these:

(3) FIG. 1 shows a perspective view of a plant for the production of a globally usable energy source, in accordance with a preferred example of embodiment of the invention;

(4) FIG. 2 shows a perspective view of a plant for the production of a globally usable energy source, in accordance with a further preferred example of embodiment in accordance with the invention;

(5) FIG. 3 shows a plan view onto a planar plant area of the plant shown in FIG. 2;

(6) FIG. 4 shows a schematic cross-section through the planar plant area of the plant shown in FIG. 3;

(7) FIG. 5 shows a flow diagram of the method for the production of a globally usable energy source with the plant shown in FIG. 1, or the plant shown in FIG. 2, and

(8) FIG. 6 shows a cross-sectional view of a power unit of a watercraft in accordance with the invention, in a preferred example of embodiment.

DESCRIPTION

(9) In what follows, the same reference numbers are utilised for the same parts, and for parts operating in the same manner.

(10) FIG. 1 shows the example of embodiment of a plant 10 that is designed for the production of a globally usable energy source in the form of methanol. The plant 10 comprises an electrolysis unit 11, a carbon dioxide sorption unit 12, a seawater desalination unit 27, and a methanol synthesis unit 34. A photovoltaic unit 24 is provided for the supply of power to the aforementioned units; this is electrically connected to the corresponding units 11, 12, 27, 34.

(11) As can be seen in FIG. 1, the aforementioned plant components are arranged on a contiguous plant site, such that the exchange of material and energy flows between the various units and the power supply takes place with the lowest possible losses. The shape of the plant is not limited to the shape shown in FIG. 1.

(12) The electrolysis unit 11 is connected to the seawater desalination unit 27 by at least one pipe (not shown) for the supply of water, in particular desalinated water. The desalinated water is fed to the electrolysis unit 11 through the pipeline. The methanol synthesis unit 34 is connected, on the one hand, to the electrolysis unit 11 by at least one pipeline, and, on the other hand, to the carbon dioxide sorption unit 12 by at least one further pipeline. The hydrogen produced in the electrolysis unit 11, and the carbon dioxide separated out in the carbon dioxide sorption unit 12, are fed to the methanol synthesis unit 34 through the two pipelines. Methanol is thereby produced in the methanol synthesis unit 34.

(13) The seawater desalination unit 27 can be designed to receive and desalinate at least 900,000 tonnes of seawater per year. The carbon dioxide sorption unit can be customised to have an extraction capacity of at least 400,000 tonnes of carbon dioxide per year, in particular at least 600,000 tonnes of carbon dioxide per year, extracted from the ambient air. The methanol synthesis unit 34 is customised to produce at least 300,000 tonnes, in particular 450,000 tonnes, of regeneratively-produced methanol per year.

(14) The photovoltaic unit 24 can have a power of approx. 1.5 GW and, depending on the solar radiation, can absorb at least 1,500 kWh/m.sup.2a. For the location in the Middle East selected in FIG. 1, the photovoltaic unit 24 is preferably customised to absorb at least 2,500 kWh/m.sup.2a.

(15) The electrolysis unit 11 is designed to separate a quantity of water M.sub.H2O by electrolysis into an oxygen component M.sub.O2, and a hydrogen component. The electrolysis unit 11 thus forms a unit for water electrolysis. The electrolysis unit 11 is connected to a water supply line 13 for the reception of the quantity of water M.sub.H2O. As can be seen in FIG. 1, a pump unit 25 is arranged between the electrolysis unit 11 and the water supply line 13. The pump unit 25 has at least one pump for the transportation of water from a water reservoir 26. The water reservoir 26 can be a sea with seawater. Alternatively, the water reservoir 26 can be a lake with fresh water. It is also possible that the water supply line 13 is connected to a river so as to draw fresh water for water electrolysis. In the plant 10 shown in FIG. 1, the water supply line 13 is connected to a sea for the extraction of seawater. The plant 10 is preferably located near the coast so as to keep the distance to be covered for the water supply short, in particular to keep the water supply line 13 short.

(16) The pump unit 25 is designed for the purpose of pumping seawater from the sea and making it available to further sub-plants or units for further processing. In order to prepare the seawater for the electrolysis process undertaken by the electrolysis unit 11, the plant 10 has a seawater desalination unit 27. The seawater desalination unit 27 is connected to the pump unit 25 by at least one pipe. The seawater desalination unit 27 is customised to separate out a certain amount of salt from the quantity of seawater M.sub.H2O delivered, so that the seawater has a reduced salt content after the desalination process by the seawater desalination unit 27. The desalinated quantity of seawater M.sub.H2O corresponds to the quantity of water M.sub.H2O, which is separated into an oxygen component M.sub.O2 and a hydrogen component by the electrolysis unit 11. The electrolysis unit 11 is connected to the seawater desalination unit 27 by at least one pipe. In order to convey the desalinated seawater from the seawater desalination unit 27 to the electrolysis unit 11, at least one further pump can be connected in between.

(17) As described above, the electrolysis unit 11 is customised to separate the absorbed quantity of water M.sub.H2O into a hydrogen component and an oxygen component M.sub.O2. The hydrogen component is fed to the methanol synthesis unit 34. The oxygen component M.sub.O2 is discharged into the environment. The electrolysis unit 11 is preferably customised to separate out an oxygen component M.sub.O2 of at least 1.2 kg and a hydrogen component of at least 0.15 kg, in particular of 0.19 kg, from an absorbed quantity of water M.sub.H2O of at least 1.5 kg. For purposes of discharging the produced oxygen component M.sub.O2, the electrolysis unit 11 has an oxygen outlet 16 which opens out into the external atmosphere. The plant 10 has a hydrogen transport device (not shown) for the supply of the hydrogen to the methanol synthesis unit 34.

(18) It is possible for the plant 10 to have a hydrogen storage unit, such that the methanol synthesis unit 34 can be fed with hydrogen as continuously as possible.

(19) As shown in FIG. 1, the carbon dioxide sorption unit 12 has an air inlet 14 for the supply of ambient air UL, and a downstream sorber device 15. It is possible for the carbon dioxide sorption unit 12 to have one or a plurality of air inlets 14. The sorber device 15 is connected to the air inlet 14. The sorber device 15 is customised so as to extract a quantity of carbon dioxide from the ambient air UL. The carbon dioxide sorption unit 12 furthermore has an air outlet 17 that is oriented upwards in the vertical direction. The air outlet 17 serves to discharge the exhaust air UL, whose carbon dioxide concentration is lower than the carbon dioxide concentration of the ambient air UL. The air outlet 17 is part of a stack 19.

(20) More specifically, the sorber device 15 is arranged between the air inlet 14 and the air outlet 17. In operation, the ambient air UL flows through the air inlet 14 to the sorber device 15, which separates out, in particular filters out, a certain amount of carbon dioxide from the air UL, wherein downstream of the sorber device 15 the filtered exhaust air UL flows through the air outlet 17 into the external atmosphere. In general, it is possible for a plurality of air inlets 14, a plurality of sorber devices 15, and a plurality of air outlets 17, to be provided.

(21) More specifically, FIG. 1 shows a single stack 19 with a height H of 200 metres, which shows in an exemplary manner the external structure of the carbon dioxide sorption unit 12. The air outlet 17 opens into the external atmosphere, as shown in FIG. 1, in the same manner as the oxygen outlet 16.

(22) The plant 10 further comprises a carbon dioxide transport device (not shown), which is designed for purposes of making the carbon dioxide quantity separated out from the ambient air UL available to a carbon dioxide storage unit, and/or to the methanol synthesis unit 34, for further processing. The carbon dioxide storage unit serves to ensure as continuous a supply of carbon dioxide as possible to the methanol synthesis unit 34.

(23) The carbon dioxide sorption unit 12 can have an extraction capacity of an amount of carbon dioxide per year of at least 400,000 tonnes, in particular 600,000 tonnes. In other words, the carbon dioxide sorption unit 12 can be customised to process an ambient quantity of air per year of at least 1,500 megatonnes. More specifically, the carbon dioxide sorption unit 12 is preferably customised to extract a carbon dioxide quantity of at least 1.4 kg from an ambient quantity of air of at least 3,300 kg.

(24) As shown in FIG. 1, the plant 10 has a planar plant area 23. The planar plant area 23 is directly adjacent to the electrolysis unit 11. A power generation unit 31, which is a photovoltaic unit 24, is arranged on the planar plant area 23. The photovoltaic unit 24 is connected to the respective units of the plant 10 for purposes of power supply. The photovoltaic unit 24 is customised in such a manner that the entire installation 10 can be operated self-sufficiently in terms of energy. This is to be understood as meaning that the electrical power for operating the entire plant 10 can be provided exclusively by solar energy by means of the photovoltaic unit 24. In other words, it is preferable that no fossil energy sources are utilised for the operation of the plant 10.

(25) The planar plant area 23 can have a longitudinal extent 32 of approximately 5,000 metres and a transverse extent 33 of approximately 2,000 metres. In other words, the planar plant area of the plant 10 preferably covers an area of 10 square kilometres. The plant area shown in FIG. 1 containing the electrolysis unit 11 can have a longitudinal sub-extent 29 of approximately two kilometres. Other longitudinal sub-extents, and longitudinal and transverse extents, 29, 32, 33 are possible.

(26) The seawater desalination unit 27 described above is connected to a water return line 28, through which a returnable quantity of seawater M.sub.H2O with an increased salt content is returned to the sea. More specifically, a certain salt content is extracted from the extracted quantity of seawater, and is then returned to the sea with a proportion of the extracted quantity of seawater as a returnable quantity of water M.sub.H2O. This provides a water cycle that is not damaging to nature.

(27) The preferred installation site of the plant 10 is near the coast of a sea. Particularly preferably, the plant 10 is set up in a desert. A methanol delivery line 35 can connect the plant 10 to a methanol delivery point, for example in a port.

(28) The plant 10 as shown in FIG. 1 is a large power plant.

(29) The plant 10 can have at least one installation area 18 that is connected to a foundation of a building and/or a structure. In general, it is possible for the electrolysis unit 11 and/or the carbon dioxide sorption unit 12 to be arranged in a common building, or in separate buildings.

(30) The power supply unit 31 preferably has a power storage unit (not shown), which is customised to supply power to the plant 10 during night-time operation.

(31) In contrast to FIG. 1, FIG. 2 shows a plant 10 in which the single carbon dioxide sorption unit 12 is replaced by a plurality of carbon dioxide sorption units 12. The particular carbon dioxide sorption unit 12 shown in FIG. 2 has a stack 19 and a flow channel 21 extending transversely to the stack 19. This is clearly visible in FIG. 4, for example. The flow channel 21 is connected to the stack 19 in a region of the stack arranged at the bottom of the structure when installed. A sorber device 15 is arranged between the flow channel 21 and the stack 19; this is designed to extract a quantity of carbon dioxide from the ambient air UL. The sorber device 15 is formed by an amine exchanger. Other types of sorber devices are possible.

(32) As FIGS. 2, 3 show, the stacks 19 are arranged along the longitudinal extent 32 of the planar plant area 23. The planar plant area 23 has a surface 22 arranged at the top of the structure when installed. The surface 22 arranged at the top of the structure is dark in colour, at least in some sections, in order to absorb solar energy. The flow channels 21 are arranged below the upper surface 22 when installed. A plurality of air inlets 14 are formed in the upper surface 22 to supply ambient air UL into the flow channels 21. The air inlets 14 form passage openings through the upper surface 22. For the sake of clarity, these are only shown on the first flow channel 21 in FIG. 3. The number of air inlets 14 is also variable.

(33) In operation, ambient air flows through the air inlets 14 into the flow channel 21 and then through the sorber device 15. Downstream of the sorber device 15, the exhaust air UL with reduced carbon dioxide concentration flows into the stack 19, and through the air outlet 17 into the external atmosphere. By virtue of the dark-coloured surface 22 arranged at the top of the structure, the ambient air located below the surface 22 in the flow channel 21 heats up during operation. The temperature of the ambient air UL in the flow channel 21 is preferably approx. 60 C. With an external temperature of the ambient air UL of approx. 40 C., natural ventilation is created by the arrangement of the stack with the flow channel 21, together with the dark-coloured surface 22. In other words, no fan or blower is necessary for the supply of the ambient air UL into the flow channel 21, or for the flow through the sorber device 15, or for the outflow of the purified ambient air UL from the stack 19.

(34) FIG. 3 shows a plan view onto the planar plant area 23 of the plant 10 shown in FIG. 2. The numbering from 1 to 40 shown along the longitudinal extent 32 represents the number of stacks 19 arranged along the longitudinal extent 32. The lines running transversely to the longitudinal extent 32 show schematic separations between the individual flow channels 21. The individual flow channels 21 are in each case assigned to a stack 19. At the same time a sorber device 15 is in each case arranged between the flow channel 21 and the stack 19. The longitudinal extent 32 of the two-dimensional plant area 23 is approximately 5,000 metres and the transverse extent 33 of the planar plant area 23 is approximately 2,000 metres. A total of forty stacks 19 with a total of forty flow channels 21 are provided in the planar plant area 23. These have a combined delivery of exhaust air UL of at least 1,800 megatonnes per year.

(35) To achieve this, the stacks 19 have a diameter D that is 25 metres. The diameter D refers to the region of the stack 19 in which the air outlet 17 is formed. The air outlet 17 is formed at a free end of the stack 19. Furthermore, the stack in question 19 has a height H of 100 metres. By this means an optimal shape is formed for the stack so as to provide natural ventilation. Other dimensions of the stacks 19 are possible.

(36) Furthermore, more than, or less than, forty stacks 19, in each case with an associated flow channel 21, can be arranged in the planar plant area 23.

(37) As can be seen in FIG. 4, the planar plant area 23 is provided with a photovoltaic unit 24 on the surface 22 arranged at the top of the structure. In other words, a photovoltaic unit 24 is arranged on the upper surface 22 of the planar plant area 23. The photovoltaic unit 24 preferably delivers 1.5 gigawatts per year. In the plant 10 shown in FIG. 2, the carbon dioxide sorption unit 12 and the photovoltaic unit 24 thereby spatially form a common unit. The photovoltaic unit 24 forms a power supply unit 31 for the energy-autonomous operation of the entire plant 10.

(38) It should be noted that the above-described plants 10, shown in FIGS. 1 and 2, are identical except for the differences that have been described.

(39) The method that can be carried out with the plant 10 shown in FIG. 1 or FIG. 2 is explained with the aid of the flow chart shown in FIG. 5:

(40) To produce a quantity of 1 kg of methanol, a quantity of approximately 2 kg of seawater is fed to the plant 10 and desalinated in the seawater desalination unit 27. This generates approx. 1.13 kg of desalinated water. The residual salt water (approx. 0.87 kg) is returned to the sea through the water return line 28. In the electrolysis unit, the desalinated water and, if necessary, further quantities of water produced in later process steps, are split into hydrogen (approx. 0.19 kg) and oxygen (approx. 1.5 kg). The carbon dioxide sorption unit 12 takes in a quantity of air of approx. 3,371.75 kg through the air inlet 14 and extracts a quantity of approx. 1.38 kg of carbon dioxide from the unit. Hydrogen and carbon dioxide are fed to the methanol synthesis unit, where they are processed into 1 kg of methanol. The excess heat generated during the synthesis is fed to the carbon dioxide sorption unit 12. The synthesis also produces a quantity of water of approximately 0.56 kg, which is fed to the electrolysis unit. For these process steps, approx. 51 kWh of solar energy is converted into approx. 12.83 kWh of usable electricity energy by the photovoltaic system.

(41) FIG. 6 shows a power unit 120 for a watercraft in accordance with the invention. The power unit 120 comprises a two-cylinder reciprocating piston engine 121, with a first cylinder-piston unit 122 and a second cylinder-piston unit 123. Each of the cylinder-piston units 122, 123 comprises a piston 124 guided in a cylinder 125. The piston 124 is coupled to a connecting rod 126, which connects the piston 124 to a crankshaft 127. The crankshafts 127 are aligned parallel to each other, and in each case carry spur gears 127a, which have external teeth. The externally-toothed spur gears 127a mesh with each other such that the spur gears 127a rotate in opposite directions.

(42) Each spur gear 127a is coupled to a generator 130 via a toothed belt 128. A total of two generators 130 are provided. The generators 130 also include balance weights 130a, which balance out the mass forces and the mass moments.

(43) The power generator 120 furthermore comprises a cam belt 131, which connects one of the crankshafts 127 to camshafts 132. Each cylinder-piston unit 122, 123 is associated with a respective camshaft 132. The camshafts 132 in each case act on valves 133, wherein each cylinder-piston unit preferably has four valves 133.

(44) Furthermore, an oil sump 134 is provided, in which an oil pump 135 is arranged. The oil pump 135 is driven by an oil pump belt 136, which connects the oil pump 135 to one of the crankshafts 127. The oil pump 135 is preferably connected to another crankshaft 127, rather than the camshafts 132. Furthermore, an oil filter 137 is arranged in the oil sump 134.

(45) As can be seen in FIG. 6, the power unit 120 has a particularly compact design. It has relatively few parts and is therefore easy to maintain and has a low weight. The two-cylinder reciprocating piston engine is particularly low in noise and vibration. In addition, the two-cylinder reciprocating piston engine can be encapsulated in a housing, wherein the housing can additionally contribute to low noise and low vibration. The propulsion system of a watercraft can include a plurality of power units 120 that act together to generate power, and feed drive batteries.

(46) FIG. 6 also shows that the cylinders 125 of the cylinder-piston units 122, 123 are arranged in an interfaced manner. In particular, the central axes of the cylinders 125 have a smaller distance from each other than the central axes of the crankshafts 127. As a result, the connecting rods 126 are slightly inclined to each other at top dead centre of the pistons 124, as shown in FIG. 6. This massively reduces vibrations when the engine is started. In particular, when starting the power generator 120, start-up mass moments are reduced in this manner, so that the otherwise familiar start-up vibrations do not occur.

(47) For the propulsion of a watercraft, the power unit 120 is preferably operated, and provides via the generators 130 the electrical energy that is required in order to use the electric motors in drive mode. A 48 volt, 400 volt or 800 volt, system is preferably integrated as the electrical system. The drive batteries are preferably dimensioned such that the watercraft can travel between 10 km and 120 km, in particular between 20 km and 100 km, in particular between 25 km and 60 km, in an exclusively electrical manner, that is to say, without operation of the power unit.

(48) The power unit 120 is preferably powered by the regeneratively-produced methanol. For this purpose, an appropriate tank is provided, which accommodates the regeneratively-produced methanol, that is to say, is filled with the latter. In this manner, a particularly economical and at the same time climate-friendly operation of the watercraft is possible.

(49) As explained with the aid of the above examples of embodiment, the invention offers a technically feasible and economical solution to the acute climate problem, which can be implemented within a reasonable time frame by virtue of the scalability of the described systems. The invention takes into account the geographical opportunities offered by certain regions of the world, and has an impressive simplicity.

LIST OF REFERENCE SYMBOLS

(50) 10 Plant 11 Electrolysis unit 12 Carbon dioxide sorption unit 13 Water supply line 14 Air inlet 15 Sorber device 16 Oxygen outlet 17 Air outlet 18 Installation area 19 Stack 21 Flow channel 22 Surface arranged at the top of the structure 23 Planar plant area 24 Photovoltaic unit 25 Pump unit 26 Water reservoir 27 Seawater desalination unit 28 Water return line 29 Longitudinal sub-extent 31 Power generation unit 32 Longitudinal extent 33 Transverse extent 34 Methanol synthesis unit 35 Methanol delivery line 120 Power generator 121 Two-cylinder reciprocating piston engine 122 First cylinder-piston unit 123 Second cylinder-piston unit 124 Piston 125 Cylinder 126 Connecting rod 127 Crankshaft 127a Spur gear 128 Toothed belt 130 Generator 130a Balance weight 131 Cam belt 132 Camshaft 133 Valve 134 Oil sump 135 Oil pump 136 Oil pump belt 137 Oil filter UL Ambient air with increased carbon dioxide concentration UL Exhaust air with lowered carbon dioxide concentration D Diameter H Height M.sub.H2O Quantity of water extracted M.sub.H2O Quantity of water recirculated M.sub.O2 Oxygen component