Ballast water desalination on a ship and use of the desalinated fresh water for cleaning large-scale photovoltaic systems

Abstract

The invention relates to a method for desalinating ballast water on a ship, in particular a methanol and / or hydrogen tanker, comprising the steps of: - pumping the ballast water from at least one ballast water tank (BW) into a desalination unit (E) on the ship by means of at least one ballast water pump, - desalinating the ballast water (BW) in the desalination unit (E) in order to produce desalinated fresh water using excess energy from a drive assembly of the ship, in particular by multi-stage flash evaporation and / or membrane distillation and / or reverse osmosis, - pumping the fresh water into at least one cargo tank (LT), in particular a methanol and / or hydrogen tank, on the ship by means of at least one fresh water pump, wherein the ballast water pump and the fresh water pump are controlled by means of a central control unit in such a way that the distribution of ballast water and fresh water between the ballast water tank (BW) and the cargo tank (LT) is balanced on the basis of environmental data on waves, wind and the ship position, in order to maintain the stability of the ship, and wherein in order to compensate for ballast water pumped out of the ballast water tank (BW) into the desalination unit (WE), sea water is pumped into the ballast water tank (BW) by means of at least one sea water pump.

Description

[0001] Ballast water desalination on a ship and use of the desalinated freshwater to clean large-scale photovoltaic systems

[0002] The invention relates to a method for desalinating ballast water on a ship. Furthermore, the invention relates to a ship with a desalination unit and a method for preventing pollution-related reductions in the energy generation capacity of a large-scale photovoltaic system in a freshwater-poor area.

[0003] Large tankers are used to transport fuels. These tankers are filled at the fuel production site. The tanker then sails to the destination port, where the cargo is unloaded. The tanker then usually returns to the loading port empty.

[0004] Because tankers with empty cargo tanks are extremely unstable, they typically have so-called ballast water tanks. These ballast water tanks are filled with seawater to compensate for the lack of cargo and provide the ship with the necessary stability. However, the use of ballast water has been criticized because of its environmental concerns. In particular, microorganisms taken up from one marine area when filling the ballast water tanks can be transported to another marine area, namely where the ballast water tanks are emptied. This can have significant undesirable impacts on marine biology.

[0005] To address this problem, several international agreements on ballast water exchange exist. For example, specific marine areas have been designated where ballast water may be taken on or discharged. Compliance with these agreements is complex and requires, for example, that ships first reach the ballast water intake areas before they can take on ballast water. On the way to these intake areas, there is the problem of unstable ship behavior, as both the cargo tanks and the ballast water tanks are empty.

[0006] A promising future application for tankers is to deliver renewably produced fuels, such as green methanol, from regions in the Earth's sunbelt to destinations such as Europe or the USA. It is foreseeable that large photovoltaic systems, so-called large-scale photovoltaic systems, will be built in the sunbelt regions to produce such green fuels. These systems will provide the energy needed to produce methanol, for example, from CO2 and water.

[0007] Particularly in the Sun Belt, which is characterized primarily by desert-like landscapes, photovoltaic panels often become dirty due to the fine desert sand. The performance of the individual photovoltaic panel decreases as a result. To compensate for this reduction in energy generation capacity, photovoltaic panels must be cleaned regularly. This poses a particular challenge in the Earth's Sun Belt, however, due to the scarcity of freshwater supplies in these regions. Cleaning photovoltaic panels with seawater is counterproductive, as the salt contained in seawater settles as particles on the photovoltaic panels, thus also reducing energy generation capacity. Furthermore, the salt particles can have an abrasive effect and thus cause permanent damage to the photovoltaic panels.

[0008] From the state of the art, in particular from WO 2013 / 004240 A1 and

[0009] From KR 10 2016 0 073 707 A it is known to desalinate seawater on board ships and to use excess energy from the ship's propulsion unit for this purpose. To do this, the ship's ballast tanks are filled with seawater when voyages without a payload. The seawater or ballast water contained in the ballast tanks is circulated between the individual ballast tanks and passed through a desalination unit which removes the salt from the ballast water. A disadvantage of the known processes is that the amount of fresh water produced is limited to the volume of the ballast tanks. A further disadvantage of the known solutions is that the ballast water is mixed with fresh water, which is detrimental to the purity of the fresh water.

[0010] Against this background, the object of the present invention is to provide a method for desalinating ballast water on a ship, thus avoiding the problem of microorganisms being carried to other marine areas and simultaneously increasing the amount of freshwater produced. Furthermore, the object of the invention is to provide a ship that can be used for such a process. Finally, the object of the invention is also to provide a method for cleaning photovoltaic panels of a large-scale photovoltaic system in the Earth's sunbelt.

[0011] According to the invention, this object is achieved with regard to the method for desalinating ballast water by the subject matter of patent claim 1, with regard to the ship by the subject matter of patent claim 6 and with regard to the method for avoiding pollution-related reduction in the energy generation capacity of a large-scale photovoltaic system by the subject matter of patent claim 13.

[0012] Specifically, the invention is based on the idea of ​​providing a method for desalinating ballast water on a ship, in particular a methanol and / or hydrogen tanker, the method comprising the following steps:

[0013] Pumping the ballast water from at least one ballast water tank into a desalination unit of the ship by at least one ballast water pump,

[0014] Desalination of ballast water in the desalination unit to produce desalinated fresh water using surplus energy from a ship's propulsion unit, in particular by multi-stage flash evaporation and / or membrane distillation and / or reverse osmosis,

[0015] Pumping the fresh water into at least one cargo tank, in particular methanol and / or hydrogen tank, of the ship by at least one fresh water pump, wherein the ballast water pump and the fresh water pump are controlled by means of a central control unit such that the distribution of ballast water and fresh water between the ballast water tank and the cargo tank is balanced in order to maintain the stability of the ship.

[0016] For the purposes of this application, ballast water is defined as saline water, particularly seawater, with a salinity of at least 3%. Fresh water is water, particularly freshwater, with a salinity of 0.1% or less.

[0017] The invention is based on the idea of ​​using the ballast water carried on board the ship, which is intended to maintain the stability of the ship, on the one hand, and the surplus energy of the ship's propulsion unit, on the other, to produce desalinated water. The ship can therefore be used efficiently on the return journey from a destination port to the loading port to produce fresh water, in particular desalinated fresh water, which can be reused at the loading port, particularly in a region of the Earth's sunbelt. In this way, an area with a scarce supply of fresh water can be supplied with fresh water easily and efficiently. The fresh water can be used, on the one hand, to clean photovoltaic panels in a large-scale photovoltaic system, but also for further processing in the context of methanol and / or hydrogen production. In principle, other possible applications for the fresh water are also conceivable.In any case, it is crucial that the method according to the invention ensures that an empty voyage of a ship is used efficiently to produce fresh water for an area with a shortage of fresh water.

[0018] To further ensure the stability of the ship, the method provides for the distribution of ballast water and fresh water between the ballast water tank and the cargo tank to be controlled. According to the invention, the control system incorporates environmental data of the ship, in particular wave, wind, and ship attitude sensors, to ensure that the stability of the ship is maintained in all conditions. The invention provides for seawater to be pumped into the ballast water tank by means of at least one seawater pump, in particular to compensate for ballast water pumped from the ballast water tank into the desalination unit. Supplementing the method according to the invention with a seawater pump that supplies seawater to the ballast water tanks can serve to further improve the stability of the ship.Furthermore, this method can also increase the capacity for freshwater production, as ballast water tanks are typically smaller than cargo tanks. Once the ballast water tanks are empty and the cargo tanks are not yet full, the desalination unit can continue to operate by adding seawater, thus increasing the amount of freshwater produced.

[0019] It is particularly preferred if the desalination process is carried out using waste heat and / or mechanical power from the propulsion unit. Propulsion units on tankers have particularly high power output, which leads to a significant excess power, especially during empty sailings. The excess power or energy is advantageously used in the invention to operate the desalination unit.

[0020] The propulsion unit of a typical tanker typically has an energy generation capacity of several tens of thousands of kWh. At half power, for example, the propulsion unit can release 16,800 kWh of energy. With a travel time from the destination port to the loading port of approximately 21 days, this energy amounts to 8.5 million kWh. At an efficiency of 55%, approximately 3.8 million kWh of surplus energy is available, particularly in the form of waste heat. This process makes effective use of this waste heat by using it to desalinate the ballast water. This is particularly true with a ballast water volume of approximately 40,000 m 3 and an energy requirement for desalination of approximately 20 kWh / m 3 Approximately 800,000 kWh are sufficient to achieve efficient desalination of the ballast water.

[0021] If the propulsion unit does not provide sufficient waste heat or excess energy in general, for example, because other consumers are operating on board the vessel, it may be advantageous for the desalination unit and / or the propulsion unit to be supplied with additional energy from the vessel's own photovoltaic or wind power system. For example, the vessel can be equipped with photovoltaic panels that capture solar energy and convert it into its own electricity. It may also be advantageous to install one or more wind turbines on the vessel, which can ultimately be powered by the airstream, thus providing increased energy generation capacity.

[0022] The method of the present invention is specifically aimed at distributing fuels produced from renewable energies, so-called green fuels, worldwide while simultaneously operating the necessary ship-based transport system as sustainably as possible. Therefore, the invention provides for the desalination of ballast water, as this achieves corresponding sustainability. In particular, the negative environmental impacts of ballast water are thereby avoided. At the same time, freshwater-scarce areas are supplied with fresh water, and the excess energy on board a ship is used efficiently.

[0023] This sustainability concept can be further supported if, as envisaged in a preferred embodiment of the invention, the ship's propulsion unit is powered by methanol. This does not preclude the ship's propulsion unit from also being powered by other green fuels, particularly hydrogen. However, the use of methanol, especially green methanol, is particularly suitable if the tanker is used to transport methanol. The tanker can therefore not only take on green methanol at the loading port, but also simultaneously use a portion of this green methanol for its own operations. This reduces CO2 emissions and, in particular, the air pollution caused by the combustion of fossil fuels.

[0024] In addition to the desalination of ballast water, the method according to the invention can provide for the intake of seawater while the ship is underway. The seawater can then be fed to a CO2 capture unit. In the CO2 capture unit, CO2 can be extracted from the seawater and stored in at least one cargo tank and / or one CO2 tank. The production of green fuels requires not only fresh water but also carbon. This is often extracted on land using systems for capturing CO2 from the air. However, it has been found that considerable amounts of CO2 are also bound in seawater. In this respect, it is advantageous if CO2 is also captured from the seawater while the ship is underway and delivered to the loading port together with the fresh water.From the loading port, the fresh water and CO2 can then be delivered to a methanol production plant, which is usually located in the Earth's sunbelt and can therefore be efficiently operated with photovoltaic power.

[0025] A secondary aspect of the invention relates to a ship, in particular a methanol and / or hydrogen tanker, comprising the following: at least one drive unit for generating propulsion energy for moving the ship, at least one ballast water tank, at least one cargo tank designed as a methanol and / or hydrogen tank, a desalination unit for generating desalinated fresh water, at least one ballast water pump for pumping salt-containing ballast water from the ballast water tank into the desalination unit, at least one fresh water pump for pumping the fresh water into the cargo tank and a central control unit for controlling the distribution of ballast water and fresh water between the ballast water tank and the cargo tank.

[0026] The advantages and preferred forwarding operations mentioned in connection with the method described above also apply analogously to the ship described here. The ship according to the invention has the advantage that it can be operated efficiently over the long term. When transporting fuels, for example methanol and / or hydrogen, the ship fulfills its transport purpose. However, on the return journey, which is usually empty, the ship and the excess propulsion energy of the propulsion unit are expediently used to generate fresh water, which can be used expediently at the destination near the loading port to operate plants for the production of green fuels. The ship therefore not only enables particularly sustainable operation but also has economic advantages, since the operating costs for the return journey from the destination port to the loading port can be offset.On the return journey, value is added in that fresh water is formed from ballast water.

[0027] According to the invention, a heat exchanger is arranged between the drive unit and the desalination unit, which converts waste heat from the drive unit into process heat for the desalination unit. The heat exchanger is connected to the cargo tank, in particular a hydrogen tank, and is configured to cool the cargo tank. A heat exchanger has a particularly high level of efficiency, so that the waste heat from the drive unit can be reused particularly efficiently as process heat. By also connecting the heat exchanger to the cargo tank, the cargo tank can be additionally cooled, which is particularly advantageous for the transport of hydrogen, which must be stored at very low temperatures. Cooling is also advantageous for the transport of methanol to prevent the methanol from evaporating.It is also possible to cool the cargo, in particular methanol and / or hydrogen, directly, for example by means of a flow cooler in a cargo circuit, in particular a cargo circulation circuit.

[0028] In the ship according to the invention, it is advantageously provided that the control unit is configured such that it balances the amount of ballast water and fresh water between the ballast water tank and the cargo tank in such a way that the stability of the ship is maintained. Furthermore, the ship can be provided with a ballast water treatment device that is connected to the ballast water tank and comprises at least one filter unit and / or at least one disinfection unit. It is generally advantageous to filter or disinfect the ballast water, for example, to eliminate microorganisms. This ensures that the fresh water produced is particularly pure. At the same time, if the ballast water treatment device is arranged upstream of the ballast water tank, it can be ensured that the ballast water tanks do not become contaminated. This prevents, for example, the formation of biofilm or other harmful contaminants.

[0029] Particularly for the elimination of microorganisms, it is advantageous if the ballast water treatment facility also includes a deoxygenation unit. The deoxygenation unit removes the oxygen content from the seawater, preventing microorganisms from spreading further, but rather significantly reducing their proportion. In a preferred variant of the invention, the ballast water treatment facility is arranged between the ballast water tank and the cargo tank, with the desalination unit being integrated into the ballast water treatment facility. In this way, the entire water treatment system on the ship is designed to be particularly compact. In particular, the integration of the desalination unit into the ballast water treatment unit saves space and is simultaneously efficient, since waste heat and / or power from the propulsion unit can be used for both the ballast water treatment facility and the desalination unit.The waste heat and / or the power of the propulsion unit does not have to be distributed to different positions in the ship, but can be directed specifically to a component that includes both the ballast water treatment system and the desalination unit.

[0030] In an advantageous embodiment of the invention, a seawater pump can be provided, which is connected to the ballast water tank and / or the ballast water treatment facility, to pump seawater into the ballast water tank. The seawater can be taken, in particular, from the sea surrounding the ship. Furthermore, at least one ship's own renewable energy generation unit, in particular a ship's own photovoltaic and / or wind turbine, can be provided, which provides energy for the propulsion unit and / or the ballast water treatment facility, in particular the desalination unit.

[0031] The invention further relates to a method for preventing pollution-related reductions in the energy generation capacity of a large-scale photovoltaic system in an area with a lack of fresh water, in particular in a region with an average vertical solar radiation of at least 2,000 kWh, preferably at least 2,500 kWh, per year and square meter, the method comprising the following steps:

[0032] Desalination of ballast water on a ship described above, in particular by a method described above,

[0033] Unloading of fresh water at a port of arrival,

[0034] Transporting the fresh water to the power generation plant and

[0035] Cleaning the photovoltaic panels of the large photovoltaic system using fresh water.

[0036] Photovoltaic panels should preferably be cleaned at regular intervals.

[0037] The use of fresh water to clean photovoltaic panels is advantageous because fresh water is typically scarce in areas that can accommodate large-scale photovoltaic systems. The use of fresh water has the advantage that the photovoltaic panels are cleaned particularly well, thus maintaining energy generation capacity over a longer period of time. This prevents a reduction in energy generation capacity due to pollution. Preferably, the large-scale photovoltaic system has an energy generation capacity of at least 1 megawatt, in particular 1.5 megawatts, in particular at least 2 megawatts.

[0038] However, the freshwater produced by the ship's desalination unit can also be used for other purposes. For example, the freshwater or freshwater can be used to produce hydrogen. The hydrogen can then be further processed into other liquid fuels, for example. Preferably, this further processing takes place into so-called e-fuels, i.e., green fuels produced primarily or exclusively using renewable energy sources.

[0039] The invention will be explained in more detail below using an exemplary embodiment with reference to the attached schematic drawings.

[0040] Fig. 1 is a cross-sectional view of a ship according to the invention according to a preferred embodiment after leaving the destination port or departure port;

[0041] Fig. 2 shows a longitudinal section through the ship according to Fig. 1 after leaving the port of destination or port of departure;

[0042] Fig. 3 shows a cross-section through the ship according to Fig. 1 before leaving the port of loading or the port of arrival;

[0043] Fig. 4 is a longitudinal sectional view of a ship according to the invention according to a further preferred embodiment;

[0044] Fig. 5 is a longitudinal sectional view of a ship according to the invention according to a further preferred embodiment; and

[0045] Fig. 6 shows a cross-section through the ship according to Fig. 5.

[0046] Fig. 1 shows a cross-section of a tanker with a cargo tank (LT) and a ballast water tank (BW). The tanker has unloaded its cargo at the port of departure. The vessel is preferably designed to load green fuels, particularly methanol. Since the cargo has been unloaded, the cargo tank (LT) is empty.

[0047] To ensure the stability of the ship during the return voyage to the port of arrival or loading, the unladen ship must be stabilized. This is achieved by the ballast water tank (BW), which is filled with ballast water after departure from the port of departure. Fig. 1 shows the ship with the filled ballast water tank (BW) and the empty cargo tank (LT).

[0048] During the crossing, which usually takes around three weeks, the ballast water on board the ship is treated by a desalination unit WE to produce fresh water. This is shown schematically in Fig. 2. In the longitudinal sectional view according to Fig. 2 it can be seen that the ballast water tank BW is being emptied. This occurs because a ballast water pump pumps the ballast water from the ballast water tank BW to a heat exchanger. The heat exchanger is preferably integrated into the desalination unit WE and absorbs waste heat from a ship's propulsion unit E and converts this into process heat for the desalination unit WE. The heat exchanger WE is therefore connected to the desalination unit WE or integrated into the desalination unit WE, with the desalination unit WE desalinating the ballast water using the process heat provided by the heat exchanger.

[0049] Alternatively or additionally, the desalination unit WE can be mechanically connected to the propulsion unit E, so that mechanical power is transferred from the propulsion unit E to the desalination unit WE. The salinity of the ballast water is significantly reduced in the desalination unit WE. Fresh water is generated, which is then pumped into the cargo tank LT via a fresh water pump. During the ship's passage, the ballast water tank BW is emptied, and the cargo tank LT is simultaneously filled with fresh water.

[0050] Since a ship's LT cargo tanks often have a higher filling volume than the BW ballast water tanks, it can also be planned to pump seawater into the BW ballast water tank(s) during the crossing, so that additional ballast water is available to continue desalination in the WE desalination unit. This process is preferably continued until the LT cargo tanks are completely filled or the ship has reached the port of arrival.

[0051] At the port of arrival, the cargo tank LT is preferably completely filled with fresh water, while the ballast water tank BW is empty. This situation is shown in Fig. 3. The fresh water in the cargo tank LT can be unloaded and used at the destination, for example, to clean photovoltaic panels or to generate hydrogen. The now unloaded ship can then be used to load it with green fuel, such as methanol, so that the ship can fulfill its primary transport task: transporting green fuel from the Earth's sunbelt to regions where the fuel is needed.

[0052] Alternatively, particularly on ships, such as container ships, that do not have a cargo tank LT for liquid goods, the reduced-salt water or fresh water produced after the desalination unit can be returned to the ballast water tank BW. This creates mixed water in the ballast water tank BW with a lower salt content than the original ballast water. The mixed water is continuously withdrawn from the ballast water tank BW and fed to the desalination unit E, so that the salt content of the mixed water in the ballast water tank BW is gradually reduced. As soon as a salt content of less than 0.1%, in particular less than 0.05%, is reached, fresh water is present.

[0053] In the desalination unit E, complete desalination can take place, so that immediately after the desalination unit E, fresh water with a salt content of less than 0.1% is available and is mixed with the ballast water in the ballast water tank BW to form mixed water. However, it is also possible for the desalination unit E to only produce reduced-salt water, i.e. water with a salt content below the salt content of the ballast water but still above the salt content of fresh water, which is then mixed with the ballast water in the ballast water tank BW to form mixed water. In both cases, the desalination process is continued until there is fresh water in the ballast water tank BW. This happens more quickly with full desalination than with salt reduction in the desalination unit E.However, less energy is required for salt reduction compared to full desalination, so this process is particularly suitable for use in smaller ships with lower energy surplus from the propulsion unit.

[0054] In addition to ballast water desalination, the vessel described here can offer the option of separating carbon dioxide from the ambient air. For this purpose, a separation device AC can be provided that takes in atmospheric ambient air and separates the carbon dioxide it contains. The energy to operate the separation device AC can be provided by the ship's propulsion unit E. To make the separation process energy-efficient, large fans for supplying ambient air to the separation device AC can be dispensed with. Instead, the separation device AC can have an air inlet positioned and aligned on the ship so that a sufficient air supply is achieved through the ship's propulsion.

[0055] By utilizing the ship's motion to supply ambient air to the AC separation device, the electrical energy otherwise required for fans is saved. The thermal energy required for the separation process can be provided by the waste heat from the propulsion unit E. Therefore, it is advantageous to provide a heat exchanger between a waste heat circuit of the propulsion unit E and the AC separation device.

[0056] The captured carbon dioxide can be stored in a cargo tank (LT) and / or a ballast water tank (BW). Storage in a cargo tank (LT) is preferred. At the ship's destination, the carbon dioxide can then be unloaded and, in particular, fed into a plant for the production of methanol fuel. This removes carbon dioxide from the atmosphere, making a significant contribution to meeting the Paris climate protection goals. The additional capture system allows a ship to operate in a CO2-neutral or even CO2-negative manner.

[0057] Fig. 4 shows an example of a ship with cargo tanks LT and ballast water tanks BW, wherein a desalination unit WE is provided which extracts salt from the ballast water and supplies the desalinated water to the cargo tanks LT. The desalination unit WE is operated by waste heat and / or excess electrical energy from a propulsion unit E of the ship. In addition, the ship according to Fig. 4 is provided with several separation devices AC. The separation devices AC each have an air inlet which is aligned in the direction of travel of the ship. Thus, ambient air is conveyed into the separation devices AC by the movement of the ship. Downstream of the air inlet in the direction of air flow is a separation chamber in which carbon dioxide is chemically separated from the air. The separated carbon dioxide can be stored in the cargo tanks LT, in particular in addition to the desalinated fresh water.It can be designed for individual cargo tanks (LT) to hold exclusively carbon dioxide, while others (LT) to hold demineralized freshwater. The carbon dioxide stored in the LT cargo tanks can be discharged at the destination and fed, for example, into a methanol production plant as a raw material.

[0058] In this way, the ship, on the one hand, removes carbon dioxide from the atmosphere during an empty voyage, thus contributing to reversing man-made climate change. On the other hand, the ship promotes climate protection technologies by providing freshwater for the production of hydrogen or methanol, or at least for the cleaning of photovoltaic systems. At the same time, the ship's energy efficiency is increased because the energy provided by the E propulsion unit is fully utilized.

[0059] Fig. 5 shows a similar ship which differs from the ship according to Fig. 4 in that instead of several separation devices AC, a single, correspondingly enlarged separation device AC is provided. The single separation device AC has an air inlet at the bow of the ship, through which air is directed into a separation chamber which extends over a large part of the length of the ship. This design avoids air turbulence which, in the ship according to Fig. 4, occurs behind separation devices AC which are at the front in the direction of travel and which can impair the air supply for downstream separation devices AC. Fig. 6 shows the ship in a cross-sectional view, wherein it can be seen that the air inlet of the separation device AC preferably extends over almost the entire width of the ship in order to ensure a high air supply.

[0060] The excess waste heat from the ship's propulsion unit E can also be used to filter microplastics from the ballast water. To do this, the thermal energy contained in the excess waste heat is used to heat the ballast water to at least 100°C to encapsulate nanoplastics or microplastics, particularly polystyrene, polyethylene, and polypropylene components with a size between 0.1 and 150 pm, and then remove them through a filter.

[0061] Specifically, the excess waste heat from the ship's propulsion unit (E) can be transferred via a heat exchanger into the ballast water in the ballast water tank (BW) to heat it to at least 100 °C. The filter, which filters the encapsulated and aggregated nanoplastic and microplastic particles from the water, can be located between the ballast water tank (BW) and the desalination unit (WE).

[0062] List of reference symbols

[0063] AC separation device

[0064] BW ballast water tank

[0065] E drive unit LT cargo tank

[0066] WE desalination unit

Claims

Patent claims 1. A method for desalinating ballast water on a ship, in particular a methanol and / or hydrogen tanker, comprising the steps: Pumping the ballast water from at least one ballast water tank (BW) into a desalination unit (WE) of the ship by at least one ballast water pump, Desalination of the ballast water in the desalination unit (WE) to produce desalinated fresh water using excess energy from a propulsion unit (E) of the ship, in particular by multi-stage flash evaporation and / or membrane distillation and / or reverse osmosis, Pumping the fresh water into at least one cargo tank (LT), in particular methanol and / or hydrogen tank, of the ship by means of at least one fresh water pump, wherein the ballast water pump and the fresh water pump are controlled by means of a central control unit in such a way that the distribution of ballast water and fresh water between the ballast water tank (BW) and the cargo tank (LT) is balanced on the basis of environmental data on waves, wind and ship position in order to maintain the stability of the ship, and wherein, to balance the ballast water pumped from the ballast water tank (BW) into the desalination unit (WE), sea water is pumped into the ballast water tank (BW) by means of at least one sea water pump.

2. Method according to claim 1, characterized in that the desalination is carried out using waste heat and / or mechanical power of the drive unit (E).

3. Method according to claim 1 or 2, characterized in that the desalination unit (WE) and / or the drive unit (E) with additional Energy is supplied from the ship's own photovoltaic and / or wind power system.

4. Method according to one of the preceding claims, characterized in that the propulsion unit (E) of the ship is operated with methanol.

5. Method according to one of the preceding claims, characterized in that during the voyage of the ship sea water is taken up and stored in a CO 2 - CO capture unit 2 taken from the seawater and stored in at least one cargo tank and / or CO 2 -Tank is stored.

6. Ship, in particular a methanol and / or hydrogen tanker, comprising: - at least one propulsion unit (E) for generating propulsion energy for moving the ship, - at least one ballast water tank (BW), - at least one cargo tank (LT) designed as a methanol and / or hydrogen tank, - a desalination unit (WE) for the production of desalinated fresh water, - at least one ballast water pump for pumping saline ballast water from the ballast water tank (BW) into the desalination unit (WE), - at least one fresh water pump for pumping the fresh water into the cargo tank (LT) and - a central control unit for controlling the distribution of ballast water and fresh water between the ballast water tank (BW) and the cargo tank (LT), wherein a heat exchanger is arranged between the propulsion unit (E) and the desalination unit (WE), which converts waste heat from the propulsion unit (E) into 20 process heat for the desalination unit (WE), and wherein the Heat exchanger connected to the cargo tank (LT) and configured to cool the cargo tank (LT).

7. Ship according to claim 6, characterized in that the control unit is configured to balance the amount of ballast water and fresh water between the ballast water tank (BW) and the cargo tank (LT) in such a way that the stability of the ship is maintained.

8. Ship according to claim 6 or 7, characterized in that a ballast water treatment device is provided which is connected to the ballast water tank and comprises at least one filter unit and / or at least one disinfection unit.

9. Ship according to claim 8, characterized in that the ballast water treatment device comprises a deoxygenation unit.

10. Ship according to claim 8 or 9, characterized in that the ballast water treatment device is arranged between the ballast water tank (BW) and the cargo tank (LT), wherein the desalination unit (WE) is integrated into the ballast water treatment device.

11. Ship according to one of claims 6 to 10, characterized in that a seawater pump is provided which is connected to the ballast water tank (BW) and / or the ballast water treatment device in order to pump seawater into the ballast water tank (BW).

12. Ship according to one of claims 6 to 11, characterized in that at least one ship's own regenerative energy generation unit, in particular a ship's own photovoltaic and / or wind power plant, is provided, which provides energy for the propulsion unit (E) and / or the ballast water treatment facility, in particular the desalination unit (WE).

13. A method for preventing pollution-related reductions in the energy production capacity of a large-scale photovoltaic system in an area with a scarce supply of fresh water, in particular in a region with an average vertical solar irradiation of at least 2,000 kWh, preferably at least 2,500 kWh, per year and square meter, comprising the following steps: Desalination of ballast water on a ship according to one of claims 6 to 12, in particular by a method according to one of claims 1 to 5, unloading the fresh water at a port of arrival, Transporting the fresh water to the energy generation plant and cleaning the photovoltaic panels of the large-scale photovoltaic plant using the fresh water.

14. Method according to claim 13, characterized in that the large-scale photovoltaic system has an energy generation capacity of at least 1 megawatt, in particular at least 1.5 megawatts, in particular at least 2 megawatts.

Images