Safety improvements for UV radiation in aquatic applications

Abstract

The invention provides an object (10) that during use is at least partly submerged in water, the object (10) further comprising an anti-bio fouling system (200) comprising an UV emitting element (210), wherein the UV emitting element (210) comprises one or more light sources (220) and is configured to irradiate with UV radiation (221) during an irradiation stage one or more of (i) a part (111) of an external surface (11) of said object (10) and (ii) water adjacent to said part (111) of said external surface (11), wherein the object (10) is selected from the group consisting of a vessel (1) and an infrastructural object (15), wherein the object (10) further comprises a water switch (400), wherein the anti-bio fouling system (200) is configured to provide said UV radiation (221) to said part (111) in dependence of the water switch (400) being in physical contact with the water.

Claims

1. A vessel that during use is at least partly submerged in water, the vessel comprising: an ultraviolet (UV) light emitting element in or on an external surface of the vessel, wherein the UV light emitting element includes one or more light sources and is configured to emit UV radiation in a direction away from the external surface of the vessel to irradiate with the UV radiation a portion of the water adjacent to a part of the external surface of the vessel; and a water switch, wherein the water switch is connected in an electrical circuit in series with a power source and the UV light emitting element, and wherein the water switch is configured to be closed by the water acting as a conductor in the electrical circuit between the power source and the UV light emitting element so as to complete the electrical circuit and provide power from the power source through the water to the UV light emitting element, and to cause the UV light emitting element to produce the UV radiation, and wherein when the water is not present at the water switch the water switch is open and the UV light emitting element does not emit the UV radiation.

2. The vessel of claim 1, further comprising a local energy harvesting system, wherein the local energy harvesting system is configured to harvest electrical energy and to provide said harvested electrical energy to said UV light emitting element.

3. The vessel of claim 2, wherein the local energy harvesting system is selected from the group consisting of a solar cell, a turbine operating in water, and a piezoelectric element operating on a pressure of waves.

4. The vessel of claim 1, wherein the UV light emitting element includes a UV radiation escape surface, and wherein the UV radiation escape surface is configured as part of said external surface of the vessel.

5. The vessel of claim 1, wherein the UV light emitting element comprises a luminescent material, wherein the luminescent material is configured to absorb part of the UV radiation and convert the absorbed part of the UV radiation into visible luminescent light, wherein the UV light emitting element is configured to provide said visible luminescent light emanating in a direction away from the external surface.

6. The vessel of claim 1, further comprising a visible light emitting device, wherein the visible light emitting device is connected in series with the UV light emitting element, and is configured to provide visible light emanating as a visible light beam in the direction away from the external surface in response to the UV light emitting element being turned on and emitting the UV radiation, wherein the visible light beam has a cross-section having a shape of a warning sign.

7. The vessel of claim 1, wherein the external surface comprises a UV radiation escape surface through which the UV light passes from the UV light emitting element, and wherein the UV radiation escape surface is provided at a position which is permanently under a water line of the water during use of the vessel.

8. The vessel of claim 1, wherein the UV light emitting element is configured to provide at least 80% of the power of the UV radiation in a direction within an angle of 0-90° from a perpendicular to the earth's surface and in a direction below the vessel, relative to the vessel during its use.

9. The vessel of claim 1, wherein the water switch is disposed at a height which is higher with respect to a water line of the water than the UV light emitting element.

10. A vessel that during use is at least partly submerged in sea water, the vessel comprising: an ultraviolet (UV) light emitting element attached to a hull of the vessel, wherein the UV light emitting element includes one or more light sources and is configured to irradiate with UV radiation a portion of the sea water adjacent to a part of the hull of the vessel; and a water switch, wherein the water switch is connected in an electrical circuit in series with a power source and the UV light emitting element, and wherein the water switch is configured to be closed by the sea water, wherein the sea water itself is a conductor in the electrical circuit between the power source and the UV light emitting element so as to complete the electrical circuit and provide power from the power source through the sea water to the UV light emitting element, and cause the UV light emitting element to produce the UV radiation, and wherein when the sea water is not present at the water switch the water switch is open and the UV light emitting element does not emit the UV radiation.

11. The vessel of claim 10, further comprising a local energy harvesting system is configured to harvest electrical energy and to provide the harvested electrical energy to the UV light emitting element.

12. The vessel of claim 10, wherein the UV light emitting element comprises a luminescent material, wherein the luminescent material is configured to absorb part of the UV radiation and convert the absorbed part of the UV radiation into visible luminescent light, and wherein the UV light emitting element is configured to provide the visible luminescent light emanating in a direction away from the hull of the vessel.

13. The vessel of claim 10, further comprising a visible light emitting device connected in series with the UV light emitting element, wherein the visible light emitting device is configured to provide visible light emanating as a visible light beam in a direction away from the hull of the vessel in response to the UV light emitting element being turned on and emitting the UV radiation, wherein the visible light beam has a cross-section having a shape of a warning sign.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

(2) FIGS. 1a-1c schematically depict some general aspects;

(3) FIGS. 2a-2f schematically depict some embodiments and variants;

(4) FIGS. 3a-3b schematically depict some further embodiments and variants;

(5) FIGS. 4a-4e schematically depict some further embodiments and variants; and

(6) FIGS. 5a-5c schematically depict some further embodiments and variants.

(7) The drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) FIGS. 1a-1b schematically depict embodiments of an object 10 that during use is at least partly submerged in water 2, see the water line 13. The object 10, such as a vessel or a sluice, see also below, further comprises an anti-biofouling system 200 comprising an UV emitting element 210, especially for application of UV radiation 221 to a part 111 of an external surface 11 of the object 10, such as a hull or part or a hull. Here, two embodiments are shown wherein the anti-biofouling system 200, or more especially the UV emitting element 210 is part of an outer surface, and thereby forms in fact part of the outer surface (FIG. 1a) or wherein the UV emitting element 210 is configured to irradiate the outer surface and does not necessarily form part of an outer surface, such as a hull of a ship (FIG. 1b). For instance, the object 10 is selected from the group consisting of a vessel 1 and an infrastructural object 15 (see also below).

(9) The UV emitting element 210 comprises one or more light sources 220 and may thus especially be configured to irradiate with said UV radiation 221 during an irradiation stage one or more of (i) said part 111 of said external surface 11 and (ii) water adjacent to said part 111 of said external surface 11. The former variant applies especially the embodiment of FIG. 1b, and the latter embodiment especially applies to both embodiments of FIGS. 1a-1b. Note however that when an external surface of the UV emitting element 210 is configured as external surface of the object 10, of course the part 111 is irradiated per se with the UV radiation 21.

(10) Hence, the UV emitting element 210 comprises a UV radiation escape surface 230 and the UV emitting element 210 is configured to provide said UV radiation 221 downstream from said UV radiation escape surface 230 of said UV emitting element 210.

(11) Especially, the light source 220 is at least controllable between a first UV radiation level and a second UV radiation level, wherein the first UV radiation level is larger than the second UV radiation level (and wherein the second UV radiation level is smaller than the first radiation level (including e.g. zero).

(12) In a specific embodiment, the object 10 further comprises a control system 300 configured to control said UV radiation 221 as function of input information comprising information of one or more of (i) a location of the object 10, (ii) movement of the object 10, (iii) a distance d of the object 10 to a second object 20, and (iv) a position of the part 111 of the external surface 11 relative to the water. This is further elucidated in amongst others FIGS. 2a-2f.

(13) As indicated above, the term “vessel”, indicated with reference 1, may e.g. refer to e.g. a boat or a ship (ref 10a in FIG. 1c), etc., such as a sail boat, a tanker, a cruise ship, a yacht, a ferry, a submarine (ref. 10d in FIG. 1c), etc. etc., like schematically indicated in FIG. 1c. The term “infrastructural object”, indicated with reference 15, may especially refer to aquatic applications that are in general arranged substantially stationary, such as a dam/sluice (references 10e/10f in FIG. 1c), a pontoon (ref. 10c in FIG. 1c), an oilrig (ref. 10b in FIG. 1c), etc. etc.

(14) As indicated above, the object 10 may further comprises a control system 300 configured to control said UV radiation 221 as function of input information comprising information of one or more of (i) a location of the object 10, (ii) movement of the object 10, (iii) a distance (d) of the object 10 to a second object 20, and (iv) a position of the part 111 of the external surface 11 relative to the water.

(15) For instance, the location of the object, especially of a vessel 10 may switch on the UV radiation when on open water, whereas the UV emitting element 210 may be switched off in a harbor. Satellite navigation may e.g. be used (for determination of the location of the object). Hence, in an embodiment the control system 300 is configured to control the UV emitting element 210 to the first UV radiation level when the location of the object 10 complies with a first predetermined location, and to the second UV radiation level when the location of the object 10 complies with a second predetermined location.

(16) Alternatively or additionally, the control system 300 may be configured to control the UV emitting element 210 to the first UV radiation level when the object 10 has a velocity of at least a predetermined minimum velocity, and to the second UV radiation level when the velocity of the objects 10 is below said predetermined minimum velocity. A low velocity may indicate a higher likelihood of people in the vicinity of the UV emitting element 210 than a high velocity.

(17) Alternatively or additionally, the control system 300 may be configured to control the UV emitting element 210 to the first UV radiation level when the distance d of the object 10 to the second object 20 meets at least a predefined threshold value, and to the second UV radiation level when the distance d of the object 10 to the second object 20 is below the predefined threshold value. This is schematically depicted in FIG. 2a.

(18) For controlling the UV emitting element 210 as function of one or more of the herein indicated parameters, the object 10 may further comprise a sensor 310, see e.g. FIG. 2a, configured to sense one or more of (i) a second object 20 and (ii) a movement of the second object (20) and configured to generate a corresponding sensor signal. The control system 300 may especially be configured to control said UV radiation 221 as function of said sensor signal. The second object may be stationary or moving. Further the second object may e.g. a human (see the example in FIG. 2a), or non-moving, such as quay (see also FIG. 2a). The sensor may optionally be comprised by the anti-bio-fouling system 200 (see e.g. FIG. 2b.

(19) FIG. 2b schematically depicts in more detail an embodiment of the anti-biofouling system 200, here by way of example including an integrated control system 300 and an integrated sensor 310.

(20) FIG. 2c schematically depicts an external surface 11 of an object 10, such as a vessel wall or a wall of an infrastructural object, with by way of example a plurality UV emitting elements 210 (here associated to a hull 21 of a vessel 1). Alternatively or additionally, a plurality of functionally coupled or independently functioning anti-biofouling systems 200 may be applied.

(21) For instance, assuming a single control system 300, which may e.g. be a master control system with subordinated slave control systems (not depicted), may e.g. be configured to control the UV emitting element 210 to the first UV radiation level when one or more of the part 111 and the UV radiation escape surface 230 are below the water line 13, and to the second UV radiation level when one or more of the part 111 and the UV radiation escape surface 230 are above the water line 13. For instance, all UV emitting elements 210 below the water (line) may be switched on, while all above the water (line) may be switched off. Note that in the schematic drawing 2c also one of the UV emitting elements 210 above the water line 3 is switched, e.g. in the case that the control system decides that it is safe to switch such UV emitting elements 210 on. Use of an additional safeguard, such as a water switch may be used as alternative or additional control (see also below).

(22) FIG. 2c also schematically depicts the embodiment wherein the anti-biofouling system 200 comprises a plurality of UV emitting elements 210 (with a plurality of light sources), a plurality of radiation escape surfaces 230, and a plurality of said parts 111, wherein the plurality of light sources 220 are configured to provide said UV radiation 221 via said plurality of radiation escape surfaces 23 to said plurality of parts 111, and wherein said plurality of parts 111 are configured at different heights of the object 10, and wherein the control system 300 is configured to control the light sources 220 individually as function of said input information. For instance, in an embodiment the control system 300 may be configured to control the light sources 220 individually as function of the positions of the parts 111 of the external surface 11 relative to the water. In a first variant, the input information comprising information of the position of the external surface 11 relative to the water is based on a loading of the vessel 1 (schematically depicted in FIG. 2c). In a second variant, the input information comprising information of the position of the external surface 11 relative to the water is based on a water line relative to the infrastructural object 15.

(23) FIG. 2d schematically depicts an embodiment wherein alternatively or additionally the object 10 further comprises a water switch 400, wherein the anti-biofouling system 200 is configured to provide said UV radiation 221 to said part 111 in dependence of the water switch being in physical contact with the water. In FIG. 2d, the water switch is in contact with the water. For instance, by electrical conductivity of seawater, the electric circuit may be closed, by which the light source 220 may provide UV radiation. An anti-biofouling system may comprise one or more of such water switches 400. Optionally, the water switch 400 and light source 220 may be part of a larger circuit with e.g. electronics to amplify the signal, etc. FIG. 2d, like the other drawings, is a schematic drawing.

(24) FIG. 2e schematically depicts an embodiment, wherein the anti-biofouling system 200 comprises a plurality of UV emitting elements 210 (with a plurality of light sources), a plurality of radiation escape surfaces 230, and a plurality of said parts 111, wherein the plurality of light sources 220 are configured to provide said UV radiation 221 via said plurality of radiation escape surfaces 230 to said plurality of parts 111, and wherein said plurality of parts 111 are configured at different heights of the object 10, and further comprising a plurality of said water switches 400, configured at the heights of the plurality of parts 111, and wherein the anti-biofouling system 200 is configured to provide said UV radiation 221 to said parts 111 when the respective water switches 400 are in physical contact with the water. Of course, the embodiment of FIG. 2e may optionally be combined with the embodiment schematically depicted in FIG. 2c.

(25) FIG. 2f schematically depicts an embodiment wherein a vessel 1, as embodiment of the object 10, comprises a plurality of anti-biofouling systems 200 and/or a one or more of such anti-biofouling systems 200 comprising a plurality of UV emitting elements 210. Dependent upon the height of the specific such anti-biofouling system 200 and/or the height of the UV emitting elements 210, such as relative to a water (line), the respective UV emitting elements 210 may be switched on.

(26) FIG. 3a schematically depicts an embodiment wherein the object, here especially the anti-biofouling system 200, further comprises a local energy harvesting system 500 configured to harvest electrical energy and to provide said energy to said anti-biofouling system 200. Here, by way of example a turbine is depicted which may provide electrical energy when the vessel is moving in water. Hence, in embodiments the local energy harvesting system 500 is comprised by said anti-biofouling system 200. The local energy harvesting system 500 may e.g. comprise a solar cell, a turbine operating in water, a piezoelectric element operating on a pressure of waves, etc.

(27) Especially, local energy harvesting systems may be applied that upon contact with the water provide electrical energy, especially energy harvesting systems that provide electrical energy when submerged in water and being subjected to a movement of water. FIG. 3b schematically depicts an embodiment wherein dependent upon the height of the specific anti-biofouling system 200 and/or the height of the UV emitting elements 210, such as relative to a the water (line), the respective UV emitting elements 210 may receive electrical energy from the local energy harvesting system 500. Hence, especially the local energy harvesting system 500 may comprise one or more of a turbine operating in water and a piezoelectric element operating on a pressure of waves.

(28) Alternatively or additionally, the local energy harvesting system comprises (i) a sacrificial electrode in electrical connection with a first electrode of the light source 220, and (ii) a second energy system electrode in electrical connection with a second electrode of the light source 220, wherein the energy system is configured to provide electrical power to said anti-biofouling system 200 when the sacrificial electrode and the second energy system electrode are in electrical contact with the water. Also such embodiment may be implemented in the configuration of FIG. 3b (see further for this embodiment FIGS. 5a-5c). Of course, the embodiment of FIG. 3b may optionally be combined with the embodiments schematically depicted in one or more of FIGS. 2c and 2e.

(29) FIG. 4a shows a chicken-wire embodiment where light sources 210, such as UV LEDs, are arranged in a grid and connected in a series of parallel connections. The LEDs can be mounted at the nodes either through soldering, glueing or any other known electrical connection technique for connecting the LEDs to the chicken wires. One or more LEDs can be placed at each node. DC or AC driving can be implemented. If AC is used, then a couple of LEDs in anti parallel configuration may be used. The person skilled in the art knows that at each node more than one couple of LEDs in anti parallel configuration can be used. The actual size of the chicken-wire grid and the distance between UV LEDs in the grid can be adjusted by stretching the harmonica structure. The chicken-wire grid may be embedded in an optical medium. Above, especially active prevention applications are described, wherein the anti-biofouling system 200 switches off, or switches specific UV emitting elements 210 or specific light sources 220 off, dependent upon contact with the water, a signal of a sensor, etc. etc. However, alternatively or additionally, also warning signals or messages may be used to warn a person of danger.

(30) Hence, the invention also provides an object 10 that during use is at least partly submerged in water, the object 10 further comprising an anti-biofouling system 200 comprising an UV emitting element 210, especially for application of UV radiation 221 to a part 111 of an external surface 11 of the object 10, wherein the UV emitting element 210 comprises one or more light sources 220 and is configured to irradiate with said UV radiation 221 during an irradiation stage one or more of (i) said part 111 of said external surface 11 and (ii) water adjacent to said part 111 of said external surface 11, wherein the UV emitting element 210 comprises a UV radiation escape surface 230 and wherein the UV emitting element 210 is configured to provide said UV radiation 221 downstream from said UV radiation escape surface 230 of said UV emitting element 210, with one or more of the functionalities indicated below.

(31) For instance, in an embodiment the UV emitting element 210 comprises a luminescent material 260 configured to absorb part of the UV radiation 221 and to convert into visible light 261, wherein the light source 220 and said luminescent material 260 are configured to provide said visible light 261 (see FIGS. 4a-4b) emanating in a direction away from the external surface 11 (see FIG. 4b). Visible light in general is indicated with reference 291, and luminescent material light in the visible is indicated with reference 261. For instance, alternatively or additionally, the UV emitting element 210 comprises a second light source 280 configured to provide visible second light source light 281, such as especially red light, of which at least part emanates in a direction away from the external surface 11 (see this variant also depicted in FIG. 4a). FIG. 4a schematically depicts a LED grid, that may e.g. be used in the UV emitting element 210 to provide UV radiation 221 (and thus optionally also visible light 291.

(32) In a specific embodiment, schematically depicted in FIGS. 4b and 4d (but optionally implicitly also in FIG. 4c) the anti-biofouling system 200 may further be configured to provide visible light 291 emanating as a light beam 292 in a direction away from the external surface 11, wherein the light beam 292 has a cross-section having the shape of a warning sign. FIG. 4c schematically depicts an arrangement of light sources 280, which may provide such warning signal (see FIG. 4d). Note that FIG. 4c schematically depicts the light sources 280 configured to generate visible light 291 (see FIG. 4d). UV light sources 220 fill the rest of the area. The light source 280 are arranged in a warning signal configuration (and may e.g. lead to the beam shown in FIG. 4d). Note that instead of visible light emitting light sources 280 also UV emitting light sources 220 in combination with a luminescent material may be applied, or a combination of such variants.

(33) In yet a further specific embodiment, the object 10 comprises e.g. a vessel 1, wherein the UV radiation escape surface 230 is configured to the external surface 11 of the object 10 at a position which is permanent under the water (line) during use of the object 10. For instance, assuming a vessel, the UV emitting element(s) may be configured below the tropical fresh water load line (TF), or even below the freshwater load line (F), or below tropical zones load line (T), or yet even below the summer load line (S), or even below the winter load line (W), yet even only below the winter North Atlantic load line (WNA). Hence, in embodiments the freeboard may be kept free from UV radiation (and from UV emitting element(s).

(34) In yet another embodiment, schematically depicted in FIG. 4e the UV emitting element 210 is configured to provide at least 80% of the power of the UV radiation in a direction within an angle θ of 0-90° from a perpendicular P to the earth's surface and in a direction below the object 10, relative to the object during its use 10.

(35) FIGS. 5a-5c schematically depicts some aspects of the anti-biofouling system and its application. It is for instance an aspect of the invention to insert UV LEDs and/or other light sources into an electrical circuit that may already be available in an object 10 having a (steel) external surface 11 and a sacrificial electrode 510 attached thereto, see FIGS. 5a-5c for a comparison between the situation without UV emitting element 210 (FIG. 5a), and with a light source (FIGS. 5b and 5c). The dashed line indicates by way of example an electrical return path through the steel external surface 11. The steel hull 21, here the external surface 11, may act as a second energy source electrode 570. In this way, energy system 500 is provided, that may be used to power a light source or UV emitting element 210. FIG. 5b shows the introduction of a UV emitting element 210 which may illuminate the external surface 11, and which may be powered by the energy system 500.

(36) FIG. 5c schematically depicts in more detail an embodiment of the anti-biofouling system 200 (here also in an embodiment of the closed unit), wherein by way of example the UV emitting element 210 is comprised by an optical medium 270. The anti-biofouling system is further elucidated amongst others with respect to this embodiment, but the invention is not limited to this embodiment. FIG. 5c schematically depicts an anti-biofouling system 200 configured for preventing or reducing (water related) biofouling on a external surface 11 of an object 10 that during use is at least temporarily exposed to an electrically conductive aqueous liquid, by providing an UV radiation (anti-fouling light) 221 to said external surface 11.

(37) Alternatively or additionally, the local energy harvesting system 500 comprises (i) a sacrificial electrode 510 in electrical connection with a first electrode (not shown) of the light source or system 200 or UV emitting element 210, and (ii) a second energy system electrode 570 in electrical connection with a second electrode (not shown) of the light source or system 200 or UV emitting element 210, wherein the energy system 500 is configured to provide electrical power to said anti-biofouling system 200 when the sacrificial electrode 510 and the second energy system electrode 570 are in electrical contact with the water.

(38) Hence, herein optical and/or electrical approaches are suggested to provide extra safety when using UV radiation. One or more of these approaches may be applied simultaneously.

(39) Optical approaches include amongst others:

(40) The use of visible LEDs in series with a UV LED: UV light is harmful to human beings. What makes it more risky, is the fact that it is invisible. This implies that human beings have no visible, audible or any other warning signs when they're exposed to UV light (This also explains why sunburns are common). The safety idea proposed here is to have a visible LED (e.g. bright red) in series with a UV LED. Because of the series connection, the visible LED will “always” be on when the UV LED is on, thus giving a clearly visible warning sign.

(41) The combination of a visible+UV light in direct series connection can be a very fundamental safety building block.

(42) Alternatively or additionally, a number of visible LEDs can be organized in a pattern on the hull of a ship, to e.g. show a warning symbol, like a triangle or exclamation mark.

(43) Another approach is to embed a phosphor in the coating, near the UV source. This phosphor should convert the UV light to a visible light wavelength. Again, the phosphor can be arranged in a pattern that conveys a warning; like above.

(44) Electrical approached include amongst others:

(45) LEDs switched on only when in contact with water. Different embodiments can be envisioned:

(46) A (temporary) contact with water flips a switch, and the whole system (or subsection) of LEDs stay on (for a pre-determined period of time)

(47) At LED level: a second electrode of the LED is directly connected to the water, implying that a closed circuit is only obtained when the LED is submerged; the water is the return electrode.

(48) Alternatively, the water can close a small gap in the circuit for each individual LED (or section of LEDs).

(49) Further, mechanical and system approaches are proposed herein. One or more of these approaches may be applied simultaneously. With ‘system approaches’, it is especially meant that the safety of the entire application (such as an entire vessel) is controlled at a system level. That is, the entire system (or large parts or subsections) are controlled at once.

(50) System approaches include amongst others:

(51) As the UV light is mainly emitted on the lower side (and outside) of the hull, people on board the ship hardly have a line of sight to the UV emitting layers. Hence they are not at risk of UV exposure. This is different for people outside of the boat; most relevant when a boat is docked in harbor. In that scenario, people are walking on the docks, and small supply vessels are sailing around the boat (fuel supply ships etc.).

(52) An embodiment is to use a sensor that detects movement and/or presence (via infrared light, generated by human beings and or small engines of small boats or cars). When movement or presence is detected, the entire UV system (or parts of it) will be switched off (temporarily). The idea is similar, yet opposite, to common household systems, where a light on the outside of a house (i.e. on the porch) is turned ON when presence or motion is detected. We switch our (UV) lights OFF.

(53) Optionally, also a timer may be employed to switch on the light again after a predetermined period of time without movement being detected.

(54) Design approaches include amongst others:

(55) As the absorption of water for UV light is fairly high, only LEDs above the waterline (or within the first 0.50 m) may emit light that actually reaches human beings (assuming they're above the water line and not swimming around the boat). Hence, only LEDs may be configured on ‘deeper’ sections of the boat, and/or only turn on the upper sections (close to the waterline) in ‘inherently safe’ circumstances, like when sailing on the open ocean. This may require the LEDs to be arranged in horizontal, striped sections, of e.g. 1 meter in height, which can be controlled individually. The actually loading of the ship may then be used to decide which sections to turn on.

(56) In a further embodiment the LEDs are only applied on the lowest parts of the boat; that never get above the waterline, not even on an empty vessel.

(57) The layout of the LEDs in the optical structure may be designed such that the light is emitted primarily outwards (as needed for all applications) and downwards. This may not completely eliminate any UV light of “escaping to above the waterline”, but it will severely limit the amount.

(58) Hence, safety improvements for an UV based anti-fouling system are proposed. The various embodiments can be used individually and/or in combinations of one or more. Thus, the risk of UV light reaching human eyes may substantially be reduced (to an acceptable level).

(59) The term “substantially” herein, such as in “substantially all light” or in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”. The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

(60) Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

(61) The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

(62) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

(63) The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

(64) The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.