ANTI-FOULING SYSTEM USING ENERGY HARVESTED FROM SALT WATER

Abstract

The invention provides an anti-fouling lighting system (1) configured for preventing or reducing biofouling on a fouling surface (1201) of an object (1200) that during use is at least temporarily exposed to a liquid, by providing an anti-fouling light (211) to said fouling surface (1201), the anti-fouling lighting system (1) comprising: a lighting module (200) comprising a light source (210) configured to generate an anti-fouling light (211); and an energy system (500) configured to locally harvest energy and configured to provide electrical power to said light lighting module (200), wherein the energy system (500) comprises (i) a sacrificial electrode (510), and (ii) a second energy system electrode (520), wherein the energy system (500) is configured to provide electrical power to the lighting module (200) when the sacrificial electrode (510) and the second energy system electrode (520) are in electrical contact with the liquid.

Claims

1. An anti-fouling lighting system configured for preventing or reducing biofouling on a fouling surface of an object that during use is at least temporarily exposed to an electrically conductive aqueous liquid, by providing an anti-fouling light to said fouling surface, the anti-fouling lighting system comprising: a lighting module comprising a light source configured to generate the anti-fouling light; and an energy system configured to locally harvest energy and configured to provide electrical power to said light lighting module, wherein the energy system comprises a sacrificial electrode in electrical connection with a first electrode of the light source, and a second energy system electrode in electrical connection with a second electrode of the light source, wherein the energy system is configured to provide electrical power to the lighting module when the sacrificial electrode and the second energy system electrode are in electrical contact with the electrically conductive aqueous liquid.

2. The anti-fouling lighting system according to claim 1, wherein the light source comprises a UV LED configured to provide one or more of UV-A and UV-C light.

3. The anti-fouling lighting system according to claim 1, wherein the sacrificial electrode comprises one or more of zinc and magnesium, wherein the second energy system electrode comprises steel iron, and wherein the anti-fouling lighting system further comprises a voltage difference enhancer configured to increase a voltage difference between the first electrode and a second electrode of the light source.

4. The anti-fouling lighting system according to claim 1, wherein anti-fouling lighting system comprises an optical medium, wherein the optical medium comprises one or more of a waveguide and an optical fiber configured to provide said anti-fouling light to the fouling surface.

5. The anti-fouling lighting system according to claim 1, wherein the lighting module further comprises an optical medium configured to receive at least part of the anti-fouling light and configured to distribute at least part of the anti-fouling light through the optical medium, the optical medium comprising an emission surface configured to emit at least part of the distributed anti-fouling light in a direction away from the optical medium, wherein the fouling surface comprises said emission surface.

6. The anti-fouling lighting system according to claim 5, wherein the light source is embedded in the optical medium, and wherein the optical medium comprises a transit for electrical connections with the light source.

7. The anti-fouling lighting system according to claim 1, wherein the lighting module and one or more of said sacrificial electrode and said second energy system electrode are comprised in an integrated unit.

8. The anti-fouling lighting system according to claim 7, wherein the integrated unit further comprises one or more of a control system and a sensor, wherein the control system is configured to control an intensity of the anti-fouling light as function of one or more of (i) a feedback signal from the sensor, the feedback signal related to a biofouling risk, and (ii) a timer for time-based varying the intensity of the anti-fouling light, and wherein the one or more of the control system and the sensor are also powered by the energy system.

9. The anti-fouling lighting system according to claim 8, configured to provide the anti-fouling light in a pulsed way wherein periods with anti-fouling light are alternated with periods without anti-fouling light.

10. An object comprising a fouling surface that during use is at least temporarily exposed to the electrically conductive aqueous liquid, the object further comprising the anti-fouling lighting system as defined in claim 1.

11. The object according to claim 10, comprising a plurality of lighting modules arranged over at least part of a height (h) of the object, wherein the control system is configured to control an intensity of the anti-fouling light from a lighting module as a function of a position of the lighting module relative to a liquid level of the electrically conductive aqueous liquid at a side of the fouling surface.

12. The object according to claim 10, wherein the object comprises a vessel, wherein the vessel comprises a steel hull, and wherein the hull is configured as second energy system electrode.

13. A method of anti-fouling a fouling surface of an object that is during use at least temporarily exposed to an electrically conductive aqueous liquid, the method comprising: providing an anti-fouling lighting system as defined in claim 1; locally harvesting energy by said energy system to provide electrical power to said light lighting module; generating the anti-fouling light by said lighting module; and providing said anti-fouling light to said fouling surface.

14. The method according to claim 13, wherein the electrically conductive aqueous liquid is seawater.

15. A method of providing an anti-fouling lighting system to an object, that during use is at least temporarily exposed to an electrically conductive aqueous liquid, the method comprising providing a lighting module and an energy system as defined in claim 1 to the object, with the lighting module configured to provide said anti-fouling light to a fouling surface of one or more of the object and the lighting module attached to the object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] 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:

[0093] FIG. 1 is a graph showing a germicidal action spectrum for different biological materials as a function of light wavelength;

[0094] FIG. 2 is a schematic cross section view of a light module with a light guide;

[0095] FIG. 3 shows an embodiment comprising a redistribution reflector and a wavelength conversion material;

[0096] FIGS. 4a-c show embodiments of a chicken-wire grid;

[0097] FIGS. 5a-5d schematically depict some aspect of the lighting system as described herein;

[0098] FIGS. 6a-6c schematically depict some aspects of the anti-fouling lighting system and its application; and

[0099] FIGS. 7a-7e schematically depict some aspects of the anti-fouling lighting system and its application.

[0100] The drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0101] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the disclosure is not limited to the disclosed embodiments.

[0102] FIG. 1 is a graph showing a germicidal action spectrum for different biological materials as a function of light wavelength, with RE indicating the relative effectiveness, with curve 1 indicating the germicidal action as derived from the IES Lighting Handbook, Application Volume, 1987, 14-19; curve 2 indicating E. Coli light absorption (as derived from W. Harm, Biological Effects of ultraviolet radiation, Cambridge University Press, 1980), and curve 3 indicating DNA absorption (as also derived from the IES handbook).

[0103] FIG. 2 shows as a basic embodiment a cross section of a lighting module 200 comprising a plurality of light sources 210 (here: side-emitting LEDs, wherein the light is emitted primarily from the side of the LED, and more or less parallel to the surface) encapsulated in a liquid-tight optical medium 220 to guide at least part of the light 211 emitted from the light sources 210 via total internal reflection through the optical medium, which optical medium is further provided with optical structures 7 to scatter light 211 and guided the light 211 out of the optical medium 220 towards an object 1200 to be targeted with the light (a biofouling organism). The optical medium 220 generally extends in two dimensions significantly further than in the third dimension so that a two-dimensional-like object is provided. Optical structures 7 to scatter light 211 may be spread in one or more portions of the optical medium material, possibly throughout all of it, wherein in such portions the distribution may be generally homogeneous or localised. Scattering centres with different structural properties may be combined to provide, besides optical, also structural characteristics, such as resistance to wear and/or impact. Suitable scatterers comprise opaque objects but largely translucent objects may be used as well, e.g. small air bubbles, glass and/or silica; a requirement is merely that a change in refractive index occurs for the wavelength(s) used.

[0104] The principle of light guiding and spreading light over a surface is well-known and widely applied in various fields. Here, the principle is applied to UV light for the purpose of anti-fouling. It is noted that the idea of making a surface, e.g. the hull of a ship self-lit with UV is a clearly different solution than the current and well established anti-fouling solutions which rely on smooth coatings, chemicals, cleaning, software to control the ship speed, etc.

[0105] Total internal reflection is one way of transmitting light through an optical medium, which is then often referred to as a light guide. To maintain the conditions for total internal reflection, the index of refraction of the light guide should be higher than that of the surrounding medium. However, the use of (partly) reflecting coatings on the light guide and/or use of the reflective properties of the protected surface, e.g. the hull of a ship, itself can also be used to establish the conditions for guiding the light through the optical medium.

[0106] In some embodiments the optical medium may be positioned relative to the protected surface, e.g. the hull of a ship, such that a small air gap is introduced between the optical medium and the protected surface; UV light may travel even betterwith less absorptionin air than in an optical medium, even when this optical medium is designed as a light guiding material. In other embodiments gas-filled channels, e.g. air channels, may be formed within silicone material. An array of separate gas-filled pockets may also be provided, e.g. in a regular pattern like a rectangular or honeycomb-pattern or in an irregular pattern. Instead of gas (e.g. air) filling, channels and/or pockets may be at least partly filled with a UV-transmissive liquid, e.g. fresh and/or purified water. In case a protected surface that is covered with such optical medium is subject to impact, e.g. a ship hitting a dockside, small pockets may soften, redistribute the impact energy and hence protect the surface, wherein liquid-filled pockets may be robuster under deformation than air-pockets which may more easily burst open.

[0107] As most materials have a (very) limited transmittance for UV light, care has to be taken in the design of the optical medium. A number of specific features and/or embodiments, which are dedicated for this purpose are listed in the following: [0108] A relatively fine pitch of low power LEDs can be chosen, to minimize the distance light has to travel through the optical medium. [0109] A hollow structure can be used, e.g. a silicone rubber mat with spacers that keep it a small distance away from the protected surface. This creates air channels, through which the UV light can propagate with high efficiency (air is very transparent for UV). Use of gas filled channels provided by such structures allows distributing the UV light over significant distances in a optical medium of material that would otherwise absorb the UV light too strongly to be useful for anti-fouling. Similarly, separate pockets may be formed. [0110] A special material can be chosen with high UV transparency, like certain silicones or UV grade (fused) silica. In embodiments, this special material can be used only for creating channels for the light to propagate the majority of the distance; a cheaper/more sturdy material can be used for the rest of the surface.

[0111] Further embodiments are disclosed in the accompanying drawings, wherein a main issue is to illuminate a large surface with anti-fouling light, preferably UV light, yet using point light sources. A typical concern is spreading of the light from point sources to surface illumination. In more detail: [0112] The protected surface area of a typical container ship is 10,000 m.sup.2. [0113] A typical LED source has an area of 1 mm.sup.2. This is 10.sup.10 smaller. [0114] Taking the required power levels into account, about 10 LEDs per m.sup.2 may be required [0115] This means light has to be spread from 1 LED over 1000 cm.sup.2 [0116] As another boundary condition is taken that the solution should be thin (order of magnitude: 1 cm), e.g. for reasons such as: [0117] To be able to add the solution as a coating to a ship [0118] To not increase drag due to an increased cross section size of the ship [0119] To keep (bulk) material costs limited.

[0120] The use of an optical medium, in particular a generally planar light guide is therefore provided. Typical dimensions of a light guide are a thickness of about 1 mm to about 10 mm. In the other directions, there is no real limit to the size, from an optical point of view; in particular not if plural light sources are provided so that decay of light intensity throughout the light guide due to partial outcoupling of light and possibly (absorption) losses are countered.

[0121] Here, it is considered that similar optical challenges apply as with the design of LCD TV backlights, although emission light intensity uniformity is less stringent in anti-fouling than with LCD TV backlights.

[0122] Additional ideas and solutions exist to obtain a better uniformity in a thinner optical structure, such as introduction of scatters and/or reflectors or other light spreaders directly in front of one or more light sources.

[0123] FIG. 3 shows (left hand side) inclusion of a light spreader in the form of a reflective cone 25 in the optical medium 220 with an apex towards the light source 210. This directs the light 211 in a direction having a component substantially parallel to the surface 101 to be protected against fouling. If the cone 25 is not fully reflective nor opaque, some light from the light source will pass through it and creation of shadows leading to reduced or ineffective anti-fouling is prevented.

[0124] Further, FIG. 3 shows a wavelength conversion material CM which is comprised in the optical medium 220. The illustrated embodiment is configured to generate at least part of the anti-fouling light by photo-exciting the wavelength conversion material CM with light from a light source 2100 with light 31 having a first wavelength causing the wavelength conversion material to emit anti-fouling light 211 at another wavelength from the optical medium 220 into the environment E, i.e. downstream from the emission surface 222. The distribution of wavelength conversion material in optical medium 220 may be spatially varying, e.g. in accordance with (expected) intensity distributions of (different wavelengths of) light in the optical medium 220.

[0125] The terms upstream and downstream relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the first light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is upstream, and a third position within the beam of light further away from the light generating means is downstream.

[0126] FIGS. 4a-4c 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 as shown in FIG. 4b either through soldering, glueing or any other known electrical connection technique for connecting the LEDs to the chicken wires 4. One or more LEDs can be placed at each node. DC or AC driving can be implemented. In case of DC, the LEDs are mounted as shown in FIG. 4c. If AC is used, then a couple of LEDs in anti parallel configuration is used as shown in FIG. 4c. 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 embed in an optical medium wherein optionally a parallel grid of scattering features are provided as illustrated in FIG. 3.

[0127] Besides anti-fouling application of hulls of ships, the following alternative applications and embodiments are envisioned: [0128] The disclosure can be applied to a wide variety of fields. Almost any object coming into contact with natural water, will over time be subject to biofouling. This can hinder e.g. water inlets of desalination plants, block pipes of pumping stations, or even cover the walls and bottom of an outdoor pool. All of these applications would benefit from the presently provided method, lighting modules and/or system, i.e. an effective thin additional surface layer, which prevents biofouling on the entire surface area. [0129] Although UV light is the preferred solution, other wavelengths are envisaged as well. Non-UV light (visible light) is also effective against biofouling. Typical micro-organisms are less sensitive to non-UV light than to UV light, but a much higher dose can be generated in the visible spectrum per unit input power to the light sources. [0130] UV LEDs are an ideal source for thin light emitting surfaces. However, UV sources other than LEDs can also be used, such as low pressure mercury vapour lamps. The form factor of these light sources are quite different; mainly the source is much bigger. This results in different optical designs, to distribute all the light from a single source over a large area. The concept of light guiding as discussed herein does not change though. Further, a significant contribution of light in desired wavelengths and/or wavelength combinations may be produced.

[0131] Instead of using a thin layer that emits UV light outward in a direction away from the protected surface in order to avoid bio-fouling, biofouling could potentially also be removed by applying UV light from the outside in the direction of the protected surface. E.g. shining a UV light onto a hull or surface comprising a suitable optical medium as described. Thus, a single optical medium emitting anti-fouling light in directions to and away from protected surfaces may be even more efficient.

[0132] FIGS. 5a-5d schematically depict some embodiments and variations of the anti-fouling system. FIG. 5a schematically depicts an anti-fouling lighting system 1 comprising a lighting module 200 and optionally a control system 300. Here, as example of an object 1200 with fouling surface 1201, a vessel 20 with said hull 21 is schematically depicted. The fouling surface 1201 may be (part of) an element 100 and/or the surface of an element or system associated with said object 1200. Element 100 indicates an element of the object, such as e.g. a hull 21 of a vessel 20. In this schematically depicted embodiment, the object 1200 further comprises the anti-fouling lighting system that includes an emissive surface (see below). Hence, the fouling surface 1201 may e.g. also comprise such emissive surface 220.

[0133] The element 100 comprises a first element surface 101 and a second face 102, the first element surface 101 comprising e.g. an area of at least 0.4 m.sup.2. For instance, the second face 102 can be the internal wall of the hull 21 of a vessel 20 (with reference 23 indicating a keel). The first element surface 101 is the face towards the exterior of, in this embodiment the vessel 20, which will during use at least partly be in contact with liquid 5, especially water. The liquid level is indicated with reference 15. As can be seen, at least part of the element 100 is submerged.

[0134] The lighting module 200 comprises a light source and optionally an optical medium 220. Especially, the light source 210 is configured to generate anti-fouling light 211, which may especially include UV light, even more especially at least UV-C light. The optical medium 220 is especially configured to receive at least part of the anti-fouling light 211 and is further configured to distribute at least part of the anti-fouling light 211 through the optical medium 220. The optical medium comprises a first medium face 221, which may for instance have an area of at least 0.4 m.sup.2 and an emission surface 222 configured to emit at least part of the distributed anti-fouling light 211 in a direction away from the first medium face 221 of the optical medium 220. Here, the first medium face 221 is directed to the first element surface 101 of the element 100. In this embodiment, the optical medium 220 is in physical contact to the first element surface 101 of the optical element. For instance, in such embodiment at least part of the lighting module 200 is thus configured to seal at least part of the first element surface 101 with the emission surface 222 configured more remote from the first element surface 101 than the first medium face 221. Further, the lighting system 1 comprises a control system 300 configured to control an intensity of the anti-fouling light 211 as function of one or more of a feedback and a timer. The optional timer is not depicted, but may optionally be integrated in the control system. Alternatively, a sensor, indicated with reference 400, may sense a time signal. Reference 230 indicates a power supply, which may locally harvest energy, or which may e.g. be a battery. Optionally, electrical power may be provided from the vessel. Reference h indicates the height of the element 100.

[0135] By way of example, the power supply 230, control system 300, and sensor 400 are all integrated in the lighting module 200, and form with the optical medium 220 a single unit. The lighting module 200 may substantially cover the entire element 100. Here, by way of example, only part of the 1.sup.st face 101 is covered. In the embodiment depicted in FIG. 5a, the 1.sup.st optical medium surface is attached to the 1.sup.st face of the element 100. FIG. 5b schematically depicts an embodiment, just by way of example, wherein the optical medium is not attached to the element 100; hereby a void 107 may be created. Note that at least part of the lighting unit seals the first element surface of the element 100. Here, by way of example the element is a wall or door or a moveable construction 40, e.g. a dam or sluice. FIG. 5c by way of examples shows a plurality of elements 100, and also a plurality lighting modules 200. The lighting system includes also a plurality of sensors 400, and a single control system 300. Further, the local energy harvesting system 230 may e.g. a photovoltaic cell. The lighting modules 200 may in an embodiment form a single integrated unit, and seal of as a whole the elements 100. With such system, it may be monitored which optical mediums 220 are below the liquid level 15. Only those which are below the liquid level 15 may provide anti-fouling light 211, as indicated in the drawing. Of course, more than the schematically depicted lighting modules may be available. FIG. 5d schematically depicts individual lighting system 1, which may optionally also be coupled. E.g., the control systems 300 may optionally communicate (wireless). However, the lighting systems may also act independently.

[0136] Reference 700 indicates an integrated unit comprising (i) the lighting module 200 and one or more of said sacrificial electrode (see below), said second energy system electrode (see below), an optional control system 300, an optional timer, and an optional sensor 400, wherein the control system 300 may e.g. be configured to control an intensity of the anti-fouling light 211 as function of one or more of (i) a feedback signal from the sensor 400 related to a biofouling risk and (ii) the timer for (periodically) varying the intensity of the anti-fouling light 211.

[0137] The integrated unit 700, as for instance shown in some of the schematically depicted embodiments, may especially be a closed unit, with the emissive surface 221 as one of the faces. In FIGS. 5a-5d the electrodes, etc., are not depicted for the sake of simplicity. These will however further be elucidated below with references to FIGS. 6a-6c and 7a-7e.

[0138] Note that the fouling surface 1201 may in some of the embodiments (also) comprise the emission surface (222), see amongst others FIGS. 5a-5b.

[0139] FIGS. 6a-6c schematically depict some aspects of the anti-fouling lighting system and its application. It is for instance an aspect of the invention to insert UV LEDs and/or other light sources 210 into an electrical circuit that may already be available in an object 1200 having a (steel) fouling surface 1201 and a sacrificial electrode 510 attached thereto, see FIGS. 6a-6c for a comparison between the situation without light source 210 (FIG. 6a), and with a light source (FIGS. 6b and 6c). The dashed line indicates by way of example an electrical return path through the steel fouling surface 1201. The steel hull 21, here the fouling surface 1201, may act as a second energy source electrode 520. In this way, energy system 500 is provided, that may be used to power a light source 210. FIG. 6b shows the introduction of a light source 210 which may illuminate the fouling surface 1201, and which may be powered by the energy system 500.

[0140] FIG. 6c schematically depicts in more detail an embodiment of the anti-fouling lighting system 1 (here also in an embodiment of the closed unit), wherein by way of example the light source 210 is comprised by an optical medium 220. The anti-fouling lighting system is further elucidated amongst others with respect to this embodiment, but the invention is not limited to this embodiment. FIG. 6c schematically depicts an anti-fouling lighting system 1 configured for preventing or reducing (water related) biofouling on a fouling surface 1201 of an object 1200 that during use is at least temporarily exposed to an electrically conductive aqueous liquid, by providing an anti-fouling light 211 to said fouling surface 1201. The anti-fouling lighting system 1 comprises (a) a lighting module 200 comprising a light source 210 configured to generate an anti-fouling light 211; and (b) an energy system 500 configured to locally harvest energy and configured to provide electrical power to said light lighting module 200, wherein the energy system 500 comprises (i) a sacrificial electrode 510 (in electrical connection with a first electrode 251 of the light source 210), and (ii) a second energy system electrode 520 (in electrical connection with a second electrode 252 of the light source 210), wherein the energy system 500 is configured to provide electrical power to the lighting module 200 when the sacrificial electrode 510 and the second energy system electrode 520 are in electrical contact with an electrically conductive aqueous liquid, such as especially seawater (such as liquid 5). The light source 210 is embedded in the optical medium 220. The optical medium 220 comprises a transit 530 for electrical connections 1251,1252 with the light source 210. Here, two transits are available. Note that the optical medium may be a polymer wherein the entire light source may be embedded. Note that surface or hull 21 is (the element with) the surface to be protected. With the arrangement of the lighting unit 1, especially the optical medium 220 to a substantial part of this surface to be protected, the fouling surface translated to a surface of the lighting unit 1, especially the optical medium. Hence, in this embodiment the anti-fouling light will anti-foul the emissive surface 221. Hence, the fouling surface 1201 here comprises of the emissive surface 222 of the optical medium 220. Therefore, in this embodiment in fact emissive surface 222 is the surface to be protected.

[0141] FIGS. 7a-7e schematically depict some aspects of the anti-fouling lighting system and its application. FIGS. 7a and 7b schematically depict in more detail some options and aspects of the invention. Further, FIG. 7a schematically depicts the application of an electrical power enhancer, indicated with reference 580, such as a joule thieve to increase a voltage difference between the first electrode 251 and the second electrode 252 of the light source 210. Additional or alternative to such joule thieve a boost converter (step-up converter) as electrical power enhancer may be applied. A boost converter is a DC-to-DC power converter with an output voltage greater than its input voltage. It is a class of switched-mode power supply (SMPS) containing at least two semiconductors (a diode and a transistor) and at least one energy storage element, a capacitor, inductor, or the two in combination. A joule thieve is a minimalist self-oscillating voltage booster that is small, low-cost, and easy to build; typically used for driving light loads. It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged (or dead). The circuit may use the self-oscillating properties of the blocking oscillator, to form an unregulated voltage boost converter. The output voltage is increased at the expense of higher current draw on the input. Alternatively or additionally, a flyback converter may be applied. The flyback converter can be used in a DC/DC conversion with galvanic isolation between the input and any outputs. More precisely, the flyback converter is a buck-boost converter with the inductor split to form a transformer, so that the voltage ratios are multiplied with an additional advantage of isolation.

[0142] In FIG. 7a, the light of the light source 210 is introduced in the optical medium, such as a fiber or waveguide, from which, optionally after distribution over the optical medium, anti-fouling light may escape (from the emissive surface 222). This anti-fouling light, shown at the top of the drawing, may be used to anti-foul a fouling surface (not depicted). FIG. 7b schematically depicts an option wherein the light source 210 is embedded in the optical medium 220, for instance a silicone foil or tile. The first electrode 251 and the second electrode 252 may extend, here as electrical connections 1251,1252, respectively, through the optical medium and may be accessible from the external from the optical medium 220 via the transits 530. These electrodes may be connected with the respective electrodes of the energy system (not depicted; see above; and see FIG. 7e).

[0143] FIGS. 7c-7d schematically depict some embodiments of the lighting unit 1 wherein in an integrated unit 700 several components are provided. The integrated unit 700 may comprising the lighting module 200 and one or more of said sacrificial electrode 510, see FIG. 7c, and said second energy system electrode 520, see FIG. 7d and optionally one or more of a control system (not depicted), a timer (not depicted) and a sensor (not depicted. Combinations of those two embodiments, such as comprising said sacrificial electrode 510 and said second energy system electrode 520, are of course also possible. The embodiment of FIG. 7c may e.g. be attached to a surface of an object 1200 (not depicted), wherein the surface is e.g. a steel hull. This may also apply to the embodiment of FIG. 7d, though this embodiment may already comprise the second energy system electrode, but this unit will also be electrically connected to a sacrificial electrode (not depicted) via electrical connection 1251.

[0144] Hence, whereas the embodiment of FIG. 7d may need an object including a sacrificial electrode, to electrically connect to the first electrode 251 of the light source, this embodiment does not necessarily need an object with a steel hull or other element that may be used as second energy system electrode 520, as this electrode is already included in the anti-fouling system 1, especially the unit 700. Hence, the type of surface to which this anti-fouling system 1, especially the unit 700 might be applied, may not be limiting. In contrast, whereas the embodiment of FIG. 7c may need an object including a second energy system electrode 520, to electrically connect to the second electrode 252 of the light source, this embodiment does not necessarily need an object with a sacrificial electrode 510, as this electrode is already included in the anti-fouling system 1, especially the unit 700. Here, the type of surface to which this anti-fouling system 1, especially the unit 700 might be applied, may be more limiting. To provide a completely autonomous system, which may be applied to anti-foul any surface, or to protect any surface, the embodiments of FIGS. 7c and 7d may be combined, as schematically shown in FIG. 7d. FIGS. 7a-7e do not depict other optional component, such as schematically depicted in FIGS. 5a-5d. however, of course also the control system, sensor, timer, etc. may also be available, and e.g. integrated in the unit 700. Further, the energy system 700 may also power such optional electronic components.

[0145] Hence, the invention provides an anti-fouling lighting system 1 configured for preventing or reducing biofouling on a fouling surface 1201 of an object 1200 that during use is at least temporarily exposed to an electrically conductive aqueous liquid, by providing an anti-fouling light 211 to said fouling surface 1201, the anti-fouling lighting system 1 comprising: a lighting module 200 comprising a light source 210 configured to generate the anti-fouling light 211; and b an energy system 500 configured to locally harvest energy and configured to provide electrical power to said light lighting module 200, wherein the energy system 500 comprises i a sacrificial electrode 510, and ii a second energy system electrode 520, wherein the energy system 500 is configured to provide electrical power to the lighting module 200 when the sacrificial electrode 510 and the second energy system electrode 520 are in electrical contact with the electrically conductive aqueous liquid.

[0146] Depending on the precise metals used for the anodes, and the precise LED being used, the voltage generated may not be enough to directly power the LEDs. In this case, a simple DC-DC converter can generate higher voltage. E.g. a so-called Joule Thief can work with a voltage as low as 0.35V. The total power required, and hence amount of sacrificial electrode need, can be estimated as follows: [0147] Energy content is about 368 Amp-hours per pound of Zinc; 1108 Amp-hours for aluminum; A current of 3 mA, at a voltage of 3V, will yield 10 mW of electrical power=1 mW of optical power in the UVC range (@ 1% conversion efficiency) [0148] 1 mW of UVC light can prevent bio-fouling on a 1 m2 area. [0149] For a large boat (10,000 m.sup.2), thus 10,000*3 mA=30 A is needed. This consumes (corrodes) one pound of zinc every 12 hours, or about 360 kg/year. Hence, with a relative simply system, and by reusing several already existing components on a ships' hull, a UV anti-fouling system can be powered.

[0150] Hence, anti-fouling solutions that release certain chemicals or biocides currently have a large market share. To be effective, these coatings have to provide an environment which is harsh for living creatures. A drawback is that over timeeither by intended release, or by the inevitable cleaning of the surfacethose chemicals are released into the water. These chemicals quite often remain active, causing adverse effects on the environment. A fundamentally different way of preventing bio-fouling is by using UV light emission. UV light is known to be effective in de-activating or even killing micro-organisms, provided a sufficient dose of a suitable wavelength is applied. An example of such is ballast-water treatment. We will present a new approach for anti-biofouling, in which an UV-light emitting layer is applied on the outside of the hull of a ship. The introduction of UV-LEDs as a light source enables thin, coating like structures, in which the UV light is spread evenly within the surface. Further optical design elements will ensure the light escapes more or less uniformly all over the coating layer. The UV emitting layer will make it reduce the possibility for micro-organisms to attach to the hull or even prevent it. In an experimental setup, we have achieved promising results in keeping a surface free from bio-fouling for an extended period of time. Two elements were arranged in seawater and kept there for four weeks. One was irradiated with UV light; the other was not irradiated with UV light. After four weeks, the former included only fouling at the spot where no UV light was received; the spot itself was free from fouling. The latter element was fully covered with fouling.