WO2005054672A1

WO2005054672A1 - Method and apparatus for treatment of a part of a wind turbine

Info

Publication number: WO2005054672A1
Application number: PCT/DK2004/000845
Authority: WO
Inventors: Paul Teichert
Original assignee: Pp Energy Aps
Priority date: 2003-12-04
Filing date: 2004-12-06
Publication date: 2005-06-16

Abstract

The invention relates to a method and an apparatus for treatment, in particular cleaning, of a surface of a part of a wind turbine such as a rotor blade or a tower. An apparatus and/or a platform is being placed in such a manner that it may be moved in relation to the surface, and a cleaning process is being performed on at least a part of said surface by the apparatus and/or by a person located on said platform, while the apparatus and/or the platform is moved in steps and/or continuously. The cleaning is performed using carbon dioxide (CO2) for example by supplying a flow of carbon dioxide (CO2) to at least one nozzle that is located in an application head. The invention provides an efficient and environmental-friendly cleaning.

Description

METHOD AND APPARATUS FOR TREATMENT OF A PART OF A WIND TURBINE

Field of the invention

The present invention relates to a method and an apparatus for treatment, e.g. cleaning of a part of a wind turbine such as e.g. rotor blade on a wind turbine.

Background of the invention

Within the field of wind turbines, it is commonly known that in order for a wind turbine to generate an optimal yield, the aerodynamic conditions of the wind turbine, including especially the aerodynamic conditions of the rotor blade, must be met. Thus, the manufacturers of wind turbines place great effort into making the rotor blades as efficient as possible in order to generate a good operating ratio. This does not only include the shape of the rotor blades, but also the surface character of the rotor blade, as it is an object to manufacture a surface which is as smooth as possible.

However, it is also realized that after a somewhat brief period of operation, e.g. six months, the rotor blades of a wind turbine may be so dirty from dust, salt coatings, dead insects, bird droppings and other surface coatings, that the efficiency of a given wind turbine may be reduced by 10 to 15% or even more depending on the relevant wind speed.

Thus, it has been realized that it is desirable to carry out a cleaning of the wind turbine wings on a regular basis, depending on the relevant location of the wind turbine.

Such cleanings have been carried out manually by bringing the wind turbine to a stop and locking it into positions in which the rotor blades point towards the ground. Subsequently, each rotor blade has been rinsed and/or cleaned with water individually and manually by using various arrangements, e.g. platforms, work cabins, to provide the personnel with the necessary work position and height. Such a hoisting arrangement is known from German utility model DE 296 03 278 U in which suspension means are fastened to each of the two rotor blades near the hub of the rotor once the wind turbine has been brought to a stop and with one rotor blade pointing straight downwards. A special work platform with a through-going slit at the bottom has been fixed to these suspension means so that the rotor blade pointing downwards could be inserted into this slit. The work platform has subsequently been hoisted upwards in a stepwise manner, while the crew has rinsed the surface of the rotor blade manually, e.g. with one person located on each side of the rotor blade.

Even with such an arrangement, it is a time-consuming process to carry out a cleaning of the rotor blades of a wind turbine, just as such a known arrangement would probably require the use of machinery, such as a crane, for fixation of the suspension means. Thus, it could be claimed that two individuals, when mid-sized wind turbines are involved, would probably not be able to clean more than 4 wind turbines per day.

Further, in connection with such prior art arrangements where water is used for cleaning of the rotor blades, it is a disadvantage that relatively large amounts of water need to be used. Either, such amounts of water must be brought up together with the work platform or using a hoisting arrangement for hoisting up e.g. water containers, or the water must be pumped up to the platform from ground level. In both cases, the considerable heights, e.g. up till 100 meters and even higher, will require energy consuming and/or special equipment, and in case the water is pumped to the required height, the water must be provided with a considerable pressure in order to overcome the pressure drop caused by the height difference.

Thus, it is an object of the invention to present a method and an apparatus, whereby an improved cleaning of a wind turbine and in particular wind turbine rotor blades may be obtained. Also, it is an object of the invention to present such a method and such an apparatus whereby a significant rationalization and a reduction of costs of the cleaning may be obtained.

Further, it is an object to present a method and an apparatus, whereby an increased efficiency gain may be obtained.

Thus, it is also an object of the invention to present a method and an apparatus, whereby the useful life of the rotor blades may be increased, and whereby the efficiency - and thus the financial gain from a wind turbine - may be improved.

Also, it is an object of the invention to present a method and an apparatus, whereby the treatment of rotor blades, including especially cleaning, may be carried out with environmentally friendly means and with minimal consumption of water and/or, cleaning articles.

Further, it is an object of the invention to present a method and an apparatus, whereby the cleaning of rotor blades may be carried out in an expedient manner with environmentally friendly means and whereby the transportation of relatively large amounts of water or other cleaning fluids may be avoided.

These and other objects are obtained by the invention as will be explained in detail in the following.

Summary of the invention

The invention relates to a method for treatment, in particular cleaning, of a surface of a part of a wind turbine such as a rotor blade or a tower whereby - an apparatus and/or a platform is being placed in such a manner that it may be moved in relation to said surface, - a cleaning process is being performed on at least a part of said surface by said apparatus and/or by a person located on said platform,

- the apparatus and/or said platform is moved in steps and/or continuously, and whereby - said cleaning is performed using carbon dioxide (CO₂).

Hereby, a number of advantages are achieved. The need to transport large amounts of water is avoided, and the carbon dioxide, which is an excellent cleaning solution, can be supplied relatively easily, e.g. from a container containing pressurized carbon dioxide. Further, carbon dioxide has the advantage that it is non-toxic, non- hazardous, non-corrosive and non-flammable. Further, carbon dioxide is also an environmentally friendly substance since it is naturally occurring as a by-product of natural processes and since cleaning with carbon dioxide will not add to global warming. Further, carbon dioxide is cheap and readily available, also caused by the fact that carbon dioxide is available as a by-product of industrial processes. Further, use of carbon dioxide as a cleaning agent does not produce solvent waste and does not require wastewater treatment. It should be mentioned that other cleaning agents may be used in addition to the carbon dioxide according to the invention, and further, extraction of such agents and dissolved dirt like hydrocarbon based grease, insects and water based minerals and salts etc. from the used carbon dioxide is relatively straightforward.

According to an advantageous embodiment, as specified in claim 2, said cleaning process may be performed by means of blasting of pellets or the like, e.g. by dry ice blasting, said pellets comprising carbon dioxide (CO₂).

Hereby a very efficient cleaning process may be obtained, e.g. caused by a relatively high cleaning speed and the nature of the dry ice pellets. Further, as mentioned above, the cleaning method is environmental-friendly since the dry ice is non-toxic and since no waste material, e.g. dirt-containing water, cleaning solutions, blasting material remains etc. is produced apart from the dislodged dirt. The surface treatment is non-abrasive and gentle to the surface of the rotor blade. Further, the transporting of a considerable amount of water, e.g. to the wind turbine site and to work location, e.g. the work platform, located at the rotor blade, is avoided. Thus, water tanks etc. are not needed when using this method, and only the comparatively light and compact containers for pressurized carbon dioxide need to be transported to the site of the wind turbine .

According to a further advantageous embodiment, as specified in claim 3, said cleaning process may comprise the application of carbon dioxide (CO₂) in gaseous form.

Hereby a cleaning method is provided where the carbon dioxide can be supplied at a relatively low pressure which may be advantageous in view of the necessary equipment, while still providing cleaning effects at a relatively high level.

According to an even further advantageous embodiment, as specified in claim 4, said cleaning process may comprise the application of carbon dioxide (CO₂) in liquid form.

Hereby a cleaning method is provided where the carbon dioxide can be supplied at a relatively low temperature, e.g. as liquid carbon dioxide (LCO₂), which may be advantageous in view of the necessary equipment, while still providing cleaning effects at a relatively high level.

According to a still further advantageous embodiment, as specified in claim 5, said cleaning process may comprise the application of carbon dioxide (CO₂) in supercritical form, i.e. at a pressure above 73 bars and a temperature above 31°C.

When using carbon dioxide in supercritical form (e.g. as SCCO₂), an enhanced cleaning effect is achieved. In supercritical from, e.g. in dense gas form, where a liquid like density and a gaseous like diffusion and viscosity is present, an improved solvating power is achieved, e.g. the ability to solvate dirt like hydrocarbon based grease, insects and water based minerals and salts etc. on the surface. Advantageously, as specified in claim 6, said carbon dioxide (CO₂) may be delivered from a container, wherein carbon dioxide (CO₂) is stored in liquid form.

Hereby, it is achieved that the carbon dioxide may be readily delivered from the pressurized container, where preferably the carbon dioxide is in liquid form, e.g. at a pressure of for example 200 bar, and where the carbon dioxide may be supplied directly to nozzles etc. without any further operation, even though it will be understood that the carbon dioxide may be pressurized and/or heated on its way to the surface.

Preferably, as specified in claim 7, at least part of said carbon dioxide (CO₂) may be accumulated for further processing, in particular for reuse, after having been utilized in the cleaning process.

Hereby, the carbon dioxide may be processed in order to accumulate the dissolved and /or dislodged dirt etc., and the carbon dioxide may be reused, e.g. after having performed a condensation in order to liquefy the carbon dioxide.

Advantageously, as specified in claim 8, heat may be applied when said carbon dioxide (CO₂) is applied to said surface.

Hereby, an improved cleaning efficiency may be achieved.

In a preferred embodiment, as specified in claim 9, a mechanical cleaning process may be performed before or after carbon dioxide (CO₂) is applied to said part of said surface.

Hereby, it is achieved that, when combining a mechanical treatment of the dirt etc. with a treatment with carbon dioxide, an improved efficiency is achieved, since for example the treatment may be performed quicker and/or a satisfactory result may be achieved within a shorter time period. Further, as specified in claim 10, a visual monitoring and/or inspection may be performed, e.g. using vision equipment.

Hereby it is achieved that the condition of the surface may be inspected before the treatment takes place, e.g. from ground level, and the result of the cleaning may be monitored. Thus, the operation of the cleaning means may be controlled, e.g. the progress of the cleaning may be inspected and if a specific surface part has not been cleaned to a satisfactory degree, the cleaning process may be prolonged at the specific spot. Further, the cleaning process is allowed to move on as soon as a satisfactory level has been achieved, thus improving the efficiency of the cleaning operation and facilitating a fast operation.

The invention also relates to an apparatus for treatment, in particular cleaning, of at least part of a surface of a part of a wind turbine such as a rotor blade or a tower, said apparatus comprising

- an application head designed to be placed on or near said part of a surface during the cleaning process, said application head comprising shielding means,

- means for supplying a flow of carbon dioxide (CO₂) to at least one nozzle, said at least one nozzle being placed in or on said application head.

Hereby, a number of advantages are achieved. When using this apparatus, the need to transport large amounts of water is avoided, and the carbon dioxide can be supplied relatively easily, e.g. from a container containing pressurized carbon dioxide. Further, carbon dioxide has the advantage that it is non-toxic, non-hazardous, non- corrosive and non-flammable. Also, carbon dioxide is an environmentally friendly substance since it is naturally occurring as a by-product of natural processes and since cleaning with carbon dioxide will not add to global warming. Further, carbon dioxide is cheap and readily available, also caused by the fact that carbon dioxide is available as a by-product of industrial processes. Still further, use of carbon dioxide as a cleaning agent does not produce solvent waste and does not require wastewater treatment. Thus, the apparatus according to the invention will provide an environmentally friendly cleaning to be performed at the relatively highly placed surfaces that are concerned when wind turbines have to be cleaned.

Preferably, as specified in claim 12, said apparatus may be designed for being operated by a person located on a platform or in a work cabin that is placed in such a manner that it may be moved in relation to said surface.

Hereby, the prior art cleaning processes may readily be modified to take advantage of the apparatus according to the invention, since the crew working from platforms etc. may operate the apparatus by hand.

In a further embodiment, as specified in claim 13, said apparatus may be designed in such a manner that at least said application head may be moved in relation to said surface in an at least partly automated manner.

Hereby, the apparatus may be used in a manner that allows a lower degree of manual handling and possibly allows the crew to be situated at ground level instead of being placed at e.g. a platform. The apparatus may form part of an apparatus for treating wind turbines as described in WO 03/048569, e.g. a device that may move controlled and/or automatically in order to treat the surface of e.g. a rotor blade.

Advantageously, as specified in claim 14, said apparatus may comprise container means designed for storing carbon dioxide (CO₂) in liquid form, said container means being located in the vicinity of said application head.

Hereby, it is achieved that the carbon dioxide may be readily delivered from the pressurized container, where preferably the carbon dioxide is in liquid form, e.g. at a pressure of for example 200 bar, and where the carbon dioxide may be supplied directly to the nozzle or nozzles etc. without any further operation, even though it will be understood that the carbon dioxide may be pressurized and/or heated on its way to the surface. In a further embodiment, as specified in claim 15, said apparatus may comprise container means designed for storing carbon dioxide (CO₂) in liquid form, said container means being located at a level below said application head, e.g. at ground or sea level.

Hereby, it is achieved that the part of the apparatus that has to be operated at the high levels, may be smaller and/or lighter, which may be advantageous in many situations.

According to an advantageous embodiment, as specified in claim 16, said application head may comprise blasting means for blasting of pellets or the like, e.g. dry ice blasting pellets, said pellets comprising carbon dioxide (CO₂).

Hereby, a very efficient cleaning apparatus is provided, e.g. caused by a relatively high cleaning speed and the nature of the dry ice pellets. Further, as mentioned above, the cleaning method used by the apparatus is environmental-friendly since the dry ice is non-toxic and since no waste material, e.g. dirt-containing water, cleaning solutions, blasting material remains etc. is produced apart from the dislodged dirt etc. The surface treatment is non-abrasive and gentle to the surface of the rotor blade. Further, the transporting of a considerable amount of water, e.g. to the wind turbine site and to work location, e.g. the work platform, located at the rotor blade, is avoided. Thus, water tanks etc. are not needed when using this apparatus, and only the comparatively light and compact containers for pressurized carbon dioxide need to be transported to the site of the wind turbine.

Advantageously, as specified in claim 17, said apparatus may comprise pumping means for increasing the pressure of the carbon dioxide (CO₂) supplied to the at least one nozzle.

Hereby, it is achieved that the efficiency of the apparatus may be enhanced and that the apparatus may apply the carbon dioxide in the form of e.g. liquid (LCO₂), supercritical (SCCO₂) and/or near-supercritical form. According to a further advantageous embodiment, as specified in claim 18, said apparatus may comprise heating means for increasing the temperature of the carbon dioxide (CO ) supplied to the at least one nozzle.

Hereby, it is achieved that the efficiency of the apparatus may be enhanced and that the apparatus may apply the carbon dioxide in the form of e.g. gaseous, supercritical (SCCO₂) and/or near-supercritical form.

According to an even further advantageous embodiment, as specified in claim 19, said apparatus may comprise heating means located in or on said application head for maintaining or increasing the temperature inside the application head.

Hereby, it is achieved that the temperature of the carbon dioxide may be controlled to attain and/or remain above a desired value in order to achieve a satisfactory efficiency at the location where the carbon dioxide is applied to the surface, i.e. inside the application head.

Preferably, as specified in claim 20, said apparatus may comprise suction means for removing at least part of the applied carbon dioxide (CO₂) from the interior of the application head.

Hereby, the carbon dioxide may be accumulated for further processing.

Advantageously, as specified in claim 21, said apparatus may comprise recirculation means for reusing at least part of the carbon dioxide (CO₂) that is being removed from the interior of the application head by said suction means.

Hereby, an improved cost-efficiency of the apparatus may be achieved due to the reduction in CO₂ consumption, and the weight of the apparatus including containers for carbon dioxide may be reduced, thus also leading to an improved efficiency. In a further preferable form, as specified in claim 22, said apparatus may comprise filtering and/or separating means for separating particles, residues etc. from the carbon dioxide (CO₂) that is being removed from the interior of the application head by said suction means.

Hereby, it is achieved that the dissolved and/or dislodged dirt etc. may be accumulated and taken care of in e.g. a prescribed manner, for example in consideration of environmental requirements.

Advantageously, as specified in claim 23, said apparatus may comprise mechanical cleaning means located in or on said application head.

Hereby, it is achieved that, when combining a mechanical treatment of the dirt etc. with a treatment with carbon dioxide, an improved efficiency of the apparatus is achieved, since for example the treatment may be performed quicker, e.g. the application head may be moved quicker along the surface, and/or a satisfactory result may be achieved within a shorter time period.

Preferably, as specified in claim 24, said mechanical cleaning means may comprise brushes, e.g. rotating brushes.

Hereby, the mechanical cleaning may be performed efficiently when using for example rotating brushes of the same type as those often used in car wash systems. Furthermore, it should be mentioned that such brushes may be positioned in such a manner that the brushes are applied to a surface before the carbon dioxide, or vice versa. Also, it should be mentioned that one single rotating brush with a length corresponding to the width of the application head may be provided, or a plurality of brushes may be applied.

In a further preferable form, as specified in claim 25, said shielding means of said application head may comprise sealing means for sealing against said surface. Hereby, an enhanced efficiency of the apparatus may be achieved, since the temperature and/or the pressure inside the application head may be controlled efficiently and it will be possible to achieve a relatively high temperature and/or pressure inside the application head. Thus, it will be possible to achieve a desired cleaning setting, e.g. using carbon dioxide in liquid (LCO₂), supercritical (SCCO₂) and/or near-supercritical form.

According to a further preferred embodiment as specified in claim 26, said apparatus may comprise equipment for performing a visual monitoring and/or inspection of said surface before, during and/or after the treatment.

Hereby, it is achieved that the condition of the surface may be inspected before the treatment takes place, e.g. from ground level, and the result of the cleaning performed by the apparatus may be monitored. Thus, the operation of the apparatus may be controlled, e.g. the progress of the cleaning may be inspected and if a specific surface part has not been cleaned to a satisfactory degree, the cleaning process may be prolonged at the specific spot. Further, the apparatus is allowed to move on as soon as a satisfactory level has been achieved, thus improving the efficiency of the cleaning operation and facilitating a fast operation when using the apparatus .

Further, is should be mentioned that the invention offers the possibility of a high degree of automation of such treatment processes, just as the treatments may be carried out quicker and more efficiently.

Naturally, this may also result in an increase in the operating ratio of a wind turbine, on which such treatment by such an apparatus has been carried out, just as an increase in the useful life of the wind turbine may be obtained, depending on the nature of treatment, thereby making it a financial gain to the owner and to society.

In particular, it should be mentioned that a number of advantages are achieved when dry ice blasting is used for cleaning the surface of e.g. a rotor blade or a tower of a wind turbine. The cleaning is very effective, e.g. caused by the high cleaning speed and the nature of the dry ice pellets. Further, the cleaning method is environmental- friendly since the dry ice is non-toxic (CO₂ is a natural part of the atmosphere) and since no waste material, e.g. water, cleaning solutions, blasting material remains etc. is produced apart from the dislodged dirt. The surface treatment is non-abrasive and gentle to the surface of the rotor blade. Further, the transporting of substantial considerable of water, e.g. to the wind turbine site and to the apparatus, e.g. the washing robot, located on the rotor blade, is avoided. Thus, water tanks etc. are not needed when using this method, and only the comparatively light and compact containers for pressurized carbon dioxide need to be transported to the site.

Figures

The invention will be described in detail in the following with reference to the drawings, in which

fig. 1 illustrates a prior art cleaning system in connection with a land-based wind mill, fig. 2 illustrates a first embodiment of the invention, fig. 3 is a sectional and schematic view of an application head for an apparatus according to a first embodiment of the invention, fig. 4 is a schematic overview of an apparatus according to further embodiments of the invention, fig. 5 show in a general view a further embodiment of an apparatus according to the invention during treatment of a rotor blade, fig. 6 is a view in a larger scale corresponding to that of fig. 5, fig. 7 shows a modified embodiment of the apparatus shown in fig. 6, and fig. 8 shows a phase diagram for carbon dioxide. Detailed description

Figure 1 illustrates a commonly known land-based wind turbine 1 seen from a position directly in front of the rotor blades. Such a commonly known wind turbine 1 comprises a wind turbine tower 2 positioned on a foundation on the ground 3. A nacelle 4 has been positioned at the top of the wind turbine tower 2, and comprises a generator, gear mechanisms, control equipment, bearings etc., which may be turned depending on the direction of the wind as already known. Thus, the nacelle 4 also carries the rotor hub 7, upon which a number, in this case three - which is most often the case -rotor blades 5, have been placed. These rotor blades 5, often applied in such a manner that they may essentially be turned around a longitudinal axis in correspondence with wind speed etc., may have wing tips 6 as illustrated depending on their type and brand. However, rotor blades without such special wing tips are also known.

An example of a prior art apparatus for treatment, e.g. washing and sealing of the rotor blades 6, is shown in fig. 1 in a stylistic manner and is generally designated 10.

This prior art the apparatus 10 may be able to move in various ways in relation to the rotor blade 6 and it will also be possible to place it or guide it up to and along the rotor blade 6 in various ways, for example using wires (not shown) anchored at the top of the tower or on the rotor hub. As shown in figure 1, a vehicle 8, e.g. a truck, mobile crane or the like, with a mounted crane 9 or a similar hoist or lift arrangement as shown in the figure, is designed to lift the apparatus 10 up towards a rotor blade 6 to be cleaned. Further, this equipment may be designed to move the apparatus up and down along the rotor blade, which, although, will require a crane 9 that will be able to reach to a very considerable height.

Instead, the apparatus 10, e.g. a washing robot, may be guided to the tip of the rotor blade 5, which is placed in a position pointing vertically downwards. Once the washing robot 10 has been guided up to an appropriate position, i.e. a position in which the washing robot 10 may grip around the rotor blade 5, the connection to the crane or the hoist arrangement 9 may be released. The washing robot may then move on its own in an automated manner in relation to the rotor blade, as explained in WO 03/048569. Alternatively, the apparatus may as mentioned be guided up and/or pulled up by means of lines, wires or the like.

As indicated, the washing robot or apparatus 10 is connected to wires and/or hoses 11, which lead down to a unit generally marked 12 via the hoist arrangement 9, and which may e.g. comprise a water tank, tank(s) with cleaning agents, surface treatment means, sealing agents etc., an air compressor etc. as explained in WO 03/048569.

Further, it should be mentioned that the prior art as well as the present invention may also be utilized in connection with sea (or water-based) wind turbines.

An apparatus according to a first embodiment of the invention will now be described with reference to fig. 2 that illustrates a work platform 20 that is suspended by means of lines, wires etc. 21 alongside a rotor blade 5 of a wind turbine. As indicated by 21', the wires 21 may extend down to ground level, or they may reach down only to the platform 20, depending on the type of hoisting arrangement. This embodiment of the cleaning apparatus is illustrated for manual operation as indicated by the worker 24 situated on the platform 20, but as it will be explained later, the invention may also be utilized in a more or less automated manner.

The apparatus comprises an application head 30 that comprises handling means 31, e.g. a handle, by means of which the worker can move the application head along the surface of the rotor blade 5 while the cleaning is performed. On the platform 20 further equipment relating to the apparatus is placed. A carbon dioxide (CO₂) container 36 is connected by means of tubes 38 either directly to the application head 30, for example through the bottom 22 of the platform 20, or indirectly to the application head 30 via auxiliary equipment 40. The auxiliary equipment 40 may comprise such means as a pressure regulator, heating equipment, possible pumping means, electric equipment, control equipment etc., which will explained in further detail later on. The auxiliary equipment 40 is connected to the application head by means of supply lines 42 and further supply lines 44, e.g. comprising electric power cables, to ground level may be provided.

By means of the application head 30 carbon dioxide can be applied to the surface of the rotor blade as a cleaning agent in different manners in dependence on the design of the apparatus, e.g. as a gas spray, a liquid spray, as a carbon dioxide snow spray, as a carbon dioxide pellet spray, e.g. similar to a bead blasting cleaning operation, in which case a supply of compressed air may be preferable as well, and/or as a supply of carbon dioxide in supercritical form (SCCO ) or near super critical form. Thus, the cleaning is performed using e.g. the solvating power of the carbon dioxide in various forms.

In fig. 3 such an application head 30 is shown in a sectional view and in a larger scale than in fig. 2. The application head comprises an encapsulation or shielding means 46, e.g. a box-shaped construction, that is open towards the surface to be cleaned, whereby a cleaning or reaction chamber 48 is produced. Further, the application head 30 may comprise special sealing means 47 in order to create a cleaning chamber that is insensitive not only to wind and temperature, but that also allows the cleaning chamber to have a pressure above the surrounding pressure, thus allowing the carbon dioxide to be applied to the surface with a desired predetermined pressure. Such sealing means 47 may for example be rubber sealings, brush sealing etc., which will be obvious to the skilled person. Further, the application head may be provided with heating means 58 located on the application head, e.g. inside the cleaning chamber 48 as illustrated in order to provide an advantageous temperature in the cleaning chamber in order to provide a desired cleaning condition, e.g. in order to allow the carbon dioxide to be applied to the surface with a specific temperature.

Such heating means 58 may for example be electric heating means that is supplied with electric power via supply lines that are generally designated 42 and may also comprise tubing for providing carbon dioxide to the nozzles 50. It should be mentioned that although two such nozzles 50 are shown in fig. 3, only one may be provided in the application head 30, or more than two may be provided, depending on the size, the application and the design in general of the application head 30 and the complete apparatus.

In fig. 3, mechanical cleaning means in the form of a rotating brush or brushes 56 are also provided for supplementing the cleaning effect of the carbon dioxide. The mechanical cleaning means may be designed in order to treat the surface before it is treated with carbon dioxide or after it is treated with carbon dioxide. Other configurations are also possible, e.g.. carbon dioxide nozzles placed on both sides of the mechanical cleaning means or vice versa.

Finally, as shown in fig. 3, means for removing the applied carbon dioxide, the dissolved and dislodged dirt, etc. is provided in the form of a suction tube 54. This tube 54 may lead to means for reusing the carbon dioxide, or the carbon dioxide may be allowed to escape into free air.

A schematic overview of an apparatus according to further embodiments of the invention is shown in fig. 4.

Here, the application head 30 is shown schematically with the cleaning chamber 48, which is provided with cleaning or solvating carbon dioxide in e.g. pressurized and liquefied form from a container 36, which may be a gas bottle, a container, or a battery of such bottles or containers. The carbon dioxide may be supplied directly to the cleaning chamber, where as explained above the temperature may be controlled by heating means 58 and the pressure is maintained at a certain level caused by the sealing effect of the shielding means 46 and the sealing means 47 that provide efficient sealing to the surface of e.g. a rotor blade. As shown, the apparatus may be provided with pumping means 64 in order to increase the pressure with which the carbon dioxide is provided, and further, heating means 66 may be provided for increasing the temperature of the liquefied carbon dioxide before it reaches the application head 30. As previously explained, the carbon dioxide may be allowed to escape into free air after use, but the carbon dioxide may be led to separator 68, where the dissolved or dislodged dirt etc. may be separated and accumulated 69 for disposal, waste treatment etc.

A filter 60, e.g., an activated carbon filter, may also be provided to further purify the carbon dioxide, and the carbon dioxide may be led to a condenser 62, where the carbon dioxide may be returned to liquid state, e.g. by cooling, in order to be reused in the circuit as indicated.

Above, the apparatus has been described in connection with manual handling, but obviously, the apparatus may be employed in a more or less automated manner, e.g. controlled by a person situated at ground level. This may be put into practice in numerous manners, which will be obvious to a skilled person. In the following, some of these will be illustrated.

Fig. 5 shows a wind turbine corresponding to the wind turbine shown in fig. 1. A vehicle 8 is parked at the root of the tower 2, and anchoring means shown in schematic form and generally designated 72 have been provided at the top of the wind turbine. From here, wires 21 are led down to the vehicle 8, which wires serve to guide and/or transport a carrier arrangement 70 up and down. This carrier arrangement serves to carry at least one application head constructed in general corresponding to the application head described above and the necessary equipment, e.g. containers for carbon dioxide etc., even though it will be understood that some of this equipment may be located at ground level.

This system may be controlled from ground level, and means for, e.g. monitoring and inspecting the progress of the cleaning operation is provided in the form of a vision system, e.g. one or more video cameras (not shown) mounted on the carrier arrangement 70 and connected to display means in or at the vehicle 8. Further, such vision systems may be arranged to perform an automatic control of the operation of the apparatus. Fig. 6 shows a similar carrier arrangement 70 as shown in fig. 5, suspended from anchoring means via wires 21. This carrier arrangement 70 is designed to climb up and down the wires 21, and as described above it may carry one or more application heads for performing a cleaning operation using carbon dioxide. It will be understood that the carrier arrangement 70 may be designed as a part that provides sealing to the rotor blade 5 and thus provides a cleaning chamber that may be shaped as a ring or that may comprise an elongated chamber on each side of the rotor blade, whereby essentially the complete width of the rotor blade may be cleaned while the carrier arrangement travels up or down the rotor blade. As mentioned above, vision equipment will preferably be provided at the carrier arrangement 70.

Fig. 7 illustrates schematically an example of such an arrangement. Here, the carrier arrangement 70 is shown featuring several treatment zones, e.g. the illustrated zones 81, 82 and 83. In the illustrated embodiment, the zones 81 and 83 have been designed as areas with a number of nozzles or the like, which may spray carbon dioxide in any form, e.g. as dry ice pellets, in gaseous, liquid, supercritical or near- supercritical form, onto the surface of the rotor blade 5, and the zone 82 has been designed as a zone for mechanical cleaning, e.g. using rotating brushes. Such a brushing zone may comprise a rotating brush positioned on each side of the rotor blade. Such a rotating brush may be designed with a longitudinally extending middle part, upon which a number of long bristles may be located extending radial outwards. Thus, the brush may be positioned with its longitudinal axis across the carrier 70 so that the bristles will brush the surface of the rotor blade, once the brush is rotated. It is obvious that other forms or brushes may be used and further, it is obvious that the carrier 70 comprises actuators, for instance electric motors, for driving the brushes, and potentially means for adjusting the distance to the rotor blade, if necessary. Sealing means will be positioned at the ends of the carrier arrangement 70.

As previously explained, the cleaning may be performed by means of dry ice blasting, i.e. a blasting method using small, compact dry ice pellets as a blasting material. These pellets or ice crystals are made by letting pressurized carbon dioxide (CO₂), e.g. liquefied CO₂ escape through a nozzle whereby the liquid CO₂ is transformed to small pellets or crystals. These pellets may be accelerated in a jet of compressed air, e.g. similar to ordinary blasting methods, towards the surface, whereby a cleaning of the surface is performed. The speed of the pellets may be adjusted and controlled by means of the compressed air, e.g. by adjusting the pressure, by controlling the throttling of the compressed air etc. When the dry ice pellets have collided with the surface, whereby dirt, grease, dust, salt coatings, dead insects, bird droppings etc. are dislodged and removed, they simply vaporize, leaving no waste material apart from the dislodged material that will normally fall downwards. The pellets collide with the surface at relatively high speeds, whereby the cleaning is enhanced. Nevertheless, the dry ice cleaning is non-abrasive (and adjustable e.g. in dependence upon the pressure of the compressed air) and therefore the surface is treated very gently when this method is used. The source of the CO₂ may be pressure containers that may be supported by the apparatus located on the rotor blade (or the tower) or that may be located on the vehicle or on the vessel. The source of compressed air or the like may preferably be an air compressor situated on the vehicle or on the vessel.

When using this method, only the nozzles for blasting the dry ice pellets and preferably the container for carbon dioxide need to be located at the apparatus placed above ground level at the part of the wind turbine, e.g. the rotor blade, that is to be treated, e.g. cleaned. The compressor for supplying the compressed air can be located at the ground, on the vehicle or on the vessel (in case of sea-based wind turbines), and one or more tubes can be connected to the nozzles. Further, the source of carbon dioxide, e.g. containers for liquefied carbon dioxide, can be placed at the ground, on the vehicle or on the vessel and connected to the nozzles by means of tubes etc.

Further, the necessary control equipment may also be located here. Such an arrangement will be able to provide effective cleaning of wind turbine parts, e.g. rotor blades, even at a considerable height, e.g. 100 meter above ground level and above, which has been confirmed by extensive testing. Further, it is noted that the nozzles for blasting of the ice pellets, e.g. the dry ice pellets may preferably be configured for being arranged controllably in relation to the surface, e.g. for being movably in the horizontal and/or the vertical direction in order to cover all parts of the surface.

A number of advantages are achieved when this method is used for cleaning the surface of a rotor blade. The cleaning is very effective, e.g. caused by the high cleaning speed and the nature of the dry ice pellets. Further, the cleaning method is environmental-friendly since the dry ice is non-toxic (CO₂ is a natural part of the atmosphere) and since no waste material, e.g. water, cleaning solutions, blasting material remains etc. is produced apart from the dislodged dirt. The surface treatment is non-abrasive and gentle to the surface of the rotor blade. Further, the transporting of a substantial amount of water and/or other cleaning agents, e.g. to the wind turbine site and to the apparatus located above ground level, e.g. on the rotor blade, is avoided. Thus, the apparatus according to the invention need not be designed for carrying such heavy loads. Also, it is noted that with this method it is possible to adjust the treatment, e.g. the cleaning procedure to the surface in question by regulating the blasting pressure, e.g. the compressed air by means of which the dry ice pellets are blasted towards the surface.

Cleaning with dry ice pellets may be used independently or may be combined with other cleaning methods.

It should be noted that an apparatus according to the invention may be provided with other equipment, for instance equipment for control and/or inspection of the rotor blade, to determine the condition of the fibre glass surface etc. Such equipment may as explained above comprise vision equipment which may also serve for guiding for the apparatus, for detecting the degree of surface soil etc.

It should also be noted that the apparatus may be provided with lighting equipment so that utilization of the apparatus according to the invention at all times of day and around the year is made easier. In order to further illustrate the forms and conditions under which carbon dioxide may be utilized in accordance with the invention, a phase diagram for carbon dioxide is illustrated in fig. 8. Here, the different phases of carbon dioxide are shown, and the critical point for transition to the supercritical state is indicated, i.e. at a temperature of app. 31°C and a pressure of app. 73 bars.

Above, the invention has been described with reference to specific embodiments illustrated by the figures. However, it is apparent that the invention may be varied in several ways within the scope of the accompanying claims.

It should also be noted that by the design of the apparatus, it is ensured that it has as low a weight as possible which is advantageous in terms of cost efficiency and in terms of the apparatus moving easily and safely up and down.

It is also noted that even though the methods and the equipment, that have been described above, have been exemplified particularly for treatment of rotor blades, it is evident that these methods and this equipment according to the invention may be utilized for treating other parts of a wind turbine such as for example the tower of a wind turbine. Thus, where the method or the apparatus according to the invention has been exemplified above specifically in relation to a rotor blade, similar will apply when the rotor blade is substituted by e.g. a tower of a wind turbine.

Reference list

1 Wind turbine

2 Wind turbine tower 3 Ground

4 Nacelle

5 Rotor blade

6 Wing tip

7 Rotor hub 8 Vehicle

9 Crane or hoist device

10. Apparatus for treatment, for instance washing of rotor blade; washing robot

11 Hose or wire connections 12 Supply tank etc.

20 Work platform

21, 21' Lines, wires and the like

22 Bottom of work platform

24 Worker 30 Application head

31 Handling means

36 Carbon dioxide container

38 Tubes for carbon dioxide

40 Auxiliary equipment 42 Supply lines to application head

44 Supply lines to ground level

46 Shielding means

47 Sealing means

48 Cleaning chamber 50 Nozzle

54 Suction tube

56 Rotating brush Heating means in cleaning chamber Filter Condenser Pumping means Heating means Separator Accumulated and separated dirt, etc. Carrier arrangement Anchoring means Nozzle zones Brushing zone

Claims

Patent Claims

1. Method for treatment, in particular cleaning, of a surface of a part of a wind turbine such as a rotor blade or a tower whereby - an apparatus and/or a platfonn is being placed in such a manner that it may be moved in relation to said surface,

" - a cleaning process is being performed on at least a part of said surface by said apparatus and/or by a person located on said platform, - the apparatus and/or said platform is moved in steps and/or continuously, and whereby - said cleaning is performed using carbon dioxide (CO₂).

2. Method according to claim 1, whereby said cleaning process is performed by means of blasting of pellets or the like, e.g. by dry ice blasting, said pellets comprising carbon dioxide(CO₂).

3. Method according to claim 1 or 2, whereby said cleaning process comprises the application of carbon dioxide (CO₂) in gaseous form.

4. Method according to one or more of claims 1 to 3, whereby said cleaning process comprises the application of carbon dioxide (CO₂) in liquid form.

5. Method according to one or more of claims 1 to 4, whereby said cleaning process comprises the application of carbon dioxide (CO₂) in supercritical form, i.e. at a pressure above 73 bars and a temperature above 31°C.

6. Method according to one or more of claims 1 to 5, whereby said carbon dioxide (CO ) is delivered from a container, wherein carbon dioxide (CO ) is stored in liquid form.

7. Method according to one or more of claims 1 to 6, whereby at least, part of said carbon dioxide (CO₂) after having been applied in the cleaning process is accumulated for further processing, in particular for reuse.

8. Method according to one or more of claims 3 to 7, whereby heat is applied when said carbon dioxide (CO₂) is applied to said surface.

9. Method according to one or more of claims 1 to 8, whereby a mechanical cleaning process is performed before or after carbon dioxide (CO₂) is applied to said part of said surface.

10. Method according to one or more of claims 1 to 9, whereby a visual monitoring and/or inspection is performed, e.g. using vision equipment.

1 1. Apparatus for treatment, in particular cleaning, of at least part of a surface of a part of a wind turbine such as a rotor blade (5) or a tower (2), said apparatus comprising

- an application head (30) designed to be placed on or near said part of a surface during the cleaning process, said application head comprising shielding means (46), - means for supplying a flow of carbon dioxide (CO₂) to at least one nozzle (50), said at least one nozzle (50) being placed in or on said application head (30). ,

12. Apparatus according to claim 11, wherein said apparatus is designed for being operated by a person (24) located on a platform (20) or in a work cabin that is placed in such a manner that it may be moved in relation to said surface (5).

13. Apparatus according to claim 11, wherein said apparatus is designed in such a manner that at least said application head (30) may be moved in relation to said surface (5) in an at least partly automated manner.

14. Apparatus according to one or more of claims 11 to 13, wherein said apparatus comprises container means (36) designed for storing carbon dioxide (CO ) in liquid form, said container means (36) being located in the vicinity of said application head (30).

15. Apparatus according to one or more of claims 11 to 13, wherein said apparatus comprises container means (36) designed for storing carbon dioxide (CO₂) in liquid form, said container means (36) being located at a level below said application head (30), e.g. at ground or sea level.

16. Apparatus according to one or more of claims 11 to 15, wherein said application head (30) comprises blasting means for blasting of pellets or the like, e.g. dry ice blasting pellets, said pellets comprising carbon dioxide (CO₂).

17. Apparatus according to one or more of claims 11 to 16, wherein said apparatus comprises pumping means (64) for increasing the pressure of the carbon dioxide (CO₂) supplied to the at least one nozzle (50).

18. Apparatus according to one or more of claims 11 to 17, wherein said apparatus comprises heating means (66) for increasing the temperature of the carbon dioxide (CO₂) supplied to the at least one nozzle (50).

19. Apparatus according to one or more of claims 11 to 18, wherein said apparatus comprises heating means (58) located in or on said application head (30) for maintaining or increasing the temperature inside the application head.

20. Apparatus according to one or more of claims 11 to 19, wherein said apparatus comprises suction means (54) for removing at least part of the applied carbon dioxide (CO₂) from the interior of the application head (30).

21. Apparatus according to claim 20, wherein said apparatus comprises recirculation means (68, 60, 62, 64) for reusing at least part of the carbon dioxide (CO₂) that is being removed from the interior of the application head (30) by said suction means (54).

22. Apparatus according to claim 20 or 21, wherein said apparatus comprises filtering (60) and/or separating means (68) for separating particles, residues etc. from the carbon dioxide (CO₂) that is being removed from the interior of the application head (30) by said suction means (54).

23. Apparatus according to one or more of claims 11 to 22, wherein said apparatus comprises mechanical cleaning means located in or on said application head.

24. Apparatus according to claim 23, wherein said mechanical cleaning means comprises brushes, e.g. rotating brushes (56).

25. Apparatus according to one or more of claims 1 1 to 24, wherein said shielding means (46) of said application head (30) comprises sealing means (47) for sealing against said surface.

26. Apparatus according to one or more of claims 11 to 25, wherein said apparatus comprises equipment for performing a visual monitoring and/or inspection of said surface before, during and/or after the treatment.