NO331394B1 - Procedure with associated devices for maintenance, repair and replacement of larger or machine components for wind turbines at sea - Google Patents

Description

The present invention relates to a method and related devices for maintenance, repair and replacement of larger or smaller machine components for wind turbines at sea.

The lifetime of the wind turbine tower itself is significantly longer than the lifetime of the propeller blades in the propeller group and the energy-producing machine components in the nacelle. Furthermore, it must be expected that technical development will progress so that there will be a practical/economic need to replace all or parts of the energy-producing components, perhaps several times, during the lifetime of the windmill.

Large and expensive lifting cranes, which are currently necessary when installing wind turbines at sea, can be very difficult to obtain at short notice, when there is a real need to keep the electrical energy production going. Lifting operations with lifting cranes at sea and at great heights are very dependent on low wave heights and not least small swells. In addition, it is very risky in terms of work to send, when lifting down, or to receive parcels, when lifting, of machine components, etc. up on top of a tall tower, even under favorable wind conditions. Waves, swells and wind cause the top of the windmill tower and the crane boom to sway out of sync and make such lifting operations very dependent on the aforementioned factors. The risk that there will be a waiting period to obtain acceptable wind and sea conditions is very large and thus disadvantageous in terms of costs.

The main purpose of the invention was to arrive at a working safe and easy access to the energy-producing nacelle and the propeller blades for maintenance,

repair and replacement of major or minor machine components, etc. without having to climb to a height of 70m or more, in order to carry out control and precision work in a nacelle swaying in the wind. For floating wind turbines, the movements are even greater than for wind turbines with fixed foundations.

A further purpose was to be able to eliminate the need for the use of lifting cranes to replace worn out/wrecked machine components, propeller blades, etc.

Another purpose was to avoid work operations with the use of external personnel such as mountain climbers or similar specialists who hang from ropes, around the propeller blades installed at high altitude, for maintenance and repair of these.

The special features of the invention are as defined in the associated patent claims.

The invention will be explained in more detail during the description of the drawings.

Figure 1 shows a windmill that is founded on or in the seabed (16). The foundation

(1) is built from suitable materials such as concrete or steel or a combination of concrete and steel. Figure 2 shows a windmill where the foundation (1) floats in the water and is anchored to the seabed with anchoring chains/cables (15). The floating foundation (1) is built from suitable materials such as steel or concrete or a combination of steel and concrete. Figure 3 shows a structure (8) which will later be used to carry out maintenance and/or repair work on the propeller group's rotor blade (17) under dry and windless working conditions. It is then towed to the windmill by/on a boat (7). The construction (8) is anchored to the windmill at its upper edge so that the side can be straightened so that a rotor blade (17) can be lowered into it. Figure 3 shows that one of the rotor blades (17) is set in a vertical position for this. Figure 4 shows the steel structure (8) aligned and anchored (9) to the foundation structure (1) at its lower edge. The upper parts of the windmill, tower (3) and lower part (13) with nacelle (4) and rotor blade (17), have been lowered and where the nacelle (4) has come level with the access platform (14) and the boat/barges (19) and or (11). Figure 5 shows that the rotor blade (17) has been detached from the nacelle (4) and suspended in the access/work platform (14) above the foundation (1). The nacelle (4) with other rotor blades can thus be lifted or slid onto a barge (11) for transport to a land-based workshop for maintenance/repair or to be replaced with a completely new nacelle (4). Figure 1 shows a wind turbine that is founded on the seabed. The foundation structure (1) can be built of concrete or steel or a combination of concrete and steel, where the central core is designed as a large tube (6). The inner surface of the tube (6) is designed with a surface structure that enables the tube (6) to function as the outer part of a very large lifting and/or lowering cylinder. The lower part of the windmill tower (13) is designed like a piston but has a support ledge where removable sections (2) have been mounted as a wreath around the piston (13). The demountable sections (2) have their own supports on the upper side of the upper part of the foundation structure (1). This wreath of sections (2) transfers the vertical load from the wind turbine tower (3) and (13), the nacelle (4) with the propeller group (17) to the foundation structure (1).

The foundation structure (1) in turn transfers the load to the seabed. Between the lower part of the wind turbine tower (13) and the pipe (6), inside the foundation structure (1), there are arranged two flanges (5A) and (5B) for transferring the load moment such as the horizontal loads from wind, eccentric loads from the tower (3), the nacelle (4) and the propeller group (17), etc., to the foundation structure (1) during the wind turbine's normal operating hours. In connection with wanting to lower the nacelle (4), the hydraulic pressure is removed on the two flanges with jacks (5A) and (5B). The load moment is then taken over by two rings of sliding devices (18A) and (18B) which sit between the lower part of the wind turbine tower (13) and the pipe (6). The sliding devices (18A) and (18B) slide against the inner surface of the tube (6). Figure 2 shows a windmill that floats in the sea and is anchored (15) to the seabed. The floating foundation structure (1) is built from suitable materials such as concrete or steel or a combination of concrete and steel. Otherwise, all other solutions and devices are identical to the description according to Figure 1. Figure 3 shows the steel structure (8) which will later be used to carry out maintenance and/or repair work on the propeller group's rotor blade (17) under dry and windless working conditions. It is towed/transported to the windmill by/on a boat/barge (11). The construction (8) is anchored to the windmill at its upper edge so that the side can be straightened so that the rotor blade (17) can be lowered into the construction (8). One of

the rotor blades (17) are therefore placed vertically within the immersion.

Figure 4 shows the upper parts of the windmill, towers (3) and (13) with the nacelle (4) and rotor blade (17) submerged and where the nacelle (4) has reached the deck level of the access and/or maintenance boats (19) used. The vertical rotor blade (17) is threaded into the structure (8) for inspection and maintenance, under dry and windless working conditions. Figure 5 shows that the rotor blade (17) has been detached from the nacelle (4) and suspended in the structure (8). The nacelle (4) can then be slid (12) over to a freight barge (11), without the use of any crane arrangement, for transport into port for total maintenance or, alternatively, be replaced with a new nacelle (4).

The very common size of the tower constructions (3) used today at sea is so large that, even with a water pressure equivalent to that of a tap in a normal residential building, it is capable of taking over, lowering or lifting loads of 500 -800 tonnes. Said lifting power is considerably more than what the actual wind turbine tower (3) and (13) with nacelle (4) and propeller group (17) weighs today. When the necessary repairs/maintenance or replacement of machine components have been done, the entire submersion operation is reversed and the wind turbine tower (3) and (13) with nacelle (4) and rotor blade (17) can be lifted back into place for further production of electrical wind energy.

With the present invention, a method has been arrived at with devices to be able to maintain, repair or replace larger or smaller machine components in the energy-producing nacelle (4) as well as the propeller blades, for wind turbines installed at sea down at the same level as the access boat (19 ) or the barge (11).

The method and devices can be used both for wind turbines that are installed on foundations that stand on the seabed or for floating wind turbine installations. In addition, the complete nacelle (4), where the downwardly protruding propeller blade (17) has been freed from the nacelle (4) and the propeller blade (17) suspended in the foundation structure (1), can easily be moved/slide the nacelle (4) onto a barge (ll) or similar without the use of any form of lifting crane. The nacelle (4) can then be transported to port for a complete renovation or to be replaced with a completely new nacelle (4). The nacelle (4) can then be transported back to the field for assembly on the submerged wind turbine tower (3) and (13), be connected to the waiting rotor blade (17) and then be lifted up to its production level.

For wind turbines with bottom foundations in shallow water where there is not enough height to be able to lower the upper tower part (3) into the foundation, the piston unit (13) is made up of several parts of piston units (13) that go inside each other so that the nacelle (4) can nevertheless is lowered to the level of the access boats (12).

The method and associated devices, according to the invention, can also be used in connection with predicted extreme weather by lowering the nacelle (4), together with the tower parts (3) and (13) and the propeller group (17), down to a lower and safer level for to reduce/eliminate any damage to the wind turbine structure, the nacelle (4) or the propeller group (17).

Claims (3)

1. Procedure for carrying out maintenance, repairs, replacement of major or minor machine components of the existing energy-producing nacelle (4) as well as maintenance, repair of the rotor blades of the propeller group for fixed-foundation or floating wind turbines at sea, and that the wind turbine tower (3) is extended down into a vertical tubular chamber (6) in the center of the windmill foundation (1) so that the tower (3), which is mounted on a nacelle (4) with an energy-producing propeller group, can be lowered/raised, inside the pipe (6), characterized by two rings of preferably horizontal jacks (5A) and (5B) and two rings of sliding devices (18A) and (18B) are arranged around the tower (3)'s extending part (13) as well as a sealing gasket at the bottom of the tower extension (13) against the inner surface in the tubular chamber (6) in the wind turbine foundation (1), so that the tower extension (13) forms a piston for the immersion and raising of the tower structure (3) and (13) as well as the nacelle (4) with the propeller group (17), as the immersion is done at first pumping a pressure medium, preferably seawater, into the pipe (6) and then removing the flange of the support sections (2) and submerging the whole by releasing the pressure medium from the pipe (6), and where said horizontal jack group (5A) and (5B) and the sliding device groups (18A) and (18B) transmit respective horizontal loads from the tower (3) and the nacelle (4) with the propeller group (17) to the foundation structure (1), and where the tower structure (3) and the nacelle (4) with the propeller group's lower rotor blade (17) , set in a vertical position, can be lowered into or lifted up from a sheath-like space on the partially submerged structure (8) for maintenance, repair of said rotor blade (17) under dry, wind-free and safe working conditions, or where the structure (8), with the rotor blade ( 17), is towed or goes by own machine to shore for replacement of the rotor blade (17). 2. Method according to claim 1, characterized by the tubular chamber (6) in the wind turbine foundation (1) and the lower part (13) of the wind turbine tower (3), both are designed as a square with rounded corners, oval or similar section, to be able to transfer torsional loads from the rotation of the nacelle around the tower structure (3) to the foundation (1). 3. Method according to claims 1 and 2, characterized by the windmill foundation (1) and the lower part of the windmill tower (13) are built from suitable materials such as concrete, preferably cast with sliding formwork, or steel or a combination of concrete and steel.