Method and arrangement related to heating of wings in wind power plants or other devices

The invention relates to a method for the application of heating mats (10) on a wing/blade of a wind power station or other devices for the purpose of achieving deicing also during operation when necessary. Temperature measurement and de-icing take place by means of pulsed current to the heating mat (10). The invention also relates to an arrangement.

TECHNICAL FIELD

The present invention relates to a method for heating of wings/blades or other devices according to the introduction in patent claim1. The invention also pertains to a device.

BACKGROUND OF THE INVENTION

It is a problem to identify and/or prevent, when needed, the icing over of wings or rotor blades of wind power stations or wind turbines subject to a weather environment where there is a risk for icing.

Purpose of the Invention

One purpose of the present invention is to achieve a method for ice detection, warming and de-icing of wings/rotor blades on wind power stations and similar devices. Another purpose of the present invention is to achieve an attractive device that facilitates the procedure according to the invention. These objectives are achieved through the characteristics defined in the patient claims.

Here it must be pointed out that the present invention is based on certain basic principles described in WO 2015/105439 A1, to which reference is made. According to the present invention a method and a device are achieved that facilitate a well-functioning application on, for example, rotor wings/blades of wind power stations or wind turbines.

Advantages of the Invention

The invention allows an extremely advantageous alternative for the prevention of ice formation on wings according to the above and without the need for operational downtime because of ice formation. This results in substantial economic benefits. The device according to the invention can easily be applied to both wings already in service and newly manufactured wings. Preventative wing warming so that ice formation cannot even begin is also made possible by the invention. Ice detection is also made possible according to the invention. The invention presents many technical and economic benefits.

DETAILED DESCRIPTION OF EMBODIMENT SHOWN

FIG. 1shows a section of a heating mat10according to the invention, which is comprised of an electrically conductive wire11featuring an electrically insulated outer layer so that adjacent cross-wiring is possible without risk of short-circuiting.

The heating mat10is produced through a knitting operation such as illustrated inFIG. 1. It shall be understood that the shape, size, knit pattern and mesh size of the mat can naturally vary according to need and preference. One can use, for example, enameled copper wire11. The desired performance of the heating mat naturally affects the choice of wire diameter and mesh size. The mat depicted, which is single-wire, creates one electrical circuit. If the heating mat is knitted from double wire, two electrical circuits, or alternatively a back-up circuit, can be created. The mesh size can also vary within any given heating mat based on need.

The heating mat10can also be produced in an alternative embodiment through a crocheting operation using an electrically conductive wire11that features an electrically insulated outer layer so that adjacent cross-wiring is possible without a risk of short-circuiting.

It shall be understood that the size, shape and crochet pattern of the mat10can naturally vary according to needs and preference. The same conditions as in the above described knit variation are applicable with respect to wire selection, mesh size, etc. If the heating mat10is made with double wire, then two circuits, or alternatively a back-up circuit, are possible. Here, too, mesh size may vary within any given heating mat according to need.

Stripshaped and insulated electrically conductive wire can also be used in the knitting and crocheting under the abovementioned conditions.

FIG. 2shows a schematic depiction of a heating mat10constructed according to one of the above alternatives, arranged between two carrier layers15,16of an incompletely cured thermoset plastic, which may be reinforced with suitable reinforcement material. The thermoset plastic may be comprised of, for example, polyester, epoxy plastic or polyurethane, and any reinforcement may be of glass fiber or other suitable fibers. Glass-fiber reinforced epoxy plastic has been found to be particularly appropriate.

The incompletely cured carrier layers15,16achieve an adhesion of the heating mat10so that they form a cohesive unit with formability/flexibility such that it can be stored rolled or folded. It is thereby advantageous to temporarily affix one or more temporary protective foils (not shown) to the side/sides of the carrier layer facing away from the heating mat to prevent sticking between carrier layers, such as during transport and subsequent handling.

The mat unit20shown inFIG. 2has been made into a cohesive unit through a certain degree of warming under simultaneous compression.

In the mat unit20shown inFIG. 2, the carrier layers15,16show an overage in relation to the heating mat10at two opposing ends so as to form overhangs. The overhangs of carrier layer15are designated35,36and the overhangs of carrier layer16are designated46,47.

FIG. 3shows a partial cross-section through the mat unit20and here it should be mentioned that if necessary, extra epoxy films (not shown) can also be included in the mat unit20to achieve a good surface finish and good adhesion to the given wing. An epoxy film (not shown) can also be arranged between the heating mat10and one or both carrier layers. Any peel-off films (not shown) are removed prior to installation.

FIG. 4shows a cross-section of a rotor wing/blade50, here, however, it shall be understood that the shape of a rotor wing may naturally vary, as may the cross-section size along a rotor wing. The rotor wing50shows a so-called stagnation point51, the approximate placement of which is indicated in the figure. On either side of the stagnation point the wing50features a pressure side52and a suction side53.

FIG. 5shows an installation procedure according to the invention through placement of a mat unit20according to the invention on a rotor wing50.

A mat unit20is first positioned on the front edge of the wing50, whereupon the protective foils are first removed. The mat unit20will thereby adhere to the surface of the wing. The connecting wires of the heating mat10are then connected to the wires appropriate for this purpose in a cable group80, which is arranged along the rotor wing50. A cover mat70, which may be made from glass fiber reinforced epoxy plastic, for example, such as shown inFIG. 5, is then applied, and on top of the cover mat a lightning conductor90is arranged.

A flexible heating plate100divided into two sections101,102, which may be made, for example, from spring steel or a similarly flexible material with a thickness of approx. 0.5 mm, is then arranged. The plate sections101,102contribute to proper levelling and a good surface finish of the mat unit20and nearby components, which helps contribute to a turbulence free transition to the wing50after completed curing and removal of the plate sections101,102. It shall be understood that the plate100in certain cases can also be made in a single piece or have additional divisions beyond what is shown here.

On the outsides of the plate sections101,102, a number of electrical heat sources (not shown) are arranged, making it possible for the curing heat to be regulated as needed in the different areas. The heating mat10can also be involved in the curing process to ensure adequate curing, and sometimes may serve as the only heat source. The heating mat10can also be used for measuring temperature during curing.

In the example shown the thermoset plastic parts101,102are arranged with a certain overlap such as shown inFIG. 5.

It is also advantageous to arrange a tensioning device110such as in the form of a so-called vacuum bag sealed against the wing50and to vacuum-set the arrangement prior to the curing process in order to maximize contact between the sections of the heating plate and the underlying components. It shall be understood that alternative tensioning devices are possible within the framework of the invention.

The abovementioned curing possibilities thus allow for adequate and desirable curing results.

Once the curing process is complete, the vacuum bag110and the forming plate/curing plate100are removed, after which the results achieved are inspected and any necessary follow-up measures can be taken.

It is also possible to carry out simultaneous installation and curing of two or more mat units20that are closely-spaced or bordering one another, whereby size adjustments of the forming- and curing plate100and the vacuum bag110must be made.

According to another embodiment, the heating mat10can be divided into two different heating mats and mat units20, whereby the dividing line between the two mat units runs preferably along the stagnation line51as defined by the stagnation point of the wing50. It is thereby possible to design the two heating mats10with a small mesh size in their end area along the stagnation line to enable increased warmth.

This has, among other things, the advantage that the two heating mats can be more easily adapted to needs of the various ice formation conditions normally prevailing on the pressure side52and suction side53of the wing50. Application and installation take place according to the principle described above and wiring is completed as necessary for the mat units to be individually controlled.

When using two separate mat units instead of one mat unit, these are connected along the stagnation line, such as by means of epoxy plastic. It shall be understood that further divisions of the heating mats and mat units are, of course, possible within the framework of the invention.

FIG. 6shows a rotor wing50fitted with the device according to the invention. The sections most prone to ice formation along the rotor wings in question50are according to the invention fitted with devices according to the invention.

The heating mat's connecting wires are successively connected to the appropriate line in the cable group80during installation of the mat units20and preferably in such a way that the heating mats are connected in parallel to facilitate individual control. Serial connection is possible in certain cases.

The lightning conductors90which are anchored in the cover mat70are successively joined lengthwise when installing the mat units and connected to the existing lighting protection system.

By varying the mesh size in the knitted or crocheted heating mats10it is possible to adapt the thermal output according to prevailing needs. Mesh size may vary within any given heating mat and be small in the section of the heating mat that will be in contact with the front part of the wing and stagnation point and larger in other parts of the heating mat. It shall be understood that several different mesh sizes can therefore occur within any given heating mat. Here it should also be mentioned that most ice formation usually occurs in the stagnation point.

From the above It shall be understood that the shape, size and detailed design of the mat unit20can be adapted to prevailing needs, whereby it can, for example include more than one heating mat10. Stacked heating mats are also possible with the addition of intermediate epoxy films, for example.

With respect to de-icing, it is usually the most advantageous to heat attack in the area of the stagnation point/stagnation line, which is made possible by the present invention.

The possibilities afforded by the invention, such as continuous temperature monitoring through individual resistance measurement in the heating mats, allow for significant energy savings in that it is possible to initiate blade warming in the correct stage and extent.

In the event of a failure in a given heating mat on a rotor wing the corresponding heating mat on other rotor wings can be temporarily disabled in order to minimize imbalance.

A central computer is also arranged, which is configured for collection of, among other things, measurement data from each heating mat and for individual control of current flow or pulsed current to the heating mats. Wireless communication with two-way communications devices in the rotor wings is thereby established.

The central computer thus monitors any ice formation on the rotor wings and directs the current pattern to the various heating mats. Any damages are also indicated. The central computer can in turn communicate remotely with a control room, for example.

The invention therefore allows different levels of heating along a wing so as to enable absence of ice along the entire wing, which is a major advantage since cooling increases going towards the tip of the wing.

It should be noted that curing usually takes place under use of pulsed current so that the intended curing temperature can be controlled to obtain adequate curing results. The curing process is monitored through pulsed current to the heating mats and resistance measurement.

During use of the device according to the invention the pulsed currents will provide information on the wings's temperature during both monitoring and heating. A precipitation indicator can sometimes serve as an energy-saving add-on.

In an alternative embodiment, a second lightning conductor can also be arranged on the side of the wing50opposite the lighting protection90, which results in even better protection in the event of a lightning strike. In this case, it is advantageous to complete the application of the second lighting protector in the same way as lighting protector90in an equivalent cover mat70, whereby the cable group80can be divided into two cable groups, which among other things is advantageous in heating mats divided along the stagnation line. The lightning conductors and cable groups are joined afterwards as additional mat units20are arranged on the wing in question. The lightning conductors are anchored in the metal tip of the wing and connected to the rest of the lightning protection system in the wind power plant.

The design of the heating plate or plates must naturally be adapted to the abovementioned conditions.

If a thermoset plastic film is applied, such as an epoxy film, on the side of the mat unit20facing away from the wing, the need for heating plates can be reduced to the areas where the cable groups and lightning conductors are located. Other parts of the mat unit20can thereby be cured using the heating mat10. The thermoset plastic film provides a good surface finish.

According to the invention a large number of heating mat units (sections)20are arranged along the length of the wing50. Each heating mat unit20offers the possibility for individual temperature measurement and individual heating during operation and also during downtime. Since heating can be adjusted to need along the length of the wing, substantial energy savings can be realized. This also allows for compensation of imbalance between different wings. Individual temperature measurement in each mat section/mat unit20therefore results in low power consumption and better de-icing.

It is also possible to adjust the size of the given heating mat units20so as to facilitate any future repairs.

A major advantage of producing the heating mat10through a knitting or crocheting process is that the impact of temperature changes in the wire will not have any effect on the mat's outer dimensions.

It is also possible to use more than two parallel wires, such as 5 wires, to adapt the heating performance of the mats to various operating conditions.

The invention is therefore not limited to what has been illustrated and described; changes and modifications to the invention are naturally conceivable within the scope of the following patent claims.