In previous comment dated 02/07/2022, we have provided a summarized review of "WIND ENERGY. Offshore Wind Turbine. Patent Database. June 2022" and basic statistical data from it. Now we will take a closer look at one of the important aspects of wind power plant operation.
In recent years, there has been an increase in patenting activity in the field of technical solutions related to the detection and elimination of ice accretions on wind turbine blades. The importance of this aspect of wind farm operation, especially in cold climate conditions, is confirmed by the fact that it directly affects both the efficiency level of power generation and the volume of operations related to maintenance and repair of wind turbines, which in turn affects the cost-efficiency of the entire power plant and creates additional risks to maintenance personnel.
Following is a brief analysis of inventions related to ice detection and de-icing means for wind turbine blades. More than 200 patent documents published in the recent years were selected for the analysis by using Advanced Energy Technologies methodology. The documents collected for this analysis were published in 14 patent offices of the world by 59 applicants from 14 countries.
In the recent years the number of documents to some extent aiming at solving the problem of ice accretion on wind turbine blades has noticeably grown, which indicates that this is an important issue that attracts attention of major wind turbine developers. The number of start documents that didn’t belong to previously formed patent families in general was about 40%. There was also a substantial number of new IPC subgroups, new applicants, and new patent offices appearing in the collection of documents on this subject in recent years, which shows that it greatly expands in terms of geography and technical coverage, and that new companies are willing to participate in the patenting process.
EPO, USPTO (US), CIPO (CA), and CNIPA (CN) are the offices where the largest number of recent patents were granted. Almost 25% of all patents collected for the present review were granted by EPO, while for USPTO (US) this value is almost 24%. In recent applications the leading offices are essentially the same, except for CNIPA (CN) holding the leading position with more than 56% of all collected applications, and WIPO appearing in the top 5 offices list.
In both cases, residents of Germany, Denmark, and China are the most active participants of the patenting process, in total accounting for about 78% of all cases in recent patents and about 86% in recent applications.
In the collection of recent patents related to de-icing of wind turbine blades, Vestas Wind Systems A/S and Wobben Properties GmbH have a strong lead by the number of documents they participated in. They are followed by General Electric, Nordex Energy Gmbh, and Senvion Deutschland GmbH. By the number of registered patent applications, Wobben Properties GmbH also is well ahead of the other participants, which are Siemens Gamesa Renewable Energy A/S, Senvion Deutschland GmbH, Vestas Wind Systems A/S, and others.
In the collection of recent patents, Vestas Wind Systems A/S (DK) and Wobben Properties GmbH (DE) are sharing the first place in terms of Market involvement ratio (Market involvement ratio = volume ratio multiplied by ownership ratio, where Volume ratio - share of applicant documents in total number of documents, Ownership ratio - applicant's participation share in total number of documents) each having a value slightly above 17%. They are followed by General Electric (US) and Nordex Energy Gmbh (DE) with almost 6% each. In recent applications, the undisputed leader is Wobben Properties GmbH (DE) with more than 20%, while the second and third places are taken by Siemens Gamesa Renewable Energy A/S (DK) and Senvion Deutschland GmbH (DE) with about 8% and 7%, respectively.
Generally, both in patents and patent applications the authors presented their ideas in the form of devices. Methods are encountered in a much smaller amount, while the number of inventions disclosing new compositions is negligible. Besides the IPC subgroup that concerns ice detection and de-icing means (F03D80/40) the most popular IPC subgroups here were F03D1/06 (Rotors), F03D80/60 (Cooling or heating of wind motors), F03D17/00 (Monitoring or testing of wind motors, e.g. diagnostics), and F03D80/00 (Details, components or accessories not provided for in groups F03D 1/00-F03D 17/00).
The largest patent family in the pool of documents collected for the present analysis includes 24 patent documents and is represented by core document WO2012059466A1 (Core document is a base document for which a complete description of the invention is available in generally-accessible patent databases). It is followed by patent families with core document US20160047356A1 (23 patent documents) and US20150204311A1 (22 documents):
ROTORBLATT MIT HEIZVORRICHTUNG FÜR EINE WINDENERGIEANLAGE (en: ROTOR BLADE WITH HEATING DEVICE FOR A WIND TURBINE) / A: WO2012059466A1 / IPC: F03D11/00 / LENSCHOW GERHARD / WOBBEN PROPERTIES GMBH, LENSCHOW GERHARD / Appl. date: 31/10/2011; Publ. date: 10/05/2012 / World Intellectual Property Organization / Core document: WO2012059466A1 / Technology categories: HWT / Technology elements: B / Problems: LEN / Technical solution types: D / Claims: 5 / Rating: 9
ROTOR BLADE OF A WIND TURBINE / A: US20160047356A1 / IPC: F03D1/06, F03D11/00, F03D1/00 / PAWlS Torsten, MIDDELSTADT Falk, SCHULZE Thomas, RUBNER Florian / WOBBEN PROPERTIES GMBH / Appl. date: 09/04/2014; Publ. date: 18/02/2016 / United States Patent and Trademark Office / Core document: US20160047356A1 / Technology categories: HWT / Technology elements: B / Problems: LEN / Technical solution types: D, M / Claims: 17 / Rating: 13
CFRP RESISTIVE SHEET HEATING / A: US20150204311A1 / IPC: F03D11/00, H01T4/08, H01T4/02, F01D5/14 / Clemens Christian / Wobben Properties GmbH / Appl. date: 06/08/2013; Publ. date: 23/07/2015 / United States Patent and Trademark Office / Core document: US20150204311A1 / Technology categories: WTU / Technology elements: B / Problems: LEN / Technical solution types: D / Claims: 19 / Rating: 11
Following are several examples of patent documents with the highest rating calculated using Advanced Energy Technologies methodology, from the collection of documents related to de-icing of wind turbine blades:
Wind energy. De-icing of blades. Prominent patent documents by rating:
Heating installation arrangement / P: EP3069020B1 / IPC: F03D1/06, F03D13/10, F03D80/40 / Cuoghi Joe, Edwards Adrian, Gregory Karl, Mccarroll Catherine Anne, Todd Paul / Vestas Wind Sys As / Appl. date: 10/11/2014; Publ. date: 10/10/2018 / European Patent Organisation / Core document: WO2015067278A1 / Technology categories: WTU / Technology elements: B / Problems: HOR, LEN / Technical solution types: D, M / Claims: 24 / Rating: 20
Heating installation arrangement / P: CA2929898C / IPC: F03D1/06, F03D80/40 / Cuoghi Joe, Edwards Adrian, Gregory Karl, Mccarroll Catherine Anne, Todd Paul / Vestas Wind Sys As / Appl. date: 10/11/2014; Publ. date: 26/06/2018 / Canadian Intellectual Property Office / Core document: WO2015067278A1 / Technology categories: WTU / Technology elements: B / Problems: HOR, LEN / Technical solution types: D, M / Claims: 24 / Rating: 20
Fixation of a heating mat to a blade of a wind turbine / P: EP2526292B1 / IPC: B64D15/12, F03D80/40 / Lind Soeren Oemann, Madsen Finn Daugaard, Schibsbye Karsten / Siemens Ag / Appl. date: 16/09/2010; Publ. date: 01/05/2019 / European Patent Organisation / Core document: US9341164B2 / Technology categories: WTU / Technology elements: B / Problems: HOR, LEN / Technical solution types: D, M / Claims: 13 / Rating: 20
Heating installation arrangement / P: US10428802B2 / IPC: F03D80/40, F03D1/06, F03D13/10 / Cuoghi Joe, Edwards Adrian, Gregory Karl, Mccarroll Catherine Anne, Todd Paul / Vestas Wind Sys As / Appl. date: 10/11/2014; Publ. date: 01/10/2019 / United States Patent and Trademark Office / Core document: WO2015067278A1 / Technology categories: WTU / Technology elements: B / Problems: HOR, LEN / Technical solution types: D, M / Claims: 25 / Rating: 19
用于风力涡轮机叶片的加热设备结构 (en: Heating device configuration for a wind turbine blade) / P: CN105705787B / IPC: F03D1/06, F03D80/40, F03D80/60 / J·科吉, A·爱德华兹, K·格雷戈里, C·A·麦卡罗尔, P·托德 / 维斯塔斯风力系统集团公司 / Appl. date: 10/11/2014; Publ. date: 17/07/2018 / National Intellectual Property Administration / Core document: WO2015067278A1 / Technology categories: WTU / Technology elements: B / Problems: HOR, LEN / Technical solution types: D, M / Claims: 19 / Rating: 19
System and method for detecting ice on a wind turbine rotor blade / P: CA2909172C / IPC: F03D7/02, F03D80/40 / Castro Jorge Gonzalez / Gen Electric / Appl. date: 19/03/2014; Publ. date: 04/09/2018 / Canadian Intellectual Property Office / Core document: US20140308122A1 / Technology categories: HWT / Technology elements: B, CSS / Problems: HOR, LEN / Technical solution types: D, M / Claims: 20 / Rating: 19
In the recent patents and patent applications related to the technologies of ice removal from wind turbine blades or ice detection techniques, the most commonly mentioned problem was Low efficiency caused by secondary natural factors. In both cases it was followed by High OPEX / Repair and replacement and High OPEX / Operational maintenance. The problem of Environmental and social impact can be encountered less often, yet it demonstrates a growth trend in the recent years.
Several examples of patented solutions that concern some of the mentioned problems with regards to de-icing of wind turbine blades are provided below:
US10428802B2 – improved accessibility for technicians is ensured by a heating arrangement allowing air to pass through a heating device within the blade and having dedicated access points to its elements.
US10066608B2 – a method for repairing a heating element of a blade by applying electrically insulating and thermally conductive repair layer. The method is aimed at simplifying the repair process.
US20190078558A1 – ice accretion on a blade is prevented by directing hot air from a heater through flow paths to exhaust holes and under a cover plate on the blade. Such blade structure is also aimed at reducing noise effect of the blade.
US9885343B2 – safety of ice removal operations is achieved by using a servicing tool that is located on a carriage inside the blade, can move along its length, and can be projected out of it through special gates.
US9638168B2 – wind turbine shutdown time is reduced by a method of detecting ice on a blade involving monitoring the amount of torque required to maintain the blade at the fixed pitch angle and comparing it to baseline data.
High OPEX / Repair and replacement
Patent US10428802B2 discloses a heating arrangement for a wind turbine blade. The heating arrangement comprises a platform in a form of a sleigh within the blade. The sleigh has a U-shaped recess that forms a lower portion of an air flow channel with an air input and an air output, between which a heating device (a heater or a fan) is positioned on special connection points. Sections of the recess form a ducting portion to channel air flow through the heating arrangement. The output directs heated air flow into the blade. The heating arrangement has upper portion sections attached to the sleigh over the recess to form ducting for channeling air flow. The sleigh has ribs for attachment to the blade structure. The ribs comprise an indentation on an outer edge to form a moisture channel, and access points for access to an area below the sleigh. An electrical junction box is used to connect the heating device to control and power lines. The heating arrangement is decoupled from loads, vibrations, and noise by flexible ducting.
The authors of the invention mention hindered accessibility for technicians as one of the drawbacks of the prior-art solutions.
The patent belongs to a family consisting of 9 patent documents published in WO, CN, CA, EP, and US in 2015-2019.
Image from: US10428802B2
A method for repairing an electrical heating element of a wind turbine blade is proposed in patent US10066608B2 by Nordex Energy Gmbh (DE). The method includes identifying a region of the heating element with a defect and applying an electrically insulating and "…thermally conductive repair layer having an underside and a specific thermal conductivity of at least 10 W/m·K" to such region so that the underside faces the defect. Electrically nonconductive base material of the repair layer is a polymer material, while thermally conductive layer can include a graphite foil and a metallic foil. Further, a cover layer is applied to the repair layer so as to be projected beyond its lateral edges. An electrically insulating ply of the repair layer or the cover layer includes glass fiber material and has a thickness of less than 0.5 mm. Thickness of the repair layer is between 0.1 mm and 1 mm. Before applying the repair layer, the electrical conductivity of the faulty heating element is restored by applying an electrically conductive adhesive and a carbon fiber or a metal foil patch, and bringing it into electrical contact with the heating element.
The object of the invention is to provide an easy-to-apply repairing method to reliably prevent further damage.
The document is a part of a family comprising 4 documents published between 2014 and 2019 in US and EP.
Image from: US10066608B2
Environmental and social impact
Patent application US20190078558A1 filed by Siemens Gamesa Renewable Energy A/S (DK) discloses a wind turbine blade using hot air for preventing or eliminating ice accretion. The blade comprises a root section; an airfoil section comprising "…a cavity and having a leading edge section, a trailing edge section, a pressure side, a suction side, and a tip section"; a flow path for receiving the hot air and extending within the cavity from the root to the tip section; and exhaust holes located on the airfoil section and connected to the flow path to emit the hot air. The blade further includes an aerodynamically shaped cover plate at the outer surface of the airfoil section to mask the exhaust holes and direct the hot air towards outside of the blade via specifically profiled paths on the inner surface of the cover plate. The cover plate comprises a thermoformed plastic and/or glassfibre material, is adhered to the airfoil section, and comprises serrations on the side of the trailing edge. The heat directed to the flow path is generated by a heating device in the nacelle of the wind turbine. The claims describe possible locations of the exhaust holes and the cover plate.
Among other aspects, the authors point out a need to reduce noise effect on the rotor blade.
The patent application is a part of a patent family comprising 8 documents published in 2019-2020 in US, CA, CN, and EP.
Image from: US20190078558A1
A blade and a servicing unit are disclosed in patent US9885343B2 granted to Alstom Renovables Espana S.L. (ES). The blade comprises a shell with an opening on a pressure side of the blade. A servicing unit is positioned along and partially inside the shell and comprises an arm that can be projected out of the shell through the opening and is attached to a carriage that is located inside the shell and is displaceable along the blade. The carriage is guided by a guide fixed to a stiffening structure of the blade. The blade also comprises a pivotably attached closing gate that in one position overlaps the opening, while in the other position allows the passage of the arm. The closing gate can be integrated into the shell, with a narrower section forming a hinge, it is flexible and locally deformable so that only longitudinal portion of the opening is exposed; the gate also comprises several portions that can be opened or closed independently. While moving along the blade, the servicing unit shifts the position of a nearby portion of the closing gate. In parking position, the servicing unit doesn’t interfere with the closing gate. The arm is equipped with a blade surface servicing tool and can be extended to the leading edge of the blade.
The authors state that by using this invention it is possible to conduct such maintenance operations as ice removal in a safe way.
The patent is a part of a family comprising 5 documents published between 2014 and 2018 in US, EP, and WO.
Image from: US9885343B2
Low efficiency caused by secondary natural factors
General Electric (US) in its patent US9638168B2 proposes a method of detecting ice on a blade of a wind turbine comprising positioning the blade at a fixed non-vertical position (ranges from about 45 degrees to about 135 degrees or from about 225 degrees to about 315 degrees), releasing a pitch brake, maintaining a fixed pitch angle of the blade by controlling an input to a pitch drive actuator, monitoring an amount of torque required to maintain the blade at the fixed pitch angle, and analysing it to determine if the ice is present. The amount of torque is monitored by monitoring a current or pressure input to a pitch drive actuator and correlating it to the amount of torque required to maintain the blade at the fixed angle. Analysis of the monitored parameter comprises comparing it to respective baseline data and determining whether it falls outside a predetermined tolerance. Claims of the invention also describe a system operating in accordance with the method above.
The authors of the invention mention that in similar prior-art solutions the inspection during which the turbine is shut down takes significant amount of time, which can affect its overall efficiency.
The invention belongs to a family of 7 documents published in US, WO, EP, and CA in 2014-2018.
Image from: US9638168B2
More detailed information about inventions in the field of wind energy, and patent research methodology can be found on aenert.com.