Final Report Summary - WALID (Wind Blade Using Cost-Effective Advanced Composite Lightweight Design)
Executive Summary:
WALiD is a four-year project, part funded by the European Commission under the Seventh Framework Programme that successfully combined design, material and process developments to introduce thermoplastic materials into offshore rotor blades. The project aimed to:
• Improve the design of the blade root, connection concept and tip
• Replace the shell core with thermoplastic foam materials
• Improve the shear web with a new modular design
• Develop a thermoplastic coating with improved environmental resistance and durability against abrasion
• Develop a predictive simulation model for rotor blade coatings
By introducing thermoplastics into rotor blades, WALiD aimed to create cost-efficient, lightweight and recyclable blades for the offshore industry.
Offshore wind turbines are becoming ever larger, and the transportation, installation, disassembly and disposal of their gigantic rotor blades are presenting operators with new challenges. Wind turbines with rotor blades measuring up to 80 meters in length and a rotor diameter of over 160 meters are designed to maximize energy yields. Since the length of the blades is limited by their weight, it is essential to develop lightweight systems with high material strength. The lower weight makes the wind turbines easier to assemble and disassemble, and also improves their long-term behaviour in operation.
The WALiD project resulted in a number of key exploitable results, including:
i. Holistic WALiD thermoplastic rotor blade
ii. A durable coating system with thermoplastic behaviour
iii. Thermoplastic compounds with enhanced properties for foams, fibres and composite components
iv. Weld seam heating to aid manufacture and assembly
v. Root attachment concept
vi. Modular shear web
The results of the project enable:
• The successful demonstration of thermoplastic materials in offshore rotor blades
• The industrial beneficiaries to transfer the results to their organisations
• The WALiD beneficiaries to increase their revenues and customers within the wind energy sector
• The partners to increase their competiveness and demonstrate their innovativeness to their customer base and target industry worldwide
• The promotion of cooperation between different segments of the supply chain
• The improvement of skill levels through the supply chain
Project Context and Objectives:
Although power has been derived from the wind for centuries, the first device for generating electricity from the wind was a windmill developed by a Scottish professor, James Blyth, in July 1887. Other developments followed and in 1903 La Cour founded the Society of Wind Electricians. In 1956 the Gedsar 200 kW three bladed wind turbine was built by Johannes Juul and this design inspired many later designs.
The 1990’s saw the first real emergence of the off-shore wind industry when the first off-shore wind farm was created at Vindeby in Denmark in 1991 using eleven 450 kW turbines. By coincidence, 1991 was also the year that the UK’s first on-shore wind farm, with ten turbines, opened in Cornwall. It took another 12 years for the UK’s first off-shore wind farm to be developed in North Hoyle, Wales; this consisted of thirty 2MW turbines. Today, both onshore and offshore wind farms are common throughout Europe and the world and many more are expected to be developed in the near future as the drive to increase the amount of energy obtained via renewable resources continues in order to meet environmental, societal and regulatory goals.
In 2015 the global offshore wind industry installed more than 3.4 GW of capacity across five markets globally, bringing total offshore wind capacity to over 12 GW. More than 91% (11.0 GW) off all offshore installations were located in waters off the coast of eleven European countries, with the UK (40%) and Germany (27%) having by far the largest shares. The remaining 9% of capacity was installed was located mainly in China, but also in Japan and South Korea.
Offshore wind power has become the least cost option when adding new capacity to the grid in an increasing number of markets and prices continue to fall. Given the urgency to cut CO2 emissions, clean the air and decrease reliance on imported fossil fuels, wind powers pivotal role in the worlds future energy supply is assured. The industry association GWEC have predicted that by 2050 global wind installations could reach 5,806 GW.
The WALiD project has developed a novel wind turbine blade that is aimed primarily at the offshore wind industry, but which may have potential to be marketed to the onshore industry as well. The EU in 2009 set a legally binding target of 20% of its energy supply to come from wind and other renewable resources by 2030. In 2008, wind power was expected to deliver 12 to 14% of the total EU electricity demand by 2020. This contribution would be split between both on-shore and offshore wind power. In addition to the 2020 target set for all renewables, the following targets were set for the wind industry:
• 180 GW installed capacity overall – includes 35 GW off shore
• Annual installations of 16.8 GW – includes 6.8 GW off-shore
This target was revised upwards by the EU in 2014 to 27% of renewable resources by the year 2030 and this translates into 46%-49% of the electricity generated. Wind energy was predicted to generate the largest share of this electricity with a contribution of at least 21%.
Although the European off-shore wind industry has seen tremendous growth over the last 10 years, it still faces challenges. Its greatest challenge is to achieve cost competitiveness, an element of which is reducing the financial outlay associated with the supply chain, such as construction facilities and installation equipment. According to analysts Ernst & Young, the European off-shore wind industry needs to shed 26% of costs to achieve cost competitiveness with conventional forms of energy by 2023. One of the contributions that the WALiD project will make to the industry is to assist them in achieving this goal.
Offshore wind turbines are becoming ever larger and the transportation, installation, disassembly and disposal of these blades are presenting the industry with new challenges. To meet this challenge, the WALiD project developed highly durable thermoplastic foams and composites, a thermoplastic coating with high erosion and UV resistance and an innovative automated fibre placement process for layup of hybrid fibre tapes for the structure of the blade, resulting in a lighter blade with an improved design and an increase in service life.
Currently, rotor blades for wind turbines are predominately made by hand from thermosetting resin systems. One of the main drawbacks is that they are not suitable for recycling as they permanently harden after being heated once. At best, granulated thermoset plastic waste is recycled as filler in simple applications.
The WALiD wind turbine blade uses a different material class – thermoplastic. These are re-meltable polymer materials that can be processed efficiently in automated production facilities with less finishing and labour requirements than traditional thermosetting types. In addition, at the end of the blades service life the goal is to be able to separate the reinforcing fibre employed and reuse the thermoplastic matrix material.
Sandwich materials made from thermoplastic foams and fibre-reinforced plastics are used for the outer shell of the blade as well as for segments of the inner supporting structure. High stiffness carbon-fibre reinforced thermoplastics are used for areas of the blade that bear the greatest load, whilst glass-fibre reinforces the less stressed areas. The introduction of a modular designed shear web and new ultralight, stiff materials with increased mechanical properties means blades can be manufactured light-weight and cost effectively.
The WALiD thermoplastic coating is a protective surface layer that has demonstrated increased durability under harsh conditions. In addition, to support the development of the coatings a new predictive model was validated to model the relationship between surface properties and erosion resistance.
The WALiD consortium is comprised of Large Enterprises, Research Partners (RTDs), SMEs and Other Enterprises:
RTDs
• Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung EV (Germany)
• Nederlandse organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO (Netherlands)
Large Enterprises
• Smithers Rapra and Smithers Pira Ltd (UK)
• PPG Industries Fiber Glass bv (Netherlands)
SMEs
• Norner Research AS (Norway)
• Comfil APS (Denmark)
• Loiretech SAS (France)
• Coriolis Composites SAS (France)
• Windrad Engineering GmbH (Germany)
• Stichting Nederlands Normalisatie – Instituut (Netherlands)
The project has been successfully and widely disseminated to a large audience and the results and demonstrators are ready for exploitation by the consortium.
Project Results:
The WALiD project combines design, material and process developments using thermoplastic materials to create cost-efficient, lightweight and recyclable blades. The developments include:
• Improved design of the blade root, connection concept and tip
• Replace the shell core with thermoplastic foam materials
• Improved modular concept of the spar design
• A thermoplastic coating
The WALiD blade design process followed the same methods as conventional rotor blade design processes, and focuses on two main aspects:
1. Blade geometry – parameters like blade length, chord length or twist. This defines the aerodynamic performance and is not directly influenced by the materials
2. Structural properties – in particular bending stiffness. Determined by the materials themselves and lay-up plan
Furthermore, the WALiD design process, and in particular the lay-up plan of fibre reinforced materials, is not only influenced by the loads but also by the specific materials and their properties which were determined by suitable tests.
The WALiD blade is made up of a number of components, and a number of these components can be exploited individually as well as the whole system. The main results can be defined as follows:
• WALiD Rotor Blade
i. Material Developments
a. Long fibre thermoplastic
b. Durable coatings
c. Thermoplastic foams
d. Thermoplastic fibres and composites
ii. Processing Developments
a. First layer adhesion
b. Foam to skin layup
c. Weld seam heating
d. Production of hybrid composites
iii. Design Developments
a. Root attachment
b. Simulation of lighter blades
c. Simulation of dynamic blade behaviour models
d. Standards
e. Wear simulation
WALiD ROTOR BLADE
The WALiD rotor blade offers an improved design of the blade root, connection concept and tip as well as a modular concept for the shear web resulting in a more durable, recyclable blade. The main competitive advantages are: a stronger blade with increased mechanical properties, use of recyclable materials and high speed and repetitive processing and manufacturing using the Automated fibre placement (AFP) lay-up.
The WALiD blade design has a length of 88 metres with a root diameter of approximately 4.5 metres. The shape is based on NACA44 airfoil profiles that determine the aerodynamic active hull. As in conventional blade design the main structural components are the upper and lower shells that are connected at the leading and trailing edge. Two shear webs keep the shells at the required distance and an appropriate bending stiffness is achieved with spar caps in both shells. Finally the whole blade is protected from the harsh environmental conditions by a coating.
Although based on some conventional design elements, WALiD specific solutions were introduced into the blade root and shear web designs. Newly developed fibre reinforced plastics, foam and coating materials were utilised within the blade structure depending on the structural requirements of the component. Where the loads are predominately in one direction, the fibre orientation is aligned to that direction. This results in a stack-up (also called plies or laminate) of single layers with unidirectional orientation. Areas where no predominant direction is present a stack-up with consecutive alternating fibre orientation is used.
The thermoplastic foam has been used in both shells, as well as in the shear web, becoming part of the sandwich structure and acts as a structural reinforcement to prevent buckling of the laminate.
The WALiD coating, which is applied as a film, covers the whole blade and has high erosion and UV resistance that has demonstrated increased durability under harsh conditions
Finally, the manufacturing of the blade is carried out using an automated fibre placement (AFP) process, that is not based on pre-manufactured and ‘fixed size’ laminate, as is currently used in the well-established blade manufacturing processes. The AFP process utilises unidirectional tapes directly yielding higher design flexibility and the ability to produce suitable lay-up plans ensuring the desired blade properties, in specific components in an efficient manufacturing process.
The WALiD rotor blade is the culmination of a number of material, design and processing developments that, when integrated, result in a lighter, cost-efficient and recyclable blade.
MATERIAL DEVELOPMENTS
Typically, the rotor blade design process is based on well-known materials meaning that the structural properties of used materials are known and fixed with the challenge being to develop a blade employing these materials that withstands the loads retrieved from a corresponding load calculation.
Within the WALiD project, the main task was to develop and research fibre reinforced materials that could be used within the blade design using a different matrix material which was not used in the blade sector before. However, the new materials are expected to be in the same range as the commonly used materials but with improved properties such as higher tensile strength or lower density. The challenge in the development process was the influence of the loads and the properties of specific materials.
There were four main material developments within the WALiD project covering resin compatible long fibre thermoplastics, a durable coating with thermoplastic behaviour, thermoplastic compounds with enhanced properties for foams and thermoplastic compounds with enhanced properties for fibres and composites.
Conventional fibre reinforced thermoplastics are made from compounding short glass fibres into thermoplastic materials to make them suitable for manufacturing processes such as injection moulding and extrusion. Such materials with glass fibre content typically between 10 and 40% by weights are substantially isotropic in mechanical properties. The glass reinforcement efficiency is limited by the fibres being approximately 0.25-0.5mm in length. This restricts enhancing mechanical strength or stiffness of the thermoplastic matrix beyond factors of two or three because of the short fibre pull out and random orientation.
To get the full benefit and value of the strength and stiffness of the reinforcement employed loads need to be transferred directly to the reinforcing fibre in a direction of the fibre orientation.
Long fibre thermoplastic technology allows products to be manufactured with the reinforcing fibre to be as long as their critical dimensions. The critical parameters are: wetting out of the reinforcing fibres by high viscosity thermoplastic melts, reinforcing fibre sizing technology to aid bonding and interfacial shear strength and accurate placement of fibres during the manufacturing process. Based on this the PPG INNOFIBER XM based fibres provide a higher modulus to the thermoplastic blade, as well as being cost effective.
Offshore wind turbines operate under harsh conditions and are subject to abrasion, fouling, ice and in particular, erosion of the leading edge by droplet impingement wear. This reduces the efficiency and power output of the blade and has a detrimental effect on the blade surfaces. Blade coatings need a rubbery character throughout as well as a scratch resistant surface.
Current state of the art blades use thermoset coatings, however, these are not particularly environmentally friendly, are difficult to recycle and are not lightweight. WALiD developed a high-resistant thermoplastic coating to improve environmental resistance with anti-icing properties and durability against abrasion.
Using Diels-Alder chemistry, thermoplastic properties were introduced into a high performing thermoset, to produce a foil coating that can be applied to the substrate either by first layer or after the substrate has been consolidated. Testing showed that the particle erosion resistance was up to 10 times better than the commercial reference coating. Furthermore, the whiteness and gloss can be tuned to the appropriate levels.
A new thermoplastic core material for wind blade applications with increased properties was developed, ensuring a lightweight and highly resistive application in a sandwich core. The foaming step is a complex interaction of different parameters, including the intrinsic material properties, parameters of the process, temperature settings, die and screw design and calibration unit.
Using an iterative development strategy diverse materials and processing technology were trialled for the intrinsic reinforcement of foams with nano-scaled particles for improved mechanical behaviour.
The WALiD foams have the benefit of increased mechanical properties and provide better properties than existing material systems. The meltable plastic foams are temperature stable and can permanently withstand higher temperatures than, for example, expanded polystyrene foam (EPS) or expanded polypropylene (EPP). They can be processed quickly, save material as they can be shaped and cut as well as being recycled due to the thermoplastic matrix materials.
The thermoplastic compounds with enhanced properties for fibres and composites were used to develop unidirectional fibre reinforced thermoplastic materials for load bearing parts. The materials included glass fibres, carbon fibres, hybrid fibres and different polymer fibres as the matrix materials. The benefits include high performance composites, excellent specific mechanical properties, the ability to adapt materials for different load areas (material tailoring) and automated processing technology.
The hybrid yarns were processed and consolidated to tapes for use in the shear web. The criteria for optimal selection of properties were Inter Laminar Shear Strength (ILSS) in combination with optimised process settings for wet out and ILSS. The stiffness in a UD laminate is dependent on the fibre (type), volume % of the fibres, evenness of the fibres, full wetting of the filaments, no porosities and uniform distribution.
The parameters for the WALiD specific materials have been determined by standardised tests and data presented validating the technologies and materials, to be able to gain maximum acceptance of the use of thermoplastics in wind rotor blades. To support this, a review of all the available standards was performed and a testing strategy developed, based on the guidance given in IEC 61400 Part 5. Part 5 is specifically for wind turbine blades and suggests a building block approach to the design process. It is called a building block approach as the design and testing processes are divided into a series of steps, or levels that start with: coupon-level tests, then move onto analysis and testing of more complicated structures; finally culminating in a full scale structural blade test. Increasingly elaborate tests are developed to evaluate the more complex loading conditions and failure modes.
The aim was to demonstrate the capability and suitability of the design and materials, by simple and inexpensive tests. Materials and designs that meet the initial desired criteria were then taken up to the next stage where more complex and more costly testing can be undertaken.
PROCESSING DEVELOPMENTS
The WALiD processing developments are mainly focussed on the rotor blade production and include: a method for first layer adhesion, the lay-up of glass/carbon fibre thermoplastic directly on to thermoplastic material and weld seam heating to weld the skin and core material together. In addition, WALiD processed hybrid tapes into consolidated plates.
A novel approach to wind blade manufacturing is the use of the Automated Fibre Placement (AFP) process. The AFP system is a system to layup, place and bond/consolidate fibres and tapes making it possible to layup large composite parts. The fibre placement system consists of a placement head, a creel and a tube for feeding the tapes. The creel provides all the necessary functions for unwinding the bobbins at high speed with low tension. The flexible pipes individually feed each fibre from the creel to the layup head while maintaining a low tension. The layup head can feed and cut independently each tape.
Moulds are designed specifically for the purpose and during layup the thermoplastic tapes are heated due to a laser diode system mounted on the AFP head. The aim is to allow a good adhesion between the fibres making the thermoplastic deformable.
Tapes processed using automated fibre placement (AFP) must meet specific requirements, with one of the most important prerequisites being that the tape has to be black for processing as they need to absorb laser light during the placement process. Whereas carbon fibre reinforced tapes do not need extra additives to blacken the tapes, it is necessary to add a colour additive to glass fibre reinforced tapes. Therefore, the level of blackness is very important for the processability.
If the level of blackness of the tapes is too low, the absorption coefficient of the tape material could be insufficient and the consolidation quality would be significantly deteriorated. On the other hand, a carbon black content that is too high could in turn influence the mechanical behaviour of the developed tape material.
Several lay-up simulations were made for the single blade components to be able to develop the layup strategies and the production duration. Parameters, such as feed velocity, cut velocity, maximum velocity and maximum accelerations were optimised in order to show a realistic production of the blade components
During layup, the issue of too little first ply adherence is a well-known when dealing with thermoplastic fibre reinforced material processing. This even applies to injection moulding of thermoplastics or filament winding applications. The reasons for the separation of the thermoplastic fibre material from the surface can be found in the high thermal stresses as they appear during heating up and sudden cooling down of the matrix and the resulting steep temperature gradients. Several strategies have been developed to help promote adhesion to the tooling.
The introduction of ‘insulation layers’ to the mould with the help of a vacuum was used in the project. In addition the moulds were heated to help limit the temperature gradients and resulting thermal stresses. By heating the mould, the laminate quality can be significantly improved and have a positive effect on the adhesion of the coating to the matrix materials of the tapes.
DESIGN DEVELOPMENTS
The design work within the WALiD project focused on the development of a detailed blade design suitable for offshore wind turbine applications. The project aimed to produce a 90 metre blade, with a comparable low weight – which follows the current state of the art in commercial blade development for wind energy applications.
One of the main tasks of the design process is to meet the high demands on the structural properties which are needed to withstand the harsh offshore conditions. To achieve this, new materials were developed - fibre reinforced materials that use new glass fibres as well as thermoplastic as the matrix material. Furthermore, an improved foam with a thermoplastic matrix was developed and used as core material within the blade shells. Finally, a new durable coating was produced which fulfilled the offshore requirements.
Using a combination of the new materials, along with the Coriolis Automated Fibre Placement (AFP) process, it is possible to apply WALiD-specific solutions for a number of blade components. For example, the new blade root design is an alternative to the more commonly used T-bolt connections. The new design makes substantial use of the AFP process and leads to a remarkable reduction of the amount of laminate used, and therefore decreases the weight of the blade root.
The second design concept, an imbedded second belt in the trailing edge area, ensures necessary stiffness properties. In addition, WALiD showed the potential to replace commonly used bonding by welding process for connection surfaces. This technique is applicable due to the thermoplastic matrix material.
All the design concepts were represented in a virtual blade model that illustrates the holistic WALiD blade design.
To ensure that the new blade is fit for purpose the design passed through several analyses in accordance to wind blade guidelines and standards. The underlying design loads are derived from a standard-compliant aeroelastic load simulation for a generic 9MW offshore turbine. These analyses are conducted for extreme loads considering that most component designs like spar caps, shear webs and shells are driven by these loads. This acts differently for the root connection which is dimensioned by fatigue loads. For its evaluation a test plan is prepared to substantiate the promising new designs. A complete verification of the blade design is pending but this was not the intention of this project. Finally as result a sound and promising blade design was established.
Based on the proposed final blade design LCA & Cost estimations were performed, which show that the WALiD blade is an improvement on current state of the art blades with regards to environmental and cost impact, as well as end of life.
A model was developed and published that can be used to predict the life of the leading edge of coated wind turbine blades. Surface fatigue, as a nucleating wear mechanism for erosion damage, can explain erosive wear and failure for brittle and ductile materials. An engineering approach to surface fatigue, using the Palmgren-Miner rule for cumulative damage, allows for the construction of a rain erosion incubation period. Coating life was described as a function of the rain intensity, the droplet diameter, the fatigue properties of the coating and the severity of the conditions. As fatigue is the dominant wear mechanism in leading edge erosion, it is clear that general counter measures to fatigue are to be applied in order to minimise the risk of damaged blade surfaces.
The model recommended that coating development should focus on reduction of the impact pressure, e.g. by developing surfaces with a low modulus of elasticity; or on enlarging the safe area by developing coatings with adjustable compressive stresses, high hardness or by developing coatings without defects and impurities in the layer just below the surface. Surface fatigue data relies heavily on standardised calculation procedures and standardised testing protocols.
A droplet erosion simulator was also developed and built, to measure erosion resistance of surfaces in an accelerated cycle, and used on thermoplastic surfaces to validate the model. This simulator can be used to test droplet erosion resistance of surfaces in an accelerated way and the model can be used to predict the life time of the surface. In turn, this information can be used to set an appropriate maintenance schedule.
A review was performed of the standards that currently apply to wind turbine blades including the materials used in construction. The main standard for wind turbine blade design is the IEC guideline 61400-5, which is currently in development. Nevertheless, the draft gives guidance on how to design a blade. In addition to the IEC guideline, the Germanischer Lloyd guidelines describe the state of the art in conventional blade designs.
As WALiD has introduced novel approaches to blade design, as well as fundamental changes in the selection of the materials used the standards were identified, reviewed and assessed for applicability the project. Current blade testing is based around the type of materials commonly used, mainly thermosetting or curing type materials. Therefore, these standards were assessed as they may, or may not be directly applicable to WALiD, or even relevant to materials used in the new blade construction.
A further study was carried out on the requirements for standardisation, and found that there was no need for a specific standardisation proposal for thermoplastic in wind turbine rotor blades. However, as wind turbine standards are developed at IEC it was decided to produce an IEC Technical Report for the construction of wind turbine rotor blades with thermoplastics instead of a CENELEC standard.
ADDITIONAL RESULTS
Life Cycle Assessments (LCA) and Life Cycle Costing (LCC) of the WALiD rotor blade were completed. The LCA and LCC were performed using a combination of publically available data and data provided by the project partners. A number of reports were produced, culminating in the ‘Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook’ which uses LCA to examine, in detail, the differences in life cycle impact between a current state of the art off shore wind blade and the newly designed WALiD blade. Further reports also show the technical benefits as well as an economic evaluation of the process.
The final ‘Plan for the Dissemination and use of Foreground (PUDF)’ was completed and contains a detailed description of all the exploitation activities undertaken by all the partners. In addition, there is a thorough investigation of the technological and economic potential and value and how the project results can be exploited in each sector. Finally specific opportunities for the project partners were identified and included in the PUDF.
The results of WALiD were disseminated to SMEs, Large Enterprises and SME Associations across Europe and to a wider audience with the aim of marketing the technology and processes developed during the project. Through the dissemination activities the partners were able to gain =feedback from their potential customers bases. For example an ‘Open Day’ was held with organisations within the Danish wind energy sector.
WALiD was widely disseminated via: Linked IN, Twitter, You Tube, 9 press releases, 38 events, 2 postcards, 2 brochures, 3 posters / banners, 5 newsletters and a project promotional folder. In addition, the project website (available at www.eu-walid.com) was regularly updated to reflect the current status of the website. It included information about the project and partners, News, downloads, technology transfer and a blog. Furthermore, three videos were added to provide visitors with a clear and easy way of finding out more about the project.
Potential Impact:
Although the future of wind energy is secure and all the indicators show that a significant amount of growth will take place throughout the world over the next 30-years there are still challenges to be met by the European offshore wind energy industry.
One of the main challenges is to compete on cost with conventional forms of energy generation. A report by Ernst and Young stated that the European offshore industry needed to shed 26% of costs to reach cost competitiveness with conventional forms by 2023. The report highlighted the following areas where it felt that savings could be found. The contribution that each area could make to these savings is also shown:
• Deployment of larger turbines to increase energy capture (9%)
• Encouragement of competition between industrial players (7%)
• Commissioning of new projects (7%)
• Tackling of challenges in the supply chain (e.g. construction facilities) (3%)
The exploitable results of the WALiD project will assist the industry to achieve a number of these savings and assist in cost cutting in other ways. For example:
• The lighter weight materials and the novel design will reduce weight and so will assist in the construction and deployment of larger turbines
• The new materials and the processes will help reduce production costs
• The materials and processes could also increase the availability of construction facilities by encouraging new organisations to enter the industry, e.g. those with experience in thermoplastics
• The new rotor blade coating will improve environmental resistance and reduce wear, and so enhance durability and lifespan
A number of valuable results have been achieved during the WALiD project that will be translated into market products or services. The project has enabled state of the art research, new ideas, concepts, production processes, services and products that can be maximised by the partners and taken to market. Furthermore, the design, material and process innovations developed in WALiD represent clearly identifiable opportunities for the beneficiaries and wider industry to benefit financially.
Indirect ways in which industry could benefit include the enhancement of a company’s standing in the market place due to the introduction of innovative and novel materials, processes, technologies and design as well as the maintenance of client relationships.
According to Ernest &Young, offshore wind in Europe currently represents one of the most stable sources of renewable energy, with increased energy capture expected due to Europe’s leading position in offshore wind R&D. Also, although offshore wind is generally said to be 10-15 years behind onshore wind, it is believed that under the right conditions the success of onshore wind can be mirrored by offshore. The industry has displayed one of the fastest growth rates of all renewable energy sources, with a five-year compound annual growth rate of 31%.
At the end of 2014 Ernest &Young summarised the European situation:
• A total of 2,488 wind turbines were installed and connected to the electricity grid in 74 offshore wind farms across the continent
• Total installed capacity had reached 8 GW, enough to cover almost 1% of the EU’s total electricity consumption in 2014
• In the space of five years, employment in offshore wind has tripled, with 75,000 Full Time Equivalents (FTE’s) in 2014. During the same period cumulative installed capacity quadrupled, showing efficiencies developed as the industry has gained experience through growth
To date the frontrunners of this development have been the UK, Denmark and Germany, with more than 80% of Europe’s operational capacity installed in their water and at present the UK is the largest global offshore market.
Industry efforts to reduce capital and operating costs mean that offshore wind will become highly competitive by 2023 when compared to other sources of energy. Levelised Cost of Electricity (LCoE) could reach €90/MWh by 2030 as long as a continual stream of projects enters the pipeline.
By using their knowledge and experience of the wind energy sector, the WALiD partners have been able to provide robust and considered predictions of the advantages that the technical and design advances achieved during the WALiD project will confer upon the industry.
i. State of the art costs for one MW installed power by wind turbine are €1 million
ii. The cost of manufacturing the turbine blades contribute up to 25% of the manufacturing costs of wind turbines
iii. The use of WALiD’s novel economic materials and concepts will enable a saving of 15% on the manufacturing cost of a wind turbine
iv. The market impact for the WALiD technology is estimated as being 30%. For example, if a 10 turbine (three blades each), 10 MW installation costs 10 million euros, the total blade costs will be 2.5 million euros. A 15% saving will therefore be equal to €375,000 for each three bladed turbine, i.e. €125,000 per turbine blade.
These assumptions have been used as an aid to quantifying the benefits that the exploitable WALiD results will provide to the wind industry and to the WALiD consortium.
The future for the wind industry looks to be extremely promising and a number of authoritative industry sources are predicting significant growth throughout the world over the next 35 years. Europe in particular is a region where the wind industry will make a substantial contribution to the amount of energy that is produced by renewable sources sector, with countries like the UK being world market leaders in offshore wind energy.
The WALiD market assessment that has been carried out has shown that to 2030, assuming a 30% market share, the technology will have generated up to €27,030 million from the growth of the offshore wind energy market and up to €51,900 million from the growth of the onshore wind energy market. Globally to 2050 it will have generated up to €1,611,900 million from the growth of the combined (offshore and onshore) wind energy market. In addition, the design, material and process developments that have taken place during the WALiD project will help reduce the costs of the wind energy sector by 15%, enabling it to make the savings that it needs to compete with conventional forms of energy generation. By 2030, these savings will reach a value of up to €13,515 million for the European offshore wind industry and up to €25,950 million for the European onshore wind industry. Globally, for the combined wind industry (offshore and onshore), these savings will reach a value of up to €805,950 million by 2050.
The projects deliverables match the needs of the wind industry and this will ensure that the WALiD technology makes a major contribution to its growth and profitability throughout Europe and the rest of the world over the next 35 years.
In conclusion, the results of WALiD will allow the beneficiaries to gain entry into this growing and lucrative market. The project has been successfully and widely disseminated to a large audience and the materials and technologies are ready for exploitation by the partners.
DISSEMINATION AND EXPLOITATION
Dissemination was an important part of the consortiums strategy to widely exploit the results of the project. The dissemination strategy was divided into different stages starting with initial awareness raising through to preparation for exploitation following the project end. All partners contributed to the dissemination efforts and maximised the use of different dissemination channels to ensure the successful future industrial adoption of WALiD materials, technologies and processes.
Posters, flyers and postcards were made available at the start of the project (and updated regularly throughout) to raise awareness of WALiD at conference, exhibitions and workshops. In addition, a number of project videos were produced covering an initial project overview, processing and production concepts and a final project summary.
A large number of events were attended and presentations given to inform the target industries of the WALiD technologies. Offshore Energy European 2016 was held on 25th and 26th October 2016, at the Amsterdam RAI. This was a key event for WALiD, and where the consortium held their ‘Education & Training Workshop’. As part of the event, Hans Knudsen (Comfil) was interviewed and filmed by the Offshore WIND expertise hub, promoting the concept of the offshore wind sector needing to focus on sustainability and this can be ensured by using large, recyclable blades made from thermoplastic materials. The interview was broadcast live at the event to over 11,500 industry professionals and further promoted by Offshore WIND via their website and social media.
The event was a huge success and generated interest in the WALiD results as well as the manufacturing and processing technologies.
WALiD also participated in ‘Wind Energy Sector – A European Challenge’, a networking workshop of EU-funded projects that had the objective of sharing the research performed in order to overcome technological challenges within the European wind energy sector. There were 50-70 participants in the workshop and during the podium discussions there was a great deal of interest in the WALiD technologies, and in particular the AFP process, thermoplastic materials in general, recycling possibilities and the durable thermoplastic coating.
To support the future exploitation stages, demonstration modules were produced as well as a knowledge library and a Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook.
A detailed market report was prepared as part of D9.14: Final report on commercial evaluation, exploitation, dissemination and education and covers market potential and value, growth sectors, future trends and other technologies. This information provides the beneficiaries with supporting data for their organisations and business planning.
The WALiD results will support the beneficiaries within the project to compete in a growing and increasingly competitive marketplace. Supporting materials such as a knowledge library, promotional videos, Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook and dynamic presentations have been produced to assist with marketing activities and support future exploitation.
List of Websites:
www.eu-walid.com
The Fraunhofer Institute for Chemical Technology (ICT) (Germany)
Contact: Florian Rapp
Website: www.fraunhofer.de
Smithers Rapra & Smithers Pira Ltd (UK)
Contact: Suzanne Johnston
Website: www.smithersrapra.com
TNO Netherlands Organisation for Applied Scientific Research (Netherlands)
Contact: Maaike le Feber
Website: www.tno.nl
PPG Industries Fiber Glass BV (Netherlands)
Contact: Craig Bourcier
Website: www.ppg.com
Norner AS (Norway)
Contact: Katrin Nord-Varhaug
Website: www.norner.no
Comfil ApS (Denmark)
Contact: Hans Knudsen
Website: www.comfil.biz
Loiretech SAS (France)
Contact: Franck Melling
Website: www.loiretech.fr
Coriolis Composites SAS (France)
Contact: Mael Farinas
Website: www.coriolis-composites.com
NEN Nederlandse Normalisatie –Instituut (Netherlands)
Contact: Martijn Geertzen
Website: www.nen.nl
WPS Windrad Power Systems GmbH (Germany)
Contact: Michael Hänler
Website: www.windrad-engineering.de
WALiD is a four-year project, part funded by the European Commission under the Seventh Framework Programme that successfully combined design, material and process developments to introduce thermoplastic materials into offshore rotor blades. The project aimed to:
• Improve the design of the blade root, connection concept and tip
• Replace the shell core with thermoplastic foam materials
• Improve the shear web with a new modular design
• Develop a thermoplastic coating with improved environmental resistance and durability against abrasion
• Develop a predictive simulation model for rotor blade coatings
By introducing thermoplastics into rotor blades, WALiD aimed to create cost-efficient, lightweight and recyclable blades for the offshore industry.
Offshore wind turbines are becoming ever larger, and the transportation, installation, disassembly and disposal of their gigantic rotor blades are presenting operators with new challenges. Wind turbines with rotor blades measuring up to 80 meters in length and a rotor diameter of over 160 meters are designed to maximize energy yields. Since the length of the blades is limited by their weight, it is essential to develop lightweight systems with high material strength. The lower weight makes the wind turbines easier to assemble and disassemble, and also improves their long-term behaviour in operation.
The WALiD project resulted in a number of key exploitable results, including:
i. Holistic WALiD thermoplastic rotor blade
ii. A durable coating system with thermoplastic behaviour
iii. Thermoplastic compounds with enhanced properties for foams, fibres and composite components
iv. Weld seam heating to aid manufacture and assembly
v. Root attachment concept
vi. Modular shear web
The results of the project enable:
• The successful demonstration of thermoplastic materials in offshore rotor blades
• The industrial beneficiaries to transfer the results to their organisations
• The WALiD beneficiaries to increase their revenues and customers within the wind energy sector
• The partners to increase their competiveness and demonstrate their innovativeness to their customer base and target industry worldwide
• The promotion of cooperation between different segments of the supply chain
• The improvement of skill levels through the supply chain
Project Context and Objectives:
Although power has been derived from the wind for centuries, the first device for generating electricity from the wind was a windmill developed by a Scottish professor, James Blyth, in July 1887. Other developments followed and in 1903 La Cour founded the Society of Wind Electricians. In 1956 the Gedsar 200 kW three bladed wind turbine was built by Johannes Juul and this design inspired many later designs.
The 1990’s saw the first real emergence of the off-shore wind industry when the first off-shore wind farm was created at Vindeby in Denmark in 1991 using eleven 450 kW turbines. By coincidence, 1991 was also the year that the UK’s first on-shore wind farm, with ten turbines, opened in Cornwall. It took another 12 years for the UK’s first off-shore wind farm to be developed in North Hoyle, Wales; this consisted of thirty 2MW turbines. Today, both onshore and offshore wind farms are common throughout Europe and the world and many more are expected to be developed in the near future as the drive to increase the amount of energy obtained via renewable resources continues in order to meet environmental, societal and regulatory goals.
In 2015 the global offshore wind industry installed more than 3.4 GW of capacity across five markets globally, bringing total offshore wind capacity to over 12 GW. More than 91% (11.0 GW) off all offshore installations were located in waters off the coast of eleven European countries, with the UK (40%) and Germany (27%) having by far the largest shares. The remaining 9% of capacity was installed was located mainly in China, but also in Japan and South Korea.
Offshore wind power has become the least cost option when adding new capacity to the grid in an increasing number of markets and prices continue to fall. Given the urgency to cut CO2 emissions, clean the air and decrease reliance on imported fossil fuels, wind powers pivotal role in the worlds future energy supply is assured. The industry association GWEC have predicted that by 2050 global wind installations could reach 5,806 GW.
The WALiD project has developed a novel wind turbine blade that is aimed primarily at the offshore wind industry, but which may have potential to be marketed to the onshore industry as well. The EU in 2009 set a legally binding target of 20% of its energy supply to come from wind and other renewable resources by 2030. In 2008, wind power was expected to deliver 12 to 14% of the total EU electricity demand by 2020. This contribution would be split between both on-shore and offshore wind power. In addition to the 2020 target set for all renewables, the following targets were set for the wind industry:
• 180 GW installed capacity overall – includes 35 GW off shore
• Annual installations of 16.8 GW – includes 6.8 GW off-shore
This target was revised upwards by the EU in 2014 to 27% of renewable resources by the year 2030 and this translates into 46%-49% of the electricity generated. Wind energy was predicted to generate the largest share of this electricity with a contribution of at least 21%.
Although the European off-shore wind industry has seen tremendous growth over the last 10 years, it still faces challenges. Its greatest challenge is to achieve cost competitiveness, an element of which is reducing the financial outlay associated with the supply chain, such as construction facilities and installation equipment. According to analysts Ernst & Young, the European off-shore wind industry needs to shed 26% of costs to achieve cost competitiveness with conventional forms of energy by 2023. One of the contributions that the WALiD project will make to the industry is to assist them in achieving this goal.
Offshore wind turbines are becoming ever larger and the transportation, installation, disassembly and disposal of these blades are presenting the industry with new challenges. To meet this challenge, the WALiD project developed highly durable thermoplastic foams and composites, a thermoplastic coating with high erosion and UV resistance and an innovative automated fibre placement process for layup of hybrid fibre tapes for the structure of the blade, resulting in a lighter blade with an improved design and an increase in service life.
Currently, rotor blades for wind turbines are predominately made by hand from thermosetting resin systems. One of the main drawbacks is that they are not suitable for recycling as they permanently harden after being heated once. At best, granulated thermoset plastic waste is recycled as filler in simple applications.
The WALiD wind turbine blade uses a different material class – thermoplastic. These are re-meltable polymer materials that can be processed efficiently in automated production facilities with less finishing and labour requirements than traditional thermosetting types. In addition, at the end of the blades service life the goal is to be able to separate the reinforcing fibre employed and reuse the thermoplastic matrix material.
Sandwich materials made from thermoplastic foams and fibre-reinforced plastics are used for the outer shell of the blade as well as for segments of the inner supporting structure. High stiffness carbon-fibre reinforced thermoplastics are used for areas of the blade that bear the greatest load, whilst glass-fibre reinforces the less stressed areas. The introduction of a modular designed shear web and new ultralight, stiff materials with increased mechanical properties means blades can be manufactured light-weight and cost effectively.
The WALiD thermoplastic coating is a protective surface layer that has demonstrated increased durability under harsh conditions. In addition, to support the development of the coatings a new predictive model was validated to model the relationship between surface properties and erosion resistance.
The WALiD consortium is comprised of Large Enterprises, Research Partners (RTDs), SMEs and Other Enterprises:
RTDs
• Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung EV (Germany)
• Nederlandse organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO (Netherlands)
Large Enterprises
• Smithers Rapra and Smithers Pira Ltd (UK)
• PPG Industries Fiber Glass bv (Netherlands)
SMEs
• Norner Research AS (Norway)
• Comfil APS (Denmark)
• Loiretech SAS (France)
• Coriolis Composites SAS (France)
• Windrad Engineering GmbH (Germany)
• Stichting Nederlands Normalisatie – Instituut (Netherlands)
The project has been successfully and widely disseminated to a large audience and the results and demonstrators are ready for exploitation by the consortium.
Project Results:
The WALiD project combines design, material and process developments using thermoplastic materials to create cost-efficient, lightweight and recyclable blades. The developments include:
• Improved design of the blade root, connection concept and tip
• Replace the shell core with thermoplastic foam materials
• Improved modular concept of the spar design
• A thermoplastic coating
The WALiD blade design process followed the same methods as conventional rotor blade design processes, and focuses on two main aspects:
1. Blade geometry – parameters like blade length, chord length or twist. This defines the aerodynamic performance and is not directly influenced by the materials
2. Structural properties – in particular bending stiffness. Determined by the materials themselves and lay-up plan
Furthermore, the WALiD design process, and in particular the lay-up plan of fibre reinforced materials, is not only influenced by the loads but also by the specific materials and their properties which were determined by suitable tests.
The WALiD blade is made up of a number of components, and a number of these components can be exploited individually as well as the whole system. The main results can be defined as follows:
• WALiD Rotor Blade
i. Material Developments
a. Long fibre thermoplastic
b. Durable coatings
c. Thermoplastic foams
d. Thermoplastic fibres and composites
ii. Processing Developments
a. First layer adhesion
b. Foam to skin layup
c. Weld seam heating
d. Production of hybrid composites
iii. Design Developments
a. Root attachment
b. Simulation of lighter blades
c. Simulation of dynamic blade behaviour models
d. Standards
e. Wear simulation
WALiD ROTOR BLADE
The WALiD rotor blade offers an improved design of the blade root, connection concept and tip as well as a modular concept for the shear web resulting in a more durable, recyclable blade. The main competitive advantages are: a stronger blade with increased mechanical properties, use of recyclable materials and high speed and repetitive processing and manufacturing using the Automated fibre placement (AFP) lay-up.
The WALiD blade design has a length of 88 metres with a root diameter of approximately 4.5 metres. The shape is based on NACA44 airfoil profiles that determine the aerodynamic active hull. As in conventional blade design the main structural components are the upper and lower shells that are connected at the leading and trailing edge. Two shear webs keep the shells at the required distance and an appropriate bending stiffness is achieved with spar caps in both shells. Finally the whole blade is protected from the harsh environmental conditions by a coating.
Although based on some conventional design elements, WALiD specific solutions were introduced into the blade root and shear web designs. Newly developed fibre reinforced plastics, foam and coating materials were utilised within the blade structure depending on the structural requirements of the component. Where the loads are predominately in one direction, the fibre orientation is aligned to that direction. This results in a stack-up (also called plies or laminate) of single layers with unidirectional orientation. Areas where no predominant direction is present a stack-up with consecutive alternating fibre orientation is used.
The thermoplastic foam has been used in both shells, as well as in the shear web, becoming part of the sandwich structure and acts as a structural reinforcement to prevent buckling of the laminate.
The WALiD coating, which is applied as a film, covers the whole blade and has high erosion and UV resistance that has demonstrated increased durability under harsh conditions
Finally, the manufacturing of the blade is carried out using an automated fibre placement (AFP) process, that is not based on pre-manufactured and ‘fixed size’ laminate, as is currently used in the well-established blade manufacturing processes. The AFP process utilises unidirectional tapes directly yielding higher design flexibility and the ability to produce suitable lay-up plans ensuring the desired blade properties, in specific components in an efficient manufacturing process.
The WALiD rotor blade is the culmination of a number of material, design and processing developments that, when integrated, result in a lighter, cost-efficient and recyclable blade.
MATERIAL DEVELOPMENTS
Typically, the rotor blade design process is based on well-known materials meaning that the structural properties of used materials are known and fixed with the challenge being to develop a blade employing these materials that withstands the loads retrieved from a corresponding load calculation.
Within the WALiD project, the main task was to develop and research fibre reinforced materials that could be used within the blade design using a different matrix material which was not used in the blade sector before. However, the new materials are expected to be in the same range as the commonly used materials but with improved properties such as higher tensile strength or lower density. The challenge in the development process was the influence of the loads and the properties of specific materials.
There were four main material developments within the WALiD project covering resin compatible long fibre thermoplastics, a durable coating with thermoplastic behaviour, thermoplastic compounds with enhanced properties for foams and thermoplastic compounds with enhanced properties for fibres and composites.
Conventional fibre reinforced thermoplastics are made from compounding short glass fibres into thermoplastic materials to make them suitable for manufacturing processes such as injection moulding and extrusion. Such materials with glass fibre content typically between 10 and 40% by weights are substantially isotropic in mechanical properties. The glass reinforcement efficiency is limited by the fibres being approximately 0.25-0.5mm in length. This restricts enhancing mechanical strength or stiffness of the thermoplastic matrix beyond factors of two or three because of the short fibre pull out and random orientation.
To get the full benefit and value of the strength and stiffness of the reinforcement employed loads need to be transferred directly to the reinforcing fibre in a direction of the fibre orientation.
Long fibre thermoplastic technology allows products to be manufactured with the reinforcing fibre to be as long as their critical dimensions. The critical parameters are: wetting out of the reinforcing fibres by high viscosity thermoplastic melts, reinforcing fibre sizing technology to aid bonding and interfacial shear strength and accurate placement of fibres during the manufacturing process. Based on this the PPG INNOFIBER XM based fibres provide a higher modulus to the thermoplastic blade, as well as being cost effective.
Offshore wind turbines operate under harsh conditions and are subject to abrasion, fouling, ice and in particular, erosion of the leading edge by droplet impingement wear. This reduces the efficiency and power output of the blade and has a detrimental effect on the blade surfaces. Blade coatings need a rubbery character throughout as well as a scratch resistant surface.
Current state of the art blades use thermoset coatings, however, these are not particularly environmentally friendly, are difficult to recycle and are not lightweight. WALiD developed a high-resistant thermoplastic coating to improve environmental resistance with anti-icing properties and durability against abrasion.
Using Diels-Alder chemistry, thermoplastic properties were introduced into a high performing thermoset, to produce a foil coating that can be applied to the substrate either by first layer or after the substrate has been consolidated. Testing showed that the particle erosion resistance was up to 10 times better than the commercial reference coating. Furthermore, the whiteness and gloss can be tuned to the appropriate levels.
A new thermoplastic core material for wind blade applications with increased properties was developed, ensuring a lightweight and highly resistive application in a sandwich core. The foaming step is a complex interaction of different parameters, including the intrinsic material properties, parameters of the process, temperature settings, die and screw design and calibration unit.
Using an iterative development strategy diverse materials and processing technology were trialled for the intrinsic reinforcement of foams with nano-scaled particles for improved mechanical behaviour.
The WALiD foams have the benefit of increased mechanical properties and provide better properties than existing material systems. The meltable plastic foams are temperature stable and can permanently withstand higher temperatures than, for example, expanded polystyrene foam (EPS) or expanded polypropylene (EPP). They can be processed quickly, save material as they can be shaped and cut as well as being recycled due to the thermoplastic matrix materials.
The thermoplastic compounds with enhanced properties for fibres and composites were used to develop unidirectional fibre reinforced thermoplastic materials for load bearing parts. The materials included glass fibres, carbon fibres, hybrid fibres and different polymer fibres as the matrix materials. The benefits include high performance composites, excellent specific mechanical properties, the ability to adapt materials for different load areas (material tailoring) and automated processing technology.
The hybrid yarns were processed and consolidated to tapes for use in the shear web. The criteria for optimal selection of properties were Inter Laminar Shear Strength (ILSS) in combination with optimised process settings for wet out and ILSS. The stiffness in a UD laminate is dependent on the fibre (type), volume % of the fibres, evenness of the fibres, full wetting of the filaments, no porosities and uniform distribution.
The parameters for the WALiD specific materials have been determined by standardised tests and data presented validating the technologies and materials, to be able to gain maximum acceptance of the use of thermoplastics in wind rotor blades. To support this, a review of all the available standards was performed and a testing strategy developed, based on the guidance given in IEC 61400 Part 5. Part 5 is specifically for wind turbine blades and suggests a building block approach to the design process. It is called a building block approach as the design and testing processes are divided into a series of steps, or levels that start with: coupon-level tests, then move onto analysis and testing of more complicated structures; finally culminating in a full scale structural blade test. Increasingly elaborate tests are developed to evaluate the more complex loading conditions and failure modes.
The aim was to demonstrate the capability and suitability of the design and materials, by simple and inexpensive tests. Materials and designs that meet the initial desired criteria were then taken up to the next stage where more complex and more costly testing can be undertaken.
PROCESSING DEVELOPMENTS
The WALiD processing developments are mainly focussed on the rotor blade production and include: a method for first layer adhesion, the lay-up of glass/carbon fibre thermoplastic directly on to thermoplastic material and weld seam heating to weld the skin and core material together. In addition, WALiD processed hybrid tapes into consolidated plates.
A novel approach to wind blade manufacturing is the use of the Automated Fibre Placement (AFP) process. The AFP system is a system to layup, place and bond/consolidate fibres and tapes making it possible to layup large composite parts. The fibre placement system consists of a placement head, a creel and a tube for feeding the tapes. The creel provides all the necessary functions for unwinding the bobbins at high speed with low tension. The flexible pipes individually feed each fibre from the creel to the layup head while maintaining a low tension. The layup head can feed and cut independently each tape.
Moulds are designed specifically for the purpose and during layup the thermoplastic tapes are heated due to a laser diode system mounted on the AFP head. The aim is to allow a good adhesion between the fibres making the thermoplastic deformable.
Tapes processed using automated fibre placement (AFP) must meet specific requirements, with one of the most important prerequisites being that the tape has to be black for processing as they need to absorb laser light during the placement process. Whereas carbon fibre reinforced tapes do not need extra additives to blacken the tapes, it is necessary to add a colour additive to glass fibre reinforced tapes. Therefore, the level of blackness is very important for the processability.
If the level of blackness of the tapes is too low, the absorption coefficient of the tape material could be insufficient and the consolidation quality would be significantly deteriorated. On the other hand, a carbon black content that is too high could in turn influence the mechanical behaviour of the developed tape material.
Several lay-up simulations were made for the single blade components to be able to develop the layup strategies and the production duration. Parameters, such as feed velocity, cut velocity, maximum velocity and maximum accelerations were optimised in order to show a realistic production of the blade components
During layup, the issue of too little first ply adherence is a well-known when dealing with thermoplastic fibre reinforced material processing. This even applies to injection moulding of thermoplastics or filament winding applications. The reasons for the separation of the thermoplastic fibre material from the surface can be found in the high thermal stresses as they appear during heating up and sudden cooling down of the matrix and the resulting steep temperature gradients. Several strategies have been developed to help promote adhesion to the tooling.
The introduction of ‘insulation layers’ to the mould with the help of a vacuum was used in the project. In addition the moulds were heated to help limit the temperature gradients and resulting thermal stresses. By heating the mould, the laminate quality can be significantly improved and have a positive effect on the adhesion of the coating to the matrix materials of the tapes.
DESIGN DEVELOPMENTS
The design work within the WALiD project focused on the development of a detailed blade design suitable for offshore wind turbine applications. The project aimed to produce a 90 metre blade, with a comparable low weight – which follows the current state of the art in commercial blade development for wind energy applications.
One of the main tasks of the design process is to meet the high demands on the structural properties which are needed to withstand the harsh offshore conditions. To achieve this, new materials were developed - fibre reinforced materials that use new glass fibres as well as thermoplastic as the matrix material. Furthermore, an improved foam with a thermoplastic matrix was developed and used as core material within the blade shells. Finally, a new durable coating was produced which fulfilled the offshore requirements.
Using a combination of the new materials, along with the Coriolis Automated Fibre Placement (AFP) process, it is possible to apply WALiD-specific solutions for a number of blade components. For example, the new blade root design is an alternative to the more commonly used T-bolt connections. The new design makes substantial use of the AFP process and leads to a remarkable reduction of the amount of laminate used, and therefore decreases the weight of the blade root.
The second design concept, an imbedded second belt in the trailing edge area, ensures necessary stiffness properties. In addition, WALiD showed the potential to replace commonly used bonding by welding process for connection surfaces. This technique is applicable due to the thermoplastic matrix material.
All the design concepts were represented in a virtual blade model that illustrates the holistic WALiD blade design.
To ensure that the new blade is fit for purpose the design passed through several analyses in accordance to wind blade guidelines and standards. The underlying design loads are derived from a standard-compliant aeroelastic load simulation for a generic 9MW offshore turbine. These analyses are conducted for extreme loads considering that most component designs like spar caps, shear webs and shells are driven by these loads. This acts differently for the root connection which is dimensioned by fatigue loads. For its evaluation a test plan is prepared to substantiate the promising new designs. A complete verification of the blade design is pending but this was not the intention of this project. Finally as result a sound and promising blade design was established.
Based on the proposed final blade design LCA & Cost estimations were performed, which show that the WALiD blade is an improvement on current state of the art blades with regards to environmental and cost impact, as well as end of life.
A model was developed and published that can be used to predict the life of the leading edge of coated wind turbine blades. Surface fatigue, as a nucleating wear mechanism for erosion damage, can explain erosive wear and failure for brittle and ductile materials. An engineering approach to surface fatigue, using the Palmgren-Miner rule for cumulative damage, allows for the construction of a rain erosion incubation period. Coating life was described as a function of the rain intensity, the droplet diameter, the fatigue properties of the coating and the severity of the conditions. As fatigue is the dominant wear mechanism in leading edge erosion, it is clear that general counter measures to fatigue are to be applied in order to minimise the risk of damaged blade surfaces.
The model recommended that coating development should focus on reduction of the impact pressure, e.g. by developing surfaces with a low modulus of elasticity; or on enlarging the safe area by developing coatings with adjustable compressive stresses, high hardness or by developing coatings without defects and impurities in the layer just below the surface. Surface fatigue data relies heavily on standardised calculation procedures and standardised testing protocols.
A droplet erosion simulator was also developed and built, to measure erosion resistance of surfaces in an accelerated cycle, and used on thermoplastic surfaces to validate the model. This simulator can be used to test droplet erosion resistance of surfaces in an accelerated way and the model can be used to predict the life time of the surface. In turn, this information can be used to set an appropriate maintenance schedule.
A review was performed of the standards that currently apply to wind turbine blades including the materials used in construction. The main standard for wind turbine blade design is the IEC guideline 61400-5, which is currently in development. Nevertheless, the draft gives guidance on how to design a blade. In addition to the IEC guideline, the Germanischer Lloyd guidelines describe the state of the art in conventional blade designs.
As WALiD has introduced novel approaches to blade design, as well as fundamental changes in the selection of the materials used the standards were identified, reviewed and assessed for applicability the project. Current blade testing is based around the type of materials commonly used, mainly thermosetting or curing type materials. Therefore, these standards were assessed as they may, or may not be directly applicable to WALiD, or even relevant to materials used in the new blade construction.
A further study was carried out on the requirements for standardisation, and found that there was no need for a specific standardisation proposal for thermoplastic in wind turbine rotor blades. However, as wind turbine standards are developed at IEC it was decided to produce an IEC Technical Report for the construction of wind turbine rotor blades with thermoplastics instead of a CENELEC standard.
ADDITIONAL RESULTS
Life Cycle Assessments (LCA) and Life Cycle Costing (LCC) of the WALiD rotor blade were completed. The LCA and LCC were performed using a combination of publically available data and data provided by the project partners. A number of reports were produced, culminating in the ‘Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook’ which uses LCA to examine, in detail, the differences in life cycle impact between a current state of the art off shore wind blade and the newly designed WALiD blade. Further reports also show the technical benefits as well as an economic evaluation of the process.
The final ‘Plan for the Dissemination and use of Foreground (PUDF)’ was completed and contains a detailed description of all the exploitation activities undertaken by all the partners. In addition, there is a thorough investigation of the technological and economic potential and value and how the project results can be exploited in each sector. Finally specific opportunities for the project partners were identified and included in the PUDF.
The results of WALiD were disseminated to SMEs, Large Enterprises and SME Associations across Europe and to a wider audience with the aim of marketing the technology and processes developed during the project. Through the dissemination activities the partners were able to gain =feedback from their potential customers bases. For example an ‘Open Day’ was held with organisations within the Danish wind energy sector.
WALiD was widely disseminated via: Linked IN, Twitter, You Tube, 9 press releases, 38 events, 2 postcards, 2 brochures, 3 posters / banners, 5 newsletters and a project promotional folder. In addition, the project website (available at www.eu-walid.com) was regularly updated to reflect the current status of the website. It included information about the project and partners, News, downloads, technology transfer and a blog. Furthermore, three videos were added to provide visitors with a clear and easy way of finding out more about the project.
Potential Impact:
Although the future of wind energy is secure and all the indicators show that a significant amount of growth will take place throughout the world over the next 30-years there are still challenges to be met by the European offshore wind energy industry.
One of the main challenges is to compete on cost with conventional forms of energy generation. A report by Ernst and Young stated that the European offshore industry needed to shed 26% of costs to reach cost competitiveness with conventional forms by 2023. The report highlighted the following areas where it felt that savings could be found. The contribution that each area could make to these savings is also shown:
• Deployment of larger turbines to increase energy capture (9%)
• Encouragement of competition between industrial players (7%)
• Commissioning of new projects (7%)
• Tackling of challenges in the supply chain (e.g. construction facilities) (3%)
The exploitable results of the WALiD project will assist the industry to achieve a number of these savings and assist in cost cutting in other ways. For example:
• The lighter weight materials and the novel design will reduce weight and so will assist in the construction and deployment of larger turbines
• The new materials and the processes will help reduce production costs
• The materials and processes could also increase the availability of construction facilities by encouraging new organisations to enter the industry, e.g. those with experience in thermoplastics
• The new rotor blade coating will improve environmental resistance and reduce wear, and so enhance durability and lifespan
A number of valuable results have been achieved during the WALiD project that will be translated into market products or services. The project has enabled state of the art research, new ideas, concepts, production processes, services and products that can be maximised by the partners and taken to market. Furthermore, the design, material and process innovations developed in WALiD represent clearly identifiable opportunities for the beneficiaries and wider industry to benefit financially.
Indirect ways in which industry could benefit include the enhancement of a company’s standing in the market place due to the introduction of innovative and novel materials, processes, technologies and design as well as the maintenance of client relationships.
According to Ernest &Young, offshore wind in Europe currently represents one of the most stable sources of renewable energy, with increased energy capture expected due to Europe’s leading position in offshore wind R&D. Also, although offshore wind is generally said to be 10-15 years behind onshore wind, it is believed that under the right conditions the success of onshore wind can be mirrored by offshore. The industry has displayed one of the fastest growth rates of all renewable energy sources, with a five-year compound annual growth rate of 31%.
At the end of 2014 Ernest &Young summarised the European situation:
• A total of 2,488 wind turbines were installed and connected to the electricity grid in 74 offshore wind farms across the continent
• Total installed capacity had reached 8 GW, enough to cover almost 1% of the EU’s total electricity consumption in 2014
• In the space of five years, employment in offshore wind has tripled, with 75,000 Full Time Equivalents (FTE’s) in 2014. During the same period cumulative installed capacity quadrupled, showing efficiencies developed as the industry has gained experience through growth
To date the frontrunners of this development have been the UK, Denmark and Germany, with more than 80% of Europe’s operational capacity installed in their water and at present the UK is the largest global offshore market.
Industry efforts to reduce capital and operating costs mean that offshore wind will become highly competitive by 2023 when compared to other sources of energy. Levelised Cost of Electricity (LCoE) could reach €90/MWh by 2030 as long as a continual stream of projects enters the pipeline.
By using their knowledge and experience of the wind energy sector, the WALiD partners have been able to provide robust and considered predictions of the advantages that the technical and design advances achieved during the WALiD project will confer upon the industry.
i. State of the art costs for one MW installed power by wind turbine are €1 million
ii. The cost of manufacturing the turbine blades contribute up to 25% of the manufacturing costs of wind turbines
iii. The use of WALiD’s novel economic materials and concepts will enable a saving of 15% on the manufacturing cost of a wind turbine
iv. The market impact for the WALiD technology is estimated as being 30%. For example, if a 10 turbine (three blades each), 10 MW installation costs 10 million euros, the total blade costs will be 2.5 million euros. A 15% saving will therefore be equal to €375,000 for each three bladed turbine, i.e. €125,000 per turbine blade.
These assumptions have been used as an aid to quantifying the benefits that the exploitable WALiD results will provide to the wind industry and to the WALiD consortium.
The future for the wind industry looks to be extremely promising and a number of authoritative industry sources are predicting significant growth throughout the world over the next 35 years. Europe in particular is a region where the wind industry will make a substantial contribution to the amount of energy that is produced by renewable sources sector, with countries like the UK being world market leaders in offshore wind energy.
The WALiD market assessment that has been carried out has shown that to 2030, assuming a 30% market share, the technology will have generated up to €27,030 million from the growth of the offshore wind energy market and up to €51,900 million from the growth of the onshore wind energy market. Globally to 2050 it will have generated up to €1,611,900 million from the growth of the combined (offshore and onshore) wind energy market. In addition, the design, material and process developments that have taken place during the WALiD project will help reduce the costs of the wind energy sector by 15%, enabling it to make the savings that it needs to compete with conventional forms of energy generation. By 2030, these savings will reach a value of up to €13,515 million for the European offshore wind industry and up to €25,950 million for the European onshore wind industry. Globally, for the combined wind industry (offshore and onshore), these savings will reach a value of up to €805,950 million by 2050.
The projects deliverables match the needs of the wind industry and this will ensure that the WALiD technology makes a major contribution to its growth and profitability throughout Europe and the rest of the world over the next 35 years.
In conclusion, the results of WALiD will allow the beneficiaries to gain entry into this growing and lucrative market. The project has been successfully and widely disseminated to a large audience and the materials and technologies are ready for exploitation by the partners.
DISSEMINATION AND EXPLOITATION
Dissemination was an important part of the consortiums strategy to widely exploit the results of the project. The dissemination strategy was divided into different stages starting with initial awareness raising through to preparation for exploitation following the project end. All partners contributed to the dissemination efforts and maximised the use of different dissemination channels to ensure the successful future industrial adoption of WALiD materials, technologies and processes.
Posters, flyers and postcards were made available at the start of the project (and updated regularly throughout) to raise awareness of WALiD at conference, exhibitions and workshops. In addition, a number of project videos were produced covering an initial project overview, processing and production concepts and a final project summary.
A large number of events were attended and presentations given to inform the target industries of the WALiD technologies. Offshore Energy European 2016 was held on 25th and 26th October 2016, at the Amsterdam RAI. This was a key event for WALiD, and where the consortium held their ‘Education & Training Workshop’. As part of the event, Hans Knudsen (Comfil) was interviewed and filmed by the Offshore WIND expertise hub, promoting the concept of the offshore wind sector needing to focus on sustainability and this can be ensured by using large, recyclable blades made from thermoplastic materials. The interview was broadcast live at the event to over 11,500 industry professionals and further promoted by Offshore WIND via their website and social media.
The event was a huge success and generated interest in the WALiD results as well as the manufacturing and processing technologies.
WALiD also participated in ‘Wind Energy Sector – A European Challenge’, a networking workshop of EU-funded projects that had the objective of sharing the research performed in order to overcome technological challenges within the European wind energy sector. There were 50-70 participants in the workshop and during the podium discussions there was a great deal of interest in the WALiD technologies, and in particular the AFP process, thermoplastic materials in general, recycling possibilities and the durable thermoplastic coating.
To support the future exploitation stages, demonstration modules were produced as well as a knowledge library and a Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook.
A detailed market report was prepared as part of D9.14: Final report on commercial evaluation, exploitation, dissemination and education and covers market potential and value, growth sectors, future trends and other technologies. This information provides the beneficiaries with supporting data for their organisations and business planning.
The WALiD results will support the beneficiaries within the project to compete in a growing and increasingly competitive marketplace. Supporting materials such as a knowledge library, promotional videos, Comparative Life Cycle Assessment of WALiD Technologies and Processes Handbook and dynamic presentations have been produced to assist with marketing activities and support future exploitation.
List of Websites:
www.eu-walid.com
The Fraunhofer Institute for Chemical Technology (ICT) (Germany)
Contact: Florian Rapp
Website: www.fraunhofer.de
Smithers Rapra & Smithers Pira Ltd (UK)
Contact: Suzanne Johnston
Website: www.smithersrapra.com
TNO Netherlands Organisation for Applied Scientific Research (Netherlands)
Contact: Maaike le Feber
Website: www.tno.nl
PPG Industries Fiber Glass BV (Netherlands)
Contact: Craig Bourcier
Website: www.ppg.com
Norner AS (Norway)
Contact: Katrin Nord-Varhaug
Website: www.norner.no
Comfil ApS (Denmark)
Contact: Hans Knudsen
Website: www.comfil.biz
Loiretech SAS (France)
Contact: Franck Melling
Website: www.loiretech.fr
Coriolis Composites SAS (France)
Contact: Mael Farinas
Website: www.coriolis-composites.com
NEN Nederlandse Normalisatie –Instituut (Netherlands)
Contact: Martijn Geertzen
Website: www.nen.nl
WPS Windrad Power Systems GmbH (Germany)
Contact: Michael Hänler
Website: www.windrad-engineering.de