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Final Report Summary - HPC-BLADE (HPC-Blade)

Executive Summary:
The design of advanced (composite) wind turbine blades continues to evolve, but central spar-like structures and bonded cores remain the primary load-bearing and profile supporting elements. Aside from structural inefficiencies, these configurations are complex and expensive to manufacture using existing processes. Construction methods, composite-metal connections and loading complexities present challenges for structural integrity, resulting in over-engineering, increased weight and variable reliability. The HPC-Blade project addresses all of these issues by pursuing a novel design and manufacturing solution for blade structures. The concept is drawn from expertise held within eStress Limited - structural analysis specialists within the aerospace industry. The HPC-Blade assembly facilitates the following technology shifts: progression from a spar and core configuration to a rib-based fully stressed blade skin; elimination of mechanically fastened or bonded composite-metal joints; an optimised and appropriate synthesis of composite and metallic materials.
Our novel concept removes the requirement for over-engineering in terms of jointing and compressive instability, and manufacturing is simplified. This provides opportunities for weight saving, improved reliability, faster manufacture, lower cost, as well as opportunities to take advantage of ease of modularity while offering scope for erosion protection features. Finally, the design is scalable, offering benefits to composite blades of all sizes. Our consortium has researched the detailed design, materials and manufacturing solutions required to exploit the HPC-Blade concept. Blades up to 5m in length have been tested within this project to prove the technology and enable SME exploitation. Application of the design philosophy and features to large scale turbine blades will require proof-of-principle results from this project and longer term testing. This project provides the SME consortium with opportunities to expand the IP landscape. We will then seek to secure licensing arrangements with global wind turbine manufacturers.
Project Context and Objectives:
1 - Project Objectives
1.1 - Blade Concept and System Modelling
• To establish the performance parameters associated with competing blade designs
• Select blade designs for a) computational analysis and b) for case studies
• To carry out system wide analysis for the HPC-Blade principles, establishing general design principles and optimised placement/arrangements of internal components
• Establish performance specifications and safety factors for the selected blades
• Establish overall design of the blade/hub connection and adapter system
• Carry out an assessment of possible manufacturing routes and economic factors
1.2 - Detailed Design of Blade
• To establish the aerodynamic forces that the case study blade(s) will be subjected to
• Establish fatigue and environmental loadings
• Carry out detailed 3-D structural analysis and refine overall design
• Design CL collection point (blade anchoring) and torque collection
• Finalise hub adaptations and blade tip arrangements
1.3 - Materials Selection and Tribological Testing
• Identify and specify materials solutions for rib components
• Conduct blade skin materials selection and specification
• Establish the most effective rib/skin adhesive bonding solution
• Identify internal metallic tube materials selection
• Carry out blade coupon tribology testing
1.4 - Internal Component manufacture
• To verify component designs against selected materials
• Manufacture of blade skins and ribs for selected case study blade design
• Manufacture of metallic tube and associated components
• Manufacture of hub mounting adapter and fastening system
• Manufacture blade/tip anchoring point and blade tip connector
1.5 - Blade Manufacture and Testing
• To integrate internal core components into the case study blade skins
• Assemble the case study blade, inspect and report on achieved tolerances
• Carry out mechanical loading and testing of case study blade
• Validation of inertial characteristics
• Validate whole blade computational modelling and analysis
1.6 - Validation and DEMO Activities
• To integrate the hub adapters with turbine hub
• Integration of case study blades into turbine
• Carry out field trials for data gathering and demonstration purposes
• Analyse performance data and carry out post-trial blade inspections
1.7 - Dissemination and Exploitation
• Protect the HPC-Blade foreground knowledge
• Disseminate project results to generate commercial interest
• Create an exploitation strategy and plan

2 - Technical Objectives
TO1: Design. The 3-D structural system modelling, respecting the design specifications and principles as specified and recommended in Standard DNV-DS-J102, will conclude with a design tool for the optimisation of rib spacing.
TO2: Analysis. The following normalised computational analysis targets (at a distance from the root of 30% overall blade length) will be the basis for comparison of HPC-Blade vs. a Spar-Blade:
Flap stiffness > 2x109Nm-2; Edge stiffness >4x109Nm-2; Torsional stiffness >0.3x109Nm-2.
TO3: Endurance. Detailed design solutions for the contact-only composite-metal hub joint will demonstrate a fatigue life >108 cycles taking into consideration notch sensitivity and Barely
Visible Impact Damage (BVID).
TO4: Mass and Cost. HPC-Blades should demonstrate an overall mass reduction of 10% and a cost reduction (including reduced composite material costs and reductions in labour and manufacturing costs) of at least 20%.
TO5: Testing. To be supervised according to ISO 17025. Test loads in accordance with IEC 61400-23. For case study blade analysis, static and fatigue blade tests shall be carried out as specified in IEC WT01 and IEC61400-23.

3 - Scientific Objectives
SO1: Establish performance requirements for current blade designs and interpret data from whole system modelling, ensuring that the HPC-Blade design can meet performance targets.
Investigate interaction of the ribs/blade skin in terms of overall flexure. Assess non-linear hoop behaviour in the skin, brazier loads, adhesive peel and impact on through-thickness composite stresses.
SO2: Gain new knowledge relating to overall blade design requirements, ensuring that load management principles are optimised and utilised. Confirm design principles using 3-D structural analysis for fatigue, environmental loadings, CL/torque collection and hub/tip contact solutions.
SO3: Understand and identify materials requirements for manufacture of overall blade and interior components. Establish manufacturing requirements and ensure that (through tribological testing), sliding and contact points can achieve specified service life.
SO4: Undertake detailed design activities for composite blade shell and internal components (tube/ribs/anchoring points and blade tip pitch control – when required). Identify blade root/hub adaptations design and rib/skin bonding solution.
SO5: Review how current manufacturing techniques can be adapted for the HPC-Blade design and utilised to minimise sensitivity to manufacturing variability. Tolerance and inspection requirements will be established.
Project Results:
HPC-Blade has throughout the project developed a complex system level design software package (specific to the HPC-Blade configuration) that allows potential users to input various options (required power output, speed, material, length and size etc.) and which facilitates rapid configuration optimisation for any size of blade. The tool confirms actual energy outputs, weight and safety margins for the chosen designs. The main outputs from the tool feed a design/analysis package (CAD/FEA or similar) to both validate the design and to enable the tooling and parts for the blade to be engineered and manufactured.
For a given wind turbine blade requirement specification, the design tool allows choices in materials and geometry to be parametrically tried and tested before committing to manufacture thus giving the opportunity to investigate bespoke configurations - offering a real time cost saving both on materials costs and manufacturing time and effort, which can then be passed onto potential customers.
In parallel to the development of the blade design software we have investigated existing blade aerodynamic cross-sections and sizes to understand and optimise the space allocation criterion for the HPC-Blade assemblage from hub to tip, and have assessed a number of materials commonly used in the wind turbine industry in order to determine the best performance versus cost for each material within the assembly for subsequent testing.

The detailed design of the HPC-Blade has been carried out based on the output from the system design software, where the range of operational loads and environmental conditions have been considered and illustrated for the selected blade study case (4.3m blade). The detailed structural assessment of the main blade external skins and internal ribs & reference tube covered static, frequency-fatigue, stability/buckling and thermal analyses.
The hub adapter has been designed to ensure the collection of the blade bending, flexural shear & torque loads as well as the centrifugal loads. Bending and flexural shear loads from the composite blade root section (circular tube) are transferred to the metallic hub adapter via an innovative design which precludes the need for expensive root rod inserts. These are then reacted to the hub via the existing hub bolted flange. During normal operational conditions, the torque and centrifugal loads are reacted into the hub via the hub adapter. This is achieved using an innovative interference fit connection between the blade skins and the hub adapter.
The tip adapter has been designed as a “fail-safe” device. An additional load path has been provided in the event of blade failure (fail safe) or loss of load transfer functionality at the hub adapter, where the centrifugal loads are reacted via the inner reference tube which runs through the profile supporting ribs. In this event, the blade skin & ribs centrifugal loads are collected at the tip by the last rib (tip rib) which in turn transfers the centrifugal loads to the reference tube. This device is designed only to retain the blade attached to the hub by reacting the blade centrifugal loads.

The materials selection and associated testing has been based on the findings from the detailed blade design and analysis. For the blade study case (4.3m blade – 10m rotor diameter), Tufnol has been selected for the internal ribs while carbon fibre reinforced epoxy resin laminates have been used for the blade skins. Aluminium Alloy has been selected for the remaining internal tube and hub adapter components.
A series of blade skin laminate coupons have been tested to verify the flexural & tensile strength & stiffness used for design, alongside specific tribological testing of the hub adaptation device. Further testing has been carried out on the rib to skin bonding materials.

Detailed 3D CAD models & drawings of the HPC-blade assembly have been produced, and used to define the blade skin moulds and assembly tooling. The internal ribs have been CNC machined while the internal tube has been sourced from standard stock. The hub and tip adapter components have been machined from the required materials. The blade skins have been manufactured from carbon fibre reinforced epoxy resin and are tapered as per design specifications. Dry assembly runs have then been carried out to define the assembly process & associated specific tooling requirements.

Four study case HPC-Blades have been produced, one in support of the bench testing, and four in support of field testing. The various processes have been documented in an assembly manual detailing the preparation of the upper and lower blade shells, the integration of the internal ribs and reference tube as well as the bonding of the ribs to the shells and the skins and associated leading and trailing edge joining straps. At the circular root end, a reinforcing carbon fibre tube insert has been used and the two support lands (rings) have been bonded to the finished blade skin. Outboard of the root end, an external strap has also been applied along the leading edge.
A series of bench tests have been carried out to verify 1 – the blade total mass and centre of gravity, 2 – the blade stiffness, 3 – the blade natural frequencies and 4 – the blade ultimate strength. The test blade was equipped with strain gauges and displacement transducers and the measurements results monitored and compared to the 3-D structural Finite Element modelling activities. Non-linear characteristics of the blade under extreme loading conditions were compared against analytical predictions and a close correlation was obtained for both failure mode and location, validating the designed margins of safety. The comparison between test results and the results from the computational analysis and testing provides a strong basis for future HPC-Blade product development.

The case study blades have been integrated into the hub mounting assemblies according to the specific assembly and hub adapter pre-load settings defined during the detailed design phase and as confirmed by test.
Field trial and performance demonstration activities were not completed within the project duration due to delays in securing the delivery of the remaining three field test blade prototypes. Contacts have been established with a wind turbine manufacturer who can offer a suitable field testing facility. This activity is planned to be undertaken post-project by the consortium. Video recordings of the field trails were therefore not produced, however extensive video and photographic footage of the blade full-scale strength tests have been produced and will be used in support of dissemination, together with the successful correlation between the test results and the concept analytical predictions.

The website has been updated throughout the project, recording key milestones for public dissemination purposes and also provides a secure entry point to the project management site exclusive to the consortium members.
Additional dissemination activities include the set-up of a dedicated LinkedIn page and attendance to several trade shows, in particular the 2015 Innovate UK (London – UK) show for which HPC-blade was awarded a display to showcase our innovation.
HPC-blade has been included in a professional publication promoting the use of advanced analytical simulation tools.

The HPC-Blade consortium has delivered a high-strength, low-weight and low-cost alternative approach to the over-engineered and costlier larger size (50m+) blades that currently exist in the market. The Consortium possesses a software design tool that allows the consortium to effectively communicate to blade manufacturers the performance and cost advantages of the HPC-Blade design over existing products. The HPC-blade case study for 10 metre rotor provides a strong proof-of-concept platform (which has been validated by test) moving forward towards future exploitation.
HPC-Blade offers the following benefits to offshore application: ease of in-situ blade fitting, facilitates modular assemblies offering transportation benefits, and provides maintenance efficiencies through the inherent erosion protection of the leading edge.
Potential Impact:
Market Analysis & Economic Opportunity for SMEs

The global wind power market resumed its advance in 2014, adding a record 51 GW—the most of any renewable technology—for a year-end total of 370 GW. An estimated 1.7
GW of grid-connected capacity was added offshore for a world total exceeding 8.5 GW.
Wind energy is the least-cost option for new power generating capacity in an increasing number of locations, and new markets continued to emerge in Africa, Asia, and Latin America. Asia remained the largest market for the seventh consecutive year, led by China, and overtook Europe in total capacity. The United States was the leading country for wind power generation. Wind power met more than 20% of electricity demand in several countries, including Denmark, Nicaragua, Portugal, and Spain.
After years of operating in the red, most turbine makers pulled back into the black with all the top 10 companies breaking installation records. Turbine designs for use on- and offshore continued to evolve to improve wind’s economics in a wider range of wind regimes and operating conditions.
The global market share data for wind power generation place the European market size in perspective. In 2011, it represented 23.1% of the global installed capacity.
Since the 1990s, the scale of wind turbines has increased significantly from less than 100kW to several mega-watts. There are over 12,000 wind turbines in Europe, accounting for 9.1% of total electricity production and by 2030, wind power will have taken over from hydro-power as the most important renewable energy source in Europe. Currently, Germany and Spain have the largest installed capacities, followed by the UK, France, Denmark and Italy. Globally, China and the US are the largest users of wind capacity. Large, utility scale wind developments dominate the market, but small-scale generation is increasingly popular for rural, urban and city environments. During 2011, Europe’s installed wind generation capacity from horizontal axis wind turbines increased by 35GW (worth some €12.6 billion) taking the total installed capacity to 896GW4.
The European Offshore Wind turbine market grew by 235 new turbines across nine wind farms, increasing capacity by 866MW. The average offshore wind farm size in 2011 was almost 29% up on the previous year. The average capacity of offshore wind turbines was 3.6MW up from 3MW in 2010. During the last two and a half years, 41 companies have, announced their intention to launch new offshore-dedicated wind turbine models. In all, 51 new models were announced. Interest in offshore wind has spread beyond Europe and is now global, with turbine announcements being made by companies in China, Japan, South Korea, USA and Israel, but Europe maintains the offshore lead for the time being. Almost half of the companies announcing new models are based in Europe. China is second with 33%, then the US with 8%. Japan, South Korea and Israel follow. This activity across the globe is creating a highly competitive environment and indicates that offshore wind energy is seen as a dynamic sector that will grow considerably in the future.
Despite the growth being experienced within all sectors of wind turbine markets, the overall prices of wind turbines have been falling, particularly in utility scale turbines. It is interesting to note that at the same time, total installed costs have increased - driven up by the costs of steel and copper for cabling and tight supply of installation vessels (for offshore farms).
According to Bloomberg New Energy Finance (BNEF), recent average global turbine prices were at €940k per megawatt, down from the market peak prices of €1.21 million per megawatt in 2007- 2008. As would be expected, offshore wind systems are more expensive than onshore. In 2010, total project capital expenses were €3.7 million per megawatt. The costs of smaller turbines range from around €2,400 for 1kW systems, €18,000 for a 2.5kW pole-mounted systems and €27,000 for a 6kW pole-mounted system. Hence, HPC-Blade targets turbines with a selling price above ~€25,000. Falling turbine prices in the higher capacity ranges are primarily due to fierce competition. In part, this is being influenced by politics within China where there are concerns regarding grid stability. This has resulted in stalling of turbine installation programmes, with Chinese manufacturers looking to export and using very aggressive pricing policies. These market dynamics demonstrate the urgent need for European manufacturers to be able to identify ways of reducing turbine manufacturing costs and this project provides excellent potential for a step change in design principles.
HPC-Blade offers benefits across all market sectors and blade sizes. However, it is recognised that it may prove difficult to convince large blade manufacturers to adopt the technology until it is proven - primarily within this project. Our exploitation targets within the small turbine market (up to 100kW) will generate significant revenue in their own right, but also support longer term opportunities for adoption within the larger blade markets. Horizontal axis wind turbines represent around 95% of the market and the majority of blade designs over 5m in length (typically 10kW and above) are suitable for the HPC-Blade technology. Smaller, rural and urban turbines have higher capital costs per kW than larger blades, but they are very useful in meeting local off-grid generation targets. In 2010, the total installed global capacity of small wind turbines reached 440MW from
656,000 turbines. An important consideration for small wind turbines is their robustness and maintenance requirements. An attractive aspect of the small turbine market is that reliability needs to be high, since in rural areas qualified maintenance personnel may not be available. Small wind turbines are also more expensive per kW generated than larger solutions. In the small-scale wind industry, five countries (Canada, China, Germany, the United Kingdom, and the United States) accounted for more than 50% of turbine manufacturers as of 2013.

Sales Potential for Partners in the EU

HPC-Blade also has excellent potential not only for new turbine blades, but also for replacement blade sets and upgrades which are becoming increasingly important. Upgrading of existing turbines involves fitting larger blades without significant increases in mass. This means that existing infrastructure (towers) can continue to be utilised whilst increasing generation capacity.
For the above reasons, we expect the HPC-Blade technology to be well received by the SME community in the shorter term and by the LE community in the longer term.
Although the ‘small’ turbine market is often overlooked, it is expected to grow four times its current size by 2020 – to around 0.48% of the total market. It is predicted that by 2020, the global wind turbine market size will be worth around €303bn. Taking these figures, it is possible to estimate that the ‘small’ turbine market size will approach €1.45bn. The majority of this market will be suitable for exploitation by HPC-Blade. It can therefore be seen that even with a very modest market penetration, the short-term market opportunity is very significant.
HPC-Blade will support the need for lower cost manufacturing. It will minimise the loadings on composite components, reduce materials requirements, simplify assembly, reduce labour costs and improve reliability.
To demonstrate the potential for HPC-Blade, we have based our partner benefits analysis primarily on the SME sector of the wind turbine industry. Although this market is small in terms of the overall market, it presents significant opportunities. Using the above figures combined with estimates that blade costs represent around 22% of the overall wind turbines installed cost, then we can say that we are aiming for an initial market share of <1% (in year 1 post project) growing to just over 5% by 2019 (5 years post project). These modest targets represent a significant opportunity for the consortium and we see that exploitation is likely to best managed by creating a Joint Venture Company after project completion.

This arrangement is shown below:

Joint Venture - To act as a supply and contact point for the broader market. To provide design
General Market - Sales of internal Blade components to additional SME
• eStress- Design and analysis
• BDI - Manufacture and sales of wind turbine blades
• Alpex – Hub, fasteners
• Wintrade - Supply of metallic
• KodiMax - Composite and/or Tufnol CND machined metallic

The 5 year partner benefits analysis carried out shows that the benefits that can be accrued by each partner with services being subcontracted through the Joint Venture Company (to be formed post-project).
Until the Joint Venture is created, SME results ownership continues.

A number of assumptions have been made for the partner benefit calculations:
• That all partners apply a 5% annual price increase for the services they provide.
• That overall market penetration grows to just over 5% at year five (starting below 1%)
• That eStress will provide design and analysis services for each new blade set design provided by the consortium. As IP owner of the blade design concept, eStress will also benefit from licensing agreements with large blade manufacturers from year 2-3 post project. eStress will also receive a royalty payment for each blade component set manufactured.
• That BDI will begin manufacturing activities using the new technology and including them in their current range at just 30 blades per year. It is assumed that the average selling price for 6-10m blades is €3550. This is weighted towards smaller blades where volumes are expected to be greatest.
• Alpex, Wintrade and KodiMax will supply components to BDI, but more importantly for these companies, the majority of their revenue will be generated from supply of components into the wider marketplace (through the Joint Venture Company when formed).
The annual consortium projected turnover in year 1 is €476k and this grows to €16.2m in year 5, representing a cumulative gross profit at that time of €6.2m. It should be noted that the partner benefits shown are forecast figures and there is some degree of uncertainty. However, the size of the overall market and the modest market penetration figures used for our commercial analysis provide confidence that considerable opportunities exist for the consortium.

Potential Direct Economic Benefit to All Partners

Although the SME consortium requires research funding to deliver specific technical solutions, our consortium is well placed to exploit the project results. The HPC-Blade concept represents a revolutionary concept in blade load management from which the consortium anticipate that significant commercial benefits will be realised.
Project results have been and will continue to be widely disseminated to ensure successful uptake of the technology. We have presented at several conferences, exhibitions and through trade articles, supported by data generated from the case study parts.
Our consortium will be capable of meeting initial demand for the HPC-Blade technology and as demand and volumes increase, we will seek financial support to enable growth. The case study blades will ensure that the technology can be effectively demonstrated and data from subsequent field trials will be used to demonstrate the advantage gained through lower inertial characteristics. The case study parts also demonstrate that we have considered practical manufacturing issues and that we are capable of delivering a comprehensive solution that is both validated and commercially sound.

Benefits to End Users, Society and the Environment

As electricity consumption increases, so does the need for more power plants. There is some controversy concerning the increased use of wind energy due to the visual impacts on the landscape and the complexity of carrying out like-for-like energy comparisons. However, it appears to be generally accepted within the scientific community that wind generated power benefits the environment overall. There have been numerous studies that show renewable power generation provides environmental benefits by reducing CO2 and SO2 emissions. Further, the energy generated by wind turbines balances the energy used to create them in a matter of months. A further advantage of wind turbine farms is that agricultural activity can continue on the site, since the land surface taken up by the tower installations represents only around 5% of the overall wind farm land use. This is not the case with traditional energy generation. The HPC-Blade concept supports the environment in a number of ways:
• Reduced ‘over-engineering’ reduces composite materials consumption
• Improved reliability reduces the need for repairs
• Blade weight savings provide lower inertia and better start-up in low wind conditions
• Optimisation of rib spacing negates the need for any stabilising cores (materials savings)
• The internal structure of the HPC-Blade offers rapid manufacturing and elimination of complex spar resin infusion processes. These factors result in cost savings
• Cost savings reduce the ‘Cost of Energy’ making wind power more attractive
• Lighter blades are easier to install and lower transportation costs
• Larger blades generate more power (for the same mass) and can be installed on existing turbine towers without modification.
• Inherent leading edge joint erosion protection feature reduces maintenance costs.
The consortium believes that the HPC-Blade concept will provide positive environmental impacts overall and generate demand from both blade manufacturers and end-users. Having a technology that can reduce the cost of energy generation is expected to generate a lot of industry interest.

Wider Benefits to the European Union

We anticipate high levels of demand for the HPC-Blade technology. Beyond Europe, Asia-Pacific is the fastest growing rotor blade market. By 2016, the market is predicted to reach €7.2 billion with annual installation of 93,243 blades. The growth of Asia-Pacific is attributed to China, where the market is growing in support of internal market drivers such as government support through various subsidies, increasing turbine demand from existing and proposed wind farms, and inexpensive raw material availability. These markets have a large proportion of small blade manufacturers and this creates additional opportunities for HPC-Blade (given effective IP protection).
Whilst our primary exploitation routes are into the SME dominated (small blade) portion of the market, we would also like to see uptake of the technology from larger wind turbine manufacturers.
As blades become larger, so the internal components will need to increase in size.
Larger blade sets will require longer internal tubes for CL and compressive load management, therefore, transportation of tubes greater than 5-6m in length would become increasingly expensive. We have already considered this issue and we will include modular tube components in our case-study blades to assess and evaluate tube joining solutions. The ability to supply modular tube components will mean that the Consortium can also service markets for longer blades whilst remaining cost competitive.
At some point in blade size (we estimate above ~20m) the market becomes dominated by LE blade manufacturers. These companies have significant investments in R&D, test facilities and they also tend to manufacture a large proportion of blade components in-house. Although LE manufacturers provide little (direct) additional benefit to our SME consortium overall, it is eStress who will license the technology to large manufacturers and these revenues are shown in the partner benefits analysis table. When the Joint venture is created, the remaining SME partners will then benefit through shared JV ownership.
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