June 2012

With wind energy still in its infancy, currently realizing only a fraction of its potential, manufacturing parts for the industry is a pure growth proposition for many suppliers of machined components. There’s nowhere to go but up, as wind-power is heavily reliant on machined parts and is only gaining traction as a clean energy source. As the industry continues to grow, parts manufacturers have already taken notice of the opportunity, and even the most niche manufacturers are no longer the only game in town. Figure 1

Competitiveness is good for the health of the industry, and suppliers have begun incorporating best practices to produce the best quality, lowest cost and most readily available parts.

Machining wind power components can be intensive, largely depending on the methods and means applied to the metal cutting process. For example: How long do shafts stay on the lathe? How up-to-date are the milling operations and cutters involved? With the sheer volume of holes being drilled, how efficient is the drilling? And how up-to-date is the gear milling process?

Taken as a whole, even otherwise minor improvements in each of these processes can represent a major competitive advantage. Improvements, for example, in tool material, aren’t just a function of durability and reliability, but core to productivity. Advancements in productivity, combined with lengthened tool life, results in faster cycle times and less down time. This factors directly into the ultimate efficiency of a shop, and maximizes capacity and delivery capability.

For instance, developments in the area of insert coatings and substrate have a huge influence on performance. New PVD-grades feature a coating process that, when applied, lowers tensile stresses in the insert by countering with compressive stresses. The high-impact treatment process results in stronger and safer edge lines, sharper cutting edges, and can improve milling processes experiencing difficulty during entry or exit cuts. Also, low stress CVD coatings combined with post-coating treatments result in more wear-resistant inserts. The latest coating and insert technologies can be especially beneficial in high heat applications.
 
Turning Heads
Turning is such a tried and true staple of the metalworking industry that developments in this area are not as dramatic, especially considering the advancements in milling and the evolution of CNC programming techniques. But behind the scenes, progress has been steadily marching forward.

Turning wind power components involves a straightforward range of operations and demands. The dominant workpiece materials are various alloyed steels and cast iron, many in the form of castings and forgings. And the pieces are big – more than 20 tons. The main shaft, for instance, is a large, uneven forging, typically made of a strong steel alloy. Up to a third of the material is removed through machining, mostly through rough turning. The sheer size of the main shaft dictates long run times, and the operations include everything from heavy-duty rough to finish turning, and each has different demands on tooling. Optimizing this process can yield substantial gains in productivity.

Additional components, such as the slewing ring, can require even harder steel materials. Because both external and internal diameters are machined on vertical lathes, and because stability and fixturing characteristics change, tool choice tends to vary. Sandvik Coromant designed coated inserts that stand up to abrasiveness and high temperatures. This means a harder insert substrate with a coating that provides a good thermal barrier is usually most suitable. That combination aides resistance to plastic deformation and crater wear, and it helps to control natural flank wear while generating long tool life. Figure 2

Successful Hard Part Turning
Hard part turning also has earned a prominent place in hardened material component processes. Many applications that once relied on grinding now fall well within the scope of hard part turning; the old standby only used for certain niche applications. Innovations in machines, component material and hardening, set-ups, and the cutting tools themselves have made turning hard parts increasingly accessible to most machine shops. The transition from grinding to hard part turning presents a considerable suite of advantages gained by switching to a single-edge chip-forming operation.

Case in point, new machining technology has made hard part turning the go-to process for the case-hardened steel realm, especially for turning parts with a hardness range of 55 to 68 HRc. Several wind power components fall within this range – mainly shafts and gearbox wheels – so HPT is an important place to look to improve competitive advantages in wind equipment manufacturing. The process is very much about maximizing productivity, while staying true to a highly precise target spec.

Hardened materials require extremely hard cutting edges. That need is easily fulfilled by cubic boron nitrate (CBN) as the basic tool material. Some degree of edge toughness is also important because of the variance in mechanical loads arising from interrupted cuts or material inclusions. The relationship between the cutting edge geometry and the grade plays a pivotal role in optimizing performance and results. Finding the right combination of CBN grade and edge treatment is the key to successful hard turning operations.
 
Adaptable Boring
The large diameter holes found on wind power components help to drive the development of a new generation of boring tools. As many wind power components continue to grow larger in size, features like the holes also grow, creating a requirement for new, unique machining processes and tooling solutions.

Consider the machining of large diameter holes in a nodular cast-iron wind power component. Tool strength for roughing and tool stability for finishing are both paramount. These twin qualities are essential for achieving acceptable productivity, predictable tool life, and consistency within the required component tolerances and surface finish levels. The new generation of boring tools can achieve these qualities. Bearing housings, hubs, and gearbox housings are all components that can benefit from new large diameter boring tools. Figure 3

The right insert grade for the operation and materials in wind power housings, be it a roughing or finishing application, is a vital factor in getting the most out of a boring tool. For finishing, inserts having relatively thin PVD coatings on a sharp edge may minimize deflection thus minimizing vibration tendencies. For roughing, a necessary combination is often toughness with a CVD coating that acts as a heat and abrasion-wear barrier. These attributes should be partnered with strong insert geometry to cope with unevenness, interruptions and chip jamming.

Milling: The Workhorse Operation
Milling some of the huge components that constitute wind power equipment requires adherence to best practices to ensure efficiency in throughput and to minimize production costs. The ability to remove material in the most efficient way available and perform various multi-axis operations is crucial to competitive production.

No other machining technique even approaches face milling and square shoulder milling in terms of the sheer volume of material removal. Good milling practices should lead to a satisfactory surface finish, and ultimately a maximum run time for the machine.

With most of the milling workpiece material being some grade of nodular cast iron, several degrees of milling cutter dedication is necessary for good performance, and recent tool developments have been up to the challenge. When face milling a short-chipping material like nodular iron, either a 45- or a 65-degree entering angle is generally regarded as the best option. These angles provide a good combination of feed-rate capability, cutting force balance for long tool-overhang, cutting edge strength and less workpiece frittering that yields optimal results.

Square shoulder milling, edging, profiling and other end milling operations limit the entering angle of the cutter to 90 degrees, necessitating specific properties in the cutter. In the past, lots of square shoulder milling, including end milling, was performed with triangular inserts, as this was the only practical means by which to attain the required edge clearance. The introduction of square inserts presented a problem – improving tool performance was the primary objective, but there had to be four effective edges to provide better tool-cost efficiency.

For the square insert concept to work, it had to have sufficient cutting edge clearance, advanced geometry, and flexible edge lines to perform medium roughing through to the edge-precision for finishing shoulders and angles. Figure 4

Round insert cutters also warrant consideration for roughing operations where the strongest of cutting edges makes a difference to performance and security.

Drilling down
When it comes to wind power components, making efficient holes is an especially competitive capability. The flange of the main shaft, the ring gear, the connecting ring, the gear-box housing, hub and main frame all demand holes, and lots of them. The majority of these holes are relatively shallow, with depths of up to five to seven times the diameter. These components are made of a variety of materials, and tolerances tend not to be as close as other operations require.

Because volume and speed are very important variables, productive hole drilling creates a ripple of positive effects on manufacturing costs and delivery times. These holes fall within the range of indexable insert drills, an area of cutting tool technology that has recently experienced considerable evolution. Today’s short hole drill exhibits excellent penetration rates and finishing capabilities, while being operationally versatile and reliable. Even power requirements have been minimized.

The newest index-able drills have improved cutting action, chip formation and evacuation, machining rates, as well as tool life security and can also generate consistent hole quality.

The application area of indexable insert drills has been considerably broadened over the years, from drills for simple bolt holes to drills for holes designed for thread tapping. Each of these innovations has proven to arrive just in time to directly benefit the manufacture of several key wind power components.

Going Deep
When a holes depth is more than ten times the diameter, it requires specialized technology with standard single- or double-tube systems in place. Some holes may reach depths of 300 x D, and for some wind power components, it’s necessary to machine features deep within those holes. This calls for specially designed tool-movement mechanisms, tool configurations, and cutting edges to make and finish chambers, grooves, screw threads, and cavities.

Drilling the center hole in the main shaft of a wind power unit requires support-pad technology for drill heads. New developments in this area of tooling, along with improvements in insert and head design, have led to innovations in deep hole drilling.

With the right tooling system in place, success is a matter of getting the small adjustments correct, and the devil is in the details. Using the best drill head with the recommended cutting data, a follow-up checklist should include: ensuring the best set-up, having acceptable chip evacuation, maintaining the required surface finish, achieving sufficiently long tool-life, reaching the demanded tolerance consistency, and last-but-not-least, good hole-straightness. Furthermore, alignment between the drill head and the component is integral in avoiding any bell mouthing in the hole.
 
Next Gen Gear Milling
Wind power is dependent on high-precision gears as a first responder in the transformation from wind energy to electricity, and 90% of gear wheel manufacturing involves gear milling with a disc cutter or hob. A new generation of gear milling tooling moves past traditional high-speed steel to more recent cemented carbide inserts, for improved performance and productivity.

Gear milling’s interrupted nature creates unique obstacles in the amount of entry and exit cuts, and in the high thermal variability seen by the cutting edge. This creates a unique demand combination of edge hardness and toughness.

New generations of steel milling insert grades adapted specifically to gear milling conditions provides a better balance of toughness and wear resistance. Sandvik Coromant’s GC4240 insert grade, for instance, is a tough CVD-coated insert designed for steel milling applications where cutting edge strength is needed to cope with severe machining conditions.

The GC1030 insert, on the other hand, is a PVD-coated insert for applications where a more positive, sharper and tougher cutting-edge line is needed.

Next generation inserts are coupled with disc cutters and hobs engineered for optimal gear milling performance. Versatility is important when it comes to a gear milling product platform – full profile or conventional hobs and roughing or finishing disc cutters – must cover the range of roughing, semi-finishing and finishing applications.

Staying Competitive
The advent of a wind powered age wouldn’t be economically possible if manufacturers weren’t able to cost-effectively create components with precision to close tolerances, and deliver them in a timely manner. That ability owes itself directly to the ongoing evolution of machine tools and tooling solutions. As wind power takes off, competition is increasing for better, faster and less expensive versions of the machined components. The only way to stay competitive is to keep pace with the onward march of progress in tooling, machining and manufacturing equipment and technology.  Working with a tooling partner that has an understanding of wind power component production; has an extensive product offering; and the ability and desire to improve and continue to evolve, can make wind power component manufacturing a breeze.  

At EWEA, Copenhagen, UK-based Romax Wind launched a new software and service platform named InSight, which it claims will improve return on wind assets by up to six per cent.

“Through close collaboration with operators, Romax was aware of the frustration in planning maintenance. There was a feeling that they were always reacting to failures,” says Nigel Parlor, Business Development Manager at Romax Technology. “Not knowing when gearboxes might fail made business planning difficult.” Figure 1

Condition Monitoring Systems in the past have provided just a few months alert before a failure. Operators wanted more warning and InSight was created to tackle these operator challenges.

Developed over five years with more than 20 years of engineering know-how, InSight is designed to deliver a change in enabling wind asset owners to visualize the fleet condition and predict the remaining operating life of wind turbines down to subcomponent level.

“Romax’s belief is that if you want a wind farm, or any other power generation asset, to achieve maximum output, you need to know both its current condition and what its future condition will be,” Parlor said. “You also need to know the necessary changes required in order to enhance future performance.”

The ability to identify, predict and resolve maintenance issues at an early stage before they become significant is directly related to wind asset profitability and return on investment.

Cost savings in operations and maintenance have a significant impact on reducing the Cost of Energy (CoE), though industry data shows that improvements in Availability have a significantly larger impact. By focusing on improvements in availability, the resulting CoE reductions can be more than 10 times as effective in reducing CoE than on OPEX savings.

“InSight is bold – we are attempting to ‘model out’ the reasons for failure and create predictive maintenance (PdM) tools that are accurate, reliable and easy to use.

It is also important to ensure that maintenance is undertaken at the optimum time. InSight has been developed to meet these requirements.”

InSight comprises three core elements. InSight Inspection and Analysis draws on experience in forensic engineering, studying machine behavior and field services to tackle maintenance issues. InSight iDS (Intelligent Diagnostic System is a powerful diagnostics platform, which provides precise visualization of fleet condition to asset managers and monitoring analysts.

InSight SCADA provides near real time visualization of fleet performance and interfaces with ERP systems such as SAP to enable optimised work scheduling and commercial control.

IDS is hardware independent, which means it can integrate data transmitted from multiple manufacturers’ CMS equipment, presenting it in a single, unified and easy to understand dashboard. Our system display allows trends and potential problems to be identified far more quickly and easily than is possible via multiple system interfaces.

With more than two decades experience of modelling, analysing, and understanding machine behavior, and the vibration signatures of rotating machinery, Romax engineers incorporated advanced diagnostic rules into IDS, which identify tell-tale sign combinations long before they turn into serious machine faults. IDS is preloaded with diagnostic rules covering many major wind turbine manufacturers’ machines and model type faults.

On-screen, InSight displays an ‘alarm’ for each turbine within a wind farm, as well as alarms for the gear, bearing, shaft and sensors of every drivetrain, with detailed diagnosis results of all alarms shown in a ‘trend’ graph.

CMS alone is limited in its ability to pinpoint the location of potential faults, with most only being able to indicate the sensor closest to the irregular vibration signature. Vibration analysis experts may also spend many hours identifying and locating the most common faults using CMS data.

The InSight system is currently geared towards conventional planetary drivetrains, although software for direct-drive transmissions is under development. Figure 2

Further development of InSight will incorporate condition monitoring of elements outside the drivetrain, with the next generation taking in componentry, including rotor blade pitch and yaw systems.

E.ON’s 30-turbine Scroby Sands project is the UK’s first offshore wind farm to have expired turbine warranties and be managed independently. This is an important early application of InSight.

“The InSight philosophy is based on experience and data collected over the past 20 years using some very clever algorithms and information,” Parlor said. “We can give our clients a far greater insight into their assets and significantly increase their yield.”

As turbines become larger and more sophisticated, operational costs and the impact on revenue resulting from bad decision-making will be significant. Offshore wind farms involve an enormous investment and maintenance is challenging. With 0.1 to 0.2 failures per year (1 failure per 5 to 10 years), the fact is the drivetrain failure rate is too high for offshore turbines, Parlor said.

With the offshore wind power market forecast to increase to 9.6 per cent of total installed capacity by 2015, InSight can make a serious contribution to operators.

Primary Causes of Turbine Failure
With the first large turbines (multi MW turbines) coming out of the warranty period, there are a number of reliability issues appearing. The main area of turbine downtime is the drivetrain, which includes the gearbox, generator and the main bearings.

There are three primary causes of failure. The first arises from maintenance issues. This is not always the fault of the operator; there are occasions when turbines do not lend themselves to component maintenance. An example is when a gearbox is well designed but the subsystem requiring maintenance is not. Similarly, if during assembly, parts were not aligned properly, future problems may arise. Figure 3

Poor siting can be a further cause of turbine reliability issues, particularly where turbines are subjected to higher than necessary wind loads.

A third area is related to design flaws where a product line has problems that result in multiple failures downstream. Blade issues are not so common, but they present a significant expense when they do occur because the remedial work causes downtime.

Offshore operations requiring a blade swap can result in high costs.

Romax is developing products that will help schedule the flow of maintenance and quality assurance of maintenance procedures to allow operators to document and monitor both improvements and defects identified in the manufacturing process. Figure 4

Giving the Operator Control
“The InSight solution comes from the technology side, rather than the service or product side” Parlor said. “This means that we are offering an independent view. This is an end-to-end solution, from a condition-monitoring hardware solution to a fleet monitoring service. We help clients put the processes in place and provide the training they need in order to operate their assets to optimum capacity. Our solutions give the owner control of everything rather than being tied to one service provider. Owner-operators can understand their assets and manage them on their own terms, so they are not tied into a hardware vendor.”

A Critical Time
As the first generation of 1.5 to 2.5 MW class wind turbines enters maturity, there is increasing evidence of main bearing failures across a variety of turbine models, turbine manufacturers and bearing types. Failures have been experienced by operators in the US, Europe and Asia and in many cases a number of failure modes and symptoms have been found to be consistent across the fleets.
The nature of these machines is very different to smaller ones in terms of cost to operate, size and revenue generated. Technology levels are higher as are the value of assets. Correct management is more important than ever. Figure 5

Romax also has a background in the design of drivetrains for multi-MW turbines, and experience in offshore wind farm product manufacturing that helps them solve customer problems.  

Every day workers risk their lives at extreme heights to accomplish tasks that are essential to the development and operation of wind turbines. With some of the tallest towers reaching several hundred feet, there is no margin for error. It is essential that all workers be protected from severe injuries in the event of a fall.

Fall Protection Standards
Every company performing work at height must have a fall protection plan in place in order to comply with the ANSI Z359.2 standard. A written fall protection plan is required whenever one or more person(s) are routinely exposed to fall hazards and need to be protected with a fall protection system. ANSI also requires a documented fall protection plan be developed by the program administrator, made specific for each site, kept up to date and stored at the worksite.

Clearly, a written fall protection plan is not enough to protect workers. Even the most comprehensive plan will fail if workers are not adequately trained to execute the program and use the equipment properly.

Training: The Way to a Safer Workplace
Formal training is crucial for any person who performs work at height. Without such training, workers may not realize the severe consequences of a fall, including serious injury or death. Eager workers may be anxious to prove themselves and, if they see safety equipment as a hindrance, may forgo using it. Others could be embarrassed to ask about the proper way to use the fall protection equipment and may use it incorrectly, which will ultimately decrease the effectiveness, comfort level and usability of the equipment. It is therefore important to instill the value of fall protection training within your workforce.

All employers in the wind energy industry should provide training programs through every step of the process, including installation of the turbine and regular maintenance activities. Training courses are in-depth sessions covering a variety of pertinent topics, such as:

• Identifying, eliminating and controlling potential fall hazards
• Selecting the right fall protection equipment for the job
• Inspecting, using and maintaining fall protection equipment on a regular basis
• Executing the tactics within a fall protection plan
• Compliance with applicable industry standards

One of the most important areas of fall protection training in the wind energy industry is rescue. Since wind turbines are frequently located in isolated locations, more time is required for rescue crews to reach an accident scene. Another issue is that most falls occur near the top of the turbine, where rescue can be nearly impossible from the ground using conventional rescue tactics.

For both of these situations, employees will need to know how to perform a prompt rescue procedure. Prompt rescue is typically defined as within four to six minutes and no longer than 15 minutes following the fall. The difference between a non-injury fall and one resulting in serious injury has to do with how quickly a worker is rescued. The longer the fallen worker is suspended or trapped, the worse the injuries he or she may sustain.

Who Should Provide Training?
Many fall protection regulations specify the involvement of a competent person as defined by OSHA regulations 29 CFR 1926.32(f). OSHA defines a competent person as “one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.” To become a competent person, one must undergo specific training and show adequate knowledge through extensive experience. Figure 1

Competent persons should be identified within the company to oversee the fall protection plan, conduct fall protection training, and ensure all employees are prepared prior to working on a turbine. If you need help addressing fall protection topics or would like to ensure your training programs are comprehensive and in compliance, contact your fall protection manufacturing company. Many manufacturing companies, including Capital Safety, offer training courses for workers of all levels, and will work with you to develop a plan that is specific to the jobsite and appropriate for your workers’ needs.

Types of Training
Since workers typically learn the most by watching and then by doing, it is best to conduct a training program with an equal amount of classroom and hands-on instruction. The key with any training program is to provide learning that approximates actual work conditions so the workers can easily apply what they’ve learned to real situations.

Classroom Training
An OSHA-defined competent person should conduct classroom training that is specific to the needs of the worksite in a controlled environment. The trainer must identify learning objectives and develop a lesson plan prior to conducting the class. Most classes combine lecture style training, including slides and video, with group discussions to apply theory to practical applications. Training manuals should be provided for workers to reference both during and following the course.

While many topics will be discussed during the course, such as those previously listed, it is crucial for trainees to review fall energy and fall clearance – the two most misunderstood topics. Many workers do not understand or even consider the amount of energy a fall generates. The force of a fall is dangerous and can extend the total fall distance considerably, leading to serious injury or death. For example, a 310-pound individual falling more than six inches will create forces up to 3,200 lbs. Understanding fall energy will help workers identify the best equipment to limit fall distance and thereby reduce the amount of energy generated in a fall event.

The other important topic to discuss in the classroom setting is calculating fall clearances. Should a fall occur, there must be sufficient clearance below the user to arrest the fall before the user strikes the ground or any other object. Fall clearance is more than a simple measurement from the worker to the nearest obstruction. The correct formula is the lanyard length + the energy absorber deceleration distance + the height of the dorsal D-ring on the harness from the worker’s feet + the clearance to obstruction during fall arrest (see figure). Each of these measurements is critical and must be taken into consideration to correctly calculate the fall clearance distance. The results of a fall can be much worse, even fatal, if this measurement is miscalculated. Figure 2

Equipment demonstrations and tutorial videos are also provided during classroom training to show workers best practices when working on the turbines. From here, workers should be prepared to move on to practical applications where they will experience firsthand how to properly use equipment and execute the fall protection plan.

Hands-on Training
Hands-on training allows workers to learn by doing and gives them the opportunity to be corrected in a safe environment. When talking about a harness, for example, there is no substitute for strapping into it, connecting to an anchor, experiencing how it feels and seeing firsthand what needs to be inspected before use. Workers can also conduct mock trials of the fall and rescue procedures to become familiar and comfortable with the tactics in the comprehensive plan.

Hands-on learning experience can be offered either on or off the worksite. Courses at an off-site facility provide controlled environments uniquely designed to offer practical experience and unique complexities of working on a turbine. On-site courses, on the other hand, apply professional training to your specific daily work activities. By training in and around the workers’ normal environment, you can ensure that the issues discussed are immediately applicable to your employees. 

Assessments
Training courses are typically competency-based, with each course having a specific and relevant unit of competency as indicated by the learning objectives and lesson plan. With these types of programs, writing assessments and/or hands-on exercises are to be completed by workers to show knowledge retention of the presented information and the ability to apply it in a work-like environment.

The Bottom Line
Wind turbine installation and maintenance calls for tight safety measures. With the sector showing enormous growth and potential for the future, the need for fall protection planning and training will be more important than ever. Give your workers the confidence they need to conduct their work safely with the right equipment and with the knowledge to help their co-workers in the event of a fall.  

Supplying materials to the wind energy market since 1995, Gurit specializes in the development of composite blade materials, meeting the demand for larger and more complex designs.

The tendency among large turbine manufacturers in the industry in recent years is to supply longer blades on existing turbine designs to suit light wind sites, or to install offshore turbines that are multi-megawatt machines, requiring larger blades, that can withstand higher loading.

The main load-bearing structure of a wind turbine blade is the spar component, which is either integrated into a structural shell as a spar cap, or constructed in parallel production to the shell as a separate spar structure complete with shear webs.

What is common to both approaches is that the utilization of unidirectional fiber (UD), glass or carbon, to provide bending strength and stiffness. The fiber also has to withstand compression loads; particularly in longer carbon blades and consequently the fibers need to remain straight and receive consistent support by the surrounding resin to prevent buckling.  In order to enable longer blades to be designed it is important that the properties of the fiber are maximized when converted into a sparcap laminate. Figure 1

Collimated fiber formats like prepreg provide a good starting point to achieve these requirements, but there are additional challenges to maintain the fiber straightness and prevent voiding during the application and cure of thick section spar components. Other factors outside of material performance also play an important role in material and manufacture process selection, such as storage and lay-up temperature and tooling specification.

Gurit has set out a clear strategy to address these barriers to allow the use of prepreg in order to maximize the performance of unidirectional fiber and enable the next generation of blades. Two key technology steps in this strategy are:

– Velinox^TM Resin Technology – to enable low cost tooling, eliminate cold storage and minimize cure time
– Airstream^TM Coating Technology – to enable very low void content laminates without debulking or the requirement for air-conditioned factories.

Velinox™ Resin Technology
Velinox^TM is a new resin technology, developed by Gurit as a next generation resin platform to enhance Gurit’s current wind energy Prepreg and SparPreg™ products. The resin has been designed specifically for the cure of thick sections, such as wind turbine blade spars and roots. This chemistry does not exotherm in the same way as a standard epoxy, enabling the cure profile to be modified to eliminate time-consuming dwell periods that control exotherms in conventional resin systems. The result is a greatly reduced production cycle improving the mould utilization with the additional benefit of lower wear on moulds due to the lower peak temperature. The system can be cured at temperatures as low as 100°C, but can also be used for rapid manufacturing of components through its 10 min cure at 130°C and 20 min at 120°C even at thicknesses up to 100mm. Therefore, both thick and thin laminates can be cured quickly and provides the option to specify low or high temperature performance tooling. Figure 2 shows the temperature profile of the centre of two 92mm glass laminates. In the laminate with the conventional epoxy system (red line) a 70°C dwell was used to minimise the peak exotherm. The Velinox^TM system (blue line) does not require a dwell and therefore can be heated directly to the preferred cure temperature (blue dotted line), which in this example is 125°C. A small exotherm is observed with a delta of only 15°C and full cure is achieved in approximately 10 minutes from the peak temperature time.

While the primary advantage of the new resin system is rapid curing and exotherm control, Velinox^TM also addresses another disadvantage of conventional prepreg materials – cold storage. Most epoxy prepreg systems have latent curing technology, which enables pre-mixing of the resin and hardener before fiber impregnation. The prepreg then remains in an uncured state until reaching higher temperatures (>70°C) to activate the catalysts. However, in practice, the prepreg will slowly cure at room temperature (from days to weeks depending on the system) and therefore for purposes of shipping and stock control the prepreg needs to be chilled or frozen. The new resin technology has different catalyst technology from conventional epoxy prepregs and therefore has significantly improved shelf life characteristics. With a shelf life of over 4 months at 35°C the need for a frozen or chilled supply chain is eliminated reducing both freight and storage costs.

Airstream Coating Technology
Velinox^TM resin technology addresses two of the common problems of using prepreg materials, of exotherm and material storage. However, this alone does not enable the manufacturing of high quality wrinkle free parts with low void content, which is critical to prevent premature failure of the laminate and maximize fiber structural contribution. The optimal utilization of the fiber properties is particularly relevant when considering the high cost of carbon fiber. Figure 2

Conventional prepregs are processed using vacuum bag technology to remove the air between the plies prior to consolidation and cure. However, as laminate thickness increases it is difficult to maintain high quality, low void content laminates without the use of multiple debulking steps and/or the use of high-pressure autoclaves to consolidate the plies. However, due to the size of spar caps and the manufacturing cost targets it is not feasible to use multiple process steps or expensive capital equipment. It is for this reason that specialised prepreg products have been developed to enable the manufacture of high quality large structures for the wind energy market.

While it is important to maintain voiding within the laminates to a low level (<3%) and to ensure individual voids are small in size (< 1-2mm diameter) what is more critical is to avoid the introduction of wrinkles in the laminate. A wrinkle of even small amplitude can produce an area of laminate that would be more susceptible to buckling under compression loading. The avoidance of wrinkles is a significant challenge in spar cap manufacture due to the geometry and thickness of the component. The tooling often has a double curvature profile, which requires the prepreg material to have significant drape capability and wrinkling resistance. This can prove a challenge for a number of reasons: the prepreg is typically only 500-600 microns thick and therefore is generally susceptible to buckling if not handled carefully; the drape increases with temperature, but the removal of inter-ply air decreases rapidly with temperature reducing the process window for good drape characteristics; and the draping of a prepreg is a time dependent viscoelastic process, which complicates rapid deposition using automated application techniques. Figure 3

One approach to increase the process window of spar manufacture is the use of a lightweight scrim laid in between each ply of prepreg. This increases the airflow between the plies under vacuum pressure enabling the removal of air between the plies and therefore reducing residual void content. However, this approach has some drawbacks as the scrim can decrease the compression strength of the laminate and the beneficial air removal effect is still limited to temperatures around 25°C at which point the tack of the prepreg becomes problematic. As a typical blade manufacturing plant can run at temperatures as high as 35-40°C in the summer months this solution has its limitations due to the high operating costs of air conditioning.

To overcome the conflicting material characteristics of low tack at the same time as high drape, and avoid any detriment to mechanical performance, the new product using a specialized coating technology to give the combination of:

• An air venting structure on the prepreg surface(s) that operates under vacuum even at temperatures as high as 40°C;
• A controlled level of tack and handling properties over a wide temperature range (15-40°C);
• And mechanical performance consistent with uncoated prepregs

The increased air permeability between the plies provided by the coating is an extremely effective way of removing inter-ply porosity when the vacuum is applied. The resulting laminate has very low void contents (<2%) even when factory temperatures are in excess of 35°C. Figure 4

The second feature of the product is the low tack and high drape it exhibits over a wide temperature range. The coated surface of the prepreg promotes sliding of the prepreg plies during layup and subsequent vacuum consolidation, preventing “stick-slip” and the formation of wrinkles.

Conventional prepreg processed at temperatures around 25°C would produce laminates with void contents in the order of 10-20% even without considering the formation of large wrinkles.

As the design of large multi-megawatt wind turbines progress, more designers are investigating the benefits that prepregs bring in terms of mechanical performance and quality assurance. As many of the designers are more familiar with infusion technology they have some reticence about the manufacturing complexities and overall cost of using prepreg. With Velinox^TM Resin Technology and Airstream^TM Coating Technology, Gurit hopes that its new prepreg developments will address many of the concerns surrounding the adoption of these materials and significantly reduce the cost of use by taking a holistic approach to material development.  

It’s a daunting endeavor for a company to competitively and successfully develop longer, lighter and higher quality wind turbines in today’s economic and political climate with so many technical and financial risks at stake.

In this context, turning to automation for the design and manufacture of wind blades holds the promise of many advantages, including faster time-to-market, reduced engineering and production costs, enhanced quality and performance, and improved design tailoring capability.

In fact, the larger wind turbines become, the more critical it is to adopt automation. Labor-intensive processes don’t make sense economically in the long run. And with the wind industry developing increasingly complex blades that may soon reach 100 meters (or 328 feet) in length, a high degree of manufacturing automation is essential to ensuring the long term viability of this industry.

But proper adoption of automation requires a reassessment of the whole development process. Using automated manufacturing systems alone doesn’t guarantee that wind turbine-manufacturing firms will profitably meet the expanding demand for high quality blades. Indeed, without a way to rapidly optimize the designs for automated processes, accurately assess the producibility of wind blades and fully integrate the design, validation and manufacturing process, automated production systems represent an incomplete solution to a complex challenge. Figure 1

Enhancing the Power of Analysis
Composite wind blade designs offer huge advantages in terms of weight savings and durability.  However, they also bring on unique challenges for the engineering analyst who has to ensure risk-free performance while dealing with complex shapes, thousands of plies, and properties that change along the entire length of the blade.

Because of this inherent complexity, composite design and analysis for wind turbine blades is a highly collaborative and iterative process. The process typically begins with early system level models that feed a computation fluid dynamics (CFD) analysis. Cross sections at various stages are derived and sent to the CAD and CAE teams. Sophisticated CAD applications are then used to generate the 3D model of the wind blade. For instance, NX® software from Siemens PLM Software can be interfaced directly with the system engineering solutions to read in scan lines or point cloud data and create a high quality surface through lofting and freeform modeling.

The early CFD analysis also provides the pressure loads that need to be mapped onto the blade for CAE analysis. So while the CAD team is busy generating the 3D model, the analysis teams can be working on preliminary sizing and optimization. Many CAE engineers use 1-D equivalent beam models for initial optimization and then build 2D models to represent the detailed structure.

The CAE applications for analyzing laminate composites derive the properties of the ply material based on defined properties for the fiber and matrix materials. They also support a range of theories that seek to predict ply strains and stresses and the onset of delamination or core failure. Typical simulations include evaluating stresses at the blade root and around bolted joints where the blade connects to the hub, vibration and modal analysis, and nonlinear buckling analysis of the skin. Additionally, engineers evaluate the blade for maximum tip deflection and fatigue loads. Since the blades are subjected to a wide range of load cases (wind direction, gusts, etc.), it is also useful to evaluate load case envelopes to identify overall margins of safety. Figure 2

The objective is to find an initial solution for where and how much material should be deposited and how it should be oriented in order to satisfy a range of performance criteria. The material and layup definitions also have a major effect on whether a part can be produced, hence the need for easy sharing of models and data between geometry design tools, CAE applications and specialized applications for composite design.

NX is a good example of an environment that supports the rapid iterations that are needed for composite blade design. Data generated in the NX CAD application is seamlessly made available within the NX CAE application, which includes a dedicated solution for the analysis of composites. Associativity is maintained throughout so that any change in design can be cascaded easily to update simulation results. Finally, the initial layup information generated in NX CAE can be shared bi-directionally with Fibersim™ composites engineering software from Siemens PLM Software.

Staying True to the Design
All too often what is being made in the factory is different from what was designed, analyzed and documented in the design office. Issues arise on the shop floor that were not expected and inevitably leads to design changes.

Software that provides the ability to perform a producibility simulation, such as Fibersim, enables an organization to verify early on in the development process that manufacturing will be able to make the parts as designed. For manufacturing organizations to be successful, designers and stress engineers must have access to producibility simulation data prior to the time their colleagues on the shop floor start manufacturing blades.

Indeed, in order to produce a wind blade to specifications with fewer risks and less waste, one should accurately simulate the manufacturing process and learn of potential problems during the time that early design and optimization are being conducted.

This is especially true for today’s football field-length blades because they are comprised of thousands of composite plies and core panels. Multiple materials, including glass and carbon fiber fabrics, various resins and bonding pastes, balsa and foam core may be used in a single blade. The ability to stack and stagger plies in different sequences and orient material fibers along specific directions enables the building of stronger and lighter blades, but it also greatly increases the amount of design and manufacturing data to deal with. Given the complexity of working with so many different materials, it is imperative to accurately simulate how they will fit together once it all hits the manufacturing floor.

By combining accurate simulation of various processes and materials and reducing the complexity for designers and structural engineers, such software solutions ensure that the components of a wind blade—skins, spar caps, web, box beam, and root laminate—will indeed be producible when manufacturing starts.

Such producibility simulation enables the timely discovery of potential problems, including fabric folding, wrinkling or bridging issues. These issues may result from excessive steering, pulling or pushing of the fabric while laying down plies or courses in the blade mold. Ultimately, it can trigger preliminary breakdown of the blade by progressive de-lamination, de-bonding and crack propagation, leading to catastrophic failure. Figure 3

If detected early by the producibility simulation, these issues can be resolved quickly by changing the ply design in various ways, including ply darting, splicing, re-draping, or material and orientation changes. This can all be done directly on the computer using Fibersim’s simulation capabilities, which drastically reduces the need for costly physical testing and shop floor rework.

What’s more, materials suppliers and transformers are constantly innovating with new types of fabric weaves or stack-ups which results in new forms of composite materials, some of which are tailored to large composite structures. Among them, Non Crimp Fabric (NCF) and multi-axial fabrics are now extensively used in the wind industry. Such materials present some new and very specific deformation behaviors when draped on the tool. For example, they are more prone to micro-buckling deformations. These deformation modes must be accounted for by the producibility simulation software in order to generate useful information for blades made with these new materials.

The benefits of producibility simulation have been proven in production across multiple industries by companies such as Bombardier Aerospace, BAE systems, Nordex, Sinomatech and others.

With the advent of automated deposition systems for wind blade layup operations, a complete and accurate producibility simulation capability is even more critical. That’s because in traditional manufacturing, the engineers and technicians who are confronted with manual layup issues on the shop floor will often have enough experience and knowledge to devise a workaround “on the fly” to get them over the hurdle. While this is less than ideal because it is not repeatable and increases the risks of an imperfect blade, at least it keeps the manufacturing process moving forward.

With automated deposition systems, the machine is unable to figure out manual workarounds “on the fly.” Events and alternatives are either pre-programmed or they are not. When the answer to an issue is not available, the machine stops, or may damage the part or the mold. Precious time is wasted halting the automated deposition process for lengthy manual interventions. Such downtimes are major productivity killers and the reason why some companies have delayed adopting automation.

In order to control the risks of new technology, such as automated deposition systems for wind blades, it is imperative to root the engineering process in a complete, accurate and reliable producibility simulation of the manufacturing process.

Avoiding Failure
As described in the previous sections, the laminate sizing and layup information along with the detailed surface representations are inputs for detailed laminate design and subsequent producibility simulations.

However, the material orientations derived from the draping simulations can vary enough from the initial definitions that an accurate final validation step is necessary. The detailed design will also have numerous ply drops and thickness variations that typically would not have been part of the initial sizing and optimization step. Figure 4

In the validation stage, high fidelity break-out models that use layered solid elements can be built. When physical test data is available, finite element models can be refined to correlate with the test results. These correlated models can then serve as a basis for detailed analysis and conducting tests in a variety of operating conditions up to the point of failure, which is prohibitive to perform on a physical part.

Incorporating Design & Manufacturing
So clearly, making sure that the part is optimized, verified, and fully producible is paramount before manufacturing starts. But there is another critical ingredient that is required to deliver an efficient and reliable blade manufacturing process: The adoption of an integrated design and manufacturing process.

Manufacturing teams making blades in the factory often encounter problems that stem from the fact that while some data may be available in the design office, either digitally or on paper or in the heads of the designers, some of that data has not made it to the shop floor. Or if it does make it, it is incomplete or not accurate enough for the manufacturing engineers to fully and precisely reproduce the design intent. They are left trying to figure out some of the details and fixing some of the apparent contradictions.

Furthermore, late modifications and design changes performed in the shop—sometimes major ones—are not communicated back to the design and analysis teams due to time pressure and other higher priority tasks.

An integrated design and manufacturing approach will remedy this type of situation.
Integrated design and manufacturing is a cornerstone of composites manufacturing. It is critical to reaping the expected benefits of automated deposition applied to wind blades.

For the automated manufacturing process of a blade to be reliable and lead to the expected time and cost savings, a complete, detailed and producible definition of the part must be communicated seamlessly from the 3D composite model to the digital manufacturing environment and, ultimately, to the machines. The goal is for the machines to produce the part exactly as designed.

A seamless link from the 3D composite model to the automated deposition system conveys consistent, complete and reliable data that reflects engineering intent, detailed ply and core layup definition, manufacturing constraints and exceptions handling.

Such a seamless link is illustrated by the connection between NX, Fibersim and the Tecnomatix® software for manufacturing simulation and planning, which allows the automated transfer of a producible wind blade design to digital manufacturing. By providing complete data about how the fabric should be laid down to avoid manufacturing problems, this link enables the fabrication of a wind blade by machine systems that can layup rolls of materials with significant time-savings compared to manual processes.

Staying True to the Plan
The wind industry is following in the footsteps of aerospace firms by moving to automated deposition of composite materials for large composite parts. While automating wind blade manufacturing can save time and reduce costs, there are significant risks if the machine system is not fed with the appropriate instructions from a producible part definition.

Within the Siemens PLM Software portfolio, composite design software, such as Fibersim, provides the ability to simulate the fabric deposition completely and accurately to ensure producibility of the design.

In addition, by combining Fibersim with the capabilities of NX CAE software for analysis and Tecnomatix Process Simulate integration, the organization can guarantee seamless communication of the detailed and validated design to the shop floor. This digital process ensures that the parts are manufactured as designed and analyzed.

Without such a blueprint, the costs could be high. Imagine a 70-meter long blade attached to a wind turbine that weighs more than several hundred tons and is raised almost 500 feet off the ground. Now imagine a failure in the blade structure. With structures as large as these, blade failure can cause catastrophic damage to lives or property. Failures can also lead to long shutdowns for costly repairs. What can engineers do to avoid blade failure?  The answer is to adopt a well-executed product development process that integrates design with performance simulation and producibility simulation to catch all the problems before they arise.

Ever since the Wright brothers used cables to strengthen the wings on their early planes, this approach has been perceived as outdated, or simply put, old fashioned. However, the Glen Lux designed, built, and patent pending Vertical Axis Wind Turbine (VAWT) is unique in that it uses this highly effective technology to reinforce its multiple blades. For example, the Lux VAWT design with a one-megawatt power generating capacity has one-third the total weight of a comparable Horizontal Axis Wind Turbine (HAWT), mainly because it does not rely upon a tower or central column. The Lux VAWT also uses the same blade profile along the entire blade length, thus the reduced construction inputs drastically reduce the capital costs. Table 1

The Lux VAWT has six evenly spaced blades that are curved into an elliptical shape. The chord length of the blades is shorter than previously used blades, but the structural part of the rotor is reinforced by the use of several small diameter cables. By strategically attaching the cables to the blades, the aerodynamic drag is minimized. The cables follow a near circular path between their blade-to-blade connections. This results in a small amount of lost power; however, the structural integrity of the rotor, which consists only of blades and cables, is significantly enhanced. There is no need for an expensive central column or struts.

From the 1970s to the 1990s researchers from Sandia Labs in Albuquerque New Mexico, and the National Research Council in Ottawa, Canada worked on VAWT or Darrieus-style turbines, with two or three blades rotating around a vertical axis. The more common type of wind turbine is the HAWT that rotates around a horizontal axis.  At that time it was unclear which style was more economically feasible. Both types had their limitations.

As these two organizations experimented with two and three bladed turbines, they tried different blade profiles, adjusting solidity ratios, height/diameter ratios, and blade curvature, offset blade angles and strut positioning. The power outputs were comparable to the HAWT, however, several of these demonstrator prototypes, including the largest VAWT ever built, a four-megawatt turbine in Quebec, encountered structural problems.  A five hundred kilowatt turbine located in Prince Edward Island had a premature structural failure, primarily due to fatigue and corrosion issues. In addition, these two bladed designs suffered from large fluctuating torque excursions that caused poor power quality.

For the past few years Canada’s National Research Council analyzed a Lux Turbine model with a diameter of 40-meters and a height of 65 meters with a one-megawatt power output. The Aerodynamic Lab used the Double Multiple Stream Tube Model computer program to predict the power output and wind loads along the entire length of each blade as the VAWT was rotated. These aerodynamic lift and drag loads, along with the centrifugal and gravitational forces were then applied to the six blades of a Finite Element Model of the Lux VAWT by the Structural and Material Performance Lab. The computer simulation program was used to determine the locations with the most damaging stresses and deformations. From the operating range of rotational stress data and using rainflow analysis they were able to predict the levels of damage to the blades, caused by these forces. The analysis performed by NRC, was for an International Electrotechnical Committee class II wind regime. Using a simulated annual wind spectrum, NRC predicted a life expectancy for the modeled blades to be measured in centuries instead of years. Deformations, even at extreme wind speeds that would be encountered once in 50 years, were exceptionally small. Further analysis on blade natural frequencies, temperature gradients, extreme wind loads and buckling were also achieved without any concerns to their long-term performance. The multiple blade design eliminated the torque excursions, a major source of structural fatigue loading, and achieved minimal torque ripple resulting in improved power quality. Table 2

The NRC also scaled the turbine to a remarkable 160-meter diameter with an approximate output of 16 MW. Surprisingly, the blade stresses remained relatively constant. It appears the maximum turbine size is only restricted to the economies of scale.  As an added plus, large VAWTs are able to take advantage of the higher winds above the earth’s surface without the use of towers, making them ideal for use off shore. Table 3

VAWTs built in the past have certainly had their problems. The government program in Canada was folded in the late-1980s and Sandia suffered a similar fate with their vertical wind turbine program. Compared to the horizontal wind turbines, the vertical turbine has had relatively little research; however, in our opinion, it has far greater potential.  In the quest for the perfect turbine, the vertical axis model has been overlooked. Some of the advantages of the Lux VAWT turbine include:

• Lower capital cost
• High power output
• Low maintenance with few moving parts
• Low overall center of gravity
• Easy access to ground level power generation
• Gearboxes and generators can be contained in sound proofed ground level facilities to reduce external noise
• Higher power output/land area by using counter rotating turbines in close proximity
• A simple Friction Drive system reduces or eliminates gearbox problems

VAWT are wind direction independent and the turbines offer uncomplicated scalability to smaller or larger sizes with excellent longevity. These are important issues, especially since the warranty period for newly designed and manufactured HAWTs has been decreasing in recent years, despite the fact that the bulk of research money over the years has been put into complex HAWTs.  Isn’t it time to rethink the direction we are headed?  

When the engineering team at International Tower Lighting, LLC considered the unique demands and requirements of obstruction lighting systems for wind turbines, they were venturing into uncharted territory. Among the multitude of challenges, the first key question was whether to modify an existing telecommunications lighting system or to design a lighting system specifically for wind turbines. Extensive industry research and consultation with experts in the field yielded the definitive answer, the designers at ITL responded with the IFH-1710 and built it entirely from the ground up to serve the requirements of the wind turbine industry.

The project began with a careful investigation of the regulatory and environmental factors governing the wind turbine industry. In addition to strict FAA requirements, the wind industry and the wind turbine environment have their own standards and concerns, especially with regard to compliance with environmental stewardship and advanced energy technologies. It was clear that, as with their original telecommunication designs and equipment, success with the IFH-1710 would require strict adherence to the industry’s most demanding specifications.

With clear guidelines for designing and manufacturing a light build to surpass the industry’s own standards, the engineering design team set the bar high. They concluded that the ultimate design of the new IFH-1710 must:

• Be highly energy efficient;
• Use sustainable materials and advanced technology;
• Be rugged enough to endure harsh environmental conditions;
• Be compact enough for the limited space available on a wind turbine nacelle; and
• Be flexible enough to meet the needs and individual requirements of different customers.

What follows is an overview of the criteria that figured heavily in every stage of the design process and how ITL’s design team addressed each engineering challenge.

FAA Requirements
In tackling regulatory compliance, the team began with the requirements specific to wind turbine farms that may be found in chapter 13 of FAA Advisory Circular AC 70/7460-1K available at www.faa.gov. The FAA defines a wind turbine farm as “wind turbine development that contains more than three (3) turbines of heights over 200 feet above ground level.”  Not every wind turbine within a farm is required to be lit.  The FAA requires unlit gaps of no more than ½ statue mile.  FAA Type L-864 red flashing lights are preferred for night-time marking and all lights are required to flash synchronously.

Detailed technical specifications for the L-864 lighting system can found in the FAA Advisory Circulars and Engineering in Table 1.

The FAA clearly states that the type L-864 red flashing lighting system is preferred for wind turbine farms, so this made the decision clearly in favor of designing the IFH-1710 as an L-864 that would flash synchronously. To avoid costly cabling between lights, the team elected to use the timing signals derived from the Global Positioning System for flash synchronization. However, further investigation revealed that not all GPS receivers are created equal. Thorough testing of several models resulted in significant differences in the speed and ability to receive the required timing signals under varying environmental conditions. Based on test results, ITL’s design team favored use of a one-piece GPS receiver manufactured by Garmin that was found to be extremely fast and reliable at achieving a satellite fix. It was also compact enough to fit inside the cover of the IFH-1710 lighting system.

LED Technology and Optics
Due to their ability to efficiently produce light, LEDs are finding their way into everything from flashlights to street lights. Choosing high power LED technology was one of the design team’s easiest choices. However, the companies that manufacture LEDs generally design them to disperse light over a wide area. The light beam of a high power LED can be as wide as 120 degrees.  FAA requirement for obstruction lighting systems require a vertical beam of only 3 degrees and heavily restrict the amount of light allowed past 10 degrees below horizontal.

Early on, ITL recognized that an efficient secondary optic would be required to tame the wide LED light beam into the tight “disc of light” required for a wind turbine obstruction lighting system.  So, the IFH-1710 includes custom-designed and molded optical grade PMMA (Acrylic) precision optics coupled with high power LEDs to meet these challenging requirements.

Thermal Design
The power dissipated by an LED, usually only about 1 watt, may sound quite low. However, this power is packed into a very small space. The light emitting area of an LED, called the die, can be as small as 1mm square. 1mm is about the diameter of the wire used to make a large paperclip.  Even a small amount of power in such a small space leads to high power density. If great care is not taken to remove heat from the LED die the temperature will rise. High temperature adversely affects LED life and efficiency, so an effective thermal design is critical to the success of an LED lighting system.

Traditionally, electronic components like LEDs have been mounted to printed circuit boards, which have a copper layer and fiberglass substrate. Fiberglass is a thermal insulator and therefore, is not well suited for most high power LED designs. Metal clad printed circuit boards (MCPCBs) replace the fiberglass substrate with an aluminum plate. The copper layer is separated from the aluminum by a thermally conductive yet electrically insulating dielectric layer. The resulting metal clad printed circuit board is highly effective at removing heat from the LED. Figure 1

For their IFH-1710 design, ITL chose metal clad printed circuit boards and mounted them to an aluminum heat sink to efficiently conduct heat away from the LEDs. A rugged cast aluminum base then conducts the heat out of the lighting system.

Power Supply
The light output of an LED is primarily determined by the DC current flowing through it. So to achieve constant light output, conversion from AC power into a DC current would be necessary.

The two main types of power supplies are the linear power supply and the switching power supply. The linear power supply is simple and rugged but dissipates excess power as heat. This is both inefficient and detrimental to the life of LEDs. Switching power supplies were specifically developed to minimize the production of unnecessary heat and can also be designed to accept a wide range of AC voltage and frequency. This flexibility makes them usable worldwide without modification. These characteristics make the switching power supply an ideal solution for driving LEDs. In the IFH-1710, the switching power supply accepts 120 to 240Vac, 50 or 60Hz to power the LEDs while minimizing the production of excess heat.

Sustainability
Aluminum accounts for over 60% of the weight of the IFH-1710. ITL’s engineers chose aluminum because of its ability to conduct heat and its sustainable nature as one of the most highly recycled metals in the United States. However, sustainability does not just mean using highly recycled materials and an energy efficient design. Sustainability also encompasses “the capacity to endure.” The IFH-1710 wind turbine obstruction light would need to endure.

Wind turbine obstruction lights are subject to extremes in weather, including heat, cold, wind, rain, and snow as well as other factors such as vibration and lightning. While ITL’s design makes every effort to prevent failure, it would also need to be repairable. A dispose-of-upon-failure design would not be a sustainable one. To be truly sustainable, the IFH-1710 obstruction light would need to be field repairable. Thus, the design must include accessibility and modularity.
 
The resulting highly accessible features of the field-repairable design of the IFH-1710 include a hinged cover that uses rugged stainless steel draw latches to secure it when closed. The interior may then be accessed in seconds, while also remaining highly secure and protected from the elements when latched closed. Figure 2

Further, modularity is achieved as all of the electronics including the controller, power supply, GPS and LED boards are included in a single replaceable assembly called the LED Light Engine.  The LED Light Engine is assembled around a custom designed aluminum extrusion. LED circuit boards and optics are installed on the outside surfaces to direct light 360 degrees around. In the center of the light engine are two card slots that house the controller circuit board and power supply circuit board. A GPS and photocell for determining day/night operating mode are mounted on top of the light engine. The entire light engine assembly can be removed from the cast aluminum base for servicing by loosening only four fasteners. All of the light engine’s components are replaceable.

Installation
The wind turbine obstruction lighting customer’s objective is to produce clean and sustainable electricity from wind, not to provide a home for an obstruction light.  With that in mind, ITL endeavored to minimize the size of its wind turbine obstruction light. The resulting design of the IFH-1710 is a complete obstruction lighting system contained within a compact flash head. What this means to the customer is that it requires virtually no space inside the nacelle.

To simplify installation, the IFH-1710 comes with a pre-wired cable for connecting power and Form-C alarm contacts. For a new wind farm, mounting the flash head and connecting the cable is all that is necessary. For existing wind farms, the IFH-1710 is designed to be flexible enough to match the flash rate of other manufacturer’s lighting systems with only the flip of switch.

Unique Circumstance; Fresh Approach
Obstruction lighting design is not a one system-fits-all-industries proposition. When venturing from telecommunications lighting systems to those for the wind turbine industry, International Tower Lighting, LLC recognized that the unique circumstances of the industry demanded a fresh design from the ground-up.

Using extensive engineering design expertise in the obstruction lighting field honed over the last twenty years, the company has now introduced its new wind turbine obstruction lighting system in the form of the IFH-1710, addressing exacting standards for energy efficiency, sustainability and ease of installation.