March 2011

Proper alignment of any bolted joint can be achieved by the use of either torque or tension methods of bolting. While both methods of securing the joint produce the same end result, the debate continues about which method delivers the most accurate and consistent bolt load value. If the proper bolt loads are not achieved during installation the integrity of the joint will be compromised, leading to misalignment and, if not checked, ultimate failure of the joint. These two methods of bolting are used in wind turbine installation and maintenance through the use of hydraulic torque wrenches and hydraulic bolt tensioners. The method used is typically determined by the turbine manufacturer and can include the use of one or both of these techniques.

Torque Techniques
To begin, look at the function of a bolt. The purpose is to hold or clamp two surfaces together. In order for the bolt to successfully achieve this function it has to be installed properly, which means applying the correct torque or tension to the bolt. The bolt can be thought of as a spring since it is stretched by either turning a nut through the use of torque, or by stretching the bolt through the use of tension. If the bolt is not stretched enough the joint will be loose and ultimately fail. If the bolt is stretched too much the bolt will be weakened and can ultimately fail. The correct amount of torque or tension applied will result in the bolt being stretched to a point where it will try to retract to its original shape and keep the proper tension on the joint. Figure 1

Hydraulic torque wrenches have been commonly used in the wind industry for many years in applications where torque requirements exceed the limits or safe use of manual torque tools. The basic principal of a hydraulic torque wrench is that the torque output is determined by the amount of hydraulic pressure that is applied to the tool. The unit of measure for torque is usually expressed in ft/lbs or Nm. The higher the pressure applied, the higher the torque output of the wrench.

Most hydraulic wrenches operate at pressures up to 10,000 psi. These wrenches come in two basic designs and multiple sizes. The square drive design employs the use of a socket attached to the wrench, and the low profile design is used where there are limited clearances that do not allow the use of a square drive tool. The square drive tool allows for economical flexibility for different size nuts by employing the use of standard impact sockets that are readily available. Low profile tools consist of a drive cylinder and an interchangeable link or cassette that is designed for a specific size nut. Proper tool selection must include torque requirements, bolt and nut sizes, clearances available, and proper reaction points for safe and accurate operation. Figure 2

Another factor that is critical for proper torque is following the guidelines for fastener lubrication. Some tests have shown that as much as 90 percent of torque when tightening a bolt is used to overcome friction. Following the manufacturer lubrication guidelines therefore becomes very critical to ensure proper tension or stretching of the bolt. For example, a 1” bolt is selected for a joint. The tension or bolt load required is determined to be 28,300 pounds of force to properly secure the joint. In order to achieve this, the torque that needs to be applied to the nut is 620 ft/lbs and is to be installed with no lubrication. If a moly-based lubricant was applied to the threads, the required torque to achieve the same tension or bolt load value would be only 219 ft/lbs. It is easy to see that if the guidelines are not followed, a moly-based lubricant is applied, and the torque value for a dry assembly is used, the bolt will be over-tensioned and will result in either immediate or future failure of the bolt.

Tension Tips
Hydraulic bolt tensioners have also been used in the wind industry for many years, in limited applications. They are becoming more common, and more bolting applications for wind turbine construction and maintenance now require the use of hydraulic bolt tensioners. The basic operation is the same as the hydraulic torque wrenches in that the more pressure applied to the tensioner, the more tension or bolt load is achieved. The unit of measure used for bolt load or tension is usually expressed in either pounds of force or Kn. Tensioner operating pressures can range from 10,000 to 22,000 psi, and in some cases even higher. The basic parts of a tensioner consist of a socket to tighten the nut once tension is achieved, a bridge that the load cell or cylinder rests on, and a puller bar that attaches to the stud.

Not unlike a torque wrench application, before a tensioner can be selected there are several measurements and specifications that need to be compiled—more measurements than required for a hydraulic torque wrench. These measurements typically are more critical for proper fit and tool selection. Some companies supply a worksheet that will assist in gathering the required information. With the exception of some wind turbine foundation tensioners that are designed to fit the two most commonly used foundation bolt sizes, most tensioners are size specific so the stud size and nut size, as well as height and washer thickness and diameter, are needed. The bolt grade and bolt load required should also be recorded. Measurement of the stud protrusion from the flange as well as the protrusion above the nut and washer are also needed. The protrusion measurements are important to ensure that the tensioner will rest on the flange once it is threaded on the stud and thread engagement in the tensioner is at a minimum equal to the diameter of the stud. If the tensioner does not rest on the flange the tensioner will react off of the nut once hydraulic pressure is applied and can lock itself onto the stud. If there is not enough thread engagement the threads can be stripped off of the stud before the proper tension is reached. Figure 3

The next measurements have to do with clearances. Measurements from the stud to the tower wall or any other surfaces that are perpendicular to the flange face as well as the distance between the studs are needed to ensure that the tensioner can be attached to the stud easily and be properly aligned. Any special measurements such as recesses in castings should also be noted and recorded. When all the information is gathered it can be determined if a stock tool can be used or if a custom design needs to be produced. Figure 4

Once a tensioner has been selected the manufacturer’s tensioning procedure and specifications should be reviewed. What is the bolt load required? What is the bolting pattern? Can the joint be tensioned to 100 percent of the bolt load required, or does it have to be tensioned in stages? Should more than one tensioner be used simultaneously to tension the joint? These are some of the elements of the tensioning procedure that need to be verified. Basic operation of the tensioner consists of attaching the tensioner to the stud and connecting the tensioner to the hydraulic pump using an appropriately rated hydraulic hose.

The next step is to adjust the hydraulic pump pressure to achieve the proper output of the tensioner. Once the proper pressure has been applied to the tensioner the bolt will be stretched and the nut that is on the flange face can be tightened. Minimal torque is required to tighten this nut, as the tensioner has already stretched the stud to the appropriate tension. The pressure can now be released, and the tensioner removed. Figure 5

Training Critical
Once the method of tightening a bolt is determined, either torque or tension, it is very important to properly train the personnel who will be performing the work. This is not only important for joint integrity, but also to prevent any injuries to the operators or damage to the application. Proper tool handling and maintenance training can go a long way in preventing these occurrences, and many tool companies will provide this upon request. Inspection of the tooling should include power cords for fraying, hydraulic hoses and couplings for proper rating, and inspection for any hydraulic oil leaks or hose and coupling damage, as well as overall condition of the tools including proper lubrication and calibration. Following these guidelines and procedures will result in a properly tightened joint that will remain aligned and be less prone to failure. Figure 6

Headquartered in Minneapolis, one of the coldest metropolitan areas in the United States, Mortenson Construction’s Renewable Energy Group has built nearly 100 utility-scale wind power projects in some of the most extreme climates throughout the United States and Canada. The successful building of wind power projects in the extreme cold requires careful preparation for equipment needs and special attention for the safety of those working in the field.

Equipment and Processes
Cold temperatures often bring snow, ice, and other conditions that warrant special equipment including personal protective equipment and clothing such as gloves, facemasks, and ice/snow traction devices that attach to heavy boots. Other requirements include enclosures for trailers, heaters, winter fuels mixed with anti-gelling additives, hot water pressure washers and anti-freezing biodegradable washer fluid for washing tower sections, concrete blankets and plastic tarps for concrete placing, and enclosures for tower grouting activates.

Snow and Ice Removal: In order to move forward safely with construction, snow and ice must be cleared from the project site to create a safe walking surface for the movement of equipment and workers. Construction can proceed during the winter and with some snow or ice on the project site. If there is an ice or snowstorm, however, construction may be halted until weather conditions improve. Once the storm has ended the contractor will remove the areas of snow accumulation before proceeding with construction. When the weather forecast predicts a snow or ice storm it is a good practice to lower the crane boom so any buildup of snow or ice can be removed. This is a must to ensure safe operation of the cranes. Construction team members will use rubber mallets to knock the snow or ice off the boom sections before the crane is placed into production operation.

Foundation Installation: Installing foundations in extreme cold temperatures requires additional equipment such as ground thaw and forced air heaters to make sure materials are within required temperature ranges during each step of the installation process. There are specific accommodations for mixing and placing the concrete. Portable concrete batch plants must be winterized sufficiently, which often means enclosing them in heavy plastic tarps or tents. The sand and aggregate must also be heated and mixed with hot water to correctly prepare the concrete.

Additionally, foundation rebar must be warmed to required temperature ranges before concrete can be placed around it. Under specific conditions the concrete must be secured under supplemental heat. Construction crews will use extra heaters and heavy insulated concrete blankets to ensure that the foundations are cured even in very cold temperatures. This type of planning also affects the placement of grout around the foundation pedestal.

Hazards and Concerns
Working in extremely cold temperatures can lead to dangerous conditions, the most significant of which are frostbite and hypothermia. Several factors contribute to the risk of injury including: temperature, wind speed, moisture (sweat or working near water), duration of exposure, clothing, work/rest schedule, work performed, and other individual characteristics.

Frostbite is the actual freezing of tissue. Exposed skin becomes vulnerable to frostbite when the air temperature drops below 0° C/32° F or when wind speeds are high creating a wind-chill effect. If skin is not protected, frostbite can lead to body tissue damage. Symptoms of frostbite vary from swelling and red coloration of the exposed area and slight pain in mild cases to extreme tissue damage with black/dark bluish-purple in severe cases. Depending on the level of exposure frostbite can occur with little or no pain or cause a burning/prickling sensation in more severe cases. If minor exposure has occurred the affected areas of the skin should be warmed slowly until normal temperatures are reached. When higher levels of exposure occur, medical attention should be initiated.

Hypothermia occurs when the body core temperature drops below 35° C/95° F. Once this happens the body loses its ability to prevent heat loss and is losing heat more quickly than it can create heat. Hypothermia is typically a gradual process, with the exception of extreme exposure such as falling through the ice on a frozen lake. As hypothermia develops the victim initially has a sensation of cold followed by pain. As time passes the level of pain increases and the body becomes numb. Symptoms of hypothermia include a decrease or absence of shivering, reduced memory and confusion, drowsiness, slurred speech, impaired coordination, a loss of dexterity, and general muscular weakness. In cases of minor hypothermia the exposed individual should be covered with heated blankets. If not identified and addressed quickly, hypothermia can lead to death. Extreme cases of hypothermia require immediate medical care from experienced medical personnel as quickly as possible.

Preparing Workers
The Layered Approach to Clothing: When selecting proper cold weather clothing a layered approach is best. Too little clothing leaves the worker exposed to the cold. Too much clothing leads to sweat, wetness, and cold, which then can lead to hypothermia. Workers must wear the appropriate amount of clothing to keep their heat loss to heat production rate neutral. When layering clothing it is best to select a windproof outer layer that is at least water resistant, but ideally waterproof. Table 1, taken from the American Conference of Governmental Industrial Hygienists (ACGIH) on Cold Stress, explains the effects of wind chill on the body. Table 2—taken from the Manitoba Work Place Safety and Health Division, Working in the Cold Bulletin-186—provides recommendations for protective clothing based on the wind chill temperature ranges. Since toes, fingers, ears, and other parts of the face are at risk of frostbite, footwear, gloves/mittens, and face protection must be used to protect the worker, taking into consideration the ability to perform the various tasks on a wind power project during construction.

Warm-up Breaks: Workers who are outside for extended periods in cold environments should take regular warm-up breaks, preferably inside a warm shelter or heated vehicle. Warm-up breaks should still be mandatory, even when appropriate winter clothing is selected and utilized effectively. Table 3, taken from the Manitoba Work Place Safety and Health Division Safe Guideline for Thermal Stress, provides recommendations on the maximum amount of time workers should be allowed to work before taking a break. If excessive sweating does occur during the warm-up break, the individual should change into dry clothing prior to reinitiating work activities.

Individual Factors: Various factors may contribute to an individual’s ability to withstand working in cold conditions. Factors such as age, physical health, acclimatization to cold, etc., can all determine the exposure time of worker in cold temperature environment.

Internal Expectations
When working on a Mortenson Renewable Energy Group project, all work ceases when the surrounding work temperature and/or wind chill is at -34° C/-30° F as defined in Risk Level 3 in Table 1. This should be based on the strain of the task and location of the work. At no time should work be performed in a Risk Level 4 or higher, as defined in Table 1. Table 2 should be used to define warm-up breaks over a four-hour work period, with maximum cold exposure time and a defined warm location.

At times certain work activities are difficult or impractical to execute with the defined warm-up periods. In these cases a plan must be developed to ensure those individuals remain warm throughout their workday. For example, tower connectors may be exposed to cold wind chill temperatures, but it is infeasible for these workers to climb down the tower for breaks in a dedicated warm location. In this case an alternative approach is necessary. This approach may include utilization of heat producing clothing; chemical heat packs for the hands, feet, and body; and warm-up breaks in an enclosed space at appropriate pause points during the turbine building processes. To manage the cold working environment it is recommended to only work within the green areas of Table 3. This schedule applies to workers wearing dry clothing doing moderate-to-heavy work with breaks of 10 minutes in a location that allows workers to warm up.

For light-to-moderate work (little physical movement), apply the schedule one step lower. For example, at -35° C/-31 ° F with no noticeable wind, a worker at a job with little physical movement should have a maximum work period of 40 minutes with four breaks in a four-hour shift instead of 55 minute work periods and three breaks. After four hours workers should be given an extended break in a warm place. In addition to monitoring the cold conditions ensure that foot traction devices are utilized to minimize slips, trips, and falls when icy/snowy conditions exist.

Preparing and Prioritizing
Extreme temperatures, hot or cold, bring many necessities for building safely and within given timeframes. Extreme heat is no less dangerous than extreme cold, and preparing adequately for these temperatures is a must for worker safety and best use of equipment. The good news is that the experienced EPC contractor can typically plan for extreme temperatures in the peak winter and summer months. A prepared contractor will budget for and pre-order the proper protective gear and equipment to ensure that construction runs smoothly and safely even in extreme weather. 

In recent years we have seen the use of wind power generation continue to increase as a viable energy solution. With this increase operators are looking for the best ways to maintain wind turbines and prevent failure. There are several ways to monitor a complex power-generation system such as a wind turbine. However, one of the largest indicators of a potential problem is vibration, which is often detected in the nacelle. If a turbine is experiencing a high amount of turbulence vibration it can be a precursor to complete turbine failure, potentially resulting in explosions, turbine blades flying hundreds of yards, and toppling towers.

Think of wind turbines as mini jet engines inside of housings that run 250 feet tall. If there is any sign that something might be going wrong in the turbine, vibration is typically one of the best places to start, as it’s a good way to look at the general health of the wind turbine and see if things are functioning the way operators are expecting. The quicker that operations and maintenance (O&M) teams can detect problem signals, the sooner that loss can be mitigated and potential disasters avoided. There’s a lot of value in vibration monitoring because it gives more predictive ability for the O&M company and the O&M technicians to look for problems before they come up. The danger in not monitoring for potential issues could result in a loose blade. A vibration reading will signal the operator before the blade actually becomes loose, preventing damages in the $2-$5 million range.

Vibration Monitoring Solutions
A common solution for monitoring is a wired, or cable solution (Figure 1). However, many operators are finding that installing additional wire is not feasible. This is mostly due to remotely located turbines and the high costs associated with installing/running additional wire. Sometimes it’s simply not possible to run wire back to the O&M office.

Recently, wireless technologies have become an option for various monitoring applications in the renewable industries. Satellite systems, for example, have broadband capabilities and tend to be reliable, but they have monthly recurring costs. Cell phone systems function in a similar fashion as satellite systems, using an existing network of communication devices with associated monthly charges. If users are within range of a cell tower, cell phone systems are a simple solution for sending data back to the O&M office, but the monthly recurring costs associated with satellite or cell phone systems can become a burden on an operating budget.

Now operators can also choose Frequency Hopping Spread Spectrum (FHSS) radios to send critical vibration-sensing data to the O&M office, without the added cost of fiber installation and without the monthly or reoccurring fees that tend to accompany cellular and satellite solutions. This class of wireless radios has proven its reliability in industries such as military, oil and gas, and water/wastewater, and it is now available as a solution for vibration monitoring in wind turbines (Figure 2). Ideal for installation in remote locations and difficult environments, they can transmit real-time data up to 60 miles line-of-sight reliably.

Why Wireless?
Wind turbines are huge investments, costing millions of dollars. Many are nearing the end of their warranties, which typically last about 20 years. Operators are being proactive about detecting problems in the turbines before the warranty period expires. This has become a great opportunity to install wireless technologies. In order to inspect the turbines for problems, an operator will physically go up and into the turbine looking for potential problems. While they are performing the inspection they can easily install a FHSS wireless data radio and monitor the turbine on a real-time basis.

Cost is another driving force for deploying wireless technologies. FHSS radios are generally much less expensive to install than cable and do not have the reoccurring fees of satellite and cell phone technologies. In addition, if the operator can stop a turbine from a potential disaster by detecting problems before they happen, they can save millions of dollars. With some wireless data radio providers the investment in an RF network isn’t only useful for vibration monitoring. The devices can be scaled to monitor wind speed coming from an anemometer, or the RPM of the actual engine itself within the turbine. With these radios, they can be expanded upon without having to add more devices.

Another main driver of wireless implementation is field scalability. Many wireless modems have multiple data ports that can be utilized in the future when additional instrumentation is needed (Figure 3), or if existing devices—lubrication particulate sensors, inverter monitors, in-tower data loggers—need to be accessed remotely later on in the life of the field. And because many RF devices are Ethernet-enabled, expanding on an existing radio network is as easy as assigning a new IP address to a new radio and installing it uptower, which shouldn’t take longer than an hour or two.

Real-World Example
A wind power company in the Southwestern United States along the Texas/New Mexico border needed a vibration monitoring solution for dozens of turbines. In this case the property owner and site operator did not want the contracting company to use their existing fiber optic network. They also didn’t have the bandwidth or the ability to use their existing fiber optic network to set up the system. So, the question became “how are we going to get vibration sensing data from the turbine back to the O&M office if we can’t use the existing fiber optic network that the site operator installed?”

Fiber optic networks are typically installed at the same time as the turbines. They consist of large webs of fiber optic cable that send and receive data all the time. They are very high-throughput and prepared for this type of application from an industrial standpoint, but in this particular case the company did not have the option to use fiber. They began looking at several wireless providers and settled on one that offers FHSS wireless data radios.

There is a class of FHSS wireless data radios that have proven to succeed even in the most difficult environments. In this particular installation all the turbines sat on top of a mesa, which offered a clear line of site. Both pier-to-pier communication and point to multi-point communication was very easy to achieve. However, each one of the turbines is composed of a mast that is about 200 feet tall by 15-20 feet in diameter and is made of corrugated steel. This could have easily created an issue with line-of-sight. There was a concern that RF would reflect off the turbines like a mirror.

Operators should always work with a wireless company that provides path studies or lender radios to ensure the products will work before they purchase them. In this situation, the tests showed that the wind turbines would not be an issue. When the wind power company did the path study it compared multiple radios, and it was able to determine which ones performed despite the potential obstruction of the huge wind turbines. One of the radios in the comparison would lose data each time a blade passed through the arc link, so they went with the solution that did not have link issues.

The chosen radio provider took the potential obstruction into consideration before installing the radios. In this case they conducted a study using a digital elevation level to indicate potential issues. That was only one way to account for the huge obstruction, however, so it was a bit of a variable. The radio provider did some additional testing by physically climbing to the top of a cell and setting up a radio inside the housing. The signal transmitted through the turbine back to the O&M office without a hitch.

Now that the FHSS wireless data radios have been deployed at this location, most of the vibration monitoring occurs inside the nacelle. In addition, vibration monitoring also occurs on the couplings that the turbine blades feed into, and on the blades themselves. There could be two dozen vibration-sensing accelerometers feeding their data back to a condition monitoring box on any single wind turbine. The accelerometers send data through a FHSS wireless data radio, which reports back to the O&M building that is central to the wind farm. Basically, the radios act like an Ethernet bridge to send and receive vibration data going through the entire network. Each turbine is reporting their vibration data roughly twice a day, sometimes three times a day, and has been doing so successfully for several months.

The deployment of these radios has been such a success that there are 11 different sites planned for installation in the next year and a half. The company is looking to install 450-500 more radios across the country.

Software Advantages
Some FHSS wireless data radios are accompanied by software programs that not only help with configuration, but offer diagnostics (Figure 4). Not all providers offer this type of solution, but it is something that O&M should take into consideration as they search for the best wireless provider for their particular installation. Some diagnostics software can tell an operator which device is talking better or worse than another; if their data packets are being lost and where; and can track the traffic down to the packet. Software programs like these provide a granular understanding of the RF network; it’s actually given many operators additional transparency in their network.

Conclusion
FHSS wireless data radios can reliably serve as the Ethernet link between a wind turbine and the O&M office. As a wind power company in New Mexico found, the right wireless provider and installation can be equally effective and far less expensive than a wired solution. Reliable wireless technologies can be easily installed as operators inspect wind turbines that are nearing the end of their warranties. After deployment the turbines are continually monitored on a real-time basis, indicating issues with vibration before they cause devastating damage. As operators learn of successful wireless installations, they are beginning to view FHSS wireless radios as a viable option for vibration monitoring. Now many radio providers offer the option of path studies, diagnostic software, and industrially hardened products that have proven their performance in other industries. 

Mechanical failure in wind turbines presents unique challenges for operations and maintenance. Unlike traditional rotating equipment assets in other power generation plants, wind turbine assets sit on top of a tower 90m in the air. We do not have the luxury of performing maintenance tasks on solid ground. Tools and replacement parts must be brought up to the work site, and if you forget a tool or a part it’s not as easy as traveling back to the shop to retrieve it. It is critical to be able to prevent mechanical failure in a wind turbine whenever possible.

We see from the chart in Figure 1 that 60 percent of wind turbine downtime is related to drive train failure: gearbox, generator, main shaft, and their associated bearings. We also know from industry studies that misalignment of rotating shafts is responsible for more than half of all bearing failures.

Precision shaft alignment is the process of aligning the centerline of the shafts of one or more rotating machines. When the shaft centerlines are co-linear they can turn freely, and the external forces that destroy key components of the system—bearings, seals, couplings, rotors—will be mitigated. Misalignment will most affect the main bearings in the gearbox and generator. Left unattended for too long, it will destroy the bearings and then go to work on other components down the line on the shaft such as seals and rotors, etc. Precision alignment at install and periodic checks can help prevent component failure, uptower repairs and catastrophic failure. A bearing failure uptower can cost $10,000-$15,000 to fix. Catastrophic failure can cost an estimated $260,000.00. A good alignment program can prevent these problems before they even start. There are various tools for alignment, some better than others. Consider these options:

Straight-edge mechanical tools
• Not a precision alignment
• Subject to gross interpretation of the user

Dial indicators
• Difficult to learn proper alignment method
• Time consuming process for the inexperienced
• Dials must be mounted on the shafts
• Shafts have to be able to turn to align with dials
• Can be subject to interpretation by user
 

Laser alignment tool
• Learning curve is short
• Very precise, even for an inexperienced user
• Many mounting options for different turbines
• Shafts do not necessarily have to turn
• No interpretation by the user, the data is the data

Precision alignment means you are using a laser alignment kit or dial indicators. A straight edge is not a precision alignment tool. Lasers have many advantages over dial indicators. Dials are hard to teach and learn. Until you have mastered the art of dial indicators, they can be very frustrating and time consuming. Lasers are a fast, easy, and accurate method of alignment. When you are performing alignment in a wind turbine there are a number of issues to consider.

Safety First
First and foremost is safety. Laser alignment tools must be mounted in such a way that they will not be able to come in contact with techs if the turbine brakes give way. Turning the shafts is critical to performing a precision alignment and O&M teams have to be aware under what conditions they can work uptower when the blades will be turned. The requirement to perform a measurement without turning the shaft is becoming more predominant. Figure 2

A sudden strong gust of wind can catch the maintenance team off guard and cause the shaft to spin freely as the brakes are being released for the alignment process. Some turbine manufacturers have developed solutions for alignment that do not require the gearbox to turn. This requires special fixtures and the coupling needs to be removed to perform the alignment. It is, however, the safest way to perform an alignment in a wind turbine. Know the guidelines that your turbine OEM has set for uptower alignment—maximum wind speed, direction the turbine should face, can the shaft covers be off or on, should the coupling be removed—make sure your maintenance teams are safety trained.

Mounting Laser Alignment Tools
In many cases we can’t mount with traditional chains and brackets on the gearbox shaft. This leaves us with the decision of where to mount the measuring (S-Unit) with a magnet. First, decide if you want to mount on the brake disc or the mounting flange for the coupler. Look for a place as close down by the shaft as possible. Check for clearance of the brake caliper.

Once you decide where to mount, check the measurement two or three times to make sure it repeats. On some turbines we have found that some components will shift when the brake is engaged. Mounting close to the shaft will minimize the effect. If your results are not repeating, look for an alternative spot to mount and re-test. If they do repeat, you have found a good solution.

Frequency of Alignment
The second consideration is deciding how often the turbine needs to be aligned. Many turbine OEMs have set requirements for turbine alignment intervals. Some OEMs only align prior to shipment from the manufacturing facility, some align when the turbine arrives “in-country,” and some align when the turbine is installed on the tower. Some do all three. It is never a bad idea to check turbine alignment. A precision alignment check should be included in your intervals of preventative maintenance. A quick check when the alignment is not scheduled to be performed can be done fairly quickly. Once you have determined that alignment is required, you can schedule it in your maintenance plan.

High-speed shafts should always be aligned during generator or gearbox change outs. Best practice says we should come back in three or so months and re-check the alignment. Again, this depends on the turbine manufacturer and their recommendations. Figure 3

Tolerances
Another important consideration is alignment tolerances. Alignment tolerances define how much misalignment is acceptable for a given model of turbine. Many turbine OEMs have established alignment tolerances for their equipment. If you don’t know the manufacturer’s tolerances, or they are not supplied, tolerance charts are available based on speed of rotation.

Dynamic Movement
The last consideration we will talk about in this article is dynamic movement. Dynamic movement is caused when the brake is released and the hub and blades turn freely. The weight and turning forces can cause the gearbox to move slightly, even imperceptibly to the human eye, and cause misalignment. You should consult your turbine manufacturer to find out if dynamic movement is present in their turbines, if they know how much it moves, and whether or not it is critical. In some cases the coupling can offset the movement when the shafts are aligned within tolerance. Once you know the amount of movement, you can add those calculations to your alignment tool. When compensating for dynamic movement, you will actually misalign the gearbox and generator at rest so that when it’s running the machines will move into alignment.

Lasers are also used in the wind industry as a valuable tool for measuring flanges on wind tower and blade root flanges. Flatness and taper measurements help ensure that these components will fit together properly during construction.

Precision alignment is a vital first step to prevent mechanical failure in wind turbines. Regardless of whether alignment is performed by the OEM, your O&M contractor, or your own O&M team, good tools and training are not optional. Remember that an ounce of prevention equals a pound of cure, lessening the chance for catastrophic machine failure uptower.

Features and Options
In addition to the design characteristics discussed, there are a number of other considerations or desirable features you should consider when building your wind farm grounding transformers.
 

First, advise the supplier whether you need a compartmental pad-mount transformer with integral tamper-proof compartment or substation design. Also consider whether the grounding transformer will be located outdoors or indoors, since even outdoor units need special attention when placed near other structures. Select the proper fluid type for the particular application—options include mineral oil, silicone, and Envirotemp® FR3™ fluid, a natural ester-based fluid with exceptional fire-resistant properties and favorable environmental attributes. Consider connectivity choices, and select the best one for the site. Options vary from dead front, live front, and spade terminals. Terminal location can be under a cover or on a sidewall, exposed or enclosed. In addition, temperature rise is assumed to be 65°C, so adjust design if necessary.

Consider site elevation or any special environmental concerns, and use special paint as required. Last, consider neutral ground resistors. The rated voltage of the NGR should be equal to the grounding transformer’s line to ground voltage. The current rating and duration should match the grounding transformer ratings. Remember to set the current rating high enough to be above the cable charging current and grounding transformer magnetizing current. 

A brand new 62,000 square-foot campus has opened its doors in the Denver metro area, changing the face of wind, solar, and renewable energy education in America. Ecotech Institute is the first and only college entirely focused on preparing America’s workforce for careers in renewable energy and sustainable design, and the facility is sure to spark interest in these fields.

The architectural team was led by Ecotech’s parent company, Education Corporation of America, and Alabama-based Rob Walker Architects. They successfully transformed a vacant, large-footprint building into a progressive campus. The building is home to 30 classrooms, 12 state of the art computer and science labs (e.g. electrical, wiring, solar, wind safety, controls and environmental science), studios, student and faculty lounges, a library, and a variety of other amenities.

Site Selection
Education Corporation of America is often focused on selecting campus sites where they can make a positive impact on a neighborhood. Empty buildings are often an eyesore and can impact neighboring businesses. In this case, an old Amazing Jake’s family fun center was the previous tenant. Once transformed, new traffic, additional consumers and a pleasing appearance will continue to yield positive results. Figure 1

“We were focused on changing the empty commercial building into a community asset that is sustainable, functional, and attractive to its neighbors,” says Celeste Prestenbach, vice president, facilities planning and new campus development at the Education Corporation of America.

Focus on Wind Energy
Although there are energy and resource savings throughout the sustainable design of the building, a major component of the building and the school’s curriculum is wind energy. To support Ecotech’s commitment to wind, the front of the building is adorned with eight small wind turbines mounted on the roof to generate up to 4.8 kilowatts of electricity. In addition, a vertical axis wind turbine was installed to generate a total capacity of 4 kilowatts.

One unique component is a wind safety lab. The square room is simple, yet revolutionary. The 771 square-foot lab has a 20-foot ladder leading up to an 8×8 platform. This is where Ecotech instructors will teach wind safety techniques and practices. The students will be using the actual harnesses that would be used to go up and down a real wind turbine, helping simulate this significant element of a career as a wind technician. “This wind lab is the first of its kind, offering students a glimpse into a career where physical activity and safety are critical,” says Glenn Wilson, academic dean of students at Ecotech Institute. Figure 2

To carry the wind theme from the outside to the inside, ECA’s in-house interior design team integrated the shape and form of the wind turbine blades into the front gallery of the building through the repetition of a similar curve along the walls. This is more evident from a plan view of the interior. In addition to wind elements the building incorporates a variety of solar aspects, as well, including: 12 polycrystalline rooftop photovoltaic solar panels with a system capacity of 2.8 kilowatts; integral thin solar technologies embedded into the glass of the front building canopy with a capacity of 9.4 kilowatts; and two solar trees, each providing 16.9 kilowatts of electricity, which will generate over 50,000 kilowatt hours per year of electricity. All told, the campus will get more than 5 percent of its peak load electricity from wind and solar sources and will generate over 65,000 kilowatt hours of electricity annually.

Additional Energy Savings
Another key component of the campus is its rigorous energy savings and demand side management processes that will cut demand significantly. Some examples include demand control ventilation to modulate ventilation based upon occupancy levels in classrooms. This will dramatically reduce the cooling/heating during partially occupied periods. All rooftop air conditioning equipment will have economizers to provide 100 percent outside air during ideal outdoor conditions for cooling, and energy efficient lighting will reduce lighting energy consumption by 30 percent below standard lighting energy levels. In addition, a measurement and verification system provides real time monitoring of the campus power, natural gas, and water consumption. This information will be displayed in the lobby for visitor knowledge, but will also be recorded and used to determine further energy saving possibilities in the future.

The building also incorporates water and lighting efficiencies. For instance, motion sensors combined with a programmed lighting schedule limit the amount of time lighting stays on when rooms are unoccupied. The campus also includes four electric car charging stations, capable of delivering a full vehicle charge in two to four hours. The campus embraces the institute’s core concerns: exceptional education and commitment to the environment. Figure 3

Ecotech Institute launched its first round of classes in July 2010 in a temporary facility and the third quarter commenced January 10, 2011 in the new facility with almost 200 students enrolled. 

Why Colorado?
Ecotech Institute chose to launch its first location in Colorado for many reasons, including its location, entrepreneurial culture, and passion for green job growth. Colorado’s culture, natural beauty, and green-leaning attitude fosters greener lifestyles, education, and careers. The campus is strategically located to serve workforce development throughout the Rocky Mountain region, one of the country’s fastest growing areas for renewable energy.

In 2009, the Colorado Governor’s Energy office, with funding from the U.S. Department of Energy and Clean Energy Funds directed by the state legislature, spent over $25.2 million in fiscal year 2009, with 9 percent, or $2,268,000, directed to renewable energy and sustainability projects.

In 2010, the State Legislature voted to increase the Renewable Energy Standard to a “Best in the West” 30 percent by 2020. The new law will create thousands of clean-energy jobs, further diversify Colorado’s overall energy portfolio and lead to 100,000 solar rooftops over the next decade.

Colorado is also home to public and private institutions that are creating innovation and employment. The National Renewable Energy Laboratory (NREL), the University of Colorado at Boulder, Colorado School of Mines, and Colorado State University created the collaboratory in 2007 to research and develop new, cleaner energy technologies. Figure 4

In wind alone, Colorado makes the grade in national rankings. In 2009 Colorado ranked ninth in wind projects installations by state, adding 178 MW of wind power, ranked eighth in installed wind capacity and eleventh in wind resources. Not only is Colorado a fantastic place to live and work, its culture lends itself to Ecotech’s mission: when you live in a state than appreciates natural beauty, it helps people to understand the importance of sustainability.

What’s Wind’s Future?
According to “Clean Tech Job Trends 2010,” three clean tech categories in particular held their ground as the dominant innovative leaders throughout 2009, based upon number of patents granted: solar (at approximately 31 percent), wind (at approximately 19 percent) and hybrid vehicles (at approximately 15 percent).

In the report “Green Collar Jobs in the U.S. and Colorado” (2009) by Roger Bezdek, principal investigator, Management Information Services, Inc., for the American Solar Energy Society, U.S. renewable energy and energy efficiency (RE&EE) industries are creating jobs faster than other leading industries. Figure 5

It stated that “In 2007, the U.S. RE&EE industries generated more than $1 trillion in sales and created more than 9 million jobs—including $10.3 billion in sales and more than 91,000 jobs in Colorado. U.S. RE&EE revenues represent substantially more than the combined 2007 sales of the three largest U.S. corporations—Wal-Mart, ExxonMobil, and General Motors ($905 billion). RE&EE industries are growing faster than the average U.S. industry and comprise some of the most rapidly growing industries in the world, including wind, photovoltaics (PV), fuel cells, recycling/remanufacturing, and biofuels.”

In 2009, the Executive Office of the President, Council of Economic Advisors, published a report “Preparing the Workers of Today for the Jobs of Tomorrow.” Here are a few of its findings:

• Jobs devoted to environmental improvement grew far faster than other occupations from 2000-2006 and the BLS projects fast relative growth through 2016;
• There are growing opportunities in these fields, particularly for workers with technical skills;
• CEA analysis suggests that particular areas of “green” potential (e.g., wind and turbine manufacturing, mass transit, or producing energy-efficient automobiles) pay more on average than otherwise comparable jobs. They also are more likely to be held by primary earners in the household and to be unionized;
• Well-trained and highly-skilled workers will be best positioned to secure high-wage jobs, thereby fueling American prosperity. Occupations requiring higher educational attainment are projected to grow much faster than those with lower education requirements, with the fastest growth among occupations that require an associate’s degree or a post-secondary vocational award.

Lastly, the research “U.S. Metro Economies: Current and Potential Green Jobs in the U.S. Economy” (2008), prepared by Global Insight for The United States Conference of Mayors and the Mayors Climate Protection Center, published some interesting insights about the wind industry.

The report states that “The bulk of jobs related to wind infrastructure will come in the manufacturing of equipment. The technology of wind electricity is relatively new, but the manufacturing base for its production is very similar to past products. Every state in the country has firms and a labor force with experience making products similar to the blades, gearboxes, brakes, hubs, cooling fans, couplings, drives, cases, bearings, generators, towers, and sensors that make up a wind tower.”

“These jobs fall into the familiar durable manufacturing sectors of plastics and rubber, primary metals, fabricated metal products, machinery, computer and electronic products, and electrical equipment. Cities across the country have the capacity to attract job growth in these important manufacturing sectors along the nation’s path to a new energy infrastructure.”