December 2010

With wind energy in North America continuing to grow at an astounding rate, and knowing that legislated requirements are already in force for some states—and right around the corner for others—it is more important than ever to build wind energy power systems that will last. This requires several essential elements, not the least of which is reliable onshore (underground) and offshore (submarine) power cable, along with dependable cable performance standards. Figure 1

From wind developers, to independent power providers (IPPs), to utilities, system reliability is critical and component performance is king. Wind towers and turbines get much of the attention because they are what everyone sees. Granted, tower height, placement, and turbine design are all important to efficiently capture the wind. However, equally as important is what you don’t see; the cables that get power from the base of the tower to the transformer, then to the grid and on to the consumer. Cable design and performance is as important as other wind farm components, and it is absolutely imperative in the ability to provide power transmission and distribution that wind farm owners, utilities, and consumers can count on throughout the life of the entire system. Figure 2

Not All Materials Are Created Equal
Wind power is intermittent, therefore system reliability is crucial. Unplanned cable repairs could be costly in terms of both downtime and maintenance expense. With that in mind, an essential part of that long-term reliability scenario is direct-buried and submarine cable made with quality raw materials and tested to perform according to industry specifications. Let’s start with materials.

There are a number of materials that can be used to construct power cable components: cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), and polyvinyl chloride (PVC), just to name a few. Cable manufacturers are looking for materials that best meet their needs for ease of processing while producing the performance attributes expected by the end user. In addition, cables are subject to many mechanical and environmental stresses during their lifespan. Flexibility, stress-crack resistance, and shield strippability are all factors to be considered for ease in cable installation. Corrosion kills cables and interrupts power supply. Therefore extreme heat, cold, and water intrusion resistance are paramount. So it becomes more important than ever for cable manufacturers, utilities, wind developers, and others in the value chain to become informed about how various materials perform in power cable applications.

XLPE emerged in the 1970s as the preferred insulation type for medium-voltage (MV) underground (UG) power cables due to its quality, cost competitiveness, and reduced long-term operating costs. However, those early cables were beset with construction and performance issues, limiting the lifespan of some of those cables. This led to the development of “water tree-retardant” XLPE, or TR-XLPE insulation, for underground power distribution cables that have now become the standard bearer. Dow Wire & Cable introduced its DOW ENDURANCE™ MV 4202 TR-XLPE in 1983. Studies show that 27 years later, buried cable made with this material exhibits little to no wear and has an expected lifespan of over 40 years.

As an example, shown in Figure 3, cables made with DOW ENDURANCE TR-XLPE exhibit excellent field operation over time. In addition, TR-XLPE cables have very low dielectric losses compared to EPR cables. In fact, recently updated Rural Utilities Service (U.S. Department of Agriculture) specifications for primary UG power cable (bulletin 1728F-U1) state “plain XLPE has been removed as acceptable insulation and TR-XLPE insulation has replaced it due to the significantly improved reliability.” This longevity and reliability is as important for wind energy power systems as it is for traditional power infrastructure. Wind farms are designed to last for many years and the collection cables must not only last, but must be reliable for the lifespan of the wind farm.

A recent conversation with a Dow customer—cable manufacturer, Southwire—corroborates this. They have provided 35KV power cables for wind farm installations from the Northeast to California, Minnesota to Texas, and many states in between. Common features for typical wind farm cable from Southwire include:

• Aluminum conductors that range in size from 1/0 AWG to 1250 MCM and are “moisture-blocked;”
• TR-XLPE insulation;
• Customized neutral configurations;
• LLDPE jackets that provide good abrasion resistance in UG applications.

“In a nutshell, wind farms have high-cost assets that at times put intense operational burden on the installed cable system,” says Ron Burchfield, director of renewable energy, Southwire Energy Division. “You need to install cables that have been proven to stand up to that challenge. We are convinced that quality manufacturing practices along with quality raw materials are necessary to produce reliable, long-lasting power cable.”

Testing, Validation, and Performance Standards
Many raw materials suppliers and cable makers serve the wind energy market. Not all of these players are created equal either. Research and development at the very front end of the supply chain is very important. When it comes to raw materials, cable makers, developers, IPPs and utilities alike should ask about the kind of technology, clean manufacturing, and packaging techniques, testing, and validation that goes into raw material production. Similarly, end users should insist on specifying cable that has gone through rigorous testing and meets at least the current minimum performance standards set by utilities. Trusting investment dollars to anything less can be risky business.

There are many testing institutes and other organizations that work with companies like Dow Wire & Cable and Southwire to ensure that raw materials as well as the cables produced with those materials, meet recognized national standards. These testing institutes and organizations include National Electric Energy Testing Research and Applications Center (NEETRAC), standards development agencies such as the Association of Edison Illuminating Companies (AEIC), and Insulated Cable Engineers Association (ICEA). In addition, cable makers like Southwire are producing cables that consistently exceed stringent long-term testing standards such as AWTT and ACLT. These long-term testing methodologies demonstrate a proven track record for ensuring long life and reliable cable performance.

No exclusive standards currently exist for cable performance in the wind energy market. So, again, it is important for end users to insist on cables that meet, or preferably exceed, the current power industry minimum standards. Think of it this way: cables form a very small percentage of the total power system cost, and polymeric materials represent an even smaller percentage. Therefore, it is imperative that the renewable energy industry take a broad view to focus on the needed system reliability that rests, to a large extent, on excellent materials, quality cable manufacturing processes and elevated performance standards.

Collaboration is Essential
As with anything worth pursuing, it takes a community of like-minded people to achieve success. The concept of wind power is not new. However, to go from the power needed to turn a millstone to the power needed to light up and connect communities in an efficient and cost-effective manner is quite another story. Collaboration is absolutely essential.

Groups like AWEA and GWEC are certainly helping as they provide a gathering place and information portals for all stakeholders. But we need collaboration in the trenches as well—between investors, developers, IPPs, utilities, equipment, cable, and material suppliers, for example—to realize the energy goals that are or soon will be legislated.

To illustrate the point, cable makers require raw materials that are consistent from batch to batch and demonstrate ease of processing, manufacturing efficiency, and the ability to deliver on the attributes needed for a reliable end product. Utilities require a long-life, reliable power supply at a reasonable cost to them and to the consumer. However, the cable purchasing decision is often made based on cost, without understanding the correlation between what the utility needs in terms of long-term reliability and what a quality cable manufacturer can deliver. All cables are not created equal. At the end of the day, to ensure long-term system reliability, cable purchase and installation decisions need to be based on more than just price.

To that end, companies like Dow Wire & Cable and their valued customers like Southwire are working together not only to validate and adopt superior products for cable construction, but to enhance market awareness about the value of building power systems with the right components, used in the best way to ensure the optimum result for the entire value chain. 

Wind farm projects are a growing business segment for many electrical construction contractors. Although wind farms have been constructed for several years, owner/operators, engineering designers, and contractors continue to learn more effective and accurate methods for designing and implementing the farm’s electrical systems—systems that offer high integrity, reliability, and efficiency. Figure 1

Factors in Electrical Construction
All construction projects are driven by a comprehensive schedule that includes procurement, engineering, site preparation, foundation installation, erection, buildings, equipment installation, electrical cable pulls, termination, testing, and startup. But there are four primary factors that affect wind farm construction schedules. These include:
 

Engineering design issues discovered during construction: A close working relationship between project engineering designers and the construction contractor is necessary for effective problem resolution. Additionally, such relationships promote timely, accurate documentation and enables teams to work and get on and off site as quickly and safely as possible.

Site access limitations (Figure 2). Many wind farms are built on private sites, government reserves, or in locations isolated from large communities. Some are also built at high elevations. A well-established site entry plan, right of way permit, and an understanding of the time and costs needed to deliver equipment and materials to these sites is important to the farm’s rapid startup.

Covering large geographical areas. This requires construction and maintenance of many miles of roadways with conditions and accessibility that can quickly be adversely affected by traffic and weather. A well-designed road system with adequate design for load bearing and washout still requires constant maintenance and repair, and startup in the midst of very dry conditions requires frequent road watering to manage dust intrusion into systems. Both scenarios slow work progress and drive up costs (Figure 3).

The site is remote. As a result, local skilled labor is often used and supervised by the contractor. This can impede continuity and experience, however, hindering construction efficiency and production. It is a challenge to manage or predict, but is best minimized by maximizing the contractor’s employee participation.

Strategies for Startup Success
During wind farm construction, the one schedule segment that is relatively short in duration but perhaps the most important for the project’s success is the electrical systems testing and startup. This begins with each wind turbine going through extensive Factory Acceptance Testing (FAT) by the manufacturer. After transport from the factory to the project location and field assembly, however, the turbine must also go through a thorough Site Acceptance Testing (SAT). The turbine SAT is often performed by the manufacturer’s representative or by a testing group under their guidance (Figure 4).

The remaining electrical apparatus, components, cabling, switchgear, metering, protection, communications, and controls for the farm are thoroughly tested and reviewed by specialized, well-trained, and highly skilled technicians. Every aspect of the electrical system, from the turbine to the substation connecting the wind farm to the grid, must be tested for proper design and operation by skilled power technicians.

More qualified service companies have power technicians with experience in electrical power testing included in every aspect of a wind farm, from the turbine to the grid. A thorough understanding of wind farm electrical design, experience with power system components, and the ability to interface with contractors, designers, and utility systems are all important to successfully starting up and connecting a wind farm to the grid.

Nevertheless, every new project brings new challenges to the startup team. For example, new electrical equipment is found in a new turbine that has come onto the market; a farm’s electrical system needs to be upgraded to meet OSHA and FPHA codes, or a power distribution and control schematic that has never been seen by the team is deployed to a new farm. Each of these can be quite challenging for even the most experienced technician.

Since protection, controls, metering, monitoring, and communication systems technology is constantly evolving, a technician’s skills must also evolve to meet the new testing requirements for these devices. Many of the newer testing tools are computer based devices, so a qualified power technician must also have proficient computer skills to effectively use these tools. Technicians must also have a mathematical aptitude since substantial mathematics and a solid understanding of three-phase power systems is needed.

Unifying Multiple Electrical Components
There are many types of electrical equipment and components from the grid back to the turbines. All of this equipment must be thoroughly tested for insulation integrity and functionality, and the use of set points must often be applied to properly insulate, control, meter, and protect each unique system. These include:

• Power cables
• Distribution transformers
• Inverters/Converters
• Capacitors/Reactors
• Switchgear
• Extra high, high, medium, and low voltage breakers
• Metering
• Relaying
• SCADA
• Communications systems
• Power transformers
• Instrument transformers
• Battery systems

In the electrical construction and startup of a wind farm, the devices and conductors are installed and tested first. After the conductors are terminated, AC and DC control systems are temporarily energized so that the protection, control, metering, and instrument transformer systems can be verified and tested for proper design and operation. Power technicians often work with construction engineering to tweak the equipment design as issues are discovered during testing. If mistakes are made by a wireman during conductor termination, the power technician will discover them during checkout and work with the wireman to make corrections. This step must be thorough to help minimize safety risks and ensure system integrity (Figure 5).

Next, all systems are protected by complex relaying devices. These relays often require the installation of programmable logic files, each of which is a set logic based on rules written as a computer-controlling program. Through the use of computer-based testing devices and sophisticated testing software, an experienced power technician will verify the protection and metering systems and then assist construction engineering with any needed changes. This step must be carefully executed, as minor mistakes in setting the files can often appear as a wiring error or an equipment flaw later and could result in taking the commissioning process down the wrong path for hours, and sometimes days. Installing the correct files and validating that they were set up correctly is critical, as it can preserve valuable startup time.

Energizing the System
After all devices and systems are tested and all problems found and corrected, technical teams work with the operations group to start up and energize the entire system. The startup energization procedure must be a sound plan that requires personnel safety and system protection. Energization most often starts at the point of connection to the grid, and then it is stepped back along the way toward open connections along the collection grid up to each turbine. The turbines are then started up and synchronized with the utility system. There are no shortcuts in this process. One has to establish zones of correctly working equipment and cabling backward from the point of grid connection to cost-effectively energize a site, otherwise commissioning untested zones with tested zones will result in lost time and money as teams backtrack to make corrections.

Each energization step requires the power technician to perform a number of verification tests such as system voltage phasing, voltage rotation, voltage and current vector relationships measured at the protective relaying, and metering equipment. Some service companies believe one test is good enough, but if there is a problem there usually is not enough information to quickly identify and address it. In comparison, it may take more time to conduct multiple tests and document the results in at the outset, but it will to help shorten problem-resolution times in the future.

Finally, a project is not complete until all drawings have been redlined and modified to reflect all field changes, all testing documentation is completed and organized, and the customer has been presented with the upgrade to the farm’s electrical system. Upgrades represent any change to a farm’s design, regardless of how minor. This is extremely important, as many service companies do not invest the time to instruct owners about the new condition of the farm, which is necessary for further farm upgrades—again, avoiding future operations and maintenance issues.

Attention to Detail
American Electric Technologies, Inc. (AETI), has been providing electrical services for more than 30 years and has service technicians with an average of more than 20 years of experience each. Leveraging its experience in industrial and marine traditional energy for wind farm electrical services, AETI has developed a unique framework for successfully addressing the issues of today’s wind farm electrical system testing, commissioning, and startup energization.

Known as AIRDAP, this framework stands for “Attention to all details, Identification of any issue, Rapid resolution of issues as they appear, Documentation of any changes to the electrical system, Avoidance of leaving any problem behind, and Presentation of all information to the operator. As discussed, the successful startup of the wind farm’s electrical systems requires significant attention to every detail to ensure safety while driving down time and cost.

As the startup progresses from the grid toward the turbines, every issue identified must be resolved before proceeding to further contain costs. And to avoid leaving issues on the farm that will hinder future progress, documentation and presentation of all findings to the operator is critical, ensuring wind farm integrity, reliability, and containment of operations costs in the long term. 

As tall objects in a field, wind turbines make ideal targets for lightning strikes. Even more so as the application continues to grow as a serious source of new electricity generation: the total wind power capacity now operating in the United States is over 35,600 MW, which corresponds to the power usage of 9.7 million homes, according to the American Wind Energy Association (AWEA). Figure 1

As in any trade, system downtime and repairs must be minimized. This is where information about critical weather parameters becomes an important part of decision making. Wind, temperature, icing, lightning—relevant weather data can prove to be a vital asset for wind farm operators and other power companies alike. Ignoring these parameters can be a costly exercise. For example, the U.S. National Lightning Safety Institute states that at one wind farm in the southwest lightning damage alone exceeded $50,000 in the first year of operation, and at another 85 percent of the downtime experienced was lightning-related.

Wind turbines are designed with grounding systems to isolate the lightning current from sensitive electronic and mechanical components to ensure safety. Industry standards require wind turbines to withstand 98 percent of natural lightning strikes. Unfortunately, no lightning protection system is completely effective, so Vaisala lightning data is used by turbine manufacturers to validate that damage was truly caused by lightning before replacing blades under the terms of the warranty. Vaisala’s STRIKEnet® Internet service allows turbine manufacturers and wind farm owners to enter the geo-coordinates of the damaged turbine and search an extensive archive of cloud-to-ground lightning strikes for up to a 72 hour time window, generating an automated report of the lightning strikes in the vicinity. Depending on the terms of the agreement, turbine manufacturers or wind farm insurers will be responsible for repairing the damage. Additionally, Vaisala’s high quality real time and archive lightning data from the National Lightning Detection Network (NLDN®) is used by the Vaisala FALLS® application for extensive forensic analysis of faults and identifying lightning strokes which have caused outages or damage to transmission lines.

Lightning is also a challenge to traditional energy and power industries. High-current lightning strikes are a significant threat to the dependability of electric power transmission, because they can cause severe damage to power lines. Being able to detect and locate these events means savings in both time and money as the fault locations can be found more quickly, and electricity can be re-routed to a different path. Recent findings in Japan show an encouraging future trend in lightning detection for power companies and demonstrate the value of accurate and timely weather data in decision-making.

Significant R&D Achievements
Lightning locating systems provide valuable information to a wide variety of applications. The demand for both data quality and the range of cloud-to-ground lightning parameters is highest for forensic applications within the electric utility industry. For years the research and operational communities within this industry in Japan have pointed out a limitation of these systems in the detection and location of damaging (high-current and large charge transfer) lightning flashes during the winter months. Most of these flashes appear to be upward-connecting discharges, frequently referred to as “ground-to-cloud” flashes [1]. Figure 2

Lightning events along the coast of the Sea of Japan during the winter months emit particularly different waveforms than the majority of other lightning events, which makes them hard to detect or classify properly. To address this problem Vaisala has worked together with Tohoku Electric Power Company and Sankosha Corporation to develop improved lightning sensor software. Tohoku Electric supplies electricity to approximately 7.7 million customers throughout the seven prefectures of the Tohoku region. The company’s electric power sales amount to over 81,101 kWh, ranking it fifth among the 10 Japanese electric power companies. Sankosha Corporation has been supplying Vaisala lightning detection systems to the electric power companies in Japan for more than 25 years. Sankosha engineers install and maintain about 100 lightning sensors operating in Japan. They work closely with Vaisala engineers and scientists to make sure that networks are operating properly and network operators take advantage of new technologies as they become available.

The result of the joint R&D effort is the latest software for the Vaisala Thunderstorm CG Enhanced Lightning Sensor LS7001, which delivers double the detection accuracy of high peak current winter lightning discharges compared to older sensors. The new sensor is able to continuously sample and process detected signals eliminating the dead time problems of previous sensor generations. Enhanced self-test and calibration capabilities permit the simulation of more complex waveforms and help achieve a significant improvement in stroke time measurements.

As a part of the cooperative research project, a six sensor network of the new sensors was deployed in the Tohoku region during the 2009/2010 winter lightning season. Data from Lightning Electromagnetic Pulse (LEMP) recording equipment operated by Tohoku Electric and information from lightning related failures in Tohoku’s transmission line systems demonstrated significant improvements in lightning detection performance. This was achieved by studying electromagnetic waveforms generated by winter lightning and then developing new parameters for their detection. “Lightning detection information is extremely important in the operation and maintenance of our electric power transmission and distribution systems,” according to Noriyasu Honma from Tohoku’s Electricity Technology Section. “Improvement in our ability to detect high current winter lightning events is a critical step forward.” Figure 3

The project in Japan will continue through the 2011 winter lightning season. The algorithm updates employed in the reprocessing will be implemented in sensor software, which will be downloadable into most existing Vaisala LS sensors, making improved detection performance available for energy and power industries around the world.

Features and Benefits
The LS7001 is a compact, lightweight sensor with optional indoor mounting capability that detects low frequency (LF) signals using magnetic direction finding combined with time-of-arrival technology to deliver higher detection efficiency, location accuracy, and redundancy than any other method for detecting cloud-to-ground lightning strokes. The LS7001 is a cost-effective solution for customers demanding high reliability, ease of installation, and ease of maintenance. Features and benefits include:

• Cloud-to-ground lightning detection for the most accurate lightning location and calibrated parameters;
• Cloud-to-ground lightning of greater than 95 percent network detection efficiency;
• Detects up to 30 percent of cloud lightning for early thunderstorm identification;
• Detects cloud-to-ground lightning at long ranges (>1500 kilometers);
• Calibrated parameters for cloud-to-ground lightning: time, location, amplitude, polarity;
•Third party validated 250 meter median location accuracy for cloud-to-ground lightning strokes;
•New efficient lightweight electronics module allows for ease of installation and maintenance;
• Sensor can be installed separately from antenna in remote severe weather locations;
• Compatible with predecessors Vaisala IMPACT and Vaisala LPATS sensors;
• Available in AC and DC versions.

Precise Weather Knowledge
Wind turbine manufacturers and wind farm operators require high quality environmental measurement systems to maximize performance, support safe operations, and fulfill industry standards. Intelligent environmental measurements can be used in control systems, for example, improving community acceptance of wind farms by dimming obstruction lights in clear weather and getting field service teams to safe ground before thunderstorms arrive. Turnkey atmospheric observation networks can provide that significant advantage to save millions of dollars, combining wind speed predictions with other business-critical environmental data. 

As the warranty expiration date on your fleet of wind turbines approaches, there are many questions to be asked and a range of risk management options you should consider. This process needs to take place well in advance of the warranty expiration date to insure that all alternatives, including new third party warranty products, have been identified and carefully evaluated. Only then can you make the best financial and risk transfer decisions regarding the future of your machines. Figure 1

Possible strategies run the gamut from full limits five-year warranty extensions to completely assuming the risk on the operator’s balance sheet with no warranty coverage in place. The following is an analysis of wind turbine warranty exposures and the various strategies that can be employed to understand and manage these risks.

Typical warranty language reads as follows: The Seller warrants to the Buyer that during the Warranty Period: (i) the Equipment to be supplied hereunder shall (a) be designed and fit for the purpose of generating electric power when operated in accordance with the Seller’s specific operating instructions and, in the absence thereof, in accordance with Prudent Wind Industry Practices (b) be new and free from defects in material, workmanship and title, (c) comply with the Technical Specification and (ii) all Services to be performed hereunder shall be performed in a competent, diligent manner in accordance with the requirements of this Contract and any other mutually agreed specifications (collectively, the “Warranty”).

With the explosive growth of the wind turbine industry over the last five years there has been a year by year increase in the number of wind turbines coming out of their original OEM warranty. Compounding the issue of warranty expiration is the fact that more than 50 percent of the U.S. wind turbine fleet may be behind in scheduled maintenance. It has been estimated that ownership and maintenance costs can increase by as much as 250 percent over the 20-year life of the wind turbine. This lag in scheduled maintenance has resulted from a number of factors, including budget constraints and a lack of trained service technicians.

This statistic has larger ramifications to the wind farm operator than simply being behind a maintenance schedule. Almost all wind turbine supply agreements are very specific about both the maintenance schedule and who is to perform the work. In addition, the typical Turbine Supply Agreement (TSA) has very specific language regarding the exclusion of warranty claims if the maintenance performed and documentation of servicing of the turbines are not in accordance with the TSA.

Exclusionary language related to warranties in a typical TSA is as follows. The exposures and potential pitfalls related to service, maintenance and record keeping should be clear: The Seller does not warrant the Equipment or any repaired or replacement parts against normal wear and tear, including that due to environment or operation. The warranties and remedies set forth herein are further conditioned upon (i) the proper storage, installation, operation, and maintenance of the Equipment conformance with the operation instruction manuals (including revisions thereto) provided to Buyer by the Seller and/or its Subcontractors or Suppliers, as applicable and, (ii) the provision and maintenance throughout the Warranty Period of a T-1 line for remote monitoring as described in the Technical Specification, and (iii) repair or modification pursuant to the Seller’s instructions or approval. The Buyer shall keep proper records of operation and maintenance during the Warranty Period. These records shall be kept in the form of log sheets and copies shall be submitted to the Seller upon its request.

As turbines approach the end of their warranty period, it is therefore critical to put into effect a well thought out end of warranty strategy.

Independent Turbine Inspections
The first step should be sourcing an independent inspection of each and every turbine that is coming off warranty. It is critical that this inspection be done before the warranty ends for several reasons.

First, the owners will want to document all possible claims and submit them, via a Reservation of Rights letter, to the original equipment manufacturer (OEM) far enough in advance so the operator can negotiate any repairs directly with the OEM. This negotiation process can be time consuming and the wind farm owner will want to allow enough lead time so any needed repairs are completed before or shortly after the end of the OEM warranty period. Figure 2

The second reason the wind farm owner needs an independent inspection is for documentation purposes as to the condition of the wind turbine at the time of the warranty expiration. This documentation may be required for the wind farm’s lenders and will certainly be required by the insurance companies participating in the coverage of the wind farm.

It is also important to note that once this report is completed it will document the areas of concern on each and every turbine. If for some reason these documented issues are not addressed at the end of the warranty by the OEM or repaired by the wind farm owner, any future insurance claims stemming from these issues will be denied as resulting from a “pre-existing condition.”

Extended Warranty Coverage
Should I purchase extended warranty coverage or not, and what are my options if so? This is the question that is now being contemplated by over 20 percent of our country’s wind turbine owners as their assets become warranty liabilities.

The goods news is there are now third-party extended warranty options available in the insurance market place. Historically, extended warranty options were limited and typically provided by the wind turbine manufacturer. These warranties were usually negotiated at the time of wind turbine purchase and the standard warranty “built into” the sales price of the turbine was two years with a three year extension available for an additional per turbine, per year charge. Figure 3

Over the last 20 years, the length of warranties has decreased dramatically. As manufacturers built substantial liabilities on their own balance sheets and established their operations and maintenance (O&M) divisions, warranty periods were reduced and the sale of warranty extensions became a substantial profit center.

Warranty Options
Balance sheet finance: As the turbine warranties expire, the wind farm operator may decide to assume responsibility for 100 percent of the costs and losses resulting from warranty related incidents. Keep in mind that the true cost of a warranty occurrence is the combination of costs associated with securing the effected turbine, obtaining and shipping the replacement part, hiring and transporting the repair equipment, providing the labor for repairs, and assuming the lost income and production tax credits, if applicable. Historically, this has been the only option available to wind farm operators since the OEM’s did not offer extended warranties past the five-year period.

Rely on property insurance: Wind farm owners who choose to forgo extended warranty coverage believing their property insurance coverage will respond to a warranty claim are likely to be surprised when that claim is denied. While some property insurance policies provide a minimal amount of coverage as outlined below, a property policy will not provide the wind farm operator with complete warranty coverage. Unlike property policies that require losses to stem from a covered peril, a warranty policy does not require you to run your equipment until it breaks in order to have coverage.

Property forms do not provide warranty coverage and can be ambiguous with exclusions or limitations so losses are subject to underwriter’s acceptance or are left for attorneys to litigate. There are too many gray areas that leave projects exposed and put lenders and investors at risk. Here are some of the major differences between property policy coverage and warranty policy coverage. Property forms provide coverage for the peril of mechanical and electrical breakdown if the failure is sudden and accidental and subject to exclusions and limitations. Coverage is excluded under a property policy for the following:

• Defects or faults in material, workmanship, or design: As an example, blades are cracking due to faulty materials or bolts are not fastened properly during construction and nacelle falls off tower.
• Wear and tear: Cable brackets are failing due to a repetitive movement over a long period of time and the cables are splitting and arcing.
• Gradual deterioration: Bearings are grinding over a long period of time, which causes your gearboxes to fail.
• Inherent vice: There are hidden defects in the equipment or materials that cause deterioration and/or damage.
• Latent defects: There are hidden defects in material and/or workmanship not discoverable through general inspection.
• Serial losses have limited coverage under a property policy: Development of a defect in equipment indemnity would be: first item 100 percent; second item 75 percent; third item 50 percent; fourth item 25 percent; subsequent 0 percent.

Warranties have a positive impact on insurance premiums as they indemnify the equipment system owner in the event a product defect that leads to losses. They do not take the place of a warranty policy, however, and should not be counted on to do so.

Purchase extended warranty from the OEM: Extended warranties might be available in several forms from the OEMs. Depending upon who the wind farm operators are, the quantities of turbines with expiring warranties and the locations, the warranty offering might be parts only or may include parts and labor. These warranties are sold on a per-turbine, per-year basis and cover the full value of the turbines with little to no deductible. Pricing for the OEM warranties range anywhere from $30,000.00 per turbine per year for a 1.5MW turbine to over $150,000.00 per turbine per year for a 3 MW machine. Using the lower pricing range, a wind farm with 100 1.5MW machines electing to purchase a five-year warranty would incur costs of $15M. (100 Turbines x five years x $30,000 = $15,000,000 warranty bill).

Purchase a third party insurance warranty: Until very recently a viable, cost-effective third-party warranty option has not been available to the wind farm operator. Today’s third-party warranty product is designed to wrap around the turbine supply agreement (TSA) to continue the coverage supplied by the OEM. The third-party warranty product can be modified to cover additional risks or to modify the risks covered in the original TSA. The third-party warranty (written on A.M. Best Rated A XV paper) covers serial defect, product defect, availability, parts, and labor. Optional coverage for power curve and noise are also available and can be added to the third-party warranty by endorsement.

The third-party warranty is generally sold in “blocks” of limits that are usable for a five-year period. Unlike the OEM warranty, the third-party warranty minimum insurance limits required are calculated on a maximum probable loss (MPL) basis. This means that under reasonable conditions, taking into consideration the make, manufacturer, current condition, and loss record of the turbines, the limits required should cover the foreseeable loss.

Third-party warranties also have annual deductible structures similar to property policies. The final decision as to the amount of limits to be purchased is made by the wind farm owner and will ultimately determine the warranty price. Significantly, third-party warranty coverage can be purchased for far less than available OEM warranty options. Consider again our hypothetical wind farm with 100 1.5MW machines electing to purchase a five-year warranty:

• OEM Warranty Costs: 100 turbines x five years x $30,000. = $15,000,000 warranty bill;
• Third Party Warranty Costs: $10M in limits, usable up to the limits of the policy, for a five-year period = $3M warranty bill.

In this example, the wind farm operator would save an estimated $12M with the purchase of a third-party warranty policy, reducing warranty costs by 80 percent. This is clearly an option that must be understood and investigated by anyone with a financial interest in wind turbines approaching the end of initial OEM warranty.

One final word of advice. Providing warranty coverage of this nature is a highly specialized discipline having many nuances. Not everyone has the experience and the knowledge to fully understand the issues and to craft the necessary strategies and solutions. No single approach will be the right one for every situation. There is no “one size fits all.” Look for insurance and financial services advisors who have a strong background in the energy industry and work extensively with alternative approaches and emerging technologies. Otherwise, you may just find yourself twisting in the wind. 

Much like the gold rush or even the space race, the goal set by the U.S. government to reach 20 percent of energy coming from wind power by 2030 has sent everyone searching for ways to get involved. A report by AWEA [1] finds that, during the decade preceding 2030, the U.S. wind industry could:

• Support roughly 500,000 jobs in the U.S., with an annual average of more than 150,000 workers directly employed by the wind industry;
• Support more than 100,000 jobs in associated industries (e.g., accountants, lawyers, steel workers, and electrical manufacturing);
• Support more than 200,000 jobs through economic expansion based on local spending;
• Increase annual property tax revenues to more than $1.5 billion by 2030, and;
• Increase annual payments to rural landowners to more than $600 million in 2030.

The biggest deterrent is that harnessing the wind is a challenge, to say the least. Installing literally tons of equipment atop a tower hundreds of feet in the air? Building a machine that can handle exposure to permanently changing loads? Climbing into the clouds to maintain the turbine in extreme weather conditions? Sure, there are those who thrive on such challenges, but new remote condition monitoring equipment and service options lower the risks involved in maintaining your investment in wind power.

The two primary factors, each with a direct correlation to project profitability, are efficiency (how well a turbine performs when it’s operating) and availability (the time a turbine is available for production). Turbine size is permanently growing, and downtime can potentially cost project owners significant revenue. By simply considering the costs associated with an unanticipated gearbox failure during peak hours at a 3 MW turbine that is five miles offshore, the advantage of having prevented such a failure becomes abundantly clear.

Having monitored more than 1,000 turbines—different sizes from 250 kW to 5 MW and more than 20 different designs, onshore as well as offshore—we know that approximately 10 percent of all turbines will experience major damage each year (Figure 1). This might seem like an insignificant number when operating only a few turbines, and you may just fall into the category of the 90 percent of “lucky” owners who do not experience damages (Figure 2). But the average wind farm in North America has between 50 and 100 turbines, and the more turbines the more relevant those statistics become. Do you want to test your luck and be unprepared to halt the use of a turbine for a repair, or would you rather catch a small glitch before it snowballs into a huge problem?

Having a tool that helps asset managers to permanently monitor the condition of major components—the main bearing, gearbox, and generator—provides the basis for the right and timely decision. This lowers the probability of a major mechanical malfunction and betters your chances for profitable margins.

The main goals of remote condition monitoring are avoiding or prolonging the replacement of costly components, reducing high maintenance costs, optimizing utilization of recourses (equipment, personnel), limiting collateral damage, and reducing inventory costs and unscheduled downtime. A typical remote monitoring system will cost you approximately $10,000.

Since the gearbox seems to be the weakest element in the drivetrain, here is an example for cost savings by implementing condition monitoring: With no condition monitoring implemented gearbox damage occurs without warning, running to approximately $130,000 for replacement costs, and four to eight weeks of downtime. With condition monitoring in place indicators for gearbox damage is detected early, maintenance can be scheduled around the wind, it will cost approximately $70,000 for repair/overhaul, and one or two weeks of downtime.

Another potential for cost savings involves the “end of warranty inspection.” It is common practice to perform a 100-percent visual inspection of all gearboxes—100 percent with regard to the number of gearboxes is correct, but 100 percent with regard to the components of the gearboxes unfortunately is not. Many components remain uninspected. With a remote condition monitoring system in place you could focus the inspection on those gearboxes showing certain indicators for wear/damage and perform a more-thorough inspection. Figure 3

Condition monitoring is not new. It is standard practice for steam turbines, gas turbines, and even hydro turbines. However, remote conditioning for wind turbines faces very unique challenges such as the very low speed of the rotor (main bearing) rotation and the permanently changing dynamic loads. “Standard” condition monitoring systems would create either tons of false alarms or no alarm at all, both of which are absolutely critical for the acceptance of a condition monitoring system.

In the early nineties Schenck and ISET (today Fraunhofer-IWES) started a project sponsored by the German government to develop technology for monitoring the condition of wind turbines. The result was the product “VIBRO-IC,” the first dedicated, industrial-proven monitor for wind turbines. It was monitoring rotor unbalance, aerodynamic unbalance, misalignment, and bearing, gear, and generator condition. VIBRO-IC got an award for “best new product of the year 1998” by Design News magazine.

In 2003 Schenck Trebel partnered with Prasentia, a system integrator and service provider to the wind power industry, to develop remote interface capability between the condition monitoring system and the SCADA system. A cooperative pilot study of the installation began at a wind farm in Palm Springs, California, that utilized 700 kW turbines. Within a short time a potential misalignment problem between the generator and the gearbox was detected by the CMS. The alignment check revealed that the misalignment was greater than the acceptable tolerance. A second observation showed high “shock pulse readings”—an indicator for bearing problems—on the NDE side of the generator. During a scheduled maintenance the lubrication system was checked and adjusted. The shock pulse readings went back to “normal” [2].

Allianz, one of the largest insurance companies in Germany, conducted vast research in condition monitoring for wind turbines and summarized the results in their final report in 2003 [3]. The report describes the basic requirements for a CMS for wind turbines. It makes clear that only online systems with remote access for a “vibration expert” are acceptable for this application. The report refers to the final report from ISET from 1999.

It is essential for the acceptance of condition monitoring for wind turbines to combine a dedicated product with the experience of vibration experts. For these reasons Schenck is not offering a product to the industry, but rather the remote condition monitoring service. Both the product as well as the service are certified by GL Garrad Hassan and approved by Allianz.

Our service center (Figure 4) will monitors turbines 24/7, providing notification in case irregularities/indicators have been detected along with an explanation of measurements, trend curves, spectra, etc., and recommendations as to actions to be taken, and with what degree of urgency. To be able to provide the service we make sure that the right sensor is picked and installed properly in the right location, that the system is set up individually for your specific turbine, the communication works reliably, and the monitoring center is available at all times. Will your turbine be one of the 10 percent to experience damage, or will you be in the 90 percent who enjoy increased profitability? Remote condition monitoring could be the determining factor. 

References:
1) www.20percentwind.org
2) Schenck balancing news 0406
3) Allianz Centre for Technology, report nr. 03.01.068

The United States government has set a goal of using wind energy to generate 20 percent of the nation’s electricity demand by 2030. As the U.S. looks to generate more wind energy onshore and expand into the technically challenging offshore wind market, it will not only need to innovate, but also learn from other countries’ approach to the installation, construction, and maintenance of offshore wind projects, which are moving farther and deeper than previously thought possible.

Scotland has already shown that it is a powerhouse in the renewable energy industry. The Scottish government recently announced its aim to generate 80 percent of Scotland’s electricity consumption through renewable sources by 2020, primarily through wind power. While these targets may seem ambitious, they are certainly not unrealistic; Scotland has fantastic wind energy resources—25 percent of the European total—and there are plenty of opportunities to generate additional power through both onshore and offshore wind energy.

Scotland now seeks to enhance its offshore wind sector by opening up much of its territorial waters to wind farm development. It currently has more than 90 onshore wind farms in operation or under construction, and it is leading the world in the development of deepwater offshore wind farms, having deployed two of the largest-capacity turbines ever constructed. Indeed, there are many lessons learned in Scotland that can be applied around the world.

Going Deeper
Scotland has led the way in offshore wind with the Beatrice Wind Farm Demonstrator Project. Located 12 miles off the country’s east coast, the project is a world first. In 150 feet of water, Beatrice is operating at almost double the depth used anywhere else, using 5MW wind turbines; the first of this size ever installed offshore in the world.

This project has paved the way for future large-scale wind development off the shores of Scotland. The proposed follow-on full-scale development of the Beatrice Demonstrator will be a wind farm of 920MW installed capacity. The Crown Estate—the body in the United Kingdom that dispenses the seabed rights in the country—has granted a number of leases to develop commercial scale wind farms in the waters around Scotland. Offshore, there will be 9,500 turbines installed around the UK in the next decade, of which Scotland’s share will amount to around £30 billion worth of investment, and up to 28,000 jobs. Currently production of 10.5GW is planned off the coast of Scotland, with 5.7GW in territorial waters and 4.8GW in the Crown Estate’s leases in the Moray Firth and the Firth of Forth. Although deepwater turbines are more expensive to install, operate, and maintain than those onshore, they provide less visual intrusion, can generate more energy, and can be developed at a much larger scale than onshore wind. Figure 1

Repurposing Resources
Scottish companies utilize proven technologies borrowed from the oil and gas industry to assemble, install, and operate the Beatrice turbines.  The substructures for the wind turbines are jacket technology (lattice towers) taken straight from offshore oil and gas experiences. Much of the supply chain that now exists to serve offshore petroleum production could be configured to support offshore wind.

The Scottish-based Burntisland Fabrication built the jackets for the Beatrice project and is now supplying jackets to several near-shore wind developments in the UK and Europe. Jackets can be installed in deeper water with less visual intrusion, they require less steel—which reduces cost—and can support much larger wind turbines (5-10MW) than conventional monopiles, which have been the solution to date in shallow water near shore projects.

Burntisland Fabrication is also deploying its oil and gas industry expertise in the area of marine energy, having recently won the main £2 million contract for the next stage of the development of one of the world’s most advanced tidal turbines, Hammerfest Strøm’s HS1000 device, which will be installed at the Scottish government-supported European Marine Energy Centre (EMEC) in Orkney in 2011. This is part of over £4 million worth of contracts awarded to Scottish businesses by Hammerfest Strøm UK, a company jointly owned by Scottish Power Renewables and Norwegian energy companies.

Expanding Onshore
Offshore wind is a new direction for renewable developments, but Scotland is already a major market for onshore wind. Europe’s largest onshore wind farm, which is already powerful enough to meet the city of Glasgow’s electricity needs, is set to expand by more than a third as part of a major green energy initiative by the Scottish government. The 322MW Whitelee wind farm south of Glasgow has been given permission to increase its capacity to a total of 215 turbines. Construction has already begun on the expansion and is expected to be completed by 2012, delivering 596MW, which is enough energy to power 180,000 homes. An ambitious scheme in the Shetland Isles has also recently been submitted to the Scottish Government for a 550MW wind farm. This will be a joint venture between the community-owned Shetland Trust and major utility company Scottish & Southern Energy. This will also include a 330 kilometer subsea cable back to the Scottish mainland.

Additionally, Scotland’s onshore wind industry presents excellent opportunities both for companies involved in supplying components such as towers, blades, gearboxes, and hubs, and those involved in operation and maintenance. Furthermore, due to the scale of the country’s onshore wind sector, many of the overseas wind turbine manufacturers have set up sales, operations, and maintenance facilities in Scotland. These companies include REpower, Siemens Wind, Nordex, Vestas, and Skycon. Figure 2

Collaboration is Key
The Scottish European Green Energy Center, which opened this August, is a government and university collaboration. A £1.6-million investment in the Aberdeen facility through the European Regional Development Fund, and more than £1 million of funding from the Scottish Government over the next three years, will allow SEGEC to focus on marine energy, offshore wind, long-distance super grid development and smart distribution grids, carbon capture and storage, renewable heat, and energy efficiency.

In the private sector, Scottish and Southern Energy, PLC, and Mitsubishi Heavy Industries Ltd (working through their European subsidiary Mitsubishi Power Systems Europe Ltd) recently signed a strategic agreement to cooperate on low carbon energy developments including offshore wind farms, carbon capture, and high-efficiency power generation. The agreement builds on SSE’s establishment last October of a Centre of Engineering Excellence in Renewable Energy in Glasgow and should lead to up to 100 additional highly skilled, engineering-based jobs being created. This is expected to grow to up to 1,000 jobs over five years.

Scotland’s Low Carbon Investment Conference in September 2010 is another example of the country’s ability to forge lasting partnerships around wind energy development. Conference attendees included Scotland’s First Minister Alex Salmond along with global politicians, industry executives, and representatives from several U.S.-based renewable energy companies and investment firms. On the first day of the conference Salmond announced the country’s move to increase its renewable energy target from 50 to 80 percent supply by 2020. Several of the expansions and new wind energy proposals that will contribute to meeting this aggressive goal were on display throughout the conference.

Academic Support
The close cooperation between Scotland’s universities and companies has created a united community of innovation to rival the world’s biggest centers of academic excellence. In collaboration with Scottish Development International (SDI) and a government determined to attract the best in academic and business excellence, Scotland offers a huge range of free support and incentives to companies investing in the country’s people and economy. Scotland’s universities house a number of research and development centers and institutes, which themselves have spawned a number of companies in the wind energy arena that have already produced advanced products and services, and others are involved in the further commercialization of research projects to add to the body of work coming out of Scotland.

Marine Innovation
Simultaneous to the rather aggressive development and deployment of wind energy technologies, Scotland is also deeply invested in leveraging innovative marine energy technology. The Scottish government is working proactively to promote continued development in tough economic times with initiatives such as the Saltire Prize, awarding a £10 million challenge prize for advances in marine renewable energy. Jaison Morgan, an advisor to President Obama and leading expert in the use of innovation prizes, recently lauded Salmond as being “ahead of the White House” for implementing this prize to drive renewable technology innovation. Scotland already has other innovative incentives in place to support the development of marine energy (wave and tidal). The Crown Estate has completed a licensing round for the Pentland Firth between mainland Scotland and the islands of Orkney, which is the first commercial scale development in the world for wave and tidal energy. This 1200MW development will be operational by 2020 and will utilize technologies trialed and tested at the EMEC in Orkney. Figure 3

In recent weeks Atlantis Resources Corporation has successfully deployed its AK1000™ tidal turbine, the world’s largest rotor diameter tidal turbine, on its subsea berth in 35 meters of water at the EMEC. The device is one of a number of technologies currently being tested at EMEC, and it is 22.5m tall, weighs 1,300 metric tons, and has a twin set of 18m diameter rotors.

In a parallel development that will take offshore wind into a new technical dimension, Statoil—a Norwegian-based oil company—is discussing the possibility of developing the world’s first floating wind farm in Scotland. The company has identified two potential sites, one off the coast of Lewis and one off of Aberdeenshire, that could be suitable for a pilot park, testing the concept of their Hywind floating turbines further.

Statoil has already constructed a full-scale prototype Hywind unit, anchored 10 kilometres offshore at Karmøy in Norway. The floating wind turbine is performing beyond expectations and has delivered power to the grid since September 2009. The next stage of the project could involve constructing between three and five Hywind units to document the commercial potential of the concept.

Scotland’s unique collaborative environment, innovative spirit, wealth of natural resources, and experience in energy research and production has allowed a nation of five million to take the reigns as a pioneer in wind energy. At a time of global need for new, alternative sources of energy, this small nation has a vital role to play in leading the way for the next generation of energy research and production, and in influencing other countries to follow suit.

Note: Scottish Development International is the country’s inward investment agency, providing advice and support to international companies looking to invest in Scotland. It also provides support to Scottish companies doing business across the globe. 

It’s no secret that the overall success of a wind farm is primarily determined by the amount of power it produces, which translates into revenue generation for its owner. Yet the prevailing industry measure of a wind turbine’s performance remains its availability to produce electricity if the wind is blowing. In fact, virtually all original equipment manufacturers base their wind turbine warranties in part or in whole on availability metrics. As a result, technicians at wind farms across the United States often find themselves scrambling to get turbines back online following an unexpected interruption in availability.

Sometimes these efforts do little to boost profitability, particularly if restoration occurs during a lull in wind resources. In other instances, wind farm operators authorize “quick fixes” instead of addressing root-cause problems that may impede high performance over the long run. At Duke Energy’s nine U.S. wind farms, the focus is simple: leave no stone unturned in the quest to maximize each turbine’s energy yield. While availability is still measured and effectively managed, achieving higher energy yields is what helps the company wring as many electrons—and dollars—as possible from its wind power assets. Duke Energy’s formula for success is based on the same strategy that helped the company become one of the largest electric power holding companies in the country.

Zero to 1,000 Megawatts
With regulated operations in five states—the Carolinas, Indiana, Kentucky, and Ohio—and more than 100 years of experience in the electric utility sector, Duke Energy knows how to get the most from its power generation and delivery assets. The company serves approximately 4 million customers, representing a population of roughly 11 million people. Its non-regulated commercial business unit, which generates about one quarter of the company’s earnings before interest and taxes, operates like an independent power producer.

In 2007 Duke Energy’s commercial unit launched aggressive plans to add wind energy generation to complement a diverse existing portfolio of assets in the Midwest and Latin America. The strategy: use a few key acquisitions to propel an ambitious organic project development plan.

First came the purchase of Austin, Texas-based Tierra Energy in 2007. Along with a healthy portfolio of development projects, Duke Energy took control of three wind farms that began generating electricity in late 2008. The company then netted a 50 percent stake totaling 283 megawatts in phases one through five of the massive Sweetwater project in Texas through the acquisition of Catamount Energy, based in Rutland, Vermont. That purchase raised the total capacity of Duke Energy’s wind projects under development to roughly 5,000 megawatts.

Duke Energy now has nearly 1,000 megawatts of capacity in operation at four wind farms in Wyoming, three in Texas, one in Colorado, and another in Pennsylvania. The company’s continuously replenished pipeline of potential development projects currently totals approximately 5,500 megawatts.

Improving Profitability
In the spring of 2009, leaders in Duke Energy’s wind unit took notice of a troubling trend: the company’s wind farms were earning very high marks for turbine availability, but some were missing their profitability targets. Upon closer inspection, they diagnosed three key problems.

First, some turbines were not producing the maximum-rated output as prescribed by their manufacturers, even though availability figures remained high. Second, maintenance schedules were often established with the sole intent of boosting availability rather than maximizing actual production and revenue generation. Finally, technicians were sometimes dispatched to return offline turbines to service just in time for periods of sustained low wind. “We kept hitting our availability targets,” according to Jason Allen, Duke Energy Generation Services vice president of operations. “When we delved deeper, however, the question soon became ‘Are we hitting the right bull’s-eye?’”

Allen assigned a team to compare the power curve specified for every wind turbine in Duke Energy’s fleet, totaling 650 units at the time, to actual output. The results were eye opening. Some turbines:

• Cut off before achieving their manufacturer-specified maximum rating (Figure 1);
• Backed off early due to high generator temperatures, possibly due to faulty thermocouples (Figure 2);
• Exhibited partial back-off tendencies due to high generator temperatures, possibly the result of additional load on generator bearings from yawing (Figure 3);
• Showed “candy-cane” behavior, where turbine performance worsened as wind speed increased instead of following the vendor’s power supply curve (Figure 4);

Other turbines’ output lagged behind the manufacturer’s power curve, or sagged through the middle of the curve. The analysis team was pleased, however, to find that most turbines yielded perfectly clustered data, with output matching the vendor’s power curve precisely. In some cases turbines actually produced more power than originally guaranteed by their manufacturers. “We achieved exceptional results through condition-based monitoring and world-class maintenance, but our analysis showed that we were still leaving money on the table,” Allen says. Figure 5

Power Operations Manager Tom Paff led the team charged with monitoring wind farm performance, working with site personnel to troubleshoot problems with underperforming turbines, and helping prevent the potential loss of future revenue. In one case his team identified a pitch ram misalignment on a turbine at Duke Energy’s Notrees Windpower Project in Ector and Winkler counties, Texas, that resulted in tens of thousands of kilowatts in lost electric generation each month. Had the combination of performance and condition-based monitoring not uncovered the problem, Duke Energy would have missed out on nearly $30,000 in annual sales from that single wind turbine. The team tackled dozens of similar seemingly minor issues, resulting in higher energy yields that translate into increased revenue for each wind farm and the company. Figure 6

In addition, Jason Allen directed regional and site managers to refine their approach to scheduling maintenance and dispatching crews for repair work. “Turbine availability is an important metric, but never more so than when the wind is blowing,” he says. “It’s bad to have a turbine come back online just in time for the wind to die down. It’s even worse to have a technician performing routine work on a turbine when we could be producing electricity at peak capacity due to very windy conditions.”

Allen’s teams at Duke Energy’s nine wind farms now try to schedule basic maintenance and equipment upgrade work when wind resources are forecasted to be low. Wind forecasts also play a major role in determining when to send technicians to restore off-line turbines.

“Why wake a technician up in the middle of the night, get him out of bed, make him drive to the site, and pay him overtime just to restore a wind turbine that won’t even produce much power or revenue during the day, when winds at some sites are typically lighter? As long as you’re fully complying with all turbine warranty guidelines it makes more sense to dispatch work crews strategically, based on wind forecasts and the time of day.” Figure 7

Predicting Mother Nature
There’s an old saying in Wyoming, where Duke Energy owns and operates four wind farms: if you don’t like the weather, wait 10 minutes and it’ll change. Accurately predicting that change is another story. That’s why Duke Energy’s wind power unit—which had been contracting with third-party vendors for weather imagery, alerts, and real-time forecasts—turned to the broader corporation’s meteorology team in the spring of 2009 for help.

“Our group had already developed a comprehensive suite of weather monitoring and forecasting tools to support power generation and delivery operations in both our regulated and commercial businesses,” says Meteorology Director Nick Keener. “The wind group came to the conclusion that Duke Energy’s in-house meteorology team could create a robust, highly customized solution, and at a fraction of the cost.” Figure 8

In addition to radar and satellite weather imagery, meteorology built a smart phone-networked notification system that allows site personnel to receive alerts when lightning is detected within a 60-mile radius of a wind farm and alarms when lightning is within 30 miles. “First and foremost, the software is designed to keep our employees and contractors safe,” Keener says.

One challenge for Duke Energy’s meteorology group involved forecasting winds at hub height, where the turbine blades connect to the nacelle. Senior Meteorologist Steve Leyton explains. “We have access to the same numerical weather prediction models as all the private vendors,” he says, “However, none of the models we looked at explicitly predict wind speeds at hub height. So we had to devise our own methodology, which involved reviewing the science and developing equations to account for different wind profiles at that height.”

Performance Monitoring
The detailed, site-specific weather reports and forecasts generated by the meteorology group’s end-to-end software solution are delivered in real-time format to wind farm personnel, as well as to staff members in Duke Energy’s new Renewable Energy Monitoring Center (REMC).

Located in Charlotte, North Carolina, where Duke Energy is headquartered, the REMC serves as the nerve center for the company’s entire renewable power fleet, including the commercial unit’s growing portfolio of solar farms. Experienced operators staff the REMC 24 hours a day, every day of the year. In addition to wind forecasting, the REMC enables virtually instantaneous turbine alarm response and remote resets.

Original equipment manufacturers monitor many of the wind turbines in Duke Energy’s fleet, pursuant to original purchase agreements. But according to Tom Paff, turbines that “trip” and go offline can sometimes go unnoticed by the OEMs for long periods of time because they have so many units to monitor throughout the country. “Time is money, and we’re saving both by learning about turbine performance issues as they occur,” he says. “Around the clock performance monitoring is a key driver for higher energy yields at Duke Energy wind farms.”

The REMC, powered in part by dependable wind and severe weather forecasts, has been so successful that Duke Energy is now accommodating requests by other wind farm operators to monitor their assets, as well. “It wasn’t part of the original game plan,” Paff explains, “but once word got around about how integral the REMC was to our success, we decided to open the doors to a select number of other renewable project operators. It’s a win-win scenario, because our clients are saving money and we’re achieving better economies of scale.”

Looking Ahead
Keith Trent, group executive and president of Duke Energy’s Commercial Businesses, believes superior operational efficiency will continue to be a key differentiator in the competitive wind power industry. “It’s more critical than ever to effectively manage the assets you have in operation,” he says. “That’s what the energy yield approach is all about—doing everything you can to make the most of what you’ve got.”