An introduction to insuring wind farms
June 8, 2010 by KRemington
Filed under Wind Power News
Curt Maloy, Vice President, Gcube Insurance, Boston
Most every wind project developer has sat staring at an empty “Insurance” line on a project financial pro-forma, wondering how to come up with a credible number his lender will accept for the annual projected cost of insuring his project. The reason is simple: It’s complicated.
First of all, we’ll assume statutory and discretionary cover-ages such as Workers Compensation, Employer’s Liability, Professional Liability, Commercial Auto, and General Liability, are in force as required for the project company, so we can concentrate on coverages specific to the wind project, and which likely will be required by the developer’s lender.
The best description of the coverage package which will be needed for a new wind farm is “cradle-to-grave” property coverage.
Secondly, project developers should select a commercial insurance broker to assist them in navigating the insurance coverage mine field. A good broker educates himself on the project exposures and technology, and runs interference with insurance companies competing for the project coverage.
Now, to the insurance: The best description of the coverage package which will be needed for a new wind farm is “cradle-to-grave” property coverage which includes both physical damage exposures and time delay exposures.
The first to be activated is Transit physical-damage coverage, effected when project compo-nents begin their journey to the construction site. Usually at the same time, Construction All Risk coverage is incepted because movement of project equipment generally coincides with commencement of work at the site. This coverage remains in full force as each turbine is erected, tested, and commissioned, and an Operating All Risk policy is activated when commercial operations begin for 100% of the project’s turbines. The ideal coverage eliminates the possibility of coverage gaps during these transitions, so no claim jurisdiction disputes can arise.
The Operating All Risk policy should include full non-warranty Mechanical and Electrical Breakdown coverage eliminating the need for a separate Boiler and Machinery policy.
Time Delay exposure protection is also always required. These coverages insure against lost power-production revenue due to Transit delays (Marine Delay in Start Up), lost revenue due to construction delays (Advance Loss of Profits), and operational revenue losses (Business Interruption), with the lost value of any applicable Federal Production Tax Credits, Renewable Energy Production Incentive payments, or other kilowatt-based governmental incentive payments fully covered by the policy. The new Investment Tax Credit grant of 30% of a project value is NOT insurable because funds once issued, cannot be reclaimed by the government, except under highly unlikely circumstances.
It is always best to have a policy form which has been written specifically for wind (as opposed to a generic energy facility policy form) to meet the specific needs of wind powered generation facilities. When reviewing a policy form for a wind project, you should never be find references to “pressure vessels”, “steam lines”, or “fuel storage”, as is common with many generic policies currently covering wind farms. The insurer should also continually refine the policy terms as practices and technology change.
Having done their homework and chosen to purchase the above property coverages, the next decision for developers is to select deductibles for each loss. Deductibles generally begin at $20,000 for physical damage and 20 days for business interruption. Higher deductibles, up to $1,000,000 and 60 days and more, are available and often preferred by clients and lenders for large projects.
Deductibles most commonly chosen are $50,000 and 20 days, and $100,000 and 30 days. A “rule of thumb” for making this decision is determining the degree to which a project owner’s payment of three or four deductibles in any one year would have on the project’s economics and cash flow. So it follows: larger projects have higher acceptable deductibles.
When required due to a project’s location, such as a “high-risk area” for windstorms (hurricanes), floods, and earthquakes, coverage arranged separately through the catastrophic insurance markets must be obtained by the basic insurance carrier. Deductibles and premiums for these coverages are separate from those described above and are significantly higher than those for projects in low-risk areas. Due to its cost, it is common to place Catastrophic insurance at less than full project replacement value.
Outside these locations, full project value coverage is standard. Commercial General Liability or GL policies cover construction and operation phases of all projects. GL and Umbrella/Excess liability coverages indemnify the insured for property damage and physical injury to a third party resulting from the operation of the wind plant. These two coverages should also seamlessly transition between phases of the project. Wind project Limits of Liability vary widely between projects based on the requirements and perceived exposures of the parties to the project. Limits of $5 million to $25 million are common.
A basic feature of the ideal wind farm insurance policy is flexibility in being able to structure coverages in a variety of ways to meet the needs of the insured. Policies should have the ability to be simply tailored, by policy endorsement, to the coverage requirements of each wind project and its contractually obligated insurance terms.
The insurance company chosen to provide these coverages should also have experts readily available to provide insurance premium estimates for individual projects, and perform reviews of the insurance provisions of project documents and contracts such as lending agreements, land leases, conditional use permits, power-purchase agreements, interconnect agreements, turbine supply and installation agreements, balance-of-plant-construction agreements, and O&M agreements. These experts should look for consistency in coverage requirements and limits, and offer observations relative to common wind industry practices as reflected in the many documents they see.
Lastly, the insurance carrier must have full time Loss Control and Claims Management personnel, in the U.S. and globally. The claims process should be known for efficiency, technical expertise, and rapid claim resolution based on the philosophy that valid claims are quickly investigated and paid, and that clear, unequivocal and compelling evidence of uninsurability must be present before they consider denying a claim.
It’s easy to see why the last line filled in on a project developer’s financial pro forma is almost always the insurance line. Each of the many participants in every wind farm development will have their own, and often divergent, views of the structure of a project’s insurance program. Keeping the information above in mind when facing insurance decisions helps ensure a gap-free, affordable, and thorough set of insurances will protect the project from the many perils it will face throughout its working life. WPE
gcube-insurance.com
Strong wind, weak policy in Wyoming
June 8, 2010 by KRemington
Filed under Condition Monitoring, Wind Power News, Wind Watch
Taylor Johnson, Senior Editor
Land procurement and development for wind farms is no walk-in-the-park. Obstacles, such as zoning and lack of transmission right-of-ways, are hampering current projects, but even more troubling are new obstacles state legislatures and city councils are implementing, such as those recently voted into Wyoming’s laws.
In that state, ranchers have a significant influence on local and state politics due to their immense land tracts. What’s more, the oil and gas industries have been the state’s primary economic source for many years. Put these two together and you find a crippled wind industry throughout the state. Though Wyoming could boast being the seventh richest in wind resources in the United States, it is only the country’s twelfth wind power producing state.
Earlier this year, the Wyoming Senate voted to impose the nation’s first excise tax on the production of wind energy. The bill will impose a one dollar per megawatt hour tax on all electricity produced by wind. Of course one dollar is not an extreme amount when one considers the greater picture, but weigh that against the tax credits and incentives other states are implementing in hopes of luring green industry to their states, and you’d think the state was trying to stifle the growth of wind energy.
Another major obstacle for the production of wind energy in Wyoming is that of power transmission. There are currently six high voltage transmission-line projects in the planning or permitting stage, but none in the building stage. This is an enormous problem for wind developers. Although they are often able to produce electricity, they are unable to distribute it to high-demand markets such as California. Again, the issue falls back to the influence ranchers and land owners have in the state. Many land owners are unwilling to offer their land for a high-voltage line, and without a straight shot out of Wyoming, power line projects cannot stay within budget.
A third issue facing development in the state is one frequently found elsewhere, wildlife and ecosystem preservation. In May 2008, the Wyoming governor’s office issued an executive order stating they would no longer issue permits for projects within a “core area”. This area covers 23% of Wyoming’s breeding grounds, migration routes, and wintering areas for the Sage Grouse, a species nearing the endangered species list. The order halted wind development of all kinds in some of Wyoming’s richest wind resource areas. In response, the Wyoming Power Producers Coalition (WPPC) has begun lobbying efforts to educate the legislature and congress in attempt to relax the state’s anti-wind policies.
Wyoming may yet see more scenes of this sort if wind-energy developers can find innovative solutions to counter what seems to be anti-wind policies.
Of course, what Wyoming and its’ people wish to do with their state is their prerogative. Perhaps this is an opportunity for project developers to find innovative solutions. For those heavily invested in the area, discounted power rates to ranchers who offer their land might be a solution. Or possibly find a system that will permanently employ some of Wyoming’s citizens. These would be preferable to bursting on and off the scene with millions in venture capital, leaving only eye sores and partitioned land. WPE
Holly Wold of Whirlwind LLC in Denver, Colo. also contributed to this article.
Google Dips Its Hands Into $38.8 Million Of Wind Power
May 5, 2010 by WindPower Engineering
Filed under Featured Wind Power Articles, Wind Power News, Wind Power Projects
Google made its first direct investment in a utility-scale renewable energy project — two wind farms that generate 169.5 megawatts of power, enough to power more than 55,000 homes. These wind farms, developed by NextEra Energy Resources, harness power from one of the world’s richest wind resources in the North Dakota plains and use existing transmission capacity to deliver clean energy to the region, reducing the use of fossil fuels. Through this $38.8 million investment, Google is aiming to accelerate the deployment of renewable energy — in a way that makes good business sense, too.
To reach a clean energy future, Google needs three things: effective policy, innovative technology and smart capital. Through Google’s philanthropic arm Google.org, Google has been pushing for energy policies that strengthen the innovation pipeline, and Google has been dedicating resources to developing new technologies, including making investments in early-stage renewable energy companies such as eSolar and AltaRock. Smart capital includes not only these early-stage company investments, but also dedicated funding for utility-scale projects. To tackle this need, Google has been looking at investments in renewable energy projects, like the one Google just signed, that can accelerate the deployment of the latest clean energy technology while providing attractive returns to Google and more capital for developers to build additional projects.
Google says that it’s excited about this first project investment because it uses some of the latest wind turbine technology and control systems to provide one of the lowest-cost sources of renewable energy to the local grid. The turbines can continuously adjust the individual blade pitch angles to achieve optimal efficiency and use larger blades with 15 percent more swept area than earlier generations, allowing capture of even more wind energy for each turbine. The control systems for these wind farms are also advanced and dynamic, allowing for remote 24/7 monitoring and operation to ensure maximum turbine up-time and power production. A couple of us got a chance to climb 80 meters up one of the 113 turbines to see firsthand how the rotating blade motion goes through a gearbox to turn the generator that makes the electricity.
A Better Way to Protect Generator Bearings
November 27, 2009 by WindPower Engineering
Filed under Bearings, Wind Maintenance, Wind Power Generators, Wind Safety
Although many wind farms in the U.S. are generating electricity and well beyond a testing stage, their debugging continues. Many of these turbines suffer design-related failures within their first few years of operation.
Damaged bearings, for instance, can cause generator failures, which lead to unplanned downtime and costly repairs. If down for a month, a failed 1.5-MW generator can account for over $48,000 of lost revenue, and a single month’s wait for parts is unrealistically short considering the worldwide shortage of bearings and other key components. On top of lost revenue, the cost of repairing failed bearings (newbearings, labor, slip rings, and other parts) can run as high as $50,000. This figure still does not include the enormous expense of renting and transporting the large crane needed for many repairs. And there is often a long wait for that as well.
Though often hidden by manufacturers’ warranties, the full cost of the failures can be quite high. Case in point: A wind farm in Oregon was plagued by repeated bearing failures. In addition to high repair costs, the owners were losing revenue due to unacceptable periods of downtime. They were also baffled by the cause of the failures.
The local representative for a manufacturer of bearing protection rings called on the wind farm and obtained permission for up-tower testing. Results revealed the bearings were being “fried” by generator shaft currents much like those seen on ac motors controlled by PWM inverters (variable frequency drives) in industrial HVAC, pumping, and processing equipment. The problem appears worse in the doubly-fed-induction generators. In this design, the stator is directly connected to the mains, while the rotor is fed by a voltage-source inverter.
When reliability engineers pointed out similarities and identified shaft currents as the suspected problem, they were allowed to install a conductive-microfiber bearing protection ring intended to protect wind turbine rotor bearings. Results indicate that this ring appears to have solved the chronic bearing failure problem.
A sequence of failures
Problems at the wind farm unfolded this way: The generator bearings in one wind turbine failed only 11 months after the unit was brought on line in May 2006. The windfarm operator replaced the bearings and slip rings, only to see the new bearings fail five months later. Again, new bearings and slip rings were installed.
A third bearing failure came 11 months later. This time, in addition to replacing a set of insulated (ceramic-coated) bearings and slip rings on both ends of the generator, the owner decided to try a conductive microfiber bearing-protection ring and shaft collar with a high conductive surface on the drive end. All components come from AEGIS and were installed by the regional distributor on September 12. Also replaced were two standard carbon-block brushes which rub on the slip ring at the non-drive end.
Three months later the crew used a probe and oscilloscope to measure shaft voltage on the generator with and without the new bearing-protection ring and collar engaged. All measurements were taken on the same circuit. Wind speed ranged from 10.2 to 13.4 mph. Data from the field tests show the conductive-microfiber bearing protection ring and collar reduced shaft voltage by an average of 84.5%.
The first measurement, taken during full-power operation with a wind speed of 12.1 mph, established a baseline voltage (the system’s ground noise level) of 2.60 volts (peak-to-peak) from the 5.824-in. dia. shaft of the turbine’s doubly fed, asynchronous 1.5- MW generator.
The crew conducted eight more measurements in two series. The Series 1 readings measured the shaft voltage with all components engaged. The bearing protection ring and collar were on the drive end of the shaft, and the standard carbon block brushes were on the non-drive end. For the Series 2 readings, the bearing protection ring was disengaged and the shaft collar removed, leaving the carbon block brushes on the non-drive-end as the only shaft-current mitigation path.
A closer look
High-frequency currents induced on the shaft of a doubly-fed induction generator come from parasitic capacitive coupling and can reach 60A and 1,200V or more. If not diverted, these stray currents discharge to ground through the generator’s bearings, causing pitting and fluting (just as electrical discharge machining would) that result in premature bearing failure and catastrophic turbine failure.
This schematic shows the grounded Aegis ring mounted on the drive end of the generator
Bearing damage has become the Achilles’ heel of this widely used generator. In it, stator windings are directly connected to the main power grid, while slip rings connect the rotor to a voltage-source inverter which uses a small fraction of the total windturbine power.
The rotor-side converter regulates the electromagnetic torque and supplies part of the reactive power to maintain constant voltage and frequency of the stator output and the power grid. This design makes it possible to use varying wind speeds while maintaining a constant stator voltage and a constant frequency output to the grid. Because the inverter’s rating can be as low as 25% of the total system power, the design also reduces inverter cost. However, the system’s high-frequency switching introduces the dangerous rotor-shaft voltages, exposing bearings, gear boxes, and other critical generator components to high-frequency currents.
Even large motors show that inadequate generator-shaft grounding significantly increases the possibility of electrical bearing damage. Viewed under a scanning electron microscope, a new bearing race wall has a relatively smooth surface. As the shaft turns, tracks eventually form where ball bearings contact the race wall. With no electrical discharge, the race wall is marked by nothing but this mechanical wear. Without proper grounding, electrical discharges begin at startup and grow progressively worse, scarring the race wall with small fusion craters. In a phenomenon called fluting, the operational frequency causes concentrated pitting at regular intervals, that form washboard-like ridges.
Mitigating bearing damage
To guard against electrical damage to bearings, stray currents must be diverted from the bearings by mitigation devices such as insulation, special current filters, an alternate path to ground, or some combination of these. The devices vary in terms of cost and effectiveness.
Insulating bearings is a partial solutionthat more often than not shifts the problem elsewhere. Blocked by insulation (usually an exterior coating of aluminum oxide), stray currents seek other paths to ground. Attached equipment, such as gearboxes, often provide the path, and frequently wind up with bearing damage of their own. In addition to being expensive, insulation is subject to contamination. Worse yet, some types of insulation can be totally selfdefeating. In certain circumstances, the insulating layer has a capacitive effect on high-frequency induced current, letting it pass through to the bearings.
Nonconductive ceramic bearings, often called hybrid bearings because the balls are ceramic but the rest of the unit (including the race wall) is metal, can divert damaging currents but leave attached equipment open to damage of its own. Due to high voltage potentials across their surfaces, the ceramic balls can also be pitted and eroded by electric discharge similar to “static electricity discharge”.
Damage to a generator’s bearing race occurs for the same reason EDMs work: An electric current through the balls chisels away at the race metal.
Another mitigation tactic uses conductive grease, in theory, to bleed off harmful currents by providing a lower-impedance path through the bearings. In practice,however, the conductive particles in the grease increase mechanical wear.
Special dv/dt current filters or common mode current filters can mitigate damaging currents in some circumstances, but field results have been mixed at best. More effective is a sinusoidal filter which allows a nearly sinusoidal line-to-line voltage at the motor terminal. However, the filter does not suppress the common mode voltage, so this option reduces the generator’s efficiency due to motor losses and noise.
Conventional spring-loaded carbon block brushes certainly help. They contact the motor shaft to provide an alternate path to ground. Unfortunately, they too have drawbacks. They are notorious for the maintenance they require, due primarily to wear. Tiny particles break off from each brush. They also build up on the generator shaft, sometimes diminishing the brush’s effectiveness only weeks after installation. Carbon block brushes also require a narrow humidity band. Levels too low or too high are detrimental to their performance.
A solution
Alternate discharge paths to ground, when properly implemented, are preferable to insulation because discharge paths neutralize shaft current. An ideal solution would provide an effective, low-cost, low resistance path from shaft to frame, affording the greatest degree of bearing protection and maximum return on investment. The AEGIS WTG Bearing Protection Ring meets the criteria. It uses principles of ionization to boost the electron-transfer rate and promote the efficient discharge of the high frequency shaft currents induced by many wind turbine generators. It safely channels harmful currents away from the bearings to ground.
A close up of the bearing protection ring shows many microfibers.
The ring surrounds the generator shaft with millions of conductive microfibers, each less than 10 microns diameter. The fibers, stiff and strong yet flexible, provide high-density contact points — parallel paths of least resistance from the motor shaft to ground. The fibers significantly reduce voltage buildup on the generator shaft by conducting instantaneous currents of many tens of amperes and discharging from tens to thousands of volts with MHz frequencies. The ring is especially suitable for use at high frequencies because its fibers tend to compensate for variations in the roughness of the shaft surface, or microscopic misalignment of the ring and shaft, or both. When a microfiber looses mechanical contact with the rotating shaft, electric contact is quickly re-established somewhere else along the ring, due to local field emissions.
A phenomenon called gaseous or electric “breakdown” can generate a gap (greater than 5 microns) between shaft and fibers. It is a cascading effect of secondary electrons that comes from collisions and the impactionization of gas ions accelerating across the gap. With a smaller gap (5 nm to 5 μm), field emissions generate a phenomena called Fowler- Nordheim tunneling in which electrons “tunnel” through a barrier in the presence of an electric field.
Thus, the ring fulfills all functions of conventional spring-loaded carbon brushes with neither the hot-spotting, thermal wear, nor the direct frictional wear common to such brushes. Because its multiple microfibers dissipate heat better than singleconductor devices, the ring tolerates higher current densities. Furthermore, unlike carbon block brushes, microfibers on the bearing protection ring are not adversely affected by oil, grease, dust, moisture, or other contaminants.
In addition, the bearing protection ring safely diverts shaft current at frequencies up to 13.5 MHz and discharges up to 3,000 volts (peak). The ring is maintenance-free for at least two years, effective at any shaft speed, and available for any size generator. The ring www.windpowerengineering.com DECEMBER 2009 Windpower Engineering 4 9 is also suitable for up-tower retrofits and preventive-maintenance programs as well as for OEM installation. A split-ring model makes on-site retrofits faster and easier than previously possible. And coating the shaft collar with conductive silver paint enhances the ring’s effectiveness.
Results from a series of tests of a turbine with the bearing protection ring installed show an average generator shaft voltage of 6.41 V (peak-to-peak). Results from a second series of tests using only the spring-loaded carbon block brushes show an average shaft voltage of 41.35 V (peak-to-peak). The difference between these averages, 34.94 V, indicates that the bearing protection ring and collar successfully divert about 84.5% of the damaging current that remains on the turbine’s generator shaft when carbon block brushes at the non-drive end are the only form of bearing protection. Furthermore, the voltage wave form with the AEGIS ring and collar engaged was a smooth wave without detectable discharge to the bearings, while the wave form without the ring and collar showed a bearing-current-discharge pattern with voltage peaks an average of 6.5 times higher.
Similar tests at a facility in Texas on a 1.5 MW wind turbine generator manufactured by another supplier yielded similar results. The ring reduced a shaft voltage from over 600 (continuous) to 30 to 40V (peak-topeak), safely diverting 50 to 60A.
Rotor-Blade Ridges Promise More Turbine Power
November 26, 2009 by WindPower Engineering
Filed under Turbine Blades, Wind Turbine Design
Tubercles seem to prevent stalling or a loss of lift, allowing for more aggressive blade pitch. Developer WhalePower says blades with the feature could let a turbine produce 20% more power.
Adding a series of ridges to the edges of a turbine blade could increase annual electrical production for wind farms by 20%, says the design firm for the feature. The idea comes from Humpback whales that tilt their fins at steep angles for more lift in the water. Too much tilt, has the opposite effect—a loss of lift or stalling. Tubercles seem to prevent stalling, allowing for more aggressive fin tilts.
Tubercle-like structures, designed by WhalePower, Toronto, Canada (whalepower.com) on turbine blades would let them work at steeper angles without stalling or creating too much drag, according to the firm. (The company’s tag line: A million years of field tests. Company president: Frank Fish. Really). In low wind, blades with steeper angles could theoretically generate more power. Wind-tunnel tests show that, in some cases, adding tubercle-like bumps to model fins pushed back the stall angle by as much as 40%. Canadian ventilation company Envira-North Systems will be the first to use tubercles on industrial fans as a power-saving feature.
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