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bankrolled the premiere major use of wind power for utility electricity. Aggregated in commodious wind resource areas, these turbines would be considered inconsequential and economically undesirable by current wind farm development protocols.
Although, wind energy’s expansion in the U.S. halted dramatically, after tax incentives were waived in the late 1980s, wind energy continued to flourish in Europe buttressed partially by a revival of environmental concerns in light of scientific studies alluding to the potentially deleterious impact on the global climate if the use of fossil fuels continued to escalate without compunction.
Wind-powered generators currently exist in a variety of size ranges: From small turbines, employed for battery charging at remote locations, to large, virtually-gigawatt-size offshore wind farms which power national electric transmission systems.
Wind turbine gearboxes being placed in desolate locales, at steep heights, and under harsh conditions are some of the major challenges that counterbalance wind power’s many advantages. In addition, routine maintenance, such as compulsory gearbox oil changes to protect components from the corroding effects of micropitting and wear also requires substantial upkeep. In light of these dilemmas, sufficient equipment lubrication is mandatory, as it can aid in safeguarding system components, diminishing unscheduled downtime, cutting costs, prolonging oil drain intervals, and reducing risk of injury, or even fatality, through lessened human-to-machine interaction.
The diligent use of high quality synthetic lubricants is one of the key elements required to get the most out of wind turbine equipment. It should be kept in mind, when it comes to choosing which lubricant will be most appropriate, that one of the most overlooked aspects is finding a balanced formulation. Employing optimal base stocks and a customized additive package, which meets, or exceeds, the specified needs of the wind industry, such as aiding in life extension of oil in spite of difficult operation factors is a critical component to successful wind equipment reliability.
Case in point, a quotidian wind turbine lubricant will have an oil drain interval of three years, while a superior synthetic lubricant, orchestrated specifically for wind, can facilitate the longevity of those intervals even more dramatically. For instance, one Mobil synthetic lubricant derived especially for wind turbine gearbox and bearings has been demonstrated to increase oil drain intervals in turbine applications for as long as 7 years. For this reason, and for many more, lubricant formulation is the single most important ingredient to cogitate when choosing a lubricant.
In order to adequately parse the importance of a balanced constitution, it is necessary to consider a few salient equipment stumbling blocks that wind operators are grappling with today:
Firstly, let’s consider a predictable stumbling block for wind turbine operators: micropitting. Micropitting can form on surface-hardened gears within the initial several hours of operation, should the gearbox not be adequately lubricated; thus, resulting in lessened gear tooth exactitude. To mollify this effect, operators should look for oils formulated with a micropitting additive package, like typical extreme pressure additives, in addition to employing a gear finish as specified by American Gear Manufacturers Association’s AGMA 6006 standard. After which, an oil formulated with advanced base fluids, that offer a high viscosity index – typically 160 or higher – and lower traction coefficient, can also help. The higher viscosity index can provide a thicker lubricant film at operating temperature, and the lower traction coefficient can help improve energy efficiency.
Another factor which must be taken into account is water
contamination; this can have a profound effect on wind turbine performance, most notably in offshore environments where water exposure is greatly increased. Water, when found in oil, can result in additive depletion, stable emulsions and higher viscosity. It can also cause equipment issues, like filter blockage and faster wear of system parts. Lubricants concocted with particular additives can help mollify the effects of these contaminants by strengthening the oil’s defense against water contamination and also bettering its wet oil filterability.
Foaming is yet another wind turbine issue which must be tackled by operators. As foam bubbles up and crashes through a shaft seal, it leaks inside the nacelle (the generator and gearbox “shell” with rotator shaft on a horizontal axis wind turbine), creating a safety hazard for slippage. Furthermore, as foam forms on the surface of the oil, it may cause a problem with the oil level float switch, causing a faulty reading which could even set off an alarm. Also, if foam enters the oil circuit, a temporary decrease of oil pressure or flow can transpire, also engendering alarm. All these occurrences would likely result in costly loss of time which could have otherwise been avoided.
A wind energy system, as would be expected with any mechanical system, requires sufficiently-tailored lubrication to function optimally. Vibration, heavy mechanical loads, dampness and contamination are all hazards to bearing and gear service life. Wind turbines can also be difficult and exorbitant to service since they extend more than 100 meters off the ground in addition to being situated in remote locations. A possible solution to these predicaments is to implement an automatic lubrication system. Automatic lubrication systems, unlike manual ones, provide unctuousness more predictably and accurately to moving components in the nacelle. By delivering the most minimal, yet effective, dose of lubricant reliably to all friction points, while the machine is running, automatic lubrication systems decrease friction inside bearings and help to prevent contamination.
Despite wind power’s obvious challenges including the following: High cost of initial investment; remote locations required; use of large amounts of land which could be better utilized; noise and aesthetic “pollution”; and possible damage to
wildlife.Conversely, there are several advantages of this form of power. For example, land-based utility-scale wind is one of the lowest price energy sources available today, and wind creates jobs. In fact, the U.S. wind sector employed more than 100,000 workers in 2016, and wind turbine technician is one of the fastest-growing American jobs of the decade. Wind also enables U.S. industry growth and competitiveness. Wind is a clean fuel source since wind energy doesn’t pollute the air. It is a domestic source of energy and sustainable, as well.
Paradoxically, wind power harkens back to the dawn of civilization, yet still manages to be an intriguing growth-oriented and ever-evolving industry at the vanguard of renewable energy advancements. Developments of cutting-edge lubricants and maintenance strategies for this extreme application are making tremendous strides toward a new standard in gear and bearing lubrication, which may even one day blow away the competition in the sphere of alternate energy.
References
Barr, D. (n.d.). Modern Wind Turbines: A Lubrication Challenge. Retrieved June 01, 2018.
https://www.machinerylubrication.com/Read/395/wind-turbine- lubrication
Hennigan, G. (2016, July 7). Maintenance and Lubrication of Wind Turbines. Retrieved June 01, 2018.
https://www.altenergymag.com/article/2016/07/maintenance- and-lubrication-of-wind-turbines/24074
History of Wind Energy. (n.d.). Retrieved June 07, 2018.
http://windenergyfoundation.org/about-wind-energy/history/
Wind turbines have been used in one way or another for more than 7,000 years, and while that is unlikely to change any time soon, wind turbine lubrication exists at the far extreme of industrial gear applications in terms of temperature, load weights, bearing wear, maintenance, accessibility and basic lubricant performance. Increasingly, for offshore applications, synthetic and biodegradable fluids are being developed. Furthermore, turbine gear oil specifications are starting to mirror the demand for higher lubricant performance through testing for enhanced oxidation and corrosion resistance, as well as for greater bearing and long-range operational performance.
Tuthill, S. (2012, August 21). Weather and Ancient Religion: Greek Mythology. Retrieved June 07, 2018.
https://www.accuweather.com/en/features/trend/weather-and- ancient-religion-g/70378
Dr. Raj Shah is a Director at Koehler Instrument Company. He is an elected Fellow of STLE, NLGI, AIC and the Energy Institute. Ms. Shana Braff is a social media and customer service specialist with Koehler Instrument Company.
Author Contact Details Dr. Raj Shah and Ms. Shana Braff, Koehler Instrument company • Holtsville, NY. • Email:
rshah@koehlerinstrument.com sbraff@koehlerinstrument.com • Web:
www.koehlerinstrument.com
AUGUST / SEPTEMBER •
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