The wind, a free and readily available energy source, has for thousands of years propelled boats, pumped water and ground grain. For the past 20 years, it has become one of the largest renewable sources of electricity generation in the world.

Global installed wind power capacity grew 9.6 percent to 591 gigawatts in 2018 compared with the end of 2017, supported by 51.3 GW of new installations, according to the Belgium-based Global Wind Energy Council.

GWEC expects that an additional 300 GW of new capacity will be installed globally by 2023, driven by growth in emerging markets and especially offshore wind farms, as the sector continues to prove its cost-competitiveness against fossil fuels around the world.

The prospects for the wind power sector are also upbeat in India, the number four market globally for installed wind power capacity and new installations, behind Germany. This world-class ranking has been spurred on by the governments focus on boosting renewable energy capacity, according to industry officials. Regional economic rival China has by far the biggest wind capacity globally.

Trade Winds

Wind generation capacity in India, the worlds second most populous country after China, has grown by 11 percent over the past five years, while overall renewables capacity grew by 16 percent, according to Tulsi Tanti, chairman and managing director of Suzlon Energy Ltd., Indias largest wind turbine maker.

India had around 37 GW of installed wind energy at the end of July, up 38 percent from 26.78 GW in 2016. Wind currently accounts for about 10 percent of all installed generation capacity in India, including fossil fuels, and around 47 percent of renewables, according to the Central Electricity Authority. The states of Tamil Nadu, Andhra Pradesh, Gujarat, Karnataka, Madhya Pradesh and Maharashtra are home to most of these turbines.

Despite rapid growth a few years ago, the pace of installation has slowed lately, according to Ajay Devaraj, secretary general at Chennai-based Indian Wind Power Association. Suzlons Tanti echoed the sentiment, and in the companys 2018-19 financial report, it said new capacity has declined primarily due to the transition from an electricity feed-in-tariff regime to a competitive bidding regime.

Even so, the government-owned Solar Energy Corp. of India and state-level auctions have helped wind turbine companies fill their order books, and new units will be delivered from 2020 onwards. Devaraj added that the governments commitment to invest in offshore wind is seen in the announcement of an auction for 5 GW of offshore capacity by 2022 and a long-term target of 30 GW of offshore projects by 2030.

This will put India in the same league as other countries harnessing offshore wind energy, Tanti stated.

Indias Ministry of New and Renewable Energy has set a target of 60 GW of wind power capacity being installed by 2022. The government is promoting wind power projects by providing various incentives, such as an accelerated depreciation benefit and concessional customs duty exemption on certain components of wind electric generators.

However, Tanti said that while the MNREs initiative is positive, it is not supported fully by some actions taken by state governments, leaving an implementation inconsistency across the country.

Theres a lot of encouragement from the center [government], but that encouragement is not percolating down, he told LubesnGreases.

This is compounded by a lack of available land for wind projects and an urgent need to improve transmission infrastructure so that electricity generated can be fed into the system, Devaraj added. However, he noted the growth prospects are bright for the wind sector.

Yaw and More

The increase in installed wind power capacity in India and other markets will certainly boost demand for lubricants and greases used in wind turbines.

United States-based consultancy Kline & Co. said wind power is a high growth sector, and its lubrication needs are expected to trend in a similar fashion. Kline, which will likely release a new study on the global wind turbine lubricants market in 2020, did not disclose its latest growth projections, but in an earlier report, it said global wind turbine lubricant demand would grow at 7.4 percent per year to reach 53,700 metric tons by 2020, up from 37,600 tons in 2015. Indias share of total demand was earlier estimated to be about 6 percent.

Lubricants play a critical role in turbine operation, maintenance and reliability, and there are a number of lubrication points in the nacelle – the cowling that houses the gears, yaw system, main shaft bearing, gearbox, generator and brake assembly – which is perched on top of a 78.5-meter tower, as is the case with the Suzlon S.82-1500 1.5-megawatt model.

Grease makes up the smallest amount of demand but is used in the most locations, including the main rotor shaft bearing, the yaw bearing, pitch or blade bearings, pitch drive gears and generator bearings. Gear box oil comprises the greatest demand, with newer models using in some cases up to 240 liters, according to Power Engineering.

Kline noted that wind turbine lubricants account for a small fraction of the global finished lubricant market, but it is an important segment due to its high performance requirements, rapid growth and penetration of synthetic lubricants. Wind turbines operate in difficult environmental conditions – in remote areas or out at sea – and regular maintenance and lubrication are major challenges compared with other industrial applications. ExxonMobil, Castrol, Shell and Kluber Lubrication are some of the key players operating in the wind turbine lubricants market, and they all have representation in India.

Blowing in the Wind

Nilesh Kadu, product manager for industrial lubricants and greases at Lubrizol India Pvt., remarked that the growth in the global installed wind power capacity has resulted in an increase in the volumes of wind turbine greases sold in the market.

Kadu was speaking at the annual meeting of the Indian chapter of the United States-based National Lubricating Grease Institute in the northeastern city of Guwahati in February 2019, where he was presenting the results of a series of tests run by Lubrizol on wind turbine greases.

Although Kadu did not share figures, he did say that many wind turbine original equipment manufacturers prefer one type of grease for all bearing applications, even though different bearings require different greases. This is likely to reduce costs and maintenance complexity.

Wind turbine bearings have numerous lubrication challenges. Low operating speeds inhibit film formation, which leads to micro-pitting. Variable wind speeds, wind direction and turbulence, as well as rapid stopping, and stress on bearings and the grease. Vibration, even when the blades are stationary, can cause fretting wear on bearing contact surfaces. Greases must also be able to combat corrosion, water ingress, salty air in offshore or coastal installations and low-temperature thickening.

Greases need to be able to lubricate fully under these operating conditions and pass standards requirements, Kadu added. Many parts of India have high humidity, which can lead to corrosion, as well as the monsoon season, which of course means water ingress.

A Test of Loads

With an objective of developing greases to meet wind turbine requirements, Lubrizol reviewed some wind turbine grease specifications and identified some of their typical properties, such as penetration and dropping point. The United States-based additives maker also identified these properties with standard test equipment as well as under non-standard conditions, such as using an FE-8 test rig for roller bearings and the riffle test, which involves subjecting a stationary ball bearing to dynamic loading using a fluid.

Based on specifications similar to Mobils SHC 460 WT – an NLGI 1.5 grade extreme pressure lithium complex grease formulated with ISO-VG 460 full synthetic oil – Lubrizol formulated two greases for testing. Grease A was formulated with a full-synthetic polyalphaolefin, and Grease B with a PAO plus an alkylated naphthalene. The company added additives to balance the greases water resistance, corrosion protection, load carrying and wear resistance properties.

Initial screening did not yield the aforementioned wind turbine requirements. Kadu said the company optimized the treat levels of the main components and developed a package and a lubricity aid, which were incorporated into the greases and tested against the complete requirements. Both Grease A and Grease B showed the same consistency with lithium complex thickener when formulated with an additive package at 5 percent, lubricity aid at 2 percent and water-resistant polymer at 0.2 percent.

Grease A passed the requirement easily, as it showed better basic properties such as dropping point, mechanical stability and high-temperature oil separation, Kadu said. An ASTM wear test, SRV (oscillating, friction and wear) test and corrosion test also showed the desired results. Kadu noted the test revealed water spray-out was higher in some cases, while the oxidation test showed far better results. The company did not conduct certain tests for Grease B, as it anticipated the grease would surpass them, he added.

Following good performance in all tests, Lubrizol carried out the remaining FE-8 and riffel tests. Grease A passed the high-torque, low-speed FE-8 AC bearing test, as well as the high-torque, low-speed FE-8 TR bearing test. The FE-8 test method (DIN 51819-2) looks at wear properties of greases in angular contact ball bearings and tapered roller bearings under a variety of test conditions. Grease A and B both passed the riffel test, Lubrizol stated.

The results were much better than the expectations, Kadu said.

The prospects for wind turbine lubricants and greases are bright in India, as well as in the global market, given governments focus on promoting clean energy to reduce greenhouse gas emissions.