John Brennan, MSc, BEng Senior Consultant - Wood Group In collaboration with Wetzel Wind Energy Services

Transcription

1 CanWEA, 5th October 2017 Smart Decisions for the Better Bottom Line Leading Edge Erosion Considerations for Successful Wind Farm Operations and Maintenance John Brennan, MSc, BEng Senior Consultant - Wood Group In collaboration with Wetzel Wind Energy Services

2 About Wood Group s Clean Energy Business Supporting renewable energy projects for over 14 years SgurrEnergy rebranded as Wood Group in May 2017 Providing engineering and technical advisory services to renewable project all around the world Global network of offices Projects in 90 countries across 6 continents Worked on over 160 GW of renewable energy projects We have assisted a number of clients in North America with the investigation into blade issues arising from leading edge erosion in collaboration with Wetzel Wind Energy Services 2

3 O&M Challenges Are Changing Traditionally, gears and bearings were the top reliability concerns when considering long term wind turbine operations and maintenance Why is the focus shifting towards Blades? Blades account for around 20% of the capital cost of a wind turbine, They generate 100% of the AEP, Produce the majority of the driving loads, Suffer the full brunt of the environmental conditions. 3

4 Leading Edge Erosion (LEE) - Cause and Effect Abrasion Abrasive particles flow over the surface of the blade causing erosion Salt (offshore, coastal) Fine grit Impact Erosion Micro fracturing of the blade surface caused by the solid impacts of course sand, hailstones and liquid impacts from rain Impact erosion caused by rain is considered the primary source of blade damage in the wind industry Contributing factors to rain erosion Blade tip speed Blade manufacturing Blade material properties - Fillers Annual rainfall Droplet size 4

5 A Short History of Leading Edge Erosion Rain erosion has been recognised for decades as a leading source of erosion in aerodynamic bodies In aircraft, for both nose cone and wing leading edge as well as propellers On fan blades of gas turbine engines The nose of most airplanes is covered with an elastomeric shield, commonly neoprene The earliest publications relating to rain erosion on aircraft was in Key findings Elastomeric and plastic materials showed superior resistance to low intensity rain erosion which is effectively the type of erosion being experienced by wind turbines The first applications of LEP in the wind industry took place by a German company called WKS in The material they used was produced by 3M for the Aerospace industry. 5

6 Wind Industry Has Seen a Steady Increase in WTG Size Tip speeds for onshore pitch regulated multi megawatt WTGs between m/s 2016 ~1990 Tip speed for onshore stall regulated <1MW WTGs m/s 6

7 Contributing factors Precipitation levels play a critical roles in LEE progression Sites with 50cm rain per year should strongly consider LEP For sites with 1m rain per year we would consider LEP a must Freeze thaw cycles on northern sites Canada Once erosion starts water permeates the putty and glass Freeze thaw cycles will break out chunks of these materials. Damage progression is sped up For northern sites we would consider LEP a must at rainfall levels of 50cm/year 7

8 Manufacturing Manufacturing practises are considered to be one of the leading factors in the early propagation of LEE Material selection is a critical decision when finishing the leading edge Durable epoxy putty fillers are superior to softer Urethane putty fillers. Spray on versus rolled on paints and LEP coatings Climate control also plays a determining factor Factory conditions are important (Location, climate etc.) Application of state of the art leading edge protection should be standard and increasingly is standard for most top tier OEMs. Factory application of LEP coatings is highly recommended as environmental factors prove too difficult to control during field applications. Finishing of leading edge determines the longevity of the LEP QA/QC throughout the manufacturing process all the way to arrival on site is also critical 8

9 Damage Categorisation Category 1 9

10 Damage Categorisation Category 2 10

11 Damage Categorisation Category 3 11

12 Damage Categorisation Category 4/5 12

13 Leading Edge Protection Technologies Elastomeric coatings and tapes These products provide an energy-absorbent layer that dissipates the impact energy released when raindrops, sand, or other particles strike the leading edge of a wind turbine rotor blade. Some of the products of choice on the market 13

14 Field Applications Material selection is key Certain materials such as LEP coatings are sensitive to humidity and will require down tower repair. Epoxy putty fillers and 3M tape can be installed in high humidity conditions. This image shows 3M tape installation using rope access. Amazingly patching is common practice within the wind industry Its critical that leading edge repair is followed by application of leading edge protection. 14

15 LEE vs AEP Loss vs Cost of Repair There are many inaccurate figures being thrown around A quick google search quotes figures as high as 20% AEP loss AEP loss of 20% is almost impossible for large pitch regulated WTGs Majority of AEP comes from operation below rated Studies into Leading Edge Roughness caused by LEE and material accumulation (insects) - Sandia National Laboratory found that: AEP reduction of ~2.5% seen on moderate wind speed sites (~8m/s) AEP reductions of ~5% seen on low wind speed sites (~5m/s) Cost is a greater concern Cost of LEP for one blade set is ~$10,000 USD Cost of blade removal and ground based repairs is ~$50,000 Cost of replacing a single blade ~$100,000 - $150,000 15

16 Operation and Maintenance Considerations Develop an appropriate blade maintenance & Inspection program Service providers will recommend annual inspections Decisions are site specific and service agreement plays a role Detailed visual inspection for EOW and every two years thereafter Problematic blades require more attention from installation. Site with high likelihood of LEE require more frequent inspection depending in OEM service contract Drones or ground based high resolution camera are good low cost options for more frequent inspections. Know your blades, detailed blade documentation is important. Service contract should demand that OEM provides full details of blade inspection and repair history. Blade cleaning and clearing drain holes is an important consideration. Experts recommend that multiple drain holes be installed at blade tip. Water build up can lead to catastrophic failure during a lightning strike. Consider CMS options 16

17 Recommendation for Smart O&M LEP should always be considered LEP is a must for high rainfall sites and sites that suffer severe winters Pay attention to blade manufacturing Location of factory, local climate, QAQC practices Develop a comprehensive blade inspection, maintenance and documentation system. Take advantage of cost effective blade inspection technologies Consider CMS options Do not carry out LEE repairs on operational sites without applying a quality leading edge protection system 17