Transcription
Practical ExpertiseExceptional Design
Small Turbine Tower DesignAWEA vs IEC 61400-2 vs TIA-222Kyle K. Wetzel, PhDCTO, Wetzel EngineeringNovember 18, 2015SMART Wind Composites VirtualMeeting on Support StructuresWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
WETZELENGINEERING Engineering Solutions Developer Clients on 4 continents Wind Energy 50 custom blade designs 20,000 blades operating Aviation Towers Engineering services to OEMs Owners and Operators Insurance Companies And others Wetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.3
Purpose of Standardsvs Purpose of Engineering Purposes of Engineering Ensure no failures Ensure most cost-effective Design Purpose of Standards Define “industry accepted” MINIMUMset of requirementsWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards AWEA Small Turbine Standard Omits Towers Flawed belief that towers are generally notcritical to turbine response for smallmachines Puzzling oversight as to how the industryis to ensure that towers have beenminimally engineeredWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards IEC 61400-2 Wind industry standard methods ofestimating loads Includes Tower Engineering Does not necessarily conform torequirements of the IBCWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 Does not reflect acceptance or input ofwind turbine engineers – reflects need tostamp drawings to satisfy US buildingcode enforcement bodies (IBC) Over-reach by non-industry standardwriting body with little to no understandingof wind turbine engineering Loads calculations are inconsistent withstandards of the wind industry Poor Fatigue Analysis MethodsWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 Claims to be “derived from” IEC 61400-2,but errors in derivation are significant “Turbine shall be modeled as a mass andan effective projected area” – misses keycharacteristics of rotor aerodynamics anddynamics that are important for estimatingloads – treats rotor as an antenna This is a completely unacceptable methodof estimating loadsWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 Design Load Condition – 49m/s (110mph)50-year return, 3-second gust at 10mheight, exposure Category C, TopoCategory 1, Extreme Wind Condition usingthe appropriate TIA Importance Factor Standard implies this is conservativeapproach in lieu of performing fatigue Notes that 110mph requirement isindependent of IEC Wind ClassWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 Loads CalculationNote SF 1.60Wetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 110mph requirement can be nonconservativeas a 50-year, 3-second extreme Previous work by WEI for Anemergonics –dynamic sims (FAST) with modified inflowCompared to TIA steady inflowwith direction changeWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 110mph requirement can be nonconservativeas a 50-year, 3-second extreme Previous work by WEI for Anemergonics Load estimations were very sensitive to theparticular turbine configuration – dynamicsof the tower, height of the tower Generally OK match on tower base loads TIA inflow generally underestimated towertop bending moments by as much as 30%Wetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Failure of Small TurbineTower Standards TIA-222-G-4-2014 TIA-222-G omits fatigue Addendum 4 recognizes fatigue is importantfor wind turbines Method of Calculating fatigue loads is obscureand based on the idea of the rotor diameteras a disk with a constant 30mph wind Accounts for some stress concentrationsusing handbook methodsWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Recommendation Loads (Static & Fatigue-Equivalent) Calculate Loads per IEC 61400-2 (orbetter yet 61400-1) using the applicableIEC Load Case and the TIA-prescribedinflow and terrain conditions Calculate Loads per TIA Use the most conservative setWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Recommendation Strength & Fatigue Calculate stresses and fatigue damage perIEC 61400-2 (or GL guidelines) Calculate stresses and fatigue per TIA-222G-4 Go with the more conservative result If there is a significant conservativediscrepancy from TIA, then ask for anexception based on sound engineering Engineers stamping drawings haveleeway to use professional judgment –standards simply provide coverWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Recommendation Options by DWEA Secure acceptance by IBC for IEC 61400-2 Include towers in AWEA STS and secureacceptance by IBC for AWEA STS Amend TIA-222-G-4 to include options formethods of loads, strength, and fatigueanalysis more consistent with IEC 61400-2Wetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
Wetzel Engineering, Inc.Office821 Grand Ave Pkwy #410Pflugerville (Austin), TX 78660Plant3914 Gattis School Rd #103Round Rock, Engineering.comWetzel Engineering, Inc., Proprietary Information. Maintain in Confidence.Copyright 2015 Wetzel Engineering, Inc. All Rights Reserved.
TIA-222-G-4-2014 110mph requirement can be nonconservative as a 50-year, 3-second extreme Previous work by WEI for Anemergonics Load estimations were very sensitive to the particular turbine configuration –dynamics of the tower, height of the tower Generally OK match on tower base loads TIA inflow generally underestimated tower top bending moments by as much as 30% .
