This document summarizes a presentation on wind plant reliability given at a Sandia workshop. It discusses the need to take a holistic plant-level view of wind reliability rather than focusing on individual turbines. Current challenges include incomplete understanding of complex wind flows, limited data exploitation, and modeling capabilities lagging behind. Improved engineering practices, models validated with field data, and new technologies are needed, as well as leveraging internal R&D and external collaborations. Concerted field tests and simulations validated with measurement data are key to advancing modeling capabilities and overcoming barriers to new technologies.

1. This Document Contains the Following
Data Types
GE Confidential
Wind Plant Reliability
Complex Flow Research Perspectives
Stefan Kern, GE Global Research, Munich
August 14, 2013

2. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Focus on Wind Plant
Holistic plant-level viewTurbine focus
Design
Siting
Operation
Reduce LCOE by improved design, operation & micrositing
Opt. performance w/ clean
blades in free-stream
Opt. plant power curve
Identical units according to
site wind class
Optimized product- &
component mix
„Cooperative“ control;
use excess margins
As independent units

3. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Complex Flow Challenges
Design Siting Control
• Incomplete physics understanding
• Lack of data / limited exploitation of existing fleet data
• Limited modeling capabilities, standards lagging behind

4. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Needs
Understand the problem & entitlement
• How much wake losses can we recover?
• Excess margins or underestimating loads?
Improved engineering practices & models
• Hierarchy of models - modular fidelity
• Proven & validated against field data
• Fleet data mining
New technology
• Rethink turbine design & siting
• Park level control strategies
Both internal R&D and collaborations with
external partners

5. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Learning from Field Data
Wake behind single turbine
Wind velocity [m/s]
Std dev
95% conf int
mean
Heightaboveground[m]
Buffalo Gap wind park - one out
of hundreds in the GE fleet
Full scale flow field measurements
• Averaged velocity profiles of isolated/interacting wind
turbines pairs & wake turbulence
• Sparse data
Operational data of GE fleet
• Recorded 10min data of hundreds of wind parks
over many years
• Data quality can be challenging
• How to define/measure ideal farm performance?
Gaps: - Best practices for fleet data analysis
- Exploiting large data to full extent
- Limited load data inside plant along with
detailed inflow conditions

6. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Learning from Scaled Experiments
Gaps: - Scalability questions for small scale models
- Medium scale experiments in largest facilities
Single turbines
• Validation data for predictions of blade aerodynamic
performance with controlled inflow
• Typically focussed on near wake, limited far wake data
Interacting turbines
• Typically models with D<50cm in ABL wind tunnels
• Limited flexibility in controlling turbine operation
Source http://wire.epfl.ch
Source http://wind.nrel.gov
NREL turbine in
NASA AMES wind tunnel
Wind farm in ABL wind tunnel
MEXICO experiment, DNW wind
tunne
Source http://www.ecn.nl

7. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Engineering Models
Rotor & wake
• Largely focused on optimizing standalone unit performance
• Limited capability to capture complex inflow
Farm level
• Limited to steady state, assumption of constant wind
direction and wind speed
• Following IEC certification requirements/common practice
Gaps: - Comprehensive calibration of farm models to field
data/high fidelity models
- Capturing of unsteady effects & complex terrain

8. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
High Fidelity Simulation & HPC
Gaps: - Comprehensive validation
- Largely limited to simple terrain
- Flowdown to engineering tools
- Exploiting large data to full extent
PSU Cyber Wind Facility
Rotor & wake
• Capture complex inflow for detailed rotor aero & wake
• Long term vision: replace expensive field tests
• Assessing modeling approaches & numerical methods
Farm level
• Assess wake impact, control strategies & new architectures
• Reduce wake losses and fatigue loading
Partners: Penn State, NREL, LLNL, UC Louvain

9. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Concerted Field Tests & Simulation
Source: energy.sandia.gov
…key to advance and validate modeling capabilities
Full scale
Wind farm
Red. scale
Few turbines
Test setup Simulation
Wind tunnel
Contr. cond
Measmt tech
Source: mexnext.org
Source: NREL
Source: Texas Tech University
Distance from rotor plane (m)
Source: mexnext.org

10. @#GECON&*
Sandia Wind Plant Reliability Workshop
August 14 2013
Conclusions
• Great momentum & progress in complex flow research
− Experimental facilities
− Measurement technology
− Simulation
• Overcome barriers to develop & deploy new technologies
− Demonstrate business value
− Flow down to engineering practices and tools