6 - a risk analysis framework for offshore wind turbines - gkoumas

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Konstantinos Gkoumas, Ph.D., P.E.

University of Rome “La Sapienza”DITS

12th International ConferenceON ENGINEERING, SCIENCE, CONSTRUCTION AND OPERATIONS IN CHALLENGING ENVIRONMENTS

EARTH&SPACE 2010

MARCH 14-17, 2010 Honolulu, HI

“A risk analysis framework for offshore wind

turbines”

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1

Research objectives

EARTH & SPACE 2010, MARCH 14-17, 2010 Honolulu, HI Konstantinos Gkoumas, PhD, PE

• To address aspects of risk analysis, as part of a

more global risk management process, for

offshore wind turbines and offshore wind farms

– Starting from the establishment of the specific risk management context, the various steps for risk

assessment are presented, along with the methods for risk (- hazard) identification, analysis and evaluation; as a final step, the options for risk

treatment are considered

– For the purpose of risk identification, a system

decomposition of the relevant elements is performed

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Presentation outline

• An overview of risk analysis issues

• Recent cases of wind turbine failures

• Issues for the offshore sector

• Risk analysis standards and codes

• Risk management phases

• Context establishment

• Risk identification

• Risk analysis

• Risk evaluation

• Risk acceptance

• Risk treatment

• Considerations and outlook

2EARTH & SPACE 2010, MARCH 14-17, 2010 Honolulu, HI Konstantinos Gkoumas, PhD, PE

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Risk analysis for OWTs – overview

• Risk analysis deals with uncertainties. For an OWT

or an OWT farm, it involves the consideration of:• safety and security (for the workers and the general

population);

• environmental and economic aspects;

• serviceability and lifetime performance.

• Consequences to be taken into account include

among else:• injury, or loss of life, due to structural collapse;

• environmental losses;

• loss of economic activity;

• reconstruction costs.


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Risk analysis – overview (2)


December 27, 2009

A 329-foot wind turbine, base to blade tip, collapsed early Sunday morning, December 27, at the Fenner wind farm in Fenner, New York.

March 7, 2009

Only a few months old, this 1.5-MW GE wind turbine in Altona, New York. part of a 65-turbine facility owned by Noble Environmental Power, collapsed on Friday, March 6.

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Risk analysis – overview (3)


July 8, 2009

Brandenburg, GermanyTurbine wing destroyed by lighting.

December 2, 2009

Uelzen ,GermanyA wind turbine burns in the German city of Uelzen. The fire on the 130 meter tall turbine caused €750,000 in damage and is believed to have been caused by a technical defect.

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Risk analysis – offshore sector

• Increased activity in the sector: many new projects

under development or planned

• Offshore wind energy’s share of EU wind power production will increase from 3.9% in 2008 to over 25% in 2020 (EWEA, 2009*)

• Given its larger potential, it can be expected that total offshore wind capacity will exceed onshore capacity at some point beyond 2030 (EWEA, 2009*)

• Limited experience

• Harsh environment

• Environmental impact*Pure Power Wind energy targets for 2020 and 2030.

A report by the European Wind Energy Association – 2009, update


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Risk analysis - Codes and Standards

• Risk analysis is defined in many International Codes and Standards usually incorporated within a more global process of risk management:

• ISO/DIS 31000, Risk management - Principles and guidelines, 2009

• AS/NZS 4360, Standards Australia and Standards New Zealand. RiskManagement,1999

• or in guidelines:

• NASA, Probabilistic Risk Assessment Procedures Guide for NASA

Managers and Practitioners, 2002

• IRM/AIRMIC/ALARM Institute of Risk Management, A Risk Management Standard, 2002

• Standards and guidelines for specific cases and/or analysis

• NORSOK STANDARD Z-013, 2001 in the offshore industry

• IEC 62305-2, Ed.1: “Protection against lightning – Risk management”,

January 2006

• Recommendations of the JCSS, 2008


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The risk management processOverview


• The objective of risk management in civil engineering is to reduce different risks to the level accepted by society, with specific reference to the safety of people, in the way prescribed or indicated in many international codes and standards.

• The risk management process may comprise the following activities

IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW

COMMUNICATE AND CONSULT

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The risk management processEstablishing the context


• Definition of the scope of the risk assessment process

• Timeframe – resources - depth of analysis.

• Definition of the strategic and organizational context

• Establish the nature of the organization in charge of the risk management and the operating environment

• Identification of the stakeholders and objectives

• Determination of the evaluation criteria

• Decide what level of risk is acceptable

IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


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The risk management processRisk identification


Hazard: a source of potential harm or a situation with a potential to cause loss.

Risk: the chance of something happening that will have an impact upon objectives.

• Hazard identification: what can happen and how can it happen

• Sub-steps for the hazard identification (Faber, 2008):

• Decomposition of the system into a number of components/subsystems

• Identification of possible states of failure

• Identification of how the hazards might be realized

IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


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The risk management processRisk identification (1) – System decomposition

STRUCTURE

Main structure

Nacelle

Rotor–nacelle assembly

Operation

Maintenance

Emergency

Support structure

ACTIONS/LOADSENVIRONMENT

Junctions/bearings

Rotor

Junctions/bearings

Blades

Junctions/bearings

Tower

Junctions

Substructure

Junctions

Foundations

Junctions

Secondary structure

Energy production

Energy transfer

Auxiliary structure

Gravitational / Inertial

Gravity

Breaking

Aviation

Seismic activity

Aerodynamic

Hydrodynamic

Actuation

Other

Wave

Current

Torque control

Mechanical breaking loads

Yaw and pitch actuator loads

Tsunami

Impact loads

Wake loads

Wind conditions

Marine conditions

Seabed movement and scour

Other conditions

Normal wind conditions

Extreme wind conditions

Waves

Sea currents

Water level

Marine growth

Air temperature

Humidity

Solar radiation

Rain, hail, snow, ice

Chemically active substances

Mechanically active substances

Environmental aggressiveness

Lighting

Seismicity

Water density

Water temperature

Maritime traffic

Normal wave conditions

Extreme wave conditions

Structural

System

Decomposition

Petrini, Manenti, Gkoumas, Bontempi, 2010

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The risk management processRisk identification (2) – Failure states identification

Bontempi, Giuliani, Gkoumas 2007

THREATS

PHYSICAL

DESIGN EXECUTION

INTRINSIC EXTERNAL

ERRORS

FAULTS

LOGICAL

FAILURESDEPENDABILITY

OF

SYSTEMS

• Failure: defined as the manifestation of an error or a fault in the system.

• Methods:

• e.g. following a bottom-up approach the critical event modeling can be neglected and an initial failure can be a-priori assumed on the structure

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The risk management processRisk identification (3) – Failure realization

Giuliani, Bontempi 2010

• Identify how the hazard might be realized for the system and/or its subsystems

• Scenarios

• example: ship impact

a. impact on one of the leg under the sea level

b. impact at the sea level

c. impact on the tower above the sea level

• Scenarios realized on the basis of “common cause” failures (realistic scenarios), fitting LPHC events

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The risk management processRisk analysis


IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


• Issues

• Probability, as the likelihood of the risk occurrence

• Impact, as the consequences if the risk occurs.

• Methods

• Qualitative Risk Analysis

• Quantified (or quantitative) Risk Analysis (QRA)

• Probabilistic Risk Analysis (PRA)

• Correlation with complexity

• Creation of scenarios from the HHM of the system

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The risk management processRisk analysis (2) – correlation with complexity


High-Probability/

Low-Consequences

(HPLC)

Low-Probability/

High-Consequences

(LPHC)

High-Probability/

Low-Consequences

(HPLC)

Low-Probability/

High-Consequences

(LPHC)

High-Probability/

Low-Consequences

(HPLC)

Low-Probability/

High-Consequences

(LPHC)

High-Probability/

Low-Consequences

(HPLC)

Stochastic

Complexity

Deterministic

Analysis

Methods

QualitativeRisk

Analysis

Quantitative/Probabilistic

RiskAnalysis

PragmaticRisk

Scenarios

Stochastic

Complexity

Deterministic

Analysis

Methods

QualitativeRisk

Analysis

Quantitative/Probabilistic

RiskAnalysis

PragmaticRisk

Scenarios

Bontempi, 2005

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The risk management processRisk analysis (3) - HHM


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The risk management processRisk evaluation


IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


• Standards

• Good practice

• ALARP

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The risk management processRisk acceptance


IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


• Target: compare against previously established criteria

• example: lighting risk

Types of loss RT (year-1)

Loss of human life 10-5

Loss of service to the public 10-3

Loss of cultural heritage 10-3

Typical values of acceptable risks (from IEC 62305-2 Risk Analysis Standard for lighting)

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The risk management processRisk treatment


• Risk treatment is the process of developing, selecting, and implementing measures to modify risk. Treatment options have to be identified for the non acceptable risks.

• Risk mitigation

• Control the occurrence of a hazard - monitoring

• Maintain a good level of structural integrity under an extreme event and accidental load

• Risk reduction

• Risk transfer

• Risk acceptance

IDENTIFY

RISKSESTABLISH

THE CONTEXT

ANALYSE

RISKS

EVALUATE

RISKSACCEPT

RISKSTREAT RISKS

MONITOR AND REVIEW


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The risk management processRisk treatment: mitigation - monitoring


• The appropriate use of information from the various

monitoring or structural control systems may lead

to the reduction of the risk of occurrence of

adverse events, or limit their consequences

Bontempi, Gkoumas, Righetti 2005

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The risk management processRisk treatment: mitigation – structural integrity


• Structural integrity: insensitivity to local

failure

• Reduce the occurrence of the action (“avoid” the action - event control)

• Reduce the effect of the action (“avoid”local damage)

• Reduce the effect of a failure – robustness (“avoid” disproportional collapse)

Giuliani, Gkoumas, Bontempi 2007

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Considerations and further research

• This paper provides an overview of the risk analysis process, with specific reference to applications in offshore wind turbines and wind farms

• Risk analysis should be a part of a more global project management plan

• Relationships among the risk management process and other engineering issues and concepts are discussed (monitoring, dependability, structural integrity, robustness assessment)

• The risk analysis process is a continuous process


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Thank you for your attention

[email protected]


6 - a risk analysis framework for offshore wind turbines - gkoumas

Design

standards risk analysis

aspects of risk analysis

risk analysis framework

risk management standard

objective of risk management

risk management principles

lightning risk management

global risk management