Hazard Identification and Risk Assessment for Wind Turbines

Components of Wind Turbines

Turbines,  the  risk  of  working  in  confined  spaces,  and  finally  the risk of ice accretion and irregular shedding when the wind turbine  is  in  operation  phase  or  even  when  it  is  stationary.  The last  type  of  risk  is  highly  observed  in  cold  climate  regions.  The four  mentioned types of risks  are the  main  ones out of the  many risks that could appear during transporting, installing, operating and  maintaining  wind  turbines.  The  main  aim  of  this  work  is  to contribute  in  the  proper  risk  assessment  of  potential  hazards, which enhances the ability to devise passive and active protection measures to reduce the effects of a catastrophic event. Keywords—risk assessment; hazard identification; risk analysis; risk evaluation; wind turbine 

There is a rising commitment towards utilizing clean energy across the world. Wind turbines happen to be an efficient choice to meet some of the demand for elecricity.  A group  of  wind  turbines  connected  to  each  other  by  electrical cables  forms  a  wind  farm.  A  wind  farm  produces  17  to  39 times  the  power  it  consumes,  which  is  more  efficient  when compared  to other  forms  of  energy  such  as  nuclear power (16 times) or coal (11 times) [1]. 

An onshore wind turbine sits on a structural support usually made  of  concrete,  called  the  Foundation,  the  importance  of  a foundation  is  to  transfer  the  horizontal  and  vertical  forces acting on the wind turbine to the surrounding ground. Whether the case is offshore or onshore, a wind turbine would essentially consist of the  same  parts. The  first component of a wind turbine is the tower whose height varies depending on the site  and  the  available  wind  speed.  Going  from  bottom  to  top, the  cross  section  of  the  tower  becomes  narrower.  Normally,  a ladder is mounted inside of the wind turbine’s tower. However, modern  towers  have  lifts  [2].  On  the  top  of  the  tower,  lies another  part  called  the  nacelle.  The  nacelle  holds  the  needed equipment  to  convert  wind  energy  into  electricity,  such  as gearbox,  braking  system,  generator  and  yawing  mechanism  to correct  the  direction  of  the  nacelle  to  face  the  wind  direction. 

The wind turbine blades are connected to the nacelle through a hub. Generated electricity is transferred via cables to a step-up transformer located at the base of the wind turbine [3]. Wind-turbines are constructions that are susceptible to windy conditions and they have many mechanical and electrical  moving  parts  and  instruments.  Therefore,  there  is  a great  need  for  awareness  of  the  types  of  hazards  that  workers might  face  when  dealing  with  wind  turbines.  This  research aims  towards  investigating  the  hazards  that  might  take  place during the installation and maintenance phases of mainly onshore wind turbines by utilizing risk assessment methodologies  to  identify  the  probable  hazards,  their  level  of risk and ways of mitigation and control. 

According  to  the  Canadian  Standards  Association  (CSA) Z1002  Standard  "Occupational  health  and  safety  –  Hazard identification and elimination and risk assessment and control", the  following  terms  used  in  the  risk  assessment  procedure  are defined as follows [4], [5]: Risk is identified as the combination of the likelihood of the occurrence of a harm and the severity of that harm. 

Types of Risks During Wind Turbines Transportation, Installation, Operation and Maintenance

Risk assessment is the overall process of hazard identification, risk analysis, and risk evaluation. 
Risk  assessment  provides  an  understanding  of  risks, their causes, consequences, and their probabilities. 
Hazard  identification  is  the  process  of  finding,  listing, and characterizing hazards. 
Risk analysis is a process for comprehending the nature of hazards and determining the level of risk. 
Risk evaluation is the process of comparing an estimated  risk  against  given  risk  criteria  to  determine the significance of the risk. 

A  decision  is  taken  based  on  risk  evaluation  in  order  to mitigate or control the risk. This step is known as Risk Control Before  implementing  risk  control  measures,  the  level  of  risk has  to  be  determined  in  order  to  decide  which  hazard  to  start treating  [5].  One  of  the  conventional  methods  used  to  rank  or prioritize risks is  the Risk Matrix shown in Table I, where  the vertical  column  shows  the  likelihood  of  the  risk  to  take  place and  the  horizontal  row  shows  risk  severity  if  it  happens.  The combination between likelihood and severity in this qualitative method determines the level of the risk; consequently a decision can be made on which measures should be taken in order to control and mitigate the risk. The following sections discuss various types of risks during wind turbines transportation, installation, operation and maintenance. 

Wind  turbines  differ  in  sizes  and  capacities.  Generally, larger  wind  turbines  are  able  to  deliver  more  electricity  at lower  cost.  This  is  because  some  costs  related  to  building  a wind turbine are independent of its size, such as the cost of the foundation, building  new roads and electrical grid connections .Transporting  large  components  on  roads  can  cause  injury 

to people and damage to materials. The likelihood and severity of  hazard  may  increase  while  transporting  large  wind  turbine 

components in particular at narrow roads with heavy traffic, or difficult road terrains. 

Transporting  large  wind  turbine  components  faces  many challenges.  As  for  onshore  wind  turbines,  components  might have  to be  transported  via  existing  public  roads,  which  allows for  limited  movement  and  poses  high  risk  to  vehicles  on  the road when conveying such parts to the construction site. On the other  hand,  marine  transportation  and  installation  equipment allow  better  handling  of  larger  parts,  therefor,  offshore  wind turbines tend to be larger than onshore ones [2]. As  an  example  of  large  wind  turbines  parts,  Siemens  is working  with  other  partners  to  create  6MW  offshore  wind turbines,  the  size  of  one  blade  of  these  turbines  is  a  fraction smaller than An A380's wingspan. Siemens says that one 6MW wind turbine is enough to supply about 6,000 European households  with  electricity.    

Kilometer  per  hour  over  a  distance  of  575  kilometers  to  the construction  site  [8].  Another  example  is  the  widely  used  GE 1.5-megawatt  wind  turbine,  which  consists  of  almost  116  ft. blade  mounted on top of 212 ft.  tower. The blade assembly of that  wind  turbine  weighs  more  than  36  tons  and  the  tower weighs.