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Repowering wind farms
Photo courtesy of Jan Arne Wold – Equinor.
AS MANY OFFSHORE OIL & GAS ASSETS ARE REACHING THEIR END OF LIFE, DECOMMISSIONING HAS BEEN A MUCH-TALKED ABOUT TOPIC IN THIS INDUSTRY. OPERATORS AND CONTRACTORS ARE AWARE OF THE CHALLENGES THERE ARE FOR AN EFFICIENT, SUSTAINABLE, SAFE, AND COST-EFFECTIVE REMOVAL. WITH THIS KNOWLEDGE IN MIND, IT IS ABOUT TIME FOR THE GROWING OFFSHORE WIND INDUSTRY, TOO TO TAKE DECOM INTO ACCOUNT.
Most wind turbines are designed and certfed for a 20-25 year service life. Afer this period, they have to be decommissioned or the accredited operatonal lifetme has to be extended, ofen accompanied by repowering. While processes for decommissioning, and repowering onshore windfarms are well known, the experience ofshore is limited. So far, only Ytrre Stengrund (Sweden) and Vindeby (Denmark) have been dismantled, plus two single near-shore turbines, namely Windfoat 1 in Portugal, and Hooksiel in Germany, as well as four turbines at Windpark Lely, which is in the Dutch lake IJsselmeer.
123 turbines in 2023 The Internatonal Renewable Energy Agency (IRENA) predicts onshore and ofshore wind combined would generate 35% of the global electricity demand by 2050. The European Commission estmates installaton of 450GW of ofshore wind capacity by 2050 in the European countries, which would meet 30% of Europe’s electricity demand. Europe has a total installed ofshore wind capacity of around 25GW connected across twelve countries. With this surge in installaton of new ofshore wind farms (OWF) and due to the ageing feet of currently operatng OWFs, the number of OWFs required to be decommissioned will increase in the coming years. It is estmated that about 3.5GW of global ofshore capacity will reach its designed operatonal life of 20-25 years by 2035. With 123 turbines already reaching their planned lifetme of 20 years by 2023, the decisions on the End of Life (EoL) scenarios should be researched as the problem will soon arise. Alternatives to decommissioning Currently, decommissioning is seen as the default opton when an OWF reaches its EoL. It refers to taking down the structures and restoring the site as close to its original state. However, as the development of ofshore wind is acceleratng and the existng ofshore feet is ageing, it is essental to look into other cost efectve and sustainable alternatves for OWF afer their planned lifetme. Diferent EoL scenarios for the ofshore wind farms are required when either the turbine reaches its designed technical lifetme, has been subjected to failure or fatgue or no longer satsfes the expectatons of the owner. Proftability, performance, and reliability of the exitng OWF and cost beneft analysis of diferent EoL scenarios
are necessary to make the optmal decision. The main scenarios which are currently With 123 turbines already reaching their discussed in the industry are: planned lifetime of 20 years by 2023, the • Lifetme extension decisions on the End of Life (EoL) scenarios should be researched as the problem will • Refurbishment soon arise. • Partal repowering • Full repowering • Decommissioning The technical and economic feasibility of considering these EoL scenarios depends on specifc windfarm sites and conditons. DecomTools project The Interreg North Sea Region DecomTools project aims at an overall sustainable approach to the ofshore windfarms’ EoLcycle. The project wants to devise and develop eco-innovatve concepts for reducing the decommissioning´s costs by 20%, and its environmental footprint by 25% (measured in CO2 equivalents). Also, it wants to increase the know-how and expertse of North Sea region involved stakeholders. As a result of the project, the report ‘Concept for repowering OWF – Comparison of CO2 and costs with decommissioning’ was recently presented.
Analysis to calculate weights of the materials with HR1 OWF parameters.
Apartfromthematerialmassestimatesofthewindfarm,theanalysisfocusedontheeconomic feasibilityofthe EoL scenarios.Thefirstgeneration OWF weresupportedbydifferentgovernmentsubsidyschemes,thatenabledthe OWF togenerateadditionalrevenue.Theextrasupport ontopofthevaryingelectricitypriceisgenerallyeffectivetillacertainagreeduponduration. Butfollowingthecurrenttrendstowardszerosubsidy OWF,itisverylikelythatextendingthe lifetimeofthe OWF,ithastorunsolelyonthefluctuatingelectricitymarketprices.Thetable 2.2 liststheforecastedday-aheadelectricitymarketpricethatthe HR1 OWF wouldbereceiving.For thepurposeoftheanalysis,anaverageyearlypriceisconsideredandforyearsfrom2031-2050, averageofprecedingyearsistakenintoaccount,duetolackofforecasteddata. AmoghGokhale EnergyClusterDenmark www.northsearegion.eu/decomtools
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The study focused on comparing various EoL scenarios that can be considered for future OWFs, and showcases the potental of gaining economic and environmental benefts from those various End of Life (EoL) scenarios. It also ofers a basis for future detailed analysis.
No clarity
The report concludes that so far through the current literature, there is stll no clarity on the core defnitons when it comes to the EoL scenarios, especially for the OWF. The scope of diferent scenarios is seen to be used interchangeably by the industry. In near future, the regulaton bodies and the wind industry should defne what is included in the various EoL scenarios. Thus the knowledge gained by such analyses can be helpful in defning common terms across the stakeholders. Furthermore, the regulaton and permitng processes for EoL scenarios difer between the European countries. Due to the updates in the environmental consents and other leasing and permitng norms afer the frst generaton of OWF were installed, extending the lifetme of those OWF under the updated regulatons could pose further difcultes. A distncton in the cases requiring repermitng and approving should be defned. A suggeston is that the projects should not be considered as ’new’ when no change of the tp height, size or locaton occurs, hence simplifying the permitng and approval process giving further incentves for the developers to consider them as optons. Also going ahead, as the scope of the OWF is extended to a full-scope with the ofshore substatons developed by the windfarm developers, there could be changes in the outcome of the EoL scenarios depending on the ease of upgrading the electrical assets.
Horns Rev 1 Offshore Windfarm
Taking Horns Rev 1 OWF as a case study, the conducted analysis tried to adapt the possible scenarios with the parameters of this wind farm showing the diferences between diferent EoL scenarios under diferent parameters. As a part of this analysis, an Excel tool was developed to calculate the fnancial feasibility and greenhouse gas impacts of the assessed scenarios. As the decision of selectng the best-suited EoL scenario depends on the accurate data of the considered OWF, the tool allows the user to customise with the values known for the OWF in consideraton. In the conducted analysis for the HR1 OWF, Lifetme Extension was seen as the benefcial fnancial decision with the lowest LCoE. This is due to extending the operatonal period of the asset with minimal efort. Refurbishment has a slightly beter climate impact. Several key assumptons regarding the structural health of the
Table3.2:Keyfinancialparameterresultsforallthe EoL scenariosof HR1 OWF. Asthesustainabilityofthewindindustryisgainingfurtherattention,asimplecomparisonof the GreenHouseGas (GHG)impactofthedifferentscenarioswasassessed.The CO2 emisFactor sionsoftheaddressed EoL Unit Scenario1 Scenario2 Scenario3 Scenario4 scenarioswascalculatedandtheirresultscanbeseenasintable NPV [’1.000 e ] 94777 62513 -2191 -512003.3.Theemissionsarecalculatedforthedifferentstagesofthewindfarm.Forthisanalysis, IRRthe GHG [%] impactfrombuildingtheexisting HR1 44.8 9.9 4.9 OWF,decommissioningallofitsstructuresand LCOE [ e/MWh] theadditionalemissionsbytheselected EoL 32.10 50.08 64.83 scenariowithitsdecommissioningwasincluded. SimplePaybackTime [years] 1.51 7.14 12.29 Primarilyabout80%ofthetotalemissionsarefromthematerialproductionandmanufacturing DiscountedPaybackTime [years] 1.69 9.52 - components.Theremainingisgeneratedbytheinstallationanddismantling.Thereisasaving ofaround25%intheemissionsbyconsideringtherecyclingcredits[19 Image courtesy of the Interreg North Sea Region DecomTool project. ].Forthemethodology ofthisanalysis,theemissionswerecalculatedwithanaddedmaterialpointofview,wherethe 3.4. GHGIMPACTemissionsofthe EoL wereaddedontopofareferencecaseofexisting HR1 OWF. Key fnancial parameter results for all the EoL scenarios of HR1 OWF. Scenario 1 (Lifetime extension) is the most preferred fnancial alternative. Asthesustainabilityofthewindindustryisgainingfurtherattention,asimplecomparisonof the GreenHouseGas (GHG)impactofthedifferentscenarioswasassessed.The CO2 emissionsoftheaddressed EoL scenarioswascalculatedandtheirresultscanbeseenasintable 3.3.Theemissionsarecalculatedforthedifferentstagesofthewindfarm.Forthisanalysis, the GHG impactfrombuildingtheexisting HR1 OWF,decommissioningallofitsstructuresand theadditionalemissionsbytheselected EoL scenariowithitsdecommissioningwasincluded. Primarilyabout80%ofthetotalemissionsarefromthematerialproductionandmanufacturing components.Theremainingisgeneratedbytheinstallationanddismantling.Thereisasaving ofaround25%intheemissionsbyconsideringtherecyclingcredits[19].Forthemethodology ofthisanalysis,theemissionswerecalculatedwithanaddedmaterialpointofview,wherethe emissionsofthe EoL wereaddedontopofareferencecaseofexisting HR1 OWF. Table3.3:Analysisresultsforthe GHG impactofallthe EoL scenariosof HR1 OWF.
Factor Unit Scenario1 Scenario2 Scenario3 Scenario4
OverallGHGimpact~ [g CO2 /kWh] 4.98 4.31 5.60 6.84
MaterialbasisGHGimpact~ [kg CO2 /kgmaterial] 2.25 2.26 2.25 2.25 Asitcanbeseenfromthetable 3.3,theScenario2(Refurbishment)givesthelowest GHG impact.Theoverall GHG impact,wascalculatedbasedonconsideringtheyearlyelectricitygenerationforeachscenario.Incaseofdecommissioning(Scenario4),theelectricitygenerated wasduringthe25yearsofoperationalphaseofexisting HR1 OWF.Thisresultedinthemost emissions,indicatingthatingeneralitisenvironmentallybeneficialtokeepthe OWF operating forlonger.Thelower GHG impactinthescenario2(Refurbishment)comparedtotheScenario 1(LifeTimeExtension)isduetotheincreasedproduction,duetohighercapapcityfactorand alsoadditionalyearsofproduction.ThesecondparameterofMaterialbased GHG impactcalculatestheamountofemissionsforaunitofmaterialusedinthewhole OWF.Astheadditional quantityofmaterialtobeusedinthe EoL scenariosisnotsignificantcomparedtothematerial usedintheexisting OWF,thevaluesareseentobecomparable.AslightincreasefortheRefurbishmentscenarioisduetotheadditionalmaterialsforgettingtherefurbishedcomponents andrelativelysmallchangeintheyearsofoperation.Allthesevaluesarelowerwhencomparing tothereferencecaseofexisting HR1 OWF whichemits2.79kg CO2 /kgmaterialused. 12
Table3.3:Analysisresultsforthe GHG impactofallthe EoL scenariosof HR1 OWF.
Factor Unit Scenario1 Scenario2 Scenario3 Scenario4
OverallGHGimpact~ [g CO2 /kWh] 4.98 4.31 5.60 6.84
MaterialbasisGHGimpact~ [kg CO2 /kgmaterial] 2.25 2.26 2.25 2.25 Image courtesy of the Interreg North Sea Region DecomTool project. Asitcanbeseenfromthetable 3.3,theScenario2(Refurbishment)givesthelowest GHGAnalysis results for the greenhouse gas impact of all the EoL scenarios of HR1 OWF. Scenario 2 impact.Theoverall GHG impact,wascalculatedbasedonconsideringtheyearlyelectricitygen-(Refurbishment) gives the lowest greenhouse gas impact. erationforeachscenario.Incaseofdecommissioning(Scenario4),theelectricitygenerated wasduringthe25yearsofoperationalphaseofexisting HR1 OWF.Thisresultedinthemost emissions,indicatingthatingeneralitisenvironmentallybeneficialtokeepthe OWF operating forlonger.Thelower GHG impactinthescenario2(Refurbishment)comparedtotheScenario components, load bearing capacites, 1(LifeTimeExtension)isduetotheincreasedproduction,duetohighercapapcityfactorand regulatons, and extent of maintenance alsoadditionalyearsofproduction.ThesecondparameterofMaterialbased GHG impactcalculatestheamountofemissionsforaunitofmaterialusedinthewhole OWF.Astheadditional quantityofmaterialtobeusedinthe EoL scenariosisnotsignificantcomparedtothematerial work were used in this analysis. However, the decision largely depends on the exact usedintheexisting OWF,thevaluesareseentobecomparable.AslightincreasefortheRestate of the assets which should be assessed furbishmentscenarioisduetotheadditionalmaterialsforgettingtherefurbishedcomponents for a more accurate decision. andrelativelysmallchangeintheyearsofoperation.Allthesevaluesarelowerwhencomparing tothereferencecaseofexisting HR1 OWF whichemits2.79kg CO2 /kgmaterialused.i. northsearegion.eu 12 AmoghGokhale EnergyClusterDenmark www.northsearegion.eu/decomtools
AmoghGokhale EnergyClusterDenmark www.northsearegion.eu/decomtools
Photo courtesy of GE Renewable Energy.
