Analysing the Cumulative Energy Demand of Product service Systems for wind Turbines Available online at www sciencedirect com 2212 8271 © 2016 The Authors Published by Elsevier B V This is an open acc[.]
Available online at www.sciencedirect.com ScienceDirect Procedia CIRP 59 (2017) 214 – 219 The 5th International Conference on Through-life Engineering Services (TESConf 2016) Analysing the Cumulative Energy Demand of Product-Service Systems for wind turbines G Merta*, B.S Linkeb, J.C Auricha* a Institute for Manufacturing Technology and Production Systems, University of Kaiserslautern, Germany b Department of Mechanical and Aerospace Engineering, University of California Davis, USA * Corresponding author Tel.: +49-631-205-4225; fax: +49-631-205-3304 E-mail address: publications.fbk@mv.uni-kl.de Abstract Many wind turbine manufacturers offer services for their products The integration of products and services, so called Product-Service Systems (PSS), are intended to support customers over the life time of a product and to ensure a long and successful customer relationship Besides of the requirements of customers, wind turbine manufacturers have to consider requirements of the government and society as well Sustainability in all three dimensions, economy, environment, and society, is increasingly relevant in engineering PSS providers have the possibility to improve sustainability of their products and services over the entire life time and supply chain For this purpose, novel methods need to be provided to support PSS providers to evaluate and improve PSS sustainability In this paper, an approach to analyse and reduce the Cumulative Energy Demand (CED) of PSS is presented to improve economic and environmental sustainability The approach is explained on a wind turbine including training as service In the approach three subgoals are addressed: First, CED of PSS is investigated Second, the impacts of changes in the CED of PSS will be analysed, potential levers will be identified and measures derived Third, strategies based on the measures will be generated which enable a reduction of the CED of PSS ©©2016 Authors Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license 2016The The Authors Published by Elsevier B.V (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the Programme Committee of the 5th International Conference on Through-life Engineering Services Peer-review responsibility of the scientific committee of the The 5th International Conference on Through-life Engineering Services (TESConf 2016) (TESConfunder 2016) Keywords: Product-Service Systems; Cumulative Energy Demand; sustainability; wind turbines Introduction Changed requirements of customers caused a trend from technology providers to service providers Customers are interested in complete and sustainable solutions ProductService Systems (PSS) aim to achieve sustainability and customer satisfaction by systematically providing various services for products [1] PSS offer life cycle-oriented services to support customers over the entire life time of their product PSS are strongly customer-oriented and it is assumed that PSS provide the ability to reduce environmental impacts However, it is not guaranteed [2] and not proven on any use cases For an evaluation of environmental impacts of PSS, an ecological assessment is needed The Cumulative Energy Demand (CED) is an opportunity to assess and evaluate the sustainability of a single product or a service based on energy It describes the “total quantity of primary energy which is necessary to produce, use and dispose a product” [3] The CED in its existing state is not suitable to evaluate a complex system consisting of products and services as it is the case for PSS It needs to be adapted and enhanced due to the PSS-specific characteristics Therefore, the paper demonstrates an approach to analyse and reduce the CED of PSS The first part starts with the state-ofthe-art about CED, followed by the state-of-art of PSS and the relevance of services for wind turbines Based on the existing research work, the need for a PSS-specific approach for determining the CED is explained The main part of the paper is dedicated to the approach which is developed in a research project It presents how to enlarge the current CED method so that it is adaptable for PSS in respect of wind turbines Finally, the paper ends with a conclusion and further research work on the approach 2212-8271 © 2016 The Authors Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the The 5th International Conference on Through-life Engineering Services (TESConf 2016) doi:10.1016/j.procir.2016.09.018 215 G Mert et al / Procedia CIRP 59 (2017) 214 – 219 State-of-the-art 2.1 Cumulative Energy Demand Cumulative Energy Demand is a part of the Life Cycle Assessment (LCA) CED enables to evaluate and compare products and services with respect to energy criteria Hereto, the primary energy demand, all energy carriers that are found in nature, will be calculated for the entire life time of the investigated product CED is the sum of the cumulative energy demands for the production (CEDP), for the use (CEDU) and for the disposal (CEDD) of the economic good [3] ܦܧܥ = ܦܧܥ + ܦܧܥ + ܦܧܥ (1) The VDI guideline 4600 suggests a method for determining CED of products and services [VDI4600] For the calculation of CED the sum of cumulative energy consumption (KEV) and the cumulative non-energy demand (KNA) are necessary The KEV includes all the final energies for heat, energy, light and other forms of effective electricity generation which are valued as primary energy The KNA defines the sum of all non-energy purposes and the inherent energy of working materials which are also valued as primary energy [3] An important basis for the calculation of the CED is the definition of the balancing boundaries and the balance-sheet items For this purpose, the material and energy flows have to be defined and quantified The boundaries can be defined according to local, temporal and technological criteria A determination of all pre and incidental process chains is not possible and the systematic limitation is a challenge because of the complexity and multiplicity of the interactions of individual processes Therefore, the delimitation between relevant and not relevant process chains is important To this, delimiting criteria exist In an ideal case the balance space is from the raw material of the deposit to the final disposal A redefinition of the criteria for the boundary setting has to be done because the balance boundaries are defined based on facts and circumstances at the beginning of an analysis and might change over time Furthermore, a sensitivity analysis with varying balance boundaries is necessary during the calculation of the CED to assess the impacts of different balance boundaries [3] Methods for balancing are the process chain analysis used in form of a material balance analysis, a micro- and macroanalysis as well as an energy input-output analysis Designing Perspective of manufacturer Perspective of customer The process chain analysis is a micro-analysis where the product flow is classified into individual processes according to the production process Originating from the final product each step from the production to the disposal is analysed which is necessary for the process chain The first step starts with an analysis of the production of the assemblies In the next, more detailed step the production of the semi-finished products and raw materials are considered For this method, the amount of data is high and it may reach its limits of practicability For the determination of CED a step-wise approximation, using a combination of micro-analytical and macro-analytical approaches, is recommended [3] The macro-analysis is based on values of input and output flows of products of homogeneous production areas The energy input-output analysis is based on national data on economic interdependence and energy use It is not suitable for the determination of the CED of individual products because of the degree of aggregation and reference to monetary values [3] For the determination of the CED of PSS the typical characteristics of PSS need to be known, analysed and adapted into the new approach The next section presents the most important characteristics of PSS 2.2 Product-Service Systems Product-Service Systems are defined as consumer-oriented solutions consisting of a technical product which is supported and enhanced over its entire life time with different services [4] Services can be classified according to the life cycle phases or by their functionality into six types [4]: technical, qualifying, process-oriented, logistical, informational and financial Technical services like maintenance are focused on recovering the functions of a product Qualifying services improve the quality of work of customer employees, e.g operator training Process-oriented services optimise the production process of the customer and logistical ones support spare part supply Informational services are reports and the supply of information for the customer Financial services help customers by providing leasings PSS have a customer-oriented perspective instead of product-oriented They have a comprehensive life cycle compared to a single product as they contain life cycle perspective of the manufacturer as well as of the customer (see figure 1) The manufacturer and customer have a cooperation during the usage of the product Both act as external and internal production factors during the whole work process [4] Implementation End-of-Life Planning Development Decision Buy Production Service Usage End-of-Life Procurement Figure 1: PSS life cycle from the perspective of manufacturer and customer [4] FBK/016_012 216 G Mert et al / Procedia CIRP 59 (2017) 214 – 219 Because PSS cannot be independently created and delivered by a single provider, the manufacturer cooperates with the extended value-added network [5, 6] The extended valueadded network defines the suppliers and service providers which are a part of the supply chain of PSS [7] PSS represents a “knowledge-intensive socio-technical system” and is characterized by the integrated and mutually determined planning, development, provision and use of product and service shares [7, 8] It is characterised by the interaction between the usage of the product and the service process and consists always of material and immaterial results during the realisation phase [7] PSS are common in many industrial sectors, as it is the case for wind turbine sector Their relevance for wind turbines and service relevant components will be explained in the next part for each component The critical components with high replacement costs are the rotor blade, the pitch, the gear and generator Noncritical components which have the first breakdown after twelve years are the transformer, the tower and the foundation In the study of [12] the frequency of failure and the period of time were demonstrated for each component in connection with the time for repair It underlined that electrical systems fail often but have a short down time Expensive parts like the gearbox, generator, drive train or rotor hub have a low failure frequency but need much more time for repair [12] This knowledge is important in relation to optimize the CED of services For critical components, services are more relevant and might have a higher impact on the CED of PSS Therefore, for the approach a use case of rotor blades and service control of their cracks might be interesting Currently, each wind turbine is remotely monitored by a SCADA-system (System Control and Data Acquisition) It collects data over status messages about the condition of the plant and failures, revenue parameter as well as operating parameters like rotational speed, performance, wind speed and wind direction This kind of data is constantly collected in the wind turbine and saved in its control and can be requested by the plant provider or wind turbine manufacturer [10] It enables to collect and analyse data for determining the economic and ecologic impact of wind turbines as well as to help providers in improving their product and services The most relevant life cycle phases and materials for the CED of a wind turbine are also of interest for the approach to analyse the CED of PSS According to [14], 84% of the CED is caused in the production phase, 8% in the usage phase and another 8% is necessary for the assembly, transport and dismantling This result is based on an example of a 2.3 MW wind turbine with a total amount of 2.096t of material: concrete (1.744t), steel (237t), cast iron (73t), glass fibre reinforced plastic (29t), copper (12t) and aluminium (1t) It was found out that the tower is responsible for 36% and the foundation for 2.3 Relevance of services for wind turbines Replacement costs [€/kW] The wind turbine industry is a growing industry and especially for China, USA and Germany of interest when considering the new installed capacity in 2015 In Germany the amount of new installed onshore wind capacity accounts of 6.013 MW which means a rise of 13.38% compared to the total installed capacity In USA the new installed capacity of MW increased by 11.55% and in China even more with 21.16% The worldwide installed capacity amounted 432.883 MW in 2015 [9] Services are of high relevance for technical products like wind turbines where the availability and reliability is crucial For wind turbines the reliability is very important because breakdowns imply high maintenance costs According to a study, the expenses for maintenance and repair of a wind turbine account for one quarter of the operating costs in 20 years of operating time [10] Although the failure rates decrease with the time, the operating costs increase due to the fact that warranty services of manufacturers are offered in the first years of the life time [11] Figure presents the reliability of wind turbine components It classifies components in critical and noncritical ones according to the first time until their repair or replacement (x-axis) The y-axis shows the replacement costs Rotor Blade Critical Components Generator Pitch Gear Control and General Electronics Yaw System Brakes Shafts Main bearing Hydraulic System 2.5 7.5 10 Tower Noncritical Components Transformer Station Foundation 12.5 15 Years until a repair or replacement [t] Figure 2: Repair costs of wind turbine components [Based on 10] 17.5 FBK/016_013 20 217 G Mert et al / Procedia CIRP 59 (2017) 214 – 219 Tasks Results Analysis of PSS-specific requirements Steps • Definition of PSS-specific requirements to determine CED of PSS regarding data collection methods, process steps etc • Enhancing the CED method based on the requirements List of requirements for determining CED of PSS Defining PSS-specific functional unit and system boundaries • Modeling of relevant resources for the entire life cycle • Identification and classification of dependencies between balance elements • Modification of methods (e.g process chain analysis) • Generalization of all findings into an approach PSS-specific approach for determining CED of PSS Analysis of dependencies and impacts of PSS changes on the CED • Identification of CED-relevant PSS changes based on the control lever • Classification of CED-relevant PSS changes • Determining the cause-effect relationship PSS-specific approach for analysing the dependencies of PSS on CED Identification of measures for reducing the CED of PSS • Analysis of impact mechanism to identify measures • Evaluation of control lever • Developing an approach for a systematic reduction of CED of PSS Approach for reducing the CED of PSS FBK/016_014 Figure 3: Overview of the approach to analyse and reduce the Cumulative Energy Demand of Product-Service Systems [Based on 16] 55% of the material demand This is also confirmed by [13] as it was figured out that the CED of wind turbines is mainly caused by the material phase which needs the highest energy and carbon foot print during the primary material production of wind turbine parts The production processes itself is the second dominant phase Energy for transportation and use phase is negligible 2.4 Research Gap CED of PSS The method CED is a possibility to evaluate and compare products according to their ecology It aggregates consistently the demand of different energy sources Within a research project a method and solution is enabled that reduces the specific energy demand in the industrial production [15] The method is based on the CED method, but focuses only on the resource energy and on the energetic usage of energy sources Thus, it is analysed how it is possible to reduce the energy demand in the usage phase by choosing applied materials which influences the energy demand of preliminary processes [15] Because of the high CED in the production phase of a wind turbine, it is interesting to analyse different materials or constructions for the foundation However, the method for calculation the CED not consider PSS-specific characteristics, e.g evaluation of complex solutions which consist of tangible and intangible elements or the interdependencies between products and services (see section 2.2) Even the ecological guideline as the LCA indirectly address and not have any specific attention to solutions like PSS that consist of both tangible and intangible elements and include behavioral changes The implementation of LCA for PSS has not been explored [2] Considering research from year 2000 to 2015 only eleven journal articles exist which demonstrate PSS cases evaluated for the use of LCA Only a few of these articles discuss the use of LCA for PSS in detail Currently, there is a limited experience on conducting LCA or CED on PSS [2] Nevertheless, CED as a part of LCA is applicable for PSS Approach to analyse and reduce the Cumulative Energy Demand of Product-Service Systems The following approach aims to enable a systematic approach for an optimisation or reduction of the CED of PSS and consists of four steps (see figure 3) After the final step the approach needs to be validated based on a use case of the wind turbine industry The approach starts with the analysis of PSS-specific requirements to determine the CED of PSS The requirements are regarding PSS characteristics, data collection methods, process steps etc The CED of PSS has to consider the perspective of the provider and of the customer So, for the customers perspective the CED implies all resources which are necessary for the usage of the wind turbine and for the service realisation process (resources in terms of time and costs for the service) as well as the end-of-life processes From the providers perspective the CED must be enhanced by considering the resources for the service realisation (see figure 4) These are for example fuel for the transportation, materials and energy for producing spare parts, service auxiliaries, service tools etc CED of wind turbine in usage and service realisation process CEDU and CEDS Customer CED of End-of-life processes CEDE CED of PSS PSS provider CEDP CEDR CED for production of wind turbine CED for providing resources for the service realisation FBK/016_015 Figure 4: CED elements for PSS [Based on 16] 218 G Mert et al / Procedia CIRP 59 (2017) 214 – 219 Furthermore, following requirements are relevant to consider to determine the CED of PSS: x Data availability, e.g data of resources for service realisation, x Effort on determining data in comparison with the relevance for the CED, e.g for which processes is it useful to determine the primary energy demand x Impact on other life cycle phases, e.g selection of material for spare parts x Using different CED methods or a hybrid method suitable for product and services x Dependencies between product and services, e.g how service effects the failure frequency of components x Defining homogenous boundaries for products and services regarding local, temporal and technological criteria (e.g production of spare parts adapted to the life time of wind turbine) The second step is the core task of any environmental assessment, the definition of a functional unit (FU) It is the quantified description of the performance of a wind turbine or a service and is an important step because the FU provides the reference to which all other data in the assessment is normalised [17] In the literature, this step is also defined as challenging because of two reasons: On the one hand, it is difficult to specify how broad the FU should be and on the other hand because of the comparability of the chosen alternatives, especially considering sub-functions [2] Another challenge is due to the fact that a result of a service is difficult to express in terms of a FU Usually services provide soft elements which are not measurable in a FU [18] For example, hotline service or training of service technicians are difficult to measure in a FU Therefore, attention should be given on the goal and scope definition The FU for PSS should be its functionality In case of a wind turbine the functionality is to produce as much energy as possible Services for wind turbines, like maintenance or condition monitoring, have the functionality to ensure the productivity of it Technical, qualifying, process-oriented and logistical services are suitable for this FU Informational and financial services have a negligible impact on the productivity of the wind turbine and can be excluded The FU can be defined as the produced kW in one hour For the system boundaries technical, time-relevant as well geographical PSS-specific limitations have to be defined The technical boundary, e.g consideration of technical state and capacity is for the wind turbine as well for the service + Amount of worker trainings Quality of production work + + Quality of product Production effort + Quality of maintenance work - Mean time to repair + Mean time between failures + Reliability + + Cumulative - Energy Demand of PSS - Amount of maintenance work FBK/016_016 Figure 5: Causal loop for worker training and its impact on the CED of PSS maintenance or spare parts delivery relevant The geographical boundary of the production of a wind turbine needs to be in consistence with the service delivery The criteria time for example for the production of a rotor blade regards the exploitation, production of raw material and semi-products, final assembly and landfilling Whereas the criteria time for services needs to concern the life time of such a rotor blade, e.g CED of controlling cracks in the rotor blade for 20 years of life time Furthermore, the presented CED methods in part 2.1 need to be modified according to the determined requirements Dependencies between balance elements have to be identified and classified In figure the impact of training on the CED of PSS in a causal loop diagram is presented It is a short example to demonstrate how the CED of PSS can be influenced by worker training and how many elements have to be regarded The interdependencies should to be analysed for each kind of service type (mentioned in section 2.2) In the third step the dependencies and impacts based on control lever have to be analysed and classified according to the relevance Another aspect in step 3, is the determination of cause-effect relationship The last step is measures for reducing the CED of PSS have to be identified For this purpose, control lever have to be evaluated and described in a final approach for a systematic reduction of CED of PSS Conclusion Due to a missing concept for evaluating the sustainability of complex solutions and determining the CED of PSS, an approach to analyse and reduce the CED of PSS is generated and presented The approach aims in developing an ecological assessment of products and services as one system and consists of four main steps The first two steps which are the analysis of PSS-specific requirements and the definition of PSS-specific functional unit and systems boundary were presented and explained The last two steps of the approach are the analysis of dependencies and impacts of PSS changes on the CED as well the identification of measures to reduce the CED These steps and a validation of the approach based on use cases will be illustrated in further work Use cases are planned from the machine tool industry, agricultural machine industry or wind turbine industry to prove the practicability of the approach The results of this project will enable to control and optimize the sustainability of PSS Acknowledgement This research was funded by the German research foundation (DFG) within the IRTG 2057 “Physical Modeling for Virtual Manufacturing Systems and Processes” References [1] Lee S, Geum Y, Lee S, Park Y Evaluating new concepts of PSS based on the customer value: Application of ANP and niche theory Expert Systems with Applications; 2015; 42: 4556-66 G 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Hereto, the primary energy demand, all energy carriers that are found in nature, will be calculated for the entire life time of the investigated product CED is the sum of the cumulative energy demands... CED of products and services [VDI4600] For the calculation of CED the sum of cumulative energy consumption (KEV) and the cumulative non -energy demand (KNA) are necessary The KEV includes all the. .. approach for a systematic reduction of CED of PSS Approach for reducing the CED of PSS FBK/016_014 Figure 3: Overview of the approach to analyse and reduce the Cumulative Energy Demand of Product-Service