Analysing the Cumulative Energy Demand of Product-service Systems for wind Turbines

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[.]

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

Procedia CIRP 59 ( 2017 ) 214 – 219

ScienceDirect

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 The Authors Published by Elsevier B.V

Peer-review under responsibility of the Programme Committee of the 5th International Conference on Through-life Engineering Services (TESConf 2016)

Keywords: Product-Service Systems; Cumulative Energy Demand; sustainability; wind turbines

1 Introduction

Changed requirements of customers caused a trend from

technology providers to service providers Customers are

interested in complete and sustainable solutions

Product-Service 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-of-the-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

© 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 scientifi c committee of the The 5th International Conference on Through-life Engineering Services (TESConf 2016)

2 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]

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

macro-analysis as well as an energy input-output macro-analysis

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]

Figure 1: PSS life cycle from the perspective of manufacturer and customer [4]

Perspective of

manufacturer

Perspective of

customer

Implementation

End-of-Life Development Production Service

Designing

Procurement

Buy Decision

Planning

FBK/016_012

Because PSS cannot be independently created and delivered by

a single provider, the manufacturer cooperates with the

extended added network [5, 6] The extended

value-added 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

2.3 Relevance of services for wind turbines

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 2 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

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

FBK/016_013

Rotor Blade

Gear

Pitch Generator

Control and General Electronics Yaw System Brakes

Main bearing

Hydraulic System Shafts

Transformer Station

Foundation Tower

Years until a repair or replacement [t]

Critical Components

Noncritical Components

Control and General Electronics

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 do 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 do 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

3 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 Figure 3: Overview of the approach to analyse and reduce the Cumulative Energy Demand of Product-Service Systems [Based on 16]

CED of PSS

CED for production of wind turbine CED for providing resources for

the service realisation

PSS provider Customer

CED of wind turbine in usage and service realisation process

CED of End-of-life processes

FBK/016_015

Analysis of PSS-specific

requirements

Defining PSS-specific functional

unit and system boundaries

Analysis of dependencies and

impacts of PSS changes on the

CED

Identification of measures for

reducing the CED of PSS

• 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

• 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

• Identification of CED-relevant PSS changes based on the control lever

• Classification of CED-relevant PSS changes

• Determining the cause-effect relationship

• Analysis of impact mechanism to identify measures

• Evaluation of control lever

• Developing an approach for a systematic reduction of CED of PSS

List of requirements for determining CED of PSS 1

2

3

4

PSS-specific approach for determining CED of PSS

PSS-specific approach for analysing the dependencies of PSS on CED

Approach for reducing the CED of PSS

FBK/016_014

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

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 5 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

4 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”

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