Introducing ergonomics requirements in the eco-design of energy-related products from users’ behaviour approach

Abstract Ergonomics has been a very important activity in the design process. However, ergonomics rarely includes the environmental requirements into the design of products. The article proposes and presents the Eco-Ergo model through its application to a real-world product, a washing machine, to allow designers and ergonomists to establish product design requirements in order to minimise environmental impacts related to user–product interaction during the use stage. This model uses a visual language of representation, Blueprinting-based, that helps designers explore problems they have not previously considered during the market research when a wide variety of products with different interaction elements is analysed. The application of this model allows direct efforts and attention on the user analysis phase in the most influential user’s actions on the environmental performance of energy-related products during use, establishing ergonomics requirements related to users behaviour at the initial design phase. Practitioner summary: This study provides a proposal to incorporate ergonomics into the practice of eco-design through the use of human factors in the establishment of initial eco-design requirements. This blueprint-based model combines an empirical and theoretical approach, based on the product test developed by designers, ergonomists and environmentalists. Abbreviations: CO2: carbon dioxide; DBIM: design behaviour intervention model; DfSB: design for sustainable behaviour; DwI Method: design with intent method; LCA: life cycle assessment; LCD: liquid cristal display; MJ: megajoule; MTM: methods-time measurement; PSS: product-service system; RPM: revolutions per minute


Introduction
The design process integrates several dimensions, including the technical, human, organisational, social and economic. The main challenge of this activity is to achieve all these tasks in terms of quality, performance, cost, and deadlines. Ergonomics has always been an important activity in the design process, ensuring that the specificity of the human factor is incorporated into the design approach. Based on knowledge, methods and tools; ergonomists advise the designer on who the user is, in order to design products adapted to user needs and help the designer assess the consequences of the design choices made in terms of safety, health, comfort and efficiency (Chapanis 1995;Sagot, Gouin, and Gomes 2003).
The integration of the environmental dimension in the design of products is managed by eco-design. This methodology aims to integrate the environmental aspects into the design process in order to improve the environmental performance of the entire lifecycle of a product (EU Directive on Eco-design) (European Council 2009).
Traditional eco-design has a strong focus on the supply side and efforts have focused on minimizing environmental impact on intrinsic characteristics of the product, like weight and mechanical strength, through technology and its efficiency. But for energy-related products, there is another important aspect to be considered at use stage: how users make use of the product (Norman 1988). This type of products may strongly influence the environmental impact and designers can try to influence this behaviour through the products they design (Wever, van Kuijk, and Boks 2008;Hebrok and Boks 2017).
In this regard, the definition of sustainable development and human factors has been slightly complicated by a minor proliferation of similar terms (Radjiyev et al. 2015). The term "eco-ergonomics" (Hanson 2010;Hedge 2008) has also been used, appearing as early as 1998 (Charytonowicz 1998), to take into account the needs of the Wordcount: 5,482 words natural environment with which humans interact. Thatcher (2012;2013), and Thatcher and Groves (2008) used the related term Green ergonomics, highlighting the design of low resource systems and products, the design of green jobs and achieving systemic behaviour change, as areas where ergonomics could contribute to conserving and restoring nature and allowing humans to benefit. Moreover, Ergoecology is a scientific and technological discipline that integrates the evaluation and intervention processes used by ergonomics and environmental management systems to establish, analyze, reduce, prevent, control and rectify the impacts derived from the relationship between humans and the environment (Saravia-Pinilla, Daza-Beltrán, and García-Acosta 2016; García-Acosta, Saravia Pinilla, and Riba I Romeva 2012).
However, the role of ergonomics in sustainability, sustainable development and sustainable design is still seldom reported or considered (Martin, Legg, and Brown 2013;Radjiyev et al. 2015), despite a call for research into ways to get people to modify their behaviour to be more ecologically conserving (Thatcher 2012). Moreover, improvements in the efficiency of products and services in the use of energy and resources could make the change towards a more sustainable behaviour much easier (Tosi 2012).
From a product design approach, Design for Sustainable Behaviour DfSB (Pettersen and Boks 2009) is an emerging research field that opens the analysis on how design can influence users' habits to reduce these environmental impacts (De Medeiros, Da Rocha, and Ribeiro 2018). DfSB is part of product design field, foregrounding how products and their communication interfaces can give users immediate and direct answers to user operations: how they are perceived, learnt or used. From a theoretical approach various theories have been developed, but few authors have materialized them into holistic models or tools to apply on environmentally sustainable innovation Wordcount: 5,482 words practices (Baldassarre et al. 2017). Tang and Bhamra (2012) proposed the DBIM (Design Behaviour Intervention Model), which links these design strategies with sociopsychological theories and models of behaviour, identifying innovative points that allow the design to influence individual behaviour and habits through elements of behavioural change related by the intention, user habits and user control through the own product.
In this regard, the Design for Circular Behaviour model (Wastling, Charnley, and Moreno 2018) offers designers a structured way to think the main behavioural targets to consider when designing product or business solutions for a circular economy.
From an empirical approach, some authors conducted various experiments with real users, following User-Centered Design methodologies (Maguire 2001), obtaining specific conclusions about user behaviour for tested products. Elias, Dekoninck and Culley (2008;2009a) proposed the User-efficient Design and Lockton, Harrison and Stanton (2010) proposed the DwI Method (Design with Intent Method). The former quantifies the energy efficiencies of product use, from the energy required to deliver the desired function to the amount of energy wasted through careless actions. The latter aims to address the lack of guides applicable by designers working on existing user behaviour problems, suggesting relevant design techniques for influencing types of behaviour, and providing examples of how similar problems have been tackled elsewhere. These models and its strategies are applied within design processes following a user-centred methodology, including: full user analysis, user observation in the environment, establishment of requirements, design, prototyping and testing.
Ergonomics and User Centered Design is essentially the study and application of ergonomics principles throughout the process of design to make it user friendly, safe and cost effective with a view to get optimal human performance (Vredenburg et al. 2002). The ergonomics of analysing the interactions between the user and the product is Wordcount: 5,482 words cognitive ergonomics; discipline that develops specifications of user behaviour with respect to the interface, broadly defined such that interactions produce desired performance. The contribution of cognitive ergonomics is to develop the specification of the knowledge which determines user behaviour (Long and Whitefield 1998). It is important to note that ergonomics have great potentialities in the utilization of valuable human resources and in the identification of scope for further improvements on the existing designs or need for developing new designs for creating better tools, equipment, workspace and work methods to reduce job related injuries, illnesses, and stresses, and to increase job satisfaction, which leads to improve productivity (Stanton, Young, and Harvey 2014). Therefore this is where ergonomics can play a key role in user-product interaction and efficiency in the use of the products (Martin, Legg, and Brown 2013).
The ergonomic approach should start at the initial design phases with a needs analysis and the establishment of design requirements, and be applied throughout the design process. The phase of the product conceptualization is very important due to the high number of characteristics of the product that are defined at this stage, for example over 80% of environmental impacts of a product are determined during the design phase (Umweltbundesamt 2005). Therefore, it is necessary to include in the initial design requirements the user-product interaction approach for a more sustainable product use. This paper introduces a new model to introduce ergonomics requirements in the eco-design of energy-related products. The organization of the paper is as follows: First, the "Motivation and scope" describe the model objectives and the potential fields of application. Subsequently, the "Material and Method" section presents the model background and the process of model design, introducing the previous information required to build it. Then, this model is applied to a real product to understand better the Wordcount: 5,482 words advantages of using this model. And finally, a comparison between this model with other models are presented and discussed.

Objectives
The article aims to propose a model for allowing designers and ergonomists to establish product design requirements for minimising environmental impacts related to userproduct interaction during the use stage, by incorporating ergonomics requirements related to the user behaviour at the initial design phase. The Eco-Ergo model aims to complement the disciplines of ergonomics and eco-design.
The aim of the model is to display the using process of energy-related products and the interrelationships between elements of the process, as well as the inputs and outputs they generate in the system. Thereby areas of environmental improvement in the process can be identified and design requirements relating to sustainable user behaviour can be introduced in future product design.

Scope of application
This model has been developed primarily in response to the need of minimising the environmental impact of energy-related products derived from the user behaviour, incorporating ergonomics requirements in the early stages of the product design process. The Eco-Ergo model represents the using sequence of a product from three different approaches: (1) User-product interaction, what the user-product interaction is like, Wordcount: 5,482 words (2) User behaviour, what freedom of behaviour exists between user and product, and (3) Environmental sustainability, how foregoing results turn in environmental impacts through inputs and outputs of system.
Initially, the scope of this study is focused on household appliances (white goods) because of being products whose use stage concentrates most of environmental impacts. Moreover they are products that are part of the standard consumer's daily routine and in which those habits of use are already set.

Eco-Ergo model background
Several studies about the efficient user behaviour in the use of household appliances have been already published: fridge and freezers (Tang and Bhamra 2012;Bhamra, Lilley, and Tang 2011;Elias, Dekoninck, and Culley 2009a; Culley 2009b) electric cookers (Oliveira, Mitchell, and Badni 2012) and kettles (Elias, Dekoninck, and Culley 2009b). Moreover, the context of application has been recently extended to more complex systems, in which is part of a system of systems (Thatcher et al. 2018;Thatcher and Yeow 2016), such as buildings (Attaianese 2016;Kalantzis, Thatcher, and Sheridan 2016) or hybrid electric vehicles (Franke et al. 2016), among others.
Focusing on the development of the Eco-Ergo model, a user-centered approach was followed to identify and analyse each product and user's action. To represent adequately and clearly the process of use, the Eco-Ergo model is based on a service design model, blueprinting. Blueprinting was initially introduced by Shostack (1982;1984) and Wordcount: 5,482 words developed further by Kingman-Brundage (1989;1993) and Kingman-Brundage, George, and Bowen (1995). This model uses a visual language of interaction based on molecular modelling, in which atoms or entities are connected in a unique molecular.
The representation of interaction processes between user and product or service, apart from facilitating the display of all elements that it comprises, helps analyse how they relate to each other.
First versions of the Blueprinting identified the relation between the activities and the standard execution times (Shostack 1984)  [ Figure 1 near here] At first Shostack (1984) and Kingman-Brundage (1989) distinguished only front office and back office areas (the part that a user sees and that which is hidden to them) and the line of sight between them. Later, with the development of the model by other authors, it was extended by adding other areas and lines of separation (Fließ and Kleinaltenkamp 2004). Moreover, blueprinting has been continuously expanding to include different issues (Bitner, Ostrom, and Morgan 2008) such as organizational structure (Biege, Lay, and Buschak 2012), physical and virtual evidences (Morelli 2002;Patrício et al. 2008), customer experience (Stickdorn and Schneider 2011;Bitner, Ostrom, and Morgan 2008;Polaine, Løvlie, and Reason 2013;Berry, Carbone, and Haeckel 2002), or product behaviour (Hara et al. 2009 From an environmental approach, there is not a widespread number of studies that uses this model to introduced or analyse product or services environmentally. But Blueprinting is already considered as an adequate tool to describe a service in the same way as a product with the help of a process tree, can be a suitable tool to obtain insight in the visible and invisible elements of a service, such as environmental impacts (Brezet et al. 2001;Costa et al. 2015). Moreover, Geum and Park (2011) proposed a more advanced blueprinting model to illustrate PSS effectively, introducing new areas and symbols. This model is used to visualise in an integrated way the PSS, representing all interrelation between manufacturer-user, product-service. However, the model does not allow the evaluation of either a qualitative or a quantitative service from an environmental point of view.
The representation of the blueprinting model provides a methodology to analyse processes based on the integrated elements and their interrelationships, seeking efficiency of the process itself. It is considered that Blueprinting model is suitable for sustainable design methodologies because the environmental impact that is generated when using a product is invisible to the user, as in the case of services with all activity remaining at back office. Therefore, the use of this visual language that relates each process with its consequences can be used to subsequently analyse of strategies and actions to implement environmental improvement in the new product. Wordcount: 5,482 words

Design of the Eco-Ergo model
A team of experts in product design, eco-design and environment develops the Eco-Ergo model in a co-design process between them. The process has actively engaged researchers and users during iterated group dynamics when Eco-Ergo model was beginning of the process, process preparation, process execution, post-processing and end of process. All the user actions will be placed in the first row and linked to an userproduct interaction in the interaction area and/or to an action of the product in the product area.  The degree of the environmental impact depends the total environmental impact of the using process, and each environmental impact has more or less contribution in total. Wordcount: 5,482 words

Fifth step: Identification of the improvements areas
Once the using process of product is represented into the Eco-Ergo model, the most significant environmental impacts will be identified, and the upstream of these impacts will be analysed. Therefore, it can know how these inputs have been incorporated in the process and who has the control of that action.

Sixth Step: Requirements proposal for a sustainable user-product interaction
Since then, the valuation of the most impacting interaction steps will results in new design requirements to reduce the environmental impacts. The requirements should incorporate measures of behaviour intervention and product design to increase the efficiency of the use of product.

Case study: The washing machine
The model is introduced being applied in a real product to facilitate the understanding of the model. The product chosen is a washing machine, a conventional product that exists in the majority of homes, and that an average user can use and understand how it works. The specific model selected as case study is already on the market and is the top selling in the washing machine sector. Moreover, this product had been also selected due to having the most efficient energy label, A+++. The selected washing machine is the model Bosch WAY28740EE (Robert Bosch 2013), world leader in the production of appliances. Wordcount: 5,482 words In order to establish the standard process of use in the case of the washing machine, the authors carried out the washing process following the user manual published by the company in order to follow the ideal using sequence.
The interaction panel is on the product front with the scheme presented in Figure   3. The interface is divided in two parts, the rotary selector to select the specific programs and the screen with the buttons to set program and options. By default the product selects a basic washing program for cotton with a medium soil with the following parameters: 60 °C, 1400 RPM (Revolutions per minute) and 2:31 hours. From the point of view of environmental sustainability, the product has two additional options: energy saving (Eco) and another shorter wash for partial loads (speed). The user is who has the final decision of selecting them.
[ Figure 3 near here] The detergent and the softener are introduced in two separate compartments for different stages of washing with specific symbols (Figure 4). The product suggests on the display the quantity of detergent necessary for the amount of clothes to wash.
[ Figure 4 near here] In relation to the consumption of energy, water and resources (detergent and softener in this case) during the washing process, the product datasheet points the following data for a cotton wash program at a temperature of 60°C (the default program). The energy consumption at full load (8 kg of clothes) is 0.75 kWh. Water consumption in this program is 45.4 liters of water and 88 milliliter of detergent per wash. Wherein the total washing time is of 2 hours and 31 minutes. Based on this inventory of energy and resources consumption, the environmental impacts will be assessed. Wordcount: 5,482 words

Application of the Eco-Ergo model
The washing process by default is the selected one to present the Eco-Ergo model. This process is explained in the user manual step by step and the resources and energy consumption is also declared. Moreover, the additional options are also taken into account, because they can be selected in addition to the default washing process.
Following the steps described in section 3.2, the Eco-Ergo model is applied for the case study ( Figure 5).

First step: Actions of user
First of all, the washing process is defined using the user manual and with a real washing machine all steps are identified and placed in the first row in chronological order. In this case, the washing process follows the usual as it can be noted in Figure 5.

Second step: Interaction related to the user action
The washing machine includes a great variety of elements of interaction, especially drives that alert the user to the correct or incorrect execution of an action or an action is over. Moreover, there are also the typical elements such as buttons, rotary and symbols, in addition to a LCD screen where the information about the washing process and different elements of behaviour intervention is showed. Once all these elements are identified, each user's action is connected with an arrow with its corresponding elements of interaction and, if any, with its elements of behaviour interaction.

Third step: Actions of product
The actions of products respond to users actions and/or their interactions; so each action Wordcount: 5,482 words of product is connected to an user's action. In this case all the product's actions are directly driven after the user executes the corresponding action. Unless in this case, after a product's action the product executes another action and, if applicable, the user is notified. For example, when the washing machine is inactive during a period of time or the washing process is finished. Moreover, the unique conditional action is the properly closure of the door, if not the process cannot start. Regarding the inputs of energy, water and chemicals required by the washing machine, as commented before, the user's manual specify them. So an inventory of inputs is possible to establish, with which to environmentally assess and obtain the corresponding outputs.

Fourth step: Environmental impact analysis
The contribution of each output is expressed from a relative manner with respect of the total impacts: using the nomenclature high (more than 50% total impacts), medium (between 25 and 50%) and low (less than 25%). The impact categories used are Global Warming Potential (kg CO2 -eq) and Cumulative Energy Demand (MJ).

Fifth step: Identification of the improvement areas in using process
Once the using process of the washing machine is represented on the Eco-Ergo model, it has been identified two "ways" or improvement areas on which incorporate eco-design requirement related to a more sustainable user-product interaction ( Figure 6).
[ Figure 6 near here] The first improvement area (A) is related to the impacts of emissions from the energy use during the washing process. This process is connected with the action of the washing program selection, and indeed with the user action. This choice determines the temperature, the washing time and the amount of water to be heated for example. The interaction between user and product is performed through various interactive elements: Wordcount: 5,482 words LCD display screen, a series of buttons for specific options on the contour of the screen and a knob with default programs. Washing programs are determined by three parameters: temperature, RPM of centrifugation and time. To select a different, the washing machine has a rotary knob with some positions marked that adjusts 3 data directly but it can also be modified each one individually. From the point of view of environmental sustainability, the product suggests two additional options, more sustainable, to the user: eco (energy saving) and speed (shorter wash for partial loads).
These features use an intervention strategy in guiding user behaviour for sustainable behaviour, but the user is who has the final decision selecting them.
The second improvement area (B) is about the impacts of wastewater generated during the washing process. This way is related to the action of the detergent and softener addition in the wash and rinse water. In this process, the information provided by the product, suggests an amount of detergent: a portion or percentage of detergent in relation to the total capacity of the drum. The device indicates this on the screen in function of the load of clothes introduced in the drum. The recommended amount of detergent is shown in the display, and works as a feedback strategy, giving all the freedom of behaviour to the user. In this way the product is intended to guide the user to a more sustainable behaviour.

Sixth step: Requirements proposal for a sustainable user-product interaction in washing machines
The selection of the washing program by the user action is where most impacts are concentrated. Accordingly several opportunities for improvement were identified: (1) Excess of washing programs and selectable options by user: pre-set programs are very specific and unusual, and additional options (eco washing) should be Wordcount: 5,482 words integrated into other programs but marketing reasons may be the cause of adding extra functions to communicate environmental sustainability. Recently, new models of washing machines control themselves the loading of laundry, having in this case a weight sensor installed.
(2) Subjectivity in the interpretation of washing parameters: the replacement of the current washing parameters (temperature, RPM of centrifugation and time) by more comprehensible ones by the user, such as the type of tissue or the dirt level. These parameters are complex for the users, and they not have the information about the necessary RPM or the water temperature to clean properly an item of clothing depending on its dirt level.
(3) Lack of control in detergent dosing: the goal of users is to get clothes completely clean, so they prefer to increase the amount of detergent in the washing process in order to ensure this goal. The capacity of the dosing drawer is well above the amount needed. It should transform the recommendation given by the product into an adjustment by the product itself. Recently, new models of washing machines dose themselves the quantity needed in function of the type and the amount of clothes, meanwhile the user only has to fill the detergent tank and select the type of clothes. This is not necessarily a good measure; maybe users feel that lose control in the process and reject the technology.
The previous improvement opportunities can be set into the following design requirements to set a more sustainable user-product interaction: • Synthesize different washing programs by reducing the number of options to choose.
• Visually rank programs according to regular use. Wordcount: 5,482 words • Using more comprehensible washing parameters to allow user to have some control over the process.
• Establish a measurement system or chemicals substances dosage in device depending on washing factors, taking into account the user's behaviour intervention approach.

Models
The Eco-Ergo model is not intended to replace previous models within the scope of the Design for sustainable behaviour such as Design Behaviour Intervention Model (DBIM) (Tang and Bhamra 2012), Design for Circular Behaviour (Wastling, Charnley, and Moreno 2018), User-efficient Design (Elias, Dekoninck, and Culley 2008;Elias, Dekoninck, and Culley 2009a) and Design with Intent (Lockton, Harrison, and Stanton 2010). These models work from a methodology of user-centred design focused on user behaviour change through design with the aim to be as sustainable as possible. For both models, DBIM and User-efficient Design, the conducted case study is also for a white good: a fridge. DBIM model was centred in general aspects of the use of a fridge, such as the distribution of food regarding the functional aspects of fridge and the cultural and social values that conduct the ordinary consumption behaviour. Tang and Bhamra (2012) proposed a wide variety of design options to change the user behaviour and also highlighted the need of improve the communication of the energy use and efficiency of fridge due to the lack of information about that. On the other hand, the User-efficient Design model was focused in the determination of the fridge's energy losses, the intrinsic losses of product and the user-related losses. This model is more focused in determine the significance of user-related losses as a proportion of total product energy use than in the proposition of design requirements. Meanwhile Design with Intent Wordcount: 5,482 words model provides to designer a range of potentially applicable design patterns and examples, with short explanations, to inspire the generation of concept solutions to the brief. The analysed product has to be adapted to provide examples and perhaps they are not well suitable to the needs. Summarising, these models analyse the sequence of use of products generally from a theoretical approach, rethinking the traditional mode of use. The proposed changes can imply a high investment in the manufacturing of products and can also suppose a risk for the user acceptance. In contrast, the Eco-Ergo model it is less ambitious and is designed for being used in specifics models of a product, more focused in the particular options, programs and operation settings. Eco-Ergo model is intended to be a complement to this type of models at first stages of a product design or redesign process, when the initial design brief is set (Gilbertson 2006;Smith and Wyatt 2006), and the design requirements have to be established. This allows direct efforts and attention on the user analysis phase in parts of the process that represent greater environmental impacts.

Conclusions
A team of experts in product design, eco-design and environmentalists has developed the Eco-Ergo model, in a collaborative process, including group dynamics with others researchers from different areas. This model uses a visual language of representation, Blueprinting, to identify the more influential user's actions on the environmental performance of energy-related products during its use. The main objective of Eco-Ergo is to allow designers and ergonomists to establish product design requirements in order to obtain a more sustainable behaviour of users.
This model has the potential to help designers explore problems they have not previously considered during the market research, when a wide variety of products with Wordcount: 5,482 words different operating modes and interaction elements is analysed. With this regard, the Eco-Ergo model allows to analyse quickly different type of products from user behaviour approach, concluding in the most and least ways of efficient interactions.
This article introduces the model describing step by step the application of the model in a washing machine, identifying some opportunities for improvement during the process of use, such as the excess of washing programs and selectable options by user, the subjectivity in the interpretation of washing parameters and the lack of control in detergent dosing.
In contrast with previous user behaviour intervention models, the Eco-Ergo model can be a complement to other user behaviour intervention models at first stages of a product design or redesign process, being used in specifics models of a product, more focused in the particular options, programs and operation settings Future research can extend the application of the model in other areas of ergonomics and design where human factors has an important role, such as sound design, services design or design innovation. This model can allow to explore new consumption patterns, new concepts of services and products; helping to design more sustainable systems but at the same time taking into account the user behaviour and its implications.