Environmental sustainability of high voltage motors: do better efficiency and repair lead to improved environmental impact?

Various circular economy (CE) strategies, for instance lifetime extension by repair or reuse, have been suggested to improve products’ environmental performance. The literature emphasises the need to better understand the consequences of those CE strategies with assessment tools such as life cycle assessment (LCA). From previous assessments, B\uf6ckin et al. (2020) identifies energy use reduction and use extension by maintenance, repair or remanufacturing as relevant CE strategies for durable and active products. However, this conclusion is based on assessments of small- and medium-size electronic products, leaving out more durable and more energy consuming bigger products. In this study, the implementation of two CE strategies, energy use reduction and use extension by repair, is explored for high voltage (HV) motors delivering 135GWh per year over at least 20 years.Electric motors are prominent active products, representing 50% of the electricity consumption in Europe. Even in small numbers, HV motors represent a significant share of this consumption due to their more intensive use and high output power. Two main HV motor technologies exist: induction motors (IM) and synchronous motors (SM), which are more energy efficient. Both are often used until failure, which frequently occurs in stator windings but could be repaired by rewinding at the expense of a slight decrease in efficiency. This study aims to compare the life-cycle environmental impact of the two motor technologies and to explore their lifetime extension by repair in comparison to their replacement.For each motor technology, a cradle-to-grave LCA is performed for global warming and mineral and metal resource depletion impact categories. The IM has an efficiency of 97.3%, the SM an efficiency of 98.3% and both are run 20 years. Results show that the impact of electricity consumption during use is dominant. Besides, the SM has a lower environmental impact than the IM. In term of resource depletion, SM manufacturing is more impactful but lower energy losses during use compensate for the difference.Repair is modelled with the production of a new stator winding and a decrease in efficiency of 0.7%. Three scenarios are compared. The IM is initially used for 20 years, and an additional 10 years of use is provided by either 1) replacing with an IM with the same efficiency, 2) replacing with the SM, or 3) repair by rewinding. LCA results show that the additional energy losses after repair in scenario 3 offset the gain from avoiding the production of a new motor compared to scenarios 1 and 2.This study shows that the long lifetime and high energy requirements of HV motors lead the energy efficiency to be an essential factor for the life-cycle environmental performance. Choosing and maintaining high energy efficiency is key in this situation, especially for lifetime extension strategies to be beneficial for the product environmental performance.Reference:B\uf6ckin et al. (2020), How product characteristics can guide measures for resource efficiency. Resources, Conservation and Recycling 154, 104582

Is repair of energy using products environmentally beneficial? The case of high voltage electric motors

Repair is advocated as a circular strategy to improve the environmental performance of products. Whether this holds for very long-lived and energy intensive products has not been addressed. This study compares environmental impacts of two high voltage motors of different energy efficiency and assesses their use extension by repair with life cycle assessment (LCA). Due to high energy use, long lifetime and intensive use, the use phase dominates all environmental impacts, even resource depletion. Therefore, a higher energy efficiency is more beneficial than extending the use by repair, and if the energy efficiency is slightly reduced, the repair is not beneficial. Therefore, product requirements and users and manufacturers of such products should ensure designs with high energy efficiency rather than making the product repairable. Finally, the results highlight the importance of including resource use from electricity production and transmission in LCA of the use extension of energy using products

Repair for high-voltage electric motors energy efficiency vs resource use?

Electric motors in the industry represent 69% of the industrial electricity consumption in Europe. Even if few in number, high voltage (HV) motors represent a significant share of this consumption due to their more intensive use and high output power. Two main HV motor technologies exist: induction motors (IM) and synchronous motors (SM), of which the latter are more energy efficient. Improving energy efficiency as well as use extension by maintenance, repair or remanufacturing have been identified as relevant circular economy strategies for improving the environmental performance of such active and durable products. However, the assessments performed focus on small- and medium-size electronic products, leaving out bigger products that are more durable and more energy consuming such as HV motors. Those motors are often used until failure, which frequently occurs in stator windings, and which could be repaired by rewinding at the expense of a slight decrease in efficiency. However, other use extension strategies such as reuse and remanufacturing are hindered by the customization of HV motors to their specific use. Finding an appropriate set-up for a second use is difficult for such motors and it is therefore performed seldom. The aim of this study is to compare the life-cycle environmental impact of lifetime extension by repair for the two motor technologies in comparison to their replacement

Reviewing life cycle assessments of carbon capture and utilisation - unclear goals lead to unclear results

Carbon dioxide capture and utilisation (CCU) is the process of capturing carbon dioxide and using it to produce a product. It is a potential strategy for mitigating greenhouse gas emissions and replacing fossil feedstock in chemical production. Life cycle assessment (LCA) is important to assess the carbon reduction capability and is often used to evaluate the environmental impacts of CCU processes. This study aims to analyse the methodological choices made in life cycle assessments of carbon capture and utilisation systems, and identify and evaluate the logics of the modelling in the studies.LCA studies of CCU processes were found through a systematic search and reviewed regarding LCA methods. The collected articles were coded on different aspects (e.g. goal, system boundaries, impact assessment) and a framework was developed to describe the different scopes the CCU systems are modelled from in the assessments.106 articles were reviewed, published between the years 2002 and 2021. 88 of them evaluate products produced through a CCU route and make a comparison to the existing conventional way.\ua0Thus many aim to do the same kind of assessment, but results from the review show that the scope differs, and the majority do not clearly state their goal with the LCA. There is likely an aim of the study which could include a reason for using LCA, but the goal of the LCA (as in goal and scope definition) is often not found in the article.It was also found that the system boundaries stated in the body of literature are often "cradle-to-gate". The cradle can however be set to different points in the system, and the scope of the studies varies a lot depending on where the cradle starts and what is included in the assessment. In the case of CCU, it is found that the cradle can be at the process the flue gases are captured from (38 cases), the capture process (44) or at the CO2 conversion process (24).\ua0\ua0The justification for not including the whole life cycle of the product (only 19 are to the "grave") can be that the product has the same use and end of life as the product it is compared to, often the conventional alternative. However, only including part of the system in the analysis can give misleading results when the emissions can be presented as negative in the shorter perspective due to the temporary storage of carbon in the product. A longer time perspective and different system boundaries are needed to see if the carbon in the product is emitted or not shortly after leaving the factory gate.Given that CCU processes are often emerging technologies, the purpose and context of the study matter for how the results can be used, but the goal of existing life cycle assessments seldom handles these aspects. The LCA results are often used for comparison with conventional technologies or for comparing the CCU product to an existing product, although not always reflected in the goal. With underdefined goals, different system boundaries and varying methods for accounting, understanding assessments of CCU becomes confusing. This highlights the need for methodological guidelines and clearer goal definitions in life cycle assessments of CCU to ensure meaningful and consistent evaluation of the environmental impacts and potential of these emerging technologies

Prospective study of lignin-based and recycled carbon fibers in composites through meta-analysis of life cycle assessments

Screening the life cycle assessment literature for information and recalculating extracted results was proven useful for identifying environmental challenges and opportunities in new, but related, contexts at early stages of technology development. The method was applied to carbon fiber reinforced polymers, a material of growing importance in industrial applications where a strong and/or light material is needed, such as in aircrafts and road vehicles. Many technology development efforts with the purpose of further improving such composite materials are on-going, in particular regarding the origin of carbon fibers. Using lignin as a bio-based feedstock and various recycling techniques have been suggested. However, these technologies do not yet exist at a scale that would enable a meaningful life cycle inventory, while the need for environmental guidance is urgent in order to ensure that only the more promising development paths are pursued before lock-in occurs. With a specific focus on the shift to lignin as a feedstock for carbon fibers and on recycled carbon fibers in composites, this article not only illustrates the type of information that can be obtained from mining and refining information from earlier life cycle assessment studies, but it also provides direct guidance on environmental opportunities and challenges specific for carbon fiber reinforced polymers. Thereby, it informs both technology development efforts and environmental assessment efforts. Amongst other things, the analysis reveals that an important factor behind the environmental impact of composites is the energy demand in carbonization of the carbon fibers and that both the shift to lignin-based and to recycled carbon fibers can potentially reduce this environmental impact. However, assessments of both lignin (as an output from a multifunctional process) and recycled carbon fibers (as an output from end-of-life activities) are connected to challenges related to the allocation of environmental impacts in an environmental assessment. Extracting and refining information from the literature proved useful for the specific task but remains to be tested in other fields of emerging technologie

Lessons learned when assessing emerging composite materials using life cycle assessment

The modern era of carbon fibres and carbon fibre reinforced polymers (CFRPs) started in the mid 1950s as the U.S. air force Materials Laboratory started producing carbon fibres to develop high strength composites. However, the historically high cost of carbon fibres has until recently kept the use to a small range of applications [1]. It is not until recently that the use of CFRP has become widespread, consequently, CFRP should be considered an emerging material [2]. This makes the environmental assessment difficult as there is a lack of available production data. On the other hand, the emerging nature still makes technology changes possible. This mitchmatch between available data for assessment and production improvements is sometimes referred to as the Collingridge Dilemma. Collingridge described a paradox between information and control: impacts are hard to predict when technology is not yet fully developed, while change becomes more difficult when the technology develops [3].This paper aims to describe a multi-year effort to use life cycle assessment (LCA) for assessing the environmental impacts of emerging composite materials, focused on the specific example of CFRP. We will describe how we started with a meta-analysis to identify hotspots and key aspects for decreasing the environmental impacts of carbon fibres and CFRPs, to more recent efforts looking into possible future multifunctional use of CFRP for both light-weighting and energy storage in electric vehicles. Results focus on key insights and lessons learned in the process of assessing emerging composite materials using LCA as well as recommendations for decreasing the environmental impacts of carbon fibre composites

Assessing efforts to reduce the environmental impacts of carbon fibre composites in vehicles

This presentation will be about the life cycle assessment of different technology development routes for decreasing the environmental impacts of carbon fibre composites in vehicles. Three main routes were assessed: The use of bio-based raw materials for the fibre production, the use of microwave technology in fibre production, and the recycling of the composites and recovery of the fibres after use. The goal was to assess which of these routes that are more promising for making the environmental impacts of carbon fibre composites in vehicles environmentally competitive to glass fibre composites, what aspects that influence this comparison, and what remaining hot spots might be

A procedure for Prospective LCA in Materials Development - The Case of Carbon Fibre Composites

1. IntroductionLife cycle assessment is a powerful tool for quantifying the environmental impacts of products and services and is an essential part of product development. It can, for example, be used to identify hotspots to find ways to keep environmental impacts as small as possible. Assessing a product or service under development requires a prospective approach. A problem in prospective life cycle assessment (pLCA) is, however, the lack of data, which can lead to inconclusive results. The prospective context, however, also implies that there is still room for process changes and improvements [1]. This paper will present a work procedure for pLCA that grew out of a multi-year project aimed at developing lignin-based carbon fibres for composites (see LIBRE [2]). The intention with this contribution is to provide practitioners guidance on how LCAs in early stages of material development can be handled.2. Method:The development ofa work procedure for pLCAWhen starting the LIBRE project, there were no data available for the production of the fibres, and efforts needed to be made to: 1) identify hotspots in the life cycle of carbon fibre composites to show the possible influence of transitioning to a lignin-based fibre, and 2) identify other important routes for decreasing the environmental impact of the composite. This was then done by developing a meta-analysis framework for using results found in available literature on LCAs of carbon fibre reinforced polymers (CFRP) and of lignin production. The results found in the literature were carefully extracted and recalculated to the same functional unit to enable comparisons between studies. The meta-analysis found that a shift to lignin could decrease the environmental impact of carbon fibre composites, but that this is heavily dependent on the allocation approach used to allocate the impacts between co-products at a mill where the lignin is produced. The meta-analysis also identified recycling and recovery of fibres as promising, but that this also is very dependent on how allocation is handled, in this case allocation between life cycles [3].To explore the influence of the allocation approach for lignin production, allocation approaches found in literature were applied to a case study of the climate impact of lignin extracted from a Kraft pulp mill (see Hermansson et al. [4] for details). In addition, two new allocation approaches were developed: 1) considering the impacts from the lignin extraction process in a subdivision style approach, and 2) partitioning the impacts of the system between energy streams and material streams based on mass conversion, followed by either energy allocation (for energy streams) or mass allocation (for material streams). Results showed that the climate impact of the lignin is highly sensitive to the choice of allocation approach. As the intention was to apply the allocation approaches in a pLCA, they were assessed based on sensitivity to changes in demand for lignin, as this is an aspect of this specific system that could change much over time. The outcome was that many allocation approaches are sensitive to the temporal settings of the study, in particular with regard to prices and/or what is considered the main reason for lignin being extracted from the mill.The influence of allocation approaches in recycling of CFRP was also assessed in a case study. Different allocation approaches were redefined to handle the multiple outputs of both polymer and fibre from composite recycling. The redefined allocation approaches were applied to different fictitious recycling systems that employed different recycling methods. Results showed that the outcome of the assessment is highly dependent on the inherent incentives for recycling in the allocation approaches. For example: The cut- off approach provides no incentive to recycle the product, whereas the end-of-life recycling approach and the circular footprint formula (CFF) do. Recommendations were to, if possible, include both the end-of-life recycling approach and the cut-off approach as two extremes in pLCAs, as the result of the case study showed a large sensitivity to quality and demand for recycled carbon fibres. The CFF, which can be seen as a compromise between the two other allocation approaches but that is dependent on information on the supply and demand for secondary material and therefore challenging to apply in a prospective context, can then be avoided [5].When different technology routes and allocation approaches had been identified, the findings were applied in a case study of carbon fibre composites in road vehicles (see Hermansson et al. [6]). The technology routes were assessed both separately and grouped into coherent scenarios, as it is likely that some technology development routes will happen simultaneously [7]. By assessing them separately, the individual routes that are most promising for decreasing the environmental impact of the system could be identified. By assessing them together, it was possible to assess under which overarching conditions in society, for example due to aspects related to legislation or R&D funding, the environmental impact would be reduced the most. The end-result, where carbon fibre composites reduced the vehicles’ environmental impact in almost all futures [6], should be seen as an indication of the possible future environmental impacts of the system under study and can provide guidance to technology development.3. Results,Discussion, and ConclusionsThe work procedure that grew out of the work in the LIBRE project is visualized in Figure 1. The procedure proved useful for tackling the issue of lack of data in early stages of materials development and helped identifying key parameters in both the technical development and in the surrounding world that would have a large influence on the end result.Figure 1: The procedure for prospective life cycle assessment in materials development, which grew out of the context of assessing carbon-fibre compositesKey findings include the usefulness of mining and extracting LCA results from available literature to identify the most important parameters in early stages of materials developments. They also include recommendations on how allocation should be handled for both multi-output processes and recycling systems in pLCAs, also including some new options for multi-output processes. While the procedure was initially used and developed for assessing CFRP, we argue that it is likely applicable to many emerging technologies, especially when the assessment of these face the same types of difficulties in terms of data availability and uncertainties regarding changes to, for example, market demand and prices.4. References[1] Arvidsson, R., et al., Environmental Assessment of Emerging Technologies: Recommendations for Prospective LCA. Journal of Industrial Ecology, 2018. 22(6): p. 1286-1294.[2] LIBRE. LIBRE-Lignin Based Carbon Fibres for Composites. 2016 [cited 2018 9:th of november]; Available from: http://libre2020.eu.[3] Hermansson, F., M. Janssen, and M. Svanstr\uf6m, Prospective study of lignin-based and recycled carbon fibers in composites through meta-analysis of life cycle assessments. Journal of Cleaner Production, 2019. 223: p. 946-956.[4] Hermansson, F., M. Janssen, and M. Svanstr\uf6m, Allocation in life cycle assessment of lignin. The International Journal of Life Cycle Assessment, 2020.[5] Hermansson, F., et al., Allocation in recycling of composites - the case of life cycle assessment of products from carbon fiber composites. The International Journal of Life Cycle Assessment, 2022. 27(3): p. 419-432.[6] Hermansson, F., et al., Can carbon fiber composites have a lower environmental impact than fiberglass? Resources, Conservation and Recycling, 2022. 181: p. 106234.[7] Langkau, S. and M. Erdmann, Environmental impacts of the future supply of rare earths for magnet applications. Journal of Industrial Ecology, 2021. 25(4): p. 1034-1050.Acknowledgement - This project has received funding from the Bio Based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 720707 and Chalmers University of Technology - Energy Area of Advance (ECE profile) Transport Area of Advance

Development and Comparison of Thermodynamic Equilibrium and Kinetic Approaches for Biomass Pyrolysis Modeling

Biomass pyrolysis is considered as a thermochemical conversion system that is performed under oxygen-depleted conditions. A large body of literature exists in which thermodynamic equilibrium (TE) and kinetic approaches have been applied to predict pyrolysis products. However, the reliability, accuracy and predictive power of both modeling approaches is an area of concern. To address these concerns, in this paper, two new simulation models based on the TE and kinetic approaches are developed using Aspen Plus, to analyze the performance of each approach. Subsequently, the results of two models are compared with modeling and experimental results available in the literature. The comparison shows that, on the one hand, the performance of the TE approach is not satisfactory and cannot be used as an effective way for pyrolysis modeling. On the other hand, the results generated by the new model based on the kinetic approach suggests that this approach is suitable for modeling biomass pyrolysis processes. Calculation of the root mean square error (RMS), to quantify the deviation of the model results from the experiment results, confirms that this kinetic model presents superior agreement with experimental data in comparison with other kinetic models in the literature. The acquired RMS for the developed kinetic method in this paper varies within the span of 1.2 to 3.2 depending on temperature (400-600 degrees C) and various feedstocks (pine spruce sawdust, bagasse, wood bark, beech wood and paddy straw)