Simplified life cycle approach: GHG variability assessment for onshore wind electricity based on Monte-Carlo simulations

International audienceThe environmental impacts of electricity production systems have been widely assessed over the past years with many published LCAs in the literature. In the special case of greenhouses gases (GHG) from wind power electricity, the LCA results variability observed is very high, for example ranging from 2 to 81 g CO2eq/kWh in a literature review performed by the IPCC in 2011. Such result might lead policy makers to consider LCA as an inconclusive method. For environmental impacts from electricity generation this is a senstivive issue. There is a need for a more comprehensive approach to assess the GHG variability so as to define generic results which meet a general consensus. Different attempts have been initiated in order to address this problematic, the use of meta-analyses in LCA being one of them. The main objective of this paper is to build a representative model of onshore wind turbines (WT) to assess environmental performances with a simplified life cycle approach. A first methodology to generate simplified models for WT environmental performances has been designed (reported in the special issue of the Journal of Industrial Ecology) and is now improved with a better identification of the GHG variability assessment. Variability of GHG performances of onshore wind turbines, generated for a representative sample, is assessed through the running of Monte-Carlo simulations to identify the key parameters having the biggest influence on the results. Based on these Monte-Carlo simulations, we plotted GHG performances distributions for two key identified parameters: the WT life time and the annual average wind speed. A set of generic GHG performances curves has been defined as a function of these key parameters. Results are ranging from 2.7 to 119.7g CO2eq/kWh, a range which is comparable to the mentionned IPCC litterature review. These results can be adjusted as a function of either one or both key parameters. This methodology will be applied later for all types of electricity generation systems to generate simplifed life cycle approaches

Global Sensitivity Analysis: a tool to analyse LCA variability of energy systems

International audiencePolicy makers are nowadays debating about the future electricity mixes that should be deployed. The environmental impacts of electricity generation systems is one of the central issue for this debate. They have been widely assessed over the past decades, in particular with the LCA approach. Several literature reviews have shown the large variability associated with these results. It leads sometimes policy makers to consider LCA as an inconclusive method. Improving the understanding of the LCA results variability origins is a key issue to extend the use of LCA as a decision support tool. One approach to adress variability are sensitivity analysis (SA). However, when dealing with environmental impact assessment, most SAs remain at a local level or evaluate the variation of the input parameters one factor at a time. These approaches only partially reflect the LCA results variability, indeed, it does not consider the full range of input parameters interval and their probability distribution. To overcome these limitations, Global Sensitivity Analysis (GSA) approach has been developped in statistics. It enables apportioning the results variability of a model to its different input parameter variability, by varying all of them simultaneously according to their probability distributions. This link between result variability and parameter variability is quantitatively evaluated by the calculation of the so called Sobol indices. While it has been applied in only a few analyses in the field of environmental impact assessment, this statistical tool is yet to be embedded in LCA methodology. Thereby, this paper aims at proposing a method to implement GSA in the LCA field to adress the results variability issue related to energy pathways

Assessing the prospective environmental impacts of photovoltaic systems based on a simplified LCA model

International audienceThe increasing electricity demand and the limited fossil energy resources require the development of new energy policies, based on more environment-friendly electricity-production technologies. The use of photovoltaic (PV) systems has been increasing a lot these last years, and this growth will probably continue. Although the environmental impacts of PV systems are small during their operating phase, they are more significant during their fabrication and recycling phases. These impacts must thus be assessed over the complete life time using life cycle analysis (LCA). However, LCA requires the collection of a large amount of data and is thus time-consuming. Besides, LCA results found in the literature corresponding to the photovoltaic energy pathway show a large variability, reflecting the heterogeneity of systems and their modeling within this energy pathway. An analysis based on 57 estimates found in 23 peer-reviewed studies revealed that the environmental performances related to climate change (defined by the ratio of the impacts related to climate change and the electricity production over the life cycle) range between 1 to 218 gCO2eq/kW

A typology for world electricity mix: Application for inventories in Consequential LCA (CLCA)

Over the past two decades, the integration of environmental concerns into decision making has been gaining prominence both at national and global levels. Sustainable development now factors into policy design as well as industrial technological choices. For this purpose, Life Cycle Assessment (LCA)–which evaluates environmental impacts of products, processes and services through their complete life cycle–is considered a crucial tool to support the integration of environmental sustainability into decision making. In particular, Consequential LCA (CLCA) has emerged as an approach to assess consequences of change, considering both direct and indirect impacts of changes. Currently, no long-term datasets of Consequential Life Cycle Inventories (CLCI) are available, particularly in the case of electricity production mixes. A first and fundamental step to begin filling this gap is to make available data on national level greenhouse gas emissions from electricity and create a typology of electricity production mixes to support policy making. The proposed typology is based on the analysis of the composition of electricity production mixes of 91 countries producing more than 10 TWh in 2012, on the one hand, and of their calculated greenhouse gas (GHG) emissions (in gCO2eq/kWh) from LCA using IPCC 2013 data, on the other hand. All types of primary energy resources are considered, and some are grouped according to similarities in their emissions intensities. Using graphical observations of these two characteristics and a boundary definition, we create a 4-group typology for GHG emissions per kWh, i.e., very low (0–37 gCO2eq/kWh), low (37–300 gCO2eq/kWh), mean (300–600 gCO2eq/kWh) and high (>600 gCO2eq/kWh). The typology is based on the general characteristics of the electric power generation fleet, corresponding respectively to power systems heavy on hydraulic and/or nuclear power with the remainder of the fleet dominated by renewables; hydraulic and/or nuclear power combined with a diversified mix; gas with a diversified mix; coal, oil and predominantly fossils. This typology describes the general tendencies of the electricity mix and, over time, it can help point to ways in which countries can transition between groups. Further steps should be devoted to the development of indicators taking into account grid interconnection, energy sector resilience in the quest for a mix optimum

FROM DETAILED LCA TO SIMPLIFIED MODEL: AN ORIENTED DECISION MAKERS APPROACH TO ASSESS ENERGY PATHWAYS

Literature reviews of energy pathways have shown a large variability of the environmental impacts over their systems. This leads decision/policy makers to sometimes consider LCA as inconclusive. We developed a methodology to assess environmental impacts of energy pathways through a simplified model: a parametric model elaborated with key parameters explaining most of the pathway variability. It is derived from the definition of a reference model enabling to calculate environmental impacts of a large sample of representative systems of energy pathways. Identification of key parameters is done using Global Sensitivity Analysis and Sobol indices. Illustration of such approach is done by defining a simplified model for assessing the GHG performance of photovoltaic electricity produced with Cadmium Telluride modules in France

Investigation of LCA simplification approach: the wind power electricity case

Abstract book: http://milano.setac.eu/milano/scientific_programme/downloads/?contentid=429International audienceScientific publications related to the electricity generation systems from Life Cycle Assessment (LCA) show great variability in their results and conclusions. Thus it leads policy makers to consider LCA somehow as an inconclusive method. Moreover, LCA is usually considered in the industry sector as time and energy consuming. This study concerns the onshore wind power electricity greenhouse gases (GHG) performances. It aims at developing a correlation facilitating access to these performances as a function of key parameters. A thorough LCA literature survey and analysis of the ecoinvent 2.1 wind turbine (WT) LCAs have highlighted the importance of a limited numbers of parameters. These, have been classified into 3 categories: technical (related to the intrinsic WTs characteristics such as weights or power curve), geographical (related to the wind conditions on the implantation site) and methodological (the lifetime defined arbitrarily). A 17 WTs sample has been selected (from 800kW to 4.5MW) which is assumed to be representative of wind turbines installed since 2003, and forecasted for the near future. The WT are characterized by their component weights, tower heights and their power curves. The WTs inventories have been built considering the main assumptions highlighted by the literature survey and the ecoinvent inventory assessment. For instance, we kept the same lifetime for both the moving and fixed part . We did not consider the end of life because this is too systems specific (regarding the possible scenarios).Then the electricity production for the WTs has been calculated according to their power curve and the mean wind speed. The correlation relating GHG impacts per kWh produced by each turbine to the key parameters has then been defined across the whole sample. A confidence interval (based on the relative standard deviation) has been found out to vary according to wind speed. For a 20 years WT lifetime, the GHG performances vary from 6.8 g CO2 eq/kWh ― 10.6% (vwind= 9 m/s) to 38.3 g CO2 eq/kWh ± 14.8% (vwind=4m/s). For average wind condition in Europe (6 m/s) the correlation results (13g CO2eq/kWh ±12.2%) are in accordance with the literature average results (13.5 g CO2 eq/kWh). Moreover, varying the life time of WTs from 10 to 30 years have induced a high variability of GHG performances from 8.7 to 26.1 gCO2eq/kWh ± 12.2% (for vwind= 6 m/s), GHG performances of WTs are therefore found to be very sensitive to this methodological parameter

Contribution of Life Cycle Assessment for the objective of carbon neutrality: Bibliographic review

The Paris Agreement adopted in 2015 (UNFCCC, United Nations Framework Convention on Climate Change, 2015) set the objective of containing the rise in the average temperature of the planet well below 2°C, ideally at 1.5°C, compared to pre-industrial levels. According to the Intergovernmental Panel on Climate Change (IPCC, 2018), this requires achieving carbon neutrality by 2050. This objective has become a major issue and has led to the development of multiple scenarios, responding to specific questions from different sectors (ADEME, 2021; Ministère de la Transition Ecologique, 2020; négaWatt, 2021; RTE, 2021) and supporting various strategies at the international, national and even regional level. France, as a signatory of the Paris Agreement, has thus developed a trajectory, described in the National Low Carbon Strategy (SNBC) (Ministère de la Transition Ecologique, 2020) to achieve carbon neutrality by 2050. However, this issue raises many methodological questions on quantification metrics. Furthermore, Life Cycle Assessment (LCA) is a recognized method for the environmental assessment of products and services, taking into account the entire life cycle. Carbon neutrality strategies would benefit from being enriched by the LCA method, on two counts: in order to extend the carbon dimension to a broader, multi-criteria environmental dimension, and in order to take into account the entire life cycle rather than just emissions from the territory. Nevertheless, the question of the feasibility of translating carbon neutrality scenarios into LCA modeling arises. This article reviews the literature on this subject. Research has highlighted the growing interest in these two subjects for several years, while revealing an ill-defined semantic around carbon neutrality: the term is mainly used to contextualize decarbonization projects. Thus, no article dealing with the carbon neutrality of France assessed by an LCA study has been identified. A test case would make it possible to understand the feasibility of such an approach: the scenario of the SNBC (Ministère de la Transition Ecologique, 2020) seems to be a relevant support for such an exercise

Methodology for multi-criteria analysis of urban mobility focused on trip motivations

International audienceEnvironmental Impacts of Commuter Trips using Motivation Perspective - a case study of Global Warming Impact in Saint-Etienne

Adapting life cycle assessment for multi-criteria analysis of a complex system: case study of urban mobility

http://berlin.setac.eu/embed/Berlin/Abstractbook1_Part2.pdfInternational audienceUrban mobility is identified as one of the most CO2 emitters in France: transport represents 34% of CO2 emissions in France in 2006 (ADEME 2006), including 25% of urban trip emissions. Some previous studies compare transport modes (Finkbeiner & Al. 2006), or assess CO2 emissions that are related to urban mobility on a real case (INSEE 2011). But literature is lacking about multi-criteria analysis of urban mobility in the general case. In particular, Life Cycle Assessment has not been largely used to qualify urban mobility impacts despite its possibility to evaluate the environmental impact (ISO14040, 2006). Nevertheless, the complexity of the system "urban mobility"is a first difficulty to the evaluation, especially concerning the definition of goal and scope. The main topic of this poster is to find out a way to complete and adapt LCA in order to enable the evaluation of a complex system under the case study of urban mobility. We propose an approach based on the System Analysis Design Technique (SADT) that allows a clear and complete definition of the "urban mobility"system. Then the possibility to include more societal indicators beyond the environmental ones (such as noise, satisfaction of consumers, time travel, costs etc) will be studied. The final aim is to provide a configurable dynamic system to evaluate different scenarios of urban mobility. The first results consist of a complete definition of the system that is based on a segmentation of urban mobility into sub-systems that constitute the "goal and objectives"step in LCA. This decomposition prepares to the next step of LCA, in which modal splits will be aggregated with elementary assessments of modes to obtain a multi-criteria analysis for several scenarios

Global warming impact assessment of urban mobility using motivation trip perspective - a case study of Saint-Etienne, France

International audienceThe anthropogenic origin of environmental impacts has become an increasing subject of interest during the last decades. Especially, the impacts of the transportation sector on Climate Change has been widely demonstrated and studied. Numerous methodologies have been proposed to calculate Greenhouse Gas emissions due to goods and passenger trips. This paper aims at proposing a methodology taken into account both the idea of trip motivation and indirect emissions of transportation. It proposes a case study: the trips of Saint-Etienne Metropole inhabitants during the week. If the results tend to confirm the major contribution of car in total GHG emissions, it also gives prominence to the disparities that occur when travelling one kilometre for one or another reason. These differences can originate from parameters that can vary in function of the motivation (such as the occupancy rates of transport modes) or from modal splits that also are peculiar to it