| With the rapid development of economy and the continuous improvement of people's living standards,the vehicle population in China has shown a trend of dramatic increase,but which also has brought about a series of negative effects inevitably,such as massive consumption of materials and resources,increasing environment pollution,etc.Automobile lightweighting is an important way to relieve the pressure of energy conservation and environmental protection,however,most previous researchers of lightweighting assessment paid their special attention to energy saving and emission reduction in the use stage rather than synthesize each stage in life cycle.Furthermore,lots of previous domestic studies of the automotive products' life cycle assessments were based on abroad data which inevitably lead to a large gap between the conclusions drew from those data and the actual conditions in China.Specific to these aforementioned problems and based on the domestic basic data,in this paper an automotive products lightweighting,life cycle comprehensive benefits assessment model has been set up and the dynamic quantitative evaluation and analysis were conducted,focusing on the impacts on materials,energy consumption,emissions and costs that benefit from automotive products' lightweighting(mainly focused on the material lightweighting).The main contents of the study in this paper include the following aspects:(1)Firstly,a static life cycle assessment model of automotive products were established,by which the materials,energy consumption,emissions and cost(MEPC)could be calculated.Different from most previous life cycle assessments which only pay their special attention to an open-loop process named as "cradle to grave",in this paper a new static assessment model named as "from cradle to regeneration" has been proposed,which is a closed-loop system with a broader boundary,wider scope of application and more universal assessment indexes.Meanwhile,this model includes all the stages from materials acquisition,materials processing,components manufacturing and processing,vehicle assembly,running and using to the final recycling;therefore,it can also be used to assess the performance of one or more indices including materials saving,energy conservation and emission reduction and its economics for automotive products and its lightweighting.(2)According to previously established static assessment model,an empirical study and a following sensitivity analysis were conducted.In the study,manufactured in the same production platform of Haima Motor Corporation,a battery electric vehicle and a traditional gasoline vehicle that belong to the same auto type Premacy were selected.Then,in the light of domestic data,the inventory analysis had been made and then led to a static assessment conclusion of these two vehicles.The results indicated that the battery electric vehicle's life cycle energy consumption was lower than its conventional gasoline counterpart.Besides,in its life cycle,the electric vehicle's emission of CO2,CH4,N2O and NMVOC were lower than conventional gasoline vehicle,while CO,SOx,NOx and PM were higher than the latter.Following the static assessment,a sensitivity analysis on the main parameters of the model has been made,by which the factors relating to the life cycle emissions and energy consumptions were ranked.(3)A life cycle impact assessment on battery electric vehicle and conventional gasoline vehicle has been made.On the basis of static assessment data,the CML2001 model was utilized to make life cycle assessment for these two types of vehicles,and the localization correction to the Abiotic Depletion Potential(ADP)module has already been made before that.Its results showed that the ADP of battery electric vehicle was obviously higher than conventional gasoline vehicle,which is because battery electric vehicle used more copper and lithium which belong to the high scarcity metallic materials.While for the index of Global Warming Potential(GWP),the former performs better than the latter.But as the indices of Health Toxic Potential(HTP),Photochemical Ozone Creation Potential(POCP)and Acid Potential(AP)were concerned,battery electric vehicle was lagging behind.The major reason is that the electric power generated in China is mainly from the thermal power plants(82.6%).Therefore,in order to increase the environmental profits of battery electric vehicle,the next stage of the research should optimize the power structure and improve the emission level of electricity generating.(4)In this paper a new dynamic model of lightweighting comprehensive benefits assessment has been proposed.The highly complexity of automotive products has determined that their effects on resources and environment are involved with many dynamic variables and uncertainty factors,if an assessment is only made from static standpoint,it is hard to avoid isolated and one-sided result,then the referential value would be much lower.In accordance with static assessment model and through the combination of life cycle assessment theory,circulation economic theory,systemic theory and some other theories,the system dynamics software Vensim has been employed to make some dynamic analysis on automotive products lightweighting life cycle MEPC and impact assessment.Through in-depth and systematic studies on automobile material consumption,energy consumption,environmental emission,life cycle cost and the major sensibility factors that result from sensibility analysis,several variables were selected to establish six sub-system flow block diagrams from life cycle perspective,those sub-systems were classified as material mass,material mineral resource consumption,energy consumption,environment emission,cost(including life cycle manufacturing cost,environmental cost and total cost of users)and impact assessment,eventually the mathematical equations of these factors were set up.(5)In addition,based on the static assessment model,the life cycle assessment equations were built up to assess the lightweight effects for these two types of vehicles,which was through substituting steel by aluminum or by magnesium,hence,the multi-objective optimization were conducted.The mess ratio of reduction of steel,increasing of aluminum and magnesium were selected as the variables,while the life cycle energy consumption,GWP and manufacturing cost were pointed as the targets.Through the optimization,the goal of reducing the life cycle energy consumption and GWP without increasing the total cost when reducing 5%of the automobile weight was achieved.(6)Finally,the dynamic analysis was conducted through the material lightweighting for the battery electric vehicle and conventional gasoline vehicle,which selected the lightweight materials such as aluminum alloy,magnesium alloy and some other lightweight materials respectively.The results showed that after the comprehensive influence was taken into account,the material lightweight by substituting steel with aluminum or magnesium on the chosen electrical vehicle led to a declination in most assessment indices,while which on the chosen conventional gasoline vehicle has made some increasing in the life cycle emissions of PM,CO and environmental cost,HTP and so on.In sum,the lightweight effects(such as life cycle energy consumption,emissions,environmental costs,and the total life cycle costs)of the chosen battery electric vehicle were better than conventional gasoline one in most indices with different degree.In addition,this paper has further demonstrated the energy conservation and emission reduction effect that benefit from the recycling.Finally,a preliminary assessment on the lightweighting effect of carbon fiber were explored,which found that the effects of using carbon fiber on life cycle environmental impact,such as single gas emission,environmental cost,GWP,HTP,POCP and AP,would be superior to that of aluminum and magnesium.While as for life cycle energy consumption,the effect of using carbon fiber would be inferior to aluminum and magnesium.The high cost of using carbon fiber leads to the automotive manufacturing cost and life cycle total cost of users increase dramatically.If these problems can be solved appropriately the prospect of using carbon fiber to realize the goal of automotive lightweighting shall be expected.In this dissertation,the static and dynamic life cycle assessment models for automotive products and its lightweighting were established and the following empirical studies were conducted accordingly.The research methods and results can serve as theoretical basis for relative enterprises to set up lightweighting assessment standards,to develop lightweighting automotive products of energy saving and emission reduction,and to provide decision-making reference for the government to make the sustainable development strategy of automobile industry. |
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