| Environmental and ecological problems caused by climate change have attracted great attention.Many countries have issued a series of greenhouse gas（GHG）emission control policies and energy conservation and emission reduction strategies.The consumption of fossil fuels in electricity generation and transportation is the main factor leading to carbon emissions.Therefore,it is essential to evaluate and optimise the carbon emissions of the household electricity consumption system in the context of the widespread promotion of electric vehicles（EVs）.Residential solar photovoltaic（PV）system and the storage system has been promoted to improve the household energy systems.However,due to the complexity of the household energy systems and the limitation of the accuracy of data acquisition,there are little researches on the carbon emission reduction assessment of the PV system and energy storage system in the household energy systems.There is almost no research on carbon emissions evaluation after EVs are popularised in households.Existing researches use the average carbon emission factors（AEFs）of the grid in the database to account for the carbon emissions of household electricity consumption throughout the year,disregarding the impact of electricity trade and power structure.Most researchers use the AEFs of the current electricity grid to evaluate carbon emissions throughout the life cycle,without considering changes in the future power structure.This could lead to considerable errors in life cycle carbon emissions results from the global increase in renewable power generation and the decrease in fossil power generation.In addition,there is little understanding of the potential to reduce emissions from household energy systems using emissions-responsive battery charging,and existing investigations use the AEFs rather than marginal.To understand the overall carbon reduction potential of the household energy system,first of all,this study constructs an electricity network composed of 28 European countries and the model for the marginal emission factors（MEFs）of the electricity grid to evaluate the impact of electricity structure and electricity trade on the grid carbon emissions.What’s more,this work builds a future grid dispatch model based on the requirements of the future electricity structure of the UK grid.This model is then coupled with the MEFs module to calculate the future MEFs and provide data support for life cycle carbon emissions assessment.Finally,the research takes the typical semi-detached houses in the UK as the research object for discussion based on the calculated MEFs and life cycle assessment methods.The work considers the emission reduction optimisation strategies of the household electricity system under carbon constraints from three perspectives:the household electricity system when only considers the electricity consumption of appliances,household EV charging and the complete household electricity consumption system including EV charging.The results show that the carbon emissions of most European countries have more than a 7%error when only considering the generation emissions compared to the network-wide emissions,which lead to more than a 10%error in the MEFs calculation.When direct transfer emissions and generation emissions are considered,a 1%error occurs in most European countries’ carbon emissions accounting compared to the network-wide emissions,which lead to more than a 2%error in the MEFs calculation.The value of the MEFs is mainly positively correlated with the proportion of fossil energy.In terms of future grid,the study obtains the power dispatch results of the grid every half hour in 2030 and 2050 according to the dispatch model.The results show that the proportion of renewable energy in the total electricity system will increase significantly in the future.With the increase in the installed capacity of distributed energy,the utilization rate of the energy storage system will increase significantly.The marginal emission factors of the grid in 2018,2030 and 2050 are calculated based on the results of dispatch model.The results reveal that the emissions factors of the grid in the UK are declined significantly with the optimization of electricity structure.Regarding the household electricity systems when only considers the electricity consumption of appliances,results show that the deployment of a rooftop PV array and lithium nickel-manganese-cobalt battery operating in response to grid emissions factors could achieve 14 tons of CO2 savings through the system’s life span,though total electricity costs would be increased by ￡6,900.The household with just a photovoltaics array and no battery storage could increase total electricity costs by ￡2,170 and achieve 12 tons of CO2 savings through the system’s life span,providing a ￡3 13/tCO2 decrease om marginal abatement costs over systems with battery storage.High cost is the main factor limiting the deployment of household battery systems.In terms of the household EV charging,results show that smart charging could further reduce emissions by up to 5%for certain types of charging events.The results reveal that countries with high marginal emission factors have higher life cycle carbon emissions from EV charging and are likely to achieve greater benefits from smart charging.The study also finds that higher charger capacities generally improve the benefits of smart charging.As for the complete household electricity consumption system,results show that the PV-battery system meets 13%of daily household electricity demand,which reduces the environmental impact and the carbon emissions by 17%and 6.3 tons respectively compared with the initial household electricity system,despite the high initial investment cost of ￡9,260.The smart charging system further disperses the household electricity load during the EV plug-in duration,and achieves a 2.5%reduction in carbon emissions and 16%reduction in electricity bills based on the PV-battery system.It is concluded that the smart charging system further disperses the household electricity load during the plug-in duration of the EV,and decreases carbon emissions by 6.8 tons based on the carbon emission reduction effect of the PV battery system.The work concludes that using MEFs is essential to understanding the greenhouse gas impacts of the household electricity system and that smart charging tied to instantaneous grid emissions factors can bring benefits.Overall,this study constructs a calculation model of the MEFs and simulates the future electricity dispatch model.This work applies the life cycle assessment method to analyse the carbon emission reduction potential and the corresponding marginal abatement costs in terms of the household electricity system when only consider the electricity consumption of appliances,the household EV charging and the complete household electricity system.While evaluating the household electricity consumption system,some household electricity optimisation scenarios are proposed to provide support for carbon emission reduction and cost control.The research combines the findings with China’s reality to provide theoretical support and practical experience for China to carry out household electricity life cycle assessment during the transition period of the low-carbon power structure.The innovations of this research are mainly summarised in three aspects.First,the study evaluates the MEFs of countries under different carbon accounting scopes and improve the MEFs calculation model.Second,the research proposes a household EV charging system based on the clustering of charging behaviours and evaluate the carbon emissions reduction potential of household electricity consumption system including EV charging.Third,based on the MEFs calculation model,national grid dispatch model,typical household energy consumption data and time-varied PV generation data,the work constructs a household electricity consumption model with the goal of carbon reduction and cost control. |
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