Life Cycle Greenhouse Gas Impacts Of Battery Energy Storage Systems In Power System Applications

Renewable penetration into the power systems is accelerating,but this poses new challenges in terms of grid reliability and peak load management.Under such circumstances,battery energy storage(BES)technologies are needed in various power system applications to support system-friendly renewable penetration,thereby decarbonizing electricity generation.However,the deployment of battery storage technologies also incurs new sources of greenhouse gas(GHG)emissions,which need to be analyzed to understand the GHG impacts of these technologies.Studies in this regard are rare,and this thesis aims to identify the life cycle GHG impacts of battery storage systems through a critical analysis of existing life cycle assessment(LCA)studies.This paper follows the steps and principles of meta-analysis to perform a systematic review and statistical analysis of LCA studies of BES systems to determine the life cycle GHG impacts of different BES technologies.It compares the life cycle GHG impact estimates expressed in carbon dioxide(CO2)equivalents of four different BES technologies-lead acid(PbA),lithium-ion(Li-ion),sodium sulfur(NaS)and all-vanadium flow batteries(VFB).Screening of 26 LCAs of BES technologies in different power systems yielded 11 qualified studies for systematic review and statistical analysis.From the reviewed studies,this paper extracted 23 estimates based on the functional unit of per unit(kWh)of battery storage capacity,which reflect life cycle GHG impacts from battery production.The paper also extracted 41 estimates based on the functional unit of per unit(kWh)of delivered electric energy from the BES systems,which reflect the life cycle GHG impacts of BES systems when they are deployed for different power system applications.These estimates focus on the cradle to gate(CTG)GHG impacts of BES systems.CTG stages include material extraction,material processing and component manufacturing.This paper identifies that application contexts have significant influences on the battery performance,and thereby change the life cycle GHG performance of BES in different power system applications.This paper emphasizes the necessity of assessing life cycle GHG impacts of BES combined with the power system application it is embedded in.Future research supported by high-quality data should be conducted to underpin the following conclusions drawn from the analysis:higher energy intensity,higher roundtrip efficiency,longer cycle life lead to lower life cycle GHG impacts of BES for various power system applications.BES systems deployed for power applications generally incur higher life cycle GHG impacts than energy applications.This paper finds that LCA studies on BES for power system applications are still at an early stage.There is still not sufficient data to design a well-performed meta-analysis to draw very robust conclusions.Two major problems have been identified in the reviewed literature.First,system boundaries are not clearly defined,especially for upstream material extraction and end-of-life treatment.Second,life cycle inventory data were sometimes outdated or repeatedly utilized by reviewed studies.In terms of LCA methodologies,the paper identifies the essential role of a clearly defined functional unit for a well-designed LCA study.Functional units should correspond to the study goals and scopes.Through comparing electricity delivered by BES to electricity generated from different power sources,this paper also emphasizes that BES systems can incur significant GHG emissions.As the share of renewable energy increases in future energy systems,impacts from BES installed in the power system will become more relevant,and further efforts to reduce such GHG impacts will become necessary.