Research On Electric/Thermal Hybrid Energy Storage Planning For Park-level Integrated Energy System Considering Retired Battery Utilization

The park-level integrated energy system is an important way to accelerate the energy transition and realize low-carbon development.Energy storage system,as a key supporting technology in park-level integrated energy system,has received widespread attention.There are still some problems in the existing energy storage planning research of park-level integrated energy system,which mainly manifest in the high investment costs,low economic benefits,and inconsistent economy with expectation.Electric/thermal hybrid energy storage and utilization of retired batteries are possible methods to solve such problems.On the one hand,electric/thermal hybrid energy storage combined with the advantages of multiple types of energy storage can help improve the economy of the system.On the other hand,echelon utilization of retired batteries in electric vehicles is considered to have the potential to break the limit of high investment cost of energy storage.In the planning of electric/thermal hybrid energy storage,the influence of battery life loss and beneficial relationships between thermal energy storage and battery energy storage should be further considered.Moreover,the application of retired batteries in the park-level integrated energy system has not been sufficiently studied.Therefore,in order to improve the economics of the energy storage planning in park-level integrated energy system,this study focused electric/thermal hybrid energy storage planning for park-level integrated energy system considering retired battery utilization.The major work is categorized as follows:1)The model of the park-level integrated energy system containing electric/thermal hybrid energy storage was proposed.The battery life loss model,retired battery model and thermal energy storage model were proposed,and the equipment models which can represent the operation characteristics of energy conversion equipment and energy production equipment in the park-level integrated energy system were proposed.The internal energy flow relationships of the park-level integrated energy system were analyzed.The model laid a model foundation for subsequent energy storage planning research.2)A bi-level optimal planning method of electric/thermal hybrid energy storage for the park-level integrated energy system considering battery life loss was proposed,during which the battery replacement cost was introduced to reflect the long-term impact of battery life loss.The lower-level model is the economic optimization of operating and the upper-level model is the economic optimization of capacity configuration,and the goal is to minimize annual cost.This method can improve the park-level integrated energy system economy and battery service life,and provided a research foundation for the study of energy storage planning research that considers the utilization of retired batteries.3)A bi-level optimal planning model of electric/thermal hybrid energy storage system considering retired batteries utilization,including an upper-level planning model and a lower-level operating model,was proposed.At the upper level,to minimize the net present value during the planning stage,the capacity of the hybrid energy storage system as well as when the retired batteries need to be replaced are optimized.At the lower level,the operation scheme are optimized to obtain the minimum annual operating cost,which are fed back to the upper level.The proposed method considers continuous capacity degradation of retired batteries and mutually beneficial relationships between thermal energy storage and retired batteries,which has improvement effect on economy and battery degeneration,and improves the economic effect of the energy storage planning method by optimizing the replacement timing of retired batteries.