System-based Integration of Electric Vehicles in an Electricity System
The support of alternative propulsion technologies like electric vehicles being integrated into transport and electricity systems must be based on efficient and economically reasonable implementation concepts. A successful integration of electric vehicles into an electricity system is affected by adequate business cases. The realisation of the mobility needs of vehicle users must be defined as a main constraint for each target function. The approach within this paper is based on systematic analysis of various charging (direction of electric current from grid to vehicle) and discharging (direction of electric current from vehicle to grid) concepts for electric vehicles, which are subdivided into: uncontrolled, controlled and intelligent charging and discharging strategies. The considered concepts are allocated to the controlled one. In all analysed applications, the discharging of batteries (in case of LiFePO4 batteries) cannot achieve sufficient revenues. This makes an economical realisation of such concepts unfeasible. The main reasons are high battery capacity losses due to discharging and the associated battery degradation costs. Therefore, the calculated revenues of discharging concepts are not able to cover inverter costs and the investments needed for the communication and control infrastructure. In terms of economic analysis and the impact of a high penetration level of electric vehicles on low voltage grids, a system-relevant integration of EVs is subdivided into two different implementation stages.
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