Future-oriented Life Cycle Assessment of the Energy System Considering the Deployment of Bidirectional Charging Strategies.

Abstract:

Vehicle-to-grid is an emerging technology enabling flexibility in energy systems through the dual use of electric vehicle batteries: on the one side to store energy for vehicle propulsion and on the other side to provide short-term storage capacity in the energy system. Deploying such bidirectional charging strategies on a large scale in the future endogenously influences the expansion of the energy system and, by extension, its consequences on the environment. The purpose of this thesis is to evaluate the prospective life cycle impacts of the difference in the overall German energy supply sector expansion induced by this flexibility option until 2050.

To characterize the difference, an inventory of the divergences in power plant construction and primary energy carrier consumption required for meeting the future energy demand is established. This is done by confronting energy system scenarios relying on the same assumptions and whose only difference lies in the ability of the available battery electric vehicle fleet to perform bidirectional charging. The major difference in endogenous energy system expansion accountable to vehicle-to-grid services resides in the avoidance of stationary 1st and 2nd battery energy storage systems manufacture. Both are subject to high greenhouse gas emissions and critical metal resource utilization. On the other hand, vehicle-to-grid requires the supplementary fabrication of information and communication technologies for electric vehicle charging infrastructure. Other energy system changes are marginal in relation to the overall energy system expansion and are majorly ascribable to the energy system model cost optimization.

Over the entire time frame, a total of 14.9 Mt CO₂-eq and 41.1 Mt Fe-eq may be saved by introducing vehicle-to-grid technologies in the German energy system. Savings in global warming potential, thus, remain marginal with respect to current levels, while the deployment of bidirectional charging strategies may confer a noticeable advantage in metal resource preservation attributable to the lesser need for stationary battery systems. Elaborated results are, however, decidedly subject to assumptions and model results due to the marginal divergences in energy system expansion brought forth by the flexibility option on the whole. A sensitivity analysis of the emission factor assigned to the manufacture of 1st life battery packs shows that for smaller values, the potential decrease in greenhouse gas emissions might be even less significant on a global scale.

The realization of the prospective life cycle assessment has been conducted by conceiving an automated framework evaluating the difference in environmental impacts on the energy system expansion induced by any given measure, technology, or policy. The thesis, accordingly, also accounts for the methodology set in place for the conception of such a framework.