  The proliferation of car sharing services in recent years presents a
promising avenue for advancing sustainable transportation. Beyond merely
reducing car ownership rates, these systems can play a pivotal role in
bolstering grid stability through the provision of ancillary services via
vehicle-to-grid (V2G) technologies - a facet that has received limited
attention in previous research. In this study, we analyze the potential of V2G
in car sharing by designing future scenarios for a national-scale service in
Switzerland. We propose an agent-based simulation pipeline that considers
population changes as well as different business strategies of the car sharing
service, and we demonstrate its successful application for simulating scenarios
for 2030. To imitate car sharing user behavior, we develop a data-driven mode
choice model. Our analysis reveals important differences in the examined
scenarios, such as higher vehicle utilization rates for a reduced fleet size as
well as in a scenario featuring new car sharing stations. These disparities
translate into variations in the power flexibility of the fleet available for
ancillary services, ranging from 12 to 50 MW, depending on the scenario and the
time of the day. Furthermore, we conduct a case study involving a subset of the
car sharing fleet, incorporating real-world electricity pricing data. The case
study substantiates the existence of a sweet spot involving monetary gains for
both power grid operators and fleet owners. Our findings provide guidelines to
decision makers and underscore the pressing need for regulatory enhancements
concerning power trading within the realm of car sharing.
