Leveraging Charging Strategies to Reduce Grid Impacts of Electric Vehicles

Abstract

Electric vehicles (EVs) can challenge or support electricity systems depending on how they are charged. Uncontrolled charging may strain electricity systems, e.g., by increasing peak demand in the evening,1 which may require cost- and emission-intensive infrastructure investments, such as grid reinforcements and peak generation capacity. In contrast, controlled charging can benefit electricity systems by providing flexibility,2 e.g., by shifting charging demand away from evening hours. Controlled charging that combines technical solutions with heterogenous EV user behaviors, supported by charging infrastructure at diverse locations, e.g., at work during midday, and incentives, can reduce peak demand to avoid grid constraints and support the integration of renewable energy.

Balancing electricity supply and demand becomes more challenging as the share of variable renewable energy sources and electrification increase. Low-carbon electricity systems likely need more short-term flexibility (on a scale of milliseconds to days) to cope with the fluctuating generation of solar and wind electricity. Growing electrification, including the adoption of EVs, can increase demand peaks, exacerbating the challenge faced by grid operators to always meet electricity demand. The International Energy Agency (IEA), in its Announced Pledges Scenario (APS), estimates that global short-term flexibility needs will double by 2030 and rise 4.5-fold by 2050 compared to today.3 In the IEA’s APS, demand-side flexibility is expected to play a crucial role in fulfilling short-term flexibility needs - meeting one third of needs by 2030 and almost half by 2050.4

The increasing relevance of demand-side flexibility represents a paradigm shift in electricity systems: end users actively shifting electricity demand across time and space according to electricity supply, rather than supply following demand. However, to leverage the potential of demand-side flexibility and achieve climate targets, the IEA emphasizes the need for digital technologies, e.g., smart meters, particularly for modernizing distribution grids.5

Those digital technologies can support controlled EV charging, which can provide flexibility in a variety of ways, including: automated charging processes that determine when and how fast an EV battery charges during a specified dwell-time; bidirectional charging that allows EVs to feed electricity back into the grid to compensate for shortfalls in renewable electricity generation; changing users’ plug-in behavior to shift demand to off-peak hours, e.g., charging during midday when solar PV electricity is available; or some combination of the aforementioned options. Controlled charging can improve the reliability of the electricity grid and provide economic benefits, such as deferring or reducing costly upgrades to grid infrastructure, increasing profits for charging station operators, and reducing charging costs for EV users.

To date, controlled EV charging has primarily focused on technical solutions that assume charging behavior can be fully controlled, e.g., by grid operators. However, the prominent role of end users in demand-side flexibility means that EV charging cannot be fully controlled. Driving patterns, charging behaviors,6 and willingness to provide flexibility services vary substantially across EV users, and this variability is expected to become more pronounced as EV adoption increases.

Changes in EV users’ behaviors could reduce peak demand substantially and thus, potentially required grid reinforcements. Yet the behavioral aspects of EV charging have received little attention compared to technical solutions, which means that some of the flexibility potential of EV charging, and particularly the spatial flexibility, is at risk of remaining untapped.