Introducing bidirectional charging in the European energy system: A life cycle analysis

How does the large-scale integration of flexibility potential from battery electric vehicles (BEVs) endogenously affect the environmental impacts of the energy system?

In the BDL Next project, we investigated this question by applying a life cycle assessment (LCA) approach on the endogenous differences in the modeling of the future European energy system induced by bidirectional charging. The full study was published as part of the 14^th International Energy Economics Conference (IEWT) at TU Wien and can be found in the download section at the end of the article.

Highlights:

• From 2025 to 2050, bidirectional charging could reduce greenhouse gas (GHG) emissions by 55 Mt CO₂-eq and metal resource utilization by 282 Mt Fe-eq in the European energy system.
• In the medium term, however, bidirectional charging could lead to an increase in GHG emissions.
• Savings in GHG emissions remain marginal compared to current levels: 02 % of the combustion-related emissions of the energy supply sector in the EU-27 in 2022 [1].
• Savings in metal resource utilization might be significant concerning future needs: 21 % of the proposed average demand in metal resources for decarbonizing the European power sector from [2].
• 2 % of the GHG emissions and 14 % of the metal utilization arising from the production of one BEV [3] can be mitigated by a bidirectional use of the vehicle in the energy system.

Motivation: BEVs can provide flexibility in smart energy systems

As a means of guaranteeing a successful integration of renewable energies (RE), bidirectional charging could support load flexibilization and short-term electricity storage in the smart energy system of tomorrow, thus substituting other electricity storage options such as stationary battery energy storage systems (BESS). Implementing bidirectional charging on a large scale inherently affects the energy system and its environmental impacts. The study provides a more comprehensive view of the long-term ecological repercussions of utilizing BEVs as flexible storage options in the European energy supply sector. Results bring insights on the global warming potential (GWP) and metal depletion (MD) resulting from changes in installed capacities and primary energy consumption, compared to a system without unidirectional controlled charging (V1G) and vehicle-to-grid (V2G), from 2025 to 2050.

How does bidirectional charging affect the future European energy system?

Two cost-optimized net-zero “ISAaR” energy system model scenarios with equal underlying assumptions, except for the possibility of using the available BEV fleet for flexibilization purposes through V1G and V2G, have been compared for the study.

Variations in constructed capacities (Fig. 1):

Large-scale implementation of bidirectional charging strategies substitutes stationary 1^st life and 2^nd life BESS because of their lower cost. Mainly all battery-based storage requirements are covered by a bidirectional integration of BEVs into the energy system. This increases the overall storage potential in the energy system, and, thus, enables an earlier deployment of PV capacities. The better integration of RE further explains the additional construction of hydrogen storage capacity in the time-steps 2026–2030 and 2046–2050, as more electrolysis is performed in hours with low electricity prices.

Variations in primary energy consumption (Fig. 2):

In a system without BEV integration, a small part of the consumption of fossil oil is substituted by green synfuel in years until 2040. The substitution is necessary to reach the emission reduction targets in such a system and compensates for the better integration of RE due to the higher flexibility provided by BEVs. After 2040, differences remain marginal, but CCS differences occur to meet the emission targets.

What are the environmental impacts of the changes to the energy system?

According to the considered scenarios, large-scale V1G and V2G implementation in smart energy systems can enable savings of 54.5 Mt CO₂-eq of GHG emissions (Fig. 3) and 282.3 Mt Fe-eq (Fig. 4) of metal resources until 2050 at European level. However, an increase in GWP can be observed in the medium term, due to the accelerated expansion of RE power plants and thus additional production emissions, as well as lower green synfuel imports. Since climate targets are reached in the long-term, this effect is mostly outbalanced by 2050. The break-even is estimated to occur around 2042.

Compared to a system without bidirectional charging, the major difference lies in avoiding the large-scale installation of stationary BESS capacities. Even though overall installed capacities are much higher for BEV-based flexibility, its environmental impact is much lower than BESS-based storage due to savings in battery pack and container production. Additional GWP and MD impacts of technological requirements for bidirectional charging infrastructure are much less significant.

Sensitivity analysis: Does battery aging have an impact on the findings?

V2G is often said to accelerate BEV battery degradation because of the increase in charging and discharging cycles [4]. On the other hand, some studies conclude that V2G could be beneficial for battery aging, when charging operations are optimized by battery management [5]. Considering these findings in literature, a range of ± 5 % has been identified for evaluating the changes in BEV battery capacity fading attributed to V2G compared to uncontrolled charging. This range has been applied to the installed V2G capacity difference in the energy system to account for the emissions of battery aging attributable to the bidirectional use of BEVs in the energy system until 2050.

When considering these changes in V2G capacity emissions, overall savings in GWP and MD until 2050 vary significantly (Fig. 5). However, no sensitivity case was found to lead to absolute additional environmental impacts brought forth by bidirectional charging in the energy system.

Interested in the analysis?

An automated Python-based tool has been developed to implement the LCA, which could be applied to investigate other scenarios and technologies in future studies.

More Information

• How Bidirectional Charging Strategies contribute to Achieving a Climate-Neutral Energy System
• Comparative study of the environmental impacts of ICT for smart charging of electric vehicles in Germany
• Green light for bidirectional charging? Unveiling grid repercussions and life cycle impacts
• Future Emission Factors for Greenhouse Gas Target Setting and Decarbonization Measure Evaluation

Literature

[1] European Environment Agency (2024). EEA greenhouse gas – data viewer. Available online at https://www.eea.europa.eu/data-and-maps/data/data-viewers/greenhouse-gases-viewer, updated on 8/13/2024, checked on 11/22/2024.

[2] Xu, L., Wang, Z., Yilmaz, H. Ü., Poganietz, W.‑R., Ren, H., & Guo, Y. (2021). Considering the Impacts of Metal Depletion on the European Electricity System. Energies, 14(6), 1560. https://doi.org/10.3390/en14061560.

[3] Sacchi, R., Bauer, C., Cox, B., & Mutel, C. (2022). When, where and how can the electrification of passenger cars reduce greenhouse gas emissions? Renewable and Sustainable Energy Reviews, 162, 112475. https://doi.org/10.1016/j.rser.2022.112475.

[4] Etxandi-Santolaya, M., Canals, L., Montes, T., & Corchero, C. (2023). Are electric vehicle batteries being underused? A review of current practices and sources of circularity. Journal of Environmental Management, 338, 117814. https://doi.org/10.1016/j.jenvman.2023.117814.

[5] Gong, J., Wasylowski, D., Figgener, J., Bihn, S., Rücker, F., Ringbeck, F., & Sauer, D. U. (2024). Quantifying the impact of V2X operation on electric vehicle battery degradation: An experimental evaluation. ETransportation, 20, 100316. https://doi.org/10.1016/j.etran.2024.100316.