Integrating Battery Energy Storage Systems to Enhance Sustainable Electric Vehicle Charging Infrastructure

Integrating Battery Energy Storage Systems for Sustainable EV Charging Infrastructure

Abstract: The transition to a low-carbon energy matrix has accelerated the electrification of vehicles (EVs). However, charging infrastructure—particularly fast direct current (DC) chargers—can adversely affect distribution networks. This study examines the integration of Battery Energy Storage Systems (BESSs) with the power grid, using the E-Lounge project in Brazil as a case study to mitigate these impacts. Results showed a remarkable 21-fold increase in charging sessions and energy consumption growth from 0.6 MWh to 10.36 MWh between June 2023 and March 2024. The integration of a 100 kW/138 kWh BESS with DC fast chargers (60 kW) and AC chargers (22 kW) effectively reduced peak demand, optimized energy management, and enhanced grid stability. These findings underscore the essential role of BESSs in creating a sustainable EV charging infrastructure, showcasing improvements in power quality and reductions in grid impacts. The research was part of a project approved under the Brazilian Electricity Regulatory Agency (ANEEL) Research and Development program, aimed at developing a modular EV charging infrastructure for fleet vehicles in Brazil with minimal distribution network impact.

Keywords: battery energy storage systems (BESSs); charging stations; electric vehicles; energy management system

1. Introduction

The global transportation sector is at a pivotal moment, facing the challenge of reducing carbon emissions while creating a sustainable energy system. Transportation is responsible for roughly one-fifth of global carbon dioxide (CO2) emissions, with road travel alone accounting for three-quarters of this figure. Passenger vehicles, such as cars and buses, contribute to 45.1% of transport-related emissions. The widespread adoption of electric vehicles (EVs) has become a key strategy to tackle these challenges by decreasing reliance on fossil fuels like diesel and gasoline and lowering greenhouse gas emissions. However, the benefits of EV adoption depend on simultaneous advancements in renewable energy integration and the development of charging infrastructure.

Current efforts are focused on lowering vehicle and battery costs while improving performance, thereby enhancing their impact. For example, a recent study proposed a new technology to predict the lifespan of lithium-ion batteries and assess their reliability. Nonetheless, the large-scale deployment of EVs must occur alongside increased renewable energy integration, such as photovoltaic (PV) solar and wind power, to prevent rising electricity demand from relying on non-renewable sources like coal and oil. Furthermore, research highlights the importance of demand response strategies and energy storage systems for the seamless integration of renewable energy sources into the power grid.

While EV adoption provides significant environmental benefits, it also poses critical challenges for power distribution networks, especially when charging infrastructure is not effectively managed. Uncoordinated charging, particularly during peak demand periods, can lead to load peaks, voltage drops, frequency variations, and power quality degradation. These issues are intensified by the operation of DC fast chargers, which exert considerable stress on the grid, resulting in harmonic distortions, voltage instability, and transformer overloads.

In response to these challenges, various strategies have been proposed and implemented. For instance, real-time charging navigation frameworks have been utilized to mitigate voltage instability at fast-charging stations, while advanced management methods regulate EV charging behavior to enhance grid performance. Additionally, dynamic charging strategies have demonstrated significant reductions in peak grid demand and improved the lifespan of batteries through efficient charge and discharge coordination.

An effective method for optimizing fast-charging stations is the integration of Energy Storage Systems (ESSs). Numerous studies have explored ESS sizing and power flow control, assessing their applications in enhancing charging station efficiency and grid stability. Battery Energy Storage Systems (BESSs) specifically have shown promise in mitigating the effects of pulsed loads in fast-charging stations by supplying energy during peak demand periods, thereby reducing investment in transformers and minimizing energy transmission losses.

The technical integration of BESS with charging stations is crucial for optimizing system performance and efficiency. The BESS serves as a buffer power source, storing electricity during low-demand periods and discharging it when demand peaks to alleviate grid stress. An Energy Management System (EMS) enables intelligent energy flow control, ensuring seamless coordination between battery charging, vehicle charging requests, and grid energy availability.

2. Methodology

2.1. The E-Lounge Case Study—An EV Fleet Charging Hub

The E-Lounge project developed innovative solutions for EV charging alongside methodologies to evaluate the distribution network’s behavior while supporting a sustainable charging station. This initiative aimed to ensure network support without significant infrastructure modifications. By integrating established EV chargers with a BESS, the project created a comprehensive solution that meets vehicle charging needs while supporting the local electric grid.

The EMS plays a central role in coordinating the interconnected components of the charging infrastructure, ensuring efficient execution of applications aligned with all system elements’ requirements. The BESS is designed with a storage capacity of 138 kWh and a power output of 100 kW, using Lithium Iron Phosphate (LFP) lithium-ion technology, known for its safety and durability.

The charging infrastructure consists of both slow and fast charging stations. The slow charging stations operate on alternating current (AC) with a total power capacity of 22 kW, suitable for extended charging sessions, while the fast-charging station operates in DC with a capacity of 60 kW for rapid charging.

2.2. BESS Operating Strategy

To assess the BESS operating strategy, key functionalities that optimize performance and enhance power quality were analyzed. Each functionality contributes to improving the efficiency and sustainability of EV charging station operations.

1. Energy Arbitrage: This functionality allows the BESS to optimize energy costs by charging during periods of low demand when energy tariffs are cheaper and discharging during peak periods when prices are higher.

2. Voltage Regulation: The BESS stabilizes voltage fluctuations by supplying or absorbing reactive power to maintain voltage levels within acceptable operational limits.

3. Power Factor Control: The BESS manages power factor control by supplying or absorbing reactive power as required, enhancing overall system performance and minimizing electrical losses.

4. Demand Control: This feature allows the BESS to regulate total power consumption of the charging station, ensuring it does not exceed contracted limits with the utility.

5. EV Charger Power Reduction: When the State of Charge (SoC) reaches critical levels, the system can reduce the power output of the EV chargers to ensure operational continuity and preserve grid integrity.

3. Results and Discussion

The analysis reveals substantial growth across all key metrics, reflecting the rapid expansion of the electric vehicle market. The number of recharge sessions increased dramatically from just 20 in June 2023 to 442 by March 2024, indicating rising demand for charging points. Energy consumption also rose sharply from 0.6 MWh in June 2023 to 10.36 MWh in March 2024, underscoring the necessity for an efficient BESS to manage demand.

The BESS operation was assessed through three tests, demonstrating its capability to manage demand control, power reduction, and peak hour operations effectively. Results confirmed that the BESS contributed significantly to stabilizing the electric grid and enhancing energy quality provided to EVs.

4. Conclusions

Integrating BESSs into EV charging stations is vital for enhancing grid stability and optimizing energy management. The findings from the E-Lounge project illustrate the effectiveness of BESSs as a strategic solution for mitigating impacts on the grid while improving operational efficiency.

Key Contributions:

• Grid Stability and Peak Demand Reduction: The BESS mitigated grid stress by supplying stored energy during high-demand periods, thereby improving voltage regulation.

• Economic Feasibility: Strategies like energy arbitrage led to cost reductions and more predictable operational expenses.

• Power Quality Improvement: The system reduced voltage variations and harmonic distortions, ensuring compliance with standards.

• Scalability and Business Model Opportunities: The success of the E-Lounge case suggests that BESS-powered charging hubs can be replicated in various contexts.

Looking ahead, further exploration of hybrid PV-BESS solutions and advanced EMS optimization strategies is essential for maximizing energy storage potential in EV charging networks. The strategic deployment of BESSs in EV charging stations represents a transformative step toward a cleaner, more efficient transportation sector, paving the way for a low-carbon and resilient energy future.