To achieve net-zero goals and accelerate the global energy transition, the International Energy Agency (IEA) stated that countries need to triple renewable energy capacity from that of 2022 by 2030, with the development of solar photovoltaics (PV) playing a crucial role. Additionally, the comprehensive electrification of combustion engine vehicles is an indispensable measure for reducing carbon emissions.
According to the latest “Global EV Outlook 2024” report released by the IEA, it is projected that the share of electric vehicle (EV) sales will increase from 15% in 2023 to 40% by 2030, and surpass 50% by 2035. In the transition to the new era of electric vehicles, charging stations not only serve as key infrastructure, but also are considered the last mile in the widespread adoption of EVs. Featuring a case study on the application of a photovoltaic charging and storage system in Southern Taiwan Science Park located in Kaohsiung, Taiwan, the article illustrates how to integrate solar photovoltaics, energy storage systems, and electric vehicle charging stations into one system, which is then connected with the city’s utility power grid. This system optimizes the efficiency of energy consumption from power generation, energy storage systems, distribution management, to energy usage with renewable energy, flexibly allocating energy resources with intelligent technologies to avoid adverse impacts on the power grid.
Concept for Photovoltaic Storage System
The photovoltaic storage system is the amalgamation of software and hardware, integrating solar energy, energy storage, electric vehicle charging stations, and energy management into one unified system. This system effectively combines various energy technologies to offer comprehensive solutions, aiming to enhance efficient energy use and promote the widespread adoption of electric vehicles.
1. Concept drawing for photovoltaic charging and storage system. Courtesy: ECOVE Environment Corp., a CTCI Company
The execution of this project involved utilizing the space of a parking lot in a shopping district to install solar power generation facilities, with the generated solar power used for charging electric vehicles and stored in the energy storage equipment (Figure 1). Through the energy management system, the energy storage equipment comes in handy during peak hours for electricity to achieve the effect of peak shaving, ensuring proper use of every resource, relieving the burden on power grids, and optimizing charging services. This solution not only enhances the use of renewable energy, but supports the needs of charging electric vehicles, thus delivering concrete results to energy transition and carbon reduction.
Planning and System Architecture of Photovoltaic Charging and Storage System in Southern Taiwan Science Park
The specific plan for the photovoltaic charging and storage system in this case is as follows. Firstly, 87 solar panels with a total capacity of 29.58 kW was planned to be installed. Then, a 146-kWh energy storage battery was incorporated, paired with a 50-kW hybrid inverter. In addition to supplying power for lighting, air conditioning, and a monitoring system in the charging room that consumes approximately 5 kW, the electricity generated by the solar photovoltaic system was stored for power consumption in an electric scooter swap station and electric vehicle charging station.
2. Planning and architecture diagram for photovoltaic charging and storage system. Courtesy: ECOVE Environment Corp., a CTCI Company
To enhance the quality of charging services and mitigate the risk of insufficient solar power generation due to consecutive unfavorable weather conditions, which may leave customers with inadequate power for charging, the system was designed to be interconnected with the city’s utility power grid. Through an energy management system (EMS), optimal power balance management was conducted, ensuring a stable power supply and effectively improving the efficiency and reliability of the overall system.
Overview of Photovoltaic Charging and Storage System Operations
The initial step in planning the photovoltaic charging and storage system was to evaluate the capacity for solar photovoltaic installation and estimate the electricity generation capacity. In this case, the main objective was to construct solar photovoltaic parking canopies in open-air parking lots near the shopping street.
To maximize power generation, the primary consideration was the installation orientation. As Taiwan is located in the northern hemisphere and the installation site is near the Tropic of Cancer, most sunlight will be inclined from the south to the solar panels after the sun rises from the east. Therefore, the installation of solar panels was south-oriented to maximize the benefits of solar exposure.
After the specifications of solar panels were selected, the layout design was conducted to determine the total number of solar panels and installation capacity based on the available installation area. Following this, parameters such as the installation orientation and fixed-tilt angle of solar panels were input into the photovoltaic system design and simulation software (PVSystem) for power generation simulation.
Based on the solar photovoltaic plan for this case, 87 solar panels were laid out, achieving a total installed capacity of 29.58 kW with an orientation angle set to 0 degrees (true south) and a tile angle of 8 degrees. Once these parameters were input into the software, it could simulate the monthly estimated electricity generation capacity of the system (Figure 3).
The next step in planning the photovoltaic charging and storage system was to assess the battery capacity required for system configuration. In addition to referencing the solar photovoltaic generation capacity, the battery configuration capacity also needed to take battery degradation rate and the health status of the used battery into consideration. As the default service life of the energy storage system in this project was 10 years, a battery configuration of 146 kWh was ultimately adopted after detailed simulation and calculation that took factors such as battery degradation estimation into account by the original manufacturer, ensuring that the battery health status remained above 80% to maintain optimal charging and discharging efficiency.
The third and final step in the planning of the photovoltaic charging and storage system involved not only the design and selection of components such as solar photovoltaic generation capacity, battery energy storage configuration, and specifications of charging piles, but also crucially focused on how to manage the solar-generated electricity, charging and discharging of electric vehicles, as well as lighting and air conditioning in the charging room (auxiliary power consumption) in a programmable and intelligent manner. This served as the key to achieving optimal operational efficiency through effective integration of all parts, leading to high-performance energy utilization and management.
Next is to explain the actual operation of this project. From the schematic diagram of real-time status of photovoltaic charging and storage system (Figure 4), it clearly illustrates the real-time generation of solar energy, load status, battery module capacity, utility power, and other statuses during the operation of the system. The EMS was initially configured to prioritize supplying the electricity generated during daytime to the lighting and air conditioning (auxiliary power consumption) in the charging room, charging stations for electric vehicles, and battery exchange stations for electric scooters, while the excess electricity was to be stored in the battery energy storage system. In the event of a lack of sunlight and when the energy storage capacity of battery modules was below 50%, the power supply will be sustained by utility power and off-peak charging will be triggered simultaneously.
Through this system, management personnel can obtain big data from the backend server, simulating and analyzing weather conditions, battery swap station usage, and electric vehicle charging status, and optimizing the charging and discharging timing of the battery energy storage system based on actual operating conditions. In this way, the system can operate efficiently under different conditions, achieving optimal energy utilization and management effectiveness.
Prospect for the Business of Photovoltaic Charging and Storage System
While the photovoltaic charging and storage system in the Southern Taiwan Science Park was only a demonstration project, it enabled the accumulation of experiences in efficient energy generation, stable power supply, optimization of solar charging and storage ratios, and simulation analysis of operational states through the execution processes.
Looking ahead, with the rapid growth of electric vehicles and charging stations, the current market is dominated by the development of vehicle-to-grid (V2G) technology, which sends the stored energy from electric vehicles back to energy storage systems or the electrical grid through charging stations. Once the technology matures, through higher-level energy management systems or electric vehicle management (EVM) charging management systems, charging stations as the core can integrate with renewable energy generation and energy storage systems. This integration contributes to create electric vehicle charging facilities based on the concept of microgrids, achieving “energy autonomy” for each individual unit. This integration method allows solar photovoltaic or other renewable energy sources to operate in a bidirectional charging/discharging manner with the energy storage systems of charging stations and the battery systems inside electric vehicles. Its aim is to maintain a stable power supply to the electric power system and increase flexibility in electricity price arbitrage to reduce grid integration and operation costs, thus maximizing the value of energy resources and ultimately achieving carbon reduction effects.
—Chi-Chia Liu is a manager at ECOVE Environment Corp., a CTCI Company.
Aug 1, 2024
by Chi-Chia Liu, .powermag.com
