Fraunhofer Institute for Energy Economics and Energy System TechnologyResearch Project PVCharge
In the project PVCharge, a consortium of two research institutions and three industrial companies is investigating how synergies between industrial photovoltaic systems and electric vehicles can be better utilized. The project focuses on larger PV systems, such as those that can be installed above or near supermarket or company parking lots.
The project has three primary objectives:
- Reducing energy conversion losses when charging electric vehicles with PV electricity in order to use renewable energies more efficiently
- Increasing the PV share in the vehicle battery through PV-dependent setpoint specifications during charging in order to replace the fossil-fuel-generated share of grid electricity with locally generated PV electricity
- Integrating vehicle batteries for grid stabilization services
Charging electric vehicles (EVs) directly from a photovoltaic (PV) system offers both ecological and economic advantages. In times of rising energy costs and increasing environmental awareness, the use of renewable energies is gaining in importance. The combination of e-vehicles and PV systems makes it possible to use the solar power generated directly and efficiently for charging vehicles. Current technologies rely on AC coupling of PV systems and charging stations.
"The electricity from the PV system has to go through at least four conversion stages before it reaches the vehicle battery. However, each of these conversion stages is associated with losses, which is why around 10% of the solar energy is lost unused. In PVCharge, we are researching an approach that allows this conversion to take place in two steps instead of four, which saves around half of the losses," says Dr. Sebastian Sprunck, coordinator of the consortium at the Fraunhofer Institute for Energy Economics and Energy System Technology IEE.
In this project, Fraunhofer IEE is developing a test environment to validate this approach in practice. For this validation, an existing rapid control prototyping system is being expanded to emulate the behavior of various current and future electric vehicles at the charging stations of such a system. In addition, a PV system at the institute will be made available for testing so that the system concept can be examined as realistically as possible with regard to system and personal safety. Furthermore, the existing laboratory infrastructure can be used to investigate the scalability of this approach for larger systems in practice.
Siemens AG is investigating these safety-related issues and the integration of the charging stations into the overall concept in the project. “The spatial extent of such a PV parking lot, the variable number of electric vehicles, and the various usage scenarios require innovative approaches for system monitoring and interaction between the various converter stages,” explains Sebastian Nielebock, project manager at Siemens. In addition to avoiding power consumption from the utility grid, application scenarios are also conceivable in which the system interacts specifically with the public power grid—for example, to buffer peak loads or to provide control power.
“This interaction with the grid requires robust, dynamic, and durable power electronics,” says Dr. Peter Friedrichs, Fellow SiC Innovation at Infineon Technologies AG. Infineon is therefore contributing its expertise and prototype components in the field of power semiconductor and controller technology and will also develop a demonstration inverter based on innovative semiconductor modules that enables this interaction.
The MPP tracker of such a PV installation must also be adapted to the changed boundary conditions. “In such a system, the MPP tracker must be able to cope with rapid and significant changes in DC voltages when the system's power balance changes at short notice, e.g., due to specifications from the grid operator, cloudy skies, or vehicles connecting and disconnecting,” explains Prof. Dr. Marco Jung, Professor of Electromobility and Electrical Infrastructure with a focus on power electronics at the Bonn-Rhein-Sieg University of Applied Sciences (H-BRS) and Head of the Power Converters and Electric Drives Department at Fraunhofer IEE. This requires power electronics that enable step-up and step-down behavior. In addition, control algorithms must be developed that allow the various system components to be operated stably and efficiently with each other. Research into these tasks is being conducted at the Power Electronics and Power Systems Laboratory at H-BRS.
This type of system depends on the involvement of electric vehicle owners, who make their vehicles available for PV-controlled charging and/or grid-supporting functions. “There are numerous user requirements, grid operator specifications, approvals, data formats, billing options, and communication interfaces to consider, all of which must be handled in real time and with a high degree of precision,” explains Georg Schmitt from Flavia IT Management GmbH. To this end, the in-house operator platform for electromobility “Gridware,” which was developed with the internal start-up Grid & Co. GmbH, is to be upgraded accordingly.
In order to take into account further requirements from component and system manufacturers as well as network operators, the project is being advised and supported by SUMIDA Components & Modules GmbH, SMA Solar Technology AG, and Städtische Werke Netz+Service GmbH as associated partners. In addition, several workshops are planned in which further stakeholders will be involved in order to incorporate additional perspectives into the project.
The PVCharge project will receive a total of €3.5 million in funding from the Federal Ministry for Economic Affairs and Energy (BMWE) during the project period from April 1, 2025, to March 31, 2028.
Figure 1: System concepts for charging electric vehicles using PV energy. The efficiencies shown are for illustrative purposes only and are not representative.
a) Conventional, AC-coupled system.
b) DC-coupled concept in PVCharge.
Funding: Federal Ministry for Economic Affairs and Energy
