UFCEVUltra-Fast Charging of Electric Vehicles
Scope of project
Electric vehicles can play a significant role for individual mobility under specific mission conditions for the benefit of specific user groups. Even though substantial progress can be expected in the area of embarked energy storage technologies, existing vehicles already feature ranges suitable to fulfill well-defined missions, thereby contributing to the reduction of CO2 emissions and other pollutions.
One of the main problems with electro-mobility is the need to provide ultra-fast charging of electric vehicles (UFCEV). This project aims to examine both direct connectivity to the distribution grid as well as new storage technologies as a means of enabling ultra-fast charging. In addition, load leve-ling methodologies should be studied, including load shifting from day to night. To demonstrate how the developed solutions may be implemented, a transportable charging station for an average-size vehicle will be developed on a small scale, including the interface to a household electricity supply.
Summary of project
One of the important problems facing electric vehicles is the possibility of short-time charging, both as seen from the battery itself as well as from the local supply system. In this context, large load variations as seen from the local pow-er system, at multiple levels, must be carefully assessed with special attention to feasible load changes at the coupling points.
Inclusion of new storage technologies may be considered, alongside the local grid, to enable ultra-fast charging of electric vehicles (UFCEV). Ultra-fast charging of electric vehicles will re-quire the deployment of several storage tech-nologies, such as high-capacity batteries, fly-wheels and suitable mixtures of highpower and high-energy density subsystems. In addition, an appropriate power flow management will imply specific and dedicated power electronics conver-sion and control.
Since ultra-fast charging systems will unavoid-ably lead to complex and hybrid equipments, detailed system reliability analysis is essential, as well as a better understanding of the limita-tions emanating from existing and future grid systems and apparatus.
Main Investigator
Alfred Rufer, EPFL
Project Partners
EPFL
ETHZ
Empa
BFH-TI
This project started in 2010.
Validation through demonstration will play a significant role in the overall problem solution methodology. Thus, within this project, it is intended to build a small-scale readily transport-able demonstrator suitable for a fam-ily car – i.e. with a battery capacity of the order of 20 to 30 kWh – including the charging unit as well as the whole interface equip-ment to a house-hold plug power supply. This concrete device will suitably complement the theoretical and mod-eling studies described above, which will nota-bly address large-scale charging stations – i.e. along motorways - equipped with various en-ergy storage means and connected to different supply distribution networks.
First part of the charging process: the battery is charged with a constant current (current value is generally less than the current capacity of the bat-tery).Second part: when the cell voltage reaches the rated voltage of the battery (4.2 V) the voltage of the cell is controlled and thus the current is de-creasing.
Competence Center for Energy and Mobility CCEM Philipp Dietrich, Managing Director Phone: +41 (0)56 310 4573 E-mail: [email protected]
Contact
Goals and activities
The first research activities focused on• the study of existing solutions for electric ve-
hicle batteries (in terms of Energy density, power density as well as in terms of security and reliability).
• the analysis of the grid to station interface, as well as the implications of the stations on the overall grid.
• an extensive preliminary study and sizing of a possible flywheel-based solution for the in-termediate storage station.
Expected results
• Impact of a UFCEV system on local distribu-tion system design: update of existing sys-tem and green-field design, with specific at-tention to high short-duration power peaks.
• Detailed assessment of various energy stor-age technologies, both stationary and em-barked, including their applicability and in-terface issues.
• Modeling and optimization of power elec-tronic converters with the aim of achieving outstanding high efficiency of the converter systems for the fast charging station.
• Design and implementation of the required control electronics, with specific attention to energy efficiency.
• Design and implementation of a high-cycle efficient and high-discharge rate energy storage system for the load-leveling at the ultra-fast charging station.
• Demonstration project based on flywheel en-ergy storage for validating the fastcharging capability and the grid integration, in col-laboration with industrial partners. A stand alone, readily transportable demonstrator unit designed for family cars with a typical battery capacity of 20 to 30 kWh and for a standard household electric plug (400V/16A) will be built including charger and grid inter-face power electronics.
• Large-scale charging stations will be con-sidered conceptually, in particular as far as their impact and integration in local LV or MV electric supply systems. Shift load scenarios involving these stations as storage means will be proposed and thoroughly evaluated.
• Assessment as to system reliability and availability, as to local grid integration, as well as to investment and operational costs.
Project Manager Prof. Alfred Rufer, EPFL Phone: +41 (0)41 693 4676 E-mail: [email protected]
a) Charge efficiency of a LiPo accumulator made of 135 cells. b) Overvoltage applied to a LiPo cell for a given charge time and series resistance. c) Power required in order to charge a 25kWh LiPo accumulator made of 135 cells.
a)
b)
c)
UFCEV 2/2
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