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Electrochemistry Laboratory
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Updated: 29.03.2012 
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Capacitors
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The figure below shows a 24 V bipolar aqueous capacitor with a maximum power of 5.7 kW and a maximum energy of 115 J. The characteristic data are given in the table.
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One of the advantages of EDLCs is the cycle stability. With a 5V bipolar capacitor (5 cells) more than 100'000 charge/discharge cycles between 0 V and 5 V were demonstrated. During this cycle test, which lasted two months, the internal resistance as well as the capacitance changed less than 10%.
This part of the project is supported by CTI (in collaboration with ABB Corporate Research and Leclanché SA) and by FIT (Federal Institutes of Technology) Board.
- 13.01.2000, Presentation of 24 V, 0.4 F Supercapacitor
- The Poster presented at the PPM Closing Event, Interlaken Nov. 11-12, 1999 is available HERE
- The Poster presented at the PPM Fall Meeting November 13, 1998 in Bern is available - PartI and PartII
High Energy Supercapacitor
In order to achieve high energy density the nominal voltage of the EDLC has to be increased using an organic electrolyte. A large capacitance is achieved using activated carbon based thin film electrodes. Such electrodes are being developed at the PSI in collaboration with Maxwell Technologies SA taking advantage of the know-how available for the processing of gas diffusion electrodes for zinc/air batteries.
Windable electrode bands were produced on a professional coating machine using the PSI formula. Capacitors with these electrodes were produced by Maxwell Technologies SA (see figure below). The capacitors showed maximum specific power above 4 kW/kg. The specific energy was about 2.5 Wh/kg at a nominal cell voltage of 2.5 V.
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800
F boostcap by montena SA utilizing PSI electrode. |
Capacitor
module with 2 x 24 capacitors resulting in 60 V , 60 F with an overall
internal resistance of < 20 mOhm. |
50 of these capacitors were mounted in series (2 x 25) to give a capacitor module with 60 V and 60 F. Voltage balancing in this module was achieved with active electronic circuits on top of the capacitors (see figure above). This module was successfully tested in combination with our fuel cell and power electronics simulating a down scaled drive train.
This part of the project aims at energy recovery in electric vehicles, preferentially in combination with a Polymer Fuel Cell. The project is supported by FIT Board.
Hybrid vehicle with fuel cell / supercapacitor drive train
HY.POWER The encouraging results of the down scaled fuel cell / supercapacitor drive train lead to the HY.POWER project where a hybrid electrical vehicle was realized on the basis of a VW Bora 4-seater car. The capacitors for this car were distributed in two boxes placed unter the hood and under the rear seat. The figure below shows the two capacitor boxes on the test bench. Each box contains 140 capacitors (70 pairs connected in series). The capacitor unit was capable of delivering a constant power of 50 kW for 15 seconds (see figure).
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Supercapacitor modules for the Bora HY.POWER |
Performance of the supercapacitors during a 50 kW constant power discharge on the test bench. Constant Power output of 50 kW during 15 s, Energy: 210 Wh @ 50 kW, ESR: 112 mΩ, Efficiency: 92 % |
The power distribution between Fuel Cell and Supercapacitors was managed by intelligent energy management system. As a result the fuel cell exhibited a rather smooth power profile while peak power demand was covered by the capacitors. In addition recuperation of braking energy was provided by the capacitors. Evaluation of the driving tests on the street showed, that recuperation of energy lead to a 15% fuel saving.
HY-LIGHT Recently, in October 2004, another fuel cell car called HY-LIGHT was presented at the Challenge Bibendum in Shanghai. This vehicle was built in a collaboration between Michelin and the PSI. The drive train is in principle similar to that of the HY.POWER with fuel cell and supercapacitors, but in contrast to HY.POWER this car was designed especially around this type of drivetrain. One of the main new features is hydrogen AND oxygen storage on board. Thus the fuel cell runs on pure oxygen (not air), which results in an improvement of the fuel cell efficiency. In addition, the HY-LIGHT has two powerfull and small electric motors on the front wheels and electric suspension, anti pitch and anti roll. Compared to the capacitor modules of the HY.POWER the newly developed module (see figure below) utilizing commercial ultracapacitors (supercapacitors) from Maxwell Technologies SA is much lighter.
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Supercapacitor module for HY-LIGHT. |
With the help of the supercapacitors as a short term storage device the HY-LIGHT accelerates from 0 to 100 km/h in less than 12 seconds. In addition braking energy is recuperated, which contributes to the high fuel efficiency.
For Characterization and Testing of the capacitors and electrodes we
use:
- Cyclic Voltammetry
- AC impedance spectroscopy
- Constant current charge/discharge cycle tests (1.2 kW, max. 60 Amp., max. 60 V)
- Constant load discharge tests (10 kW, max. 500 Amp.)
- Constant voltage hold tests (up to 120ºC)
- XPS, AES, and SEM
- BET
- DEMS (in collaboration with the Li-Battery group)
- Dilatometrie
- In situ X-ray diffraction and small angle scattering
Research Team top
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Contact Point top
If you have a problem for which our expertise could be of use, we would like to become YOUR partner - please do not hesitate to contact us!
Dr. Rüdiger Kötz Paul Scherrer Institut phone +41 56 310 2057 CH-5232 Villigen PSI fax +41 56 310 4415 SWITZERLAND e-mail see PSI Phone Book