The clean technology company Danish Power Systems (DPS), with partners at the Technical University of Denmark (DTU) and the University of Chemistry and Technology in Prague, Czech Republic, reports the best operating stability for high-temperature polymer fuel cells (HTPEMFC) yet.
In a 9,000-hour long test at 160 ˚C under constant load, the DPS cell exhibited a degradation rate of 0.5 μV h−1—equivalent to degradation of 0.00008% per hour—compared to 2.6 μV h−1 for a reference membrane. For the full test period of 13,000 h, the average voltage decay rate was about 1.4 and 4.6 μV h−1 for cells equipped with cross-linked and linear polybenzimidazole membranes, respectively. Results are published in the Journal of Power Sources.
Danish Power Systems manufactures the MEA (membrane electrode assembly), and is one of the few companies that can manufacture the material-polybenzimidazole (PBI), of which the fuel cell’s plastic membrane are made. The polymer can operate at a higher temperature than traditional PEM cells. HTPEM operates at 160-200 °C and can use several fuels such as natural gas, biogas or methanol.
The company was founded in 1994 by three researchers at DTU and two development engineers from the battery factory Hellesens, Denmark. The company currently has approximately 24 employees, of whom 12 are academics.
Phosphoric acid doped membranes based on polybenzimidazoles … have been developed as one of the most promising electrolyte materials for high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) operating under dry conditions. In a typical operating temperature range of 120=180 ˚C, HT-PEMFCs exhibit advantages such as good CO tolerance along with simple water and thermal management. However, improving the long-term durability remains a most critical and challenging task to address for the commercialisation of the HT-PEMFC technology. Understanding the mechanisms responsible for the degradation is far from trivial though, because the predominant degradation modes vary depending on the operating conditions.
… With respect to the membrane, several approaches for improving the long-term durability of HT-PEMFCs have been reported. These include increasing the linear average molecular weight of the polymer, minimizing metal impurity contamination, and development of the membrane systems such as composites, cross-linked structures, or alternative polymer chemistries. Furthermore, thermal treatment of the membranes at temperatures up to 350 ˚C prior to acid doping result in non-specific cross-linking of the polymer matrix. This has recently been proven as an effective strategy for mitigating degradation of HT-PEMFCs. In the present work, thermally cross-linked m-PBI membranes were further evaluated in extended durability tests using membranes based on linear m-PBI as a reference.—
Testing in the Czech Republic was a part of the successful European Union project “CISTEM” that was coordinated by the German research institution Next Energy (now part of DLR).
The Danish Power Systems fuel cell stacks use methanol as fuel. Methanol is cheap to produce and it is easy to extract methanol from biological resources. To assemble full fuel cell stacks, Danish Power Systems collaborated with SerEnergy, based in Aalborg, Denmark—financially supported by the Danish Ministry of Energy’s EUDP-program. Additionally, SerEnergy’s operating stability results on cell-stacks, fabricated of Danish Power Systems’ cells, have also shown very low degradation rates.
In recent years, Danish Power Systems has focused on increasing exports of fuel cell products where they are successful in manufacturing the special high-temperature plastic contained in the cells. The company projects that the technology is so mature that actual commercialization is in the near future.
This world record is a milestone in our work towards a commercialization. The advantage of using both hydrogen and methanol is that the systems can generate electricity with almost no pollution and on fuels made from biological ‘green’ materials. Fuel cells can be used in electric vehicles without a hydrogen infrastructure. With [this] durability we are rapidly approaching a breakthrough for large-scale production.—managing director of Danish Power Systems Hans Aage Hjuler
Tonny Søndergaard, Lars Nilausen Cleemann, Hans Becker, David Aili, Thomas Steenberg, Hans Aage Hjuler, Larisa Seerup, Qingfeng Li, Jens Oluf Jensen (2017) “Long-term durability of HT-PEM fuel cells based on thermally cross-linked polybenzimidazole,” Journal of Power Sources, Volume 342, Pages 570-578 doi: 10.1016/j.jpowsour.2016.12.075