Norway’s Nordic Power Systems (NPS) and California-based SAFCell Inc., in collaboration with Caltech, are testing the combination of a cool flame fuel reformer and a solid-acid fuel cell (SAFC) as the core components of a new electric auxiliary power unit (APU). The power supply unit can run on biodiesel as well as regular diesel.
In trials, a 250-W solid-acid fuel cell stack ran on both pure hydrogen and on hydrogen produced from diesel by the unit’s reformer, with only an insignificant difference in performance. This result, noted SAFCell, showed that the fuel cell could operate with up to 10% CO without any effect on the performance.
The electric generator is being developed and produced by the Norwegian company Nordic Power Systems (NPS). SAFCell Inc., established to market and commercialize the solid acid fuel cell (SAFC) technology developed and patented at the California Institute of Technology, is delivering the stack. Dag Øvrebø, Technical Director of NPS, has been working closely with Caltech on this technology.
The project is funded by the Research Council of Norway under its RENERGI program. The project has an overall budget of NOK 11.8 million (US$2 million), with NOK 5.9 million(US$1 million) of funding under the RENERGI program.
Cool flame reformer. A significant challenge in designing a diesel reformer is the creation of an optimized mixture of fuel and oxidant before contact with the catalysts, while preventing autoignition. Several approaches to solving this have been taken, including direct evaporation in preheated steam and or cool flame reforming.
Unfavourable mixtures of liquid fuels, water and air lead to degradation by local hot spots in the sensitive catalysts and to formation of unwanted by-products in the reformer. Furthermore the vaporiser has to work with dynamic changes in the heat transfer, residence times and educt compositions.
By using exothermal pre-reactions in the form of cool flames it is possible to realise a complete and residue-free evaporation of liquid hydrocarbon mixtures. The conditions whether cool flames can be stabilised or not is related to the heat release of the pre-reactions in comparison to the heat losses of the system.—Hartmann et al.
NPS acquired licensing rights to the cool flame reformer technology developed at RWTH Aachen University in the late 1990s. The reformer converts hydrocarbons into hydrogen, CO2 and heat. Due to the unit’s high efficiency, CO2 emissions are substantially lower than in conventional combustion engines, and no other demonstrable exhaust is discharged—i.e., diesel particulates, black carbon soot, NOx and carbon monoxide (CO) are eliminated. The reformer emits no smoke or odor, according to NPS.
SAFC. Superprotonic solid-acid fuel cells are a new type of fuel cell, developed by a group led by Sossina Haile of the California Institute of Technology. Unlike other fuel cells, SAFCs operate at warm temperatures using a solid acid electrolyte. Solid acids are chemical intermediates between normal salts and normal acids—“acid salts”. The solid acids support direct H+ transport, are humidity insensitive, and are impermeable.
The occurrence of liquid-like proton transport in a noncorrosive, solid material implies unique opportunities for new approaches to fuel cell design, construction, and operation, SAFCell notes.
The current generation of SAFCell stacks operate at mid-range temperatures around 250 °C, and tolerate fuel impurities that pose obstacles to other fuel cell technologies. This allows SAFCell stacks to run more easily on commercially available gas fuels (e.g., propane and butane) or liquid fuels (e.g., methanol, diesel and bio-oils), further reducing the overall fuel cell system complexity and cost.
In 2009, NPS secured usage rights to the new US solid-acid technology for use with various fuel types such as diesel and biofuels.
Tor-Geir Engebretsen, Managing Director of NPS said that now that they have demonstrated that the solid-acid technology works, the next step is to test a larger unit of 1.2 kW.
Engebretsen points out that since the technology is scalable, it is well suited for future generators in electric vehicles. The company’s first market is power supply for the defence industry; NPS has a technology development agreement with the Royal Norwegian Armed Forces. In addition, NPS has a product development agreement with Marshall Land Systems, of the UK, with the aim of supplying silent-running generators for the British Armed Forces.
If all goes according to plan, the unit being developed with Marshall will be ready for market launch by mid-2011, while the solid-acid fuel cell will be phased in somewhat later. An assembly plant in Høyanger, Norway, is scheduled to open in early 2012 with Industrial Development Corporation of Norway (SIVA) as contractor.
Lutz Hartmann et al. (2006) Cool flame evaporation for diesel reforming technology. (ECS 203)
Calum R.I. Chisholm et al. (2009) From Laboratory Breakthrough to Technological Realization: The Development Path for Solid Acid Fuel Cells. The Electrochemical Society Interface
Dane A. Boysen et al. (2004) High-Performance Solid Acid Fuel Cells Through Humidity Stabilization. Science, vol 303, pg 68.
Sossina M. Haile et al. (2001) Solid acids as fuel cell electrolytes. Nature, vol 410, pg 910 doi: 10.1038/35073536