Innovation in Ammonia Fuel Cells

Two years ago, the Innovation Research Incentive offered funding to Canadian federal and provincial laboratories for proposals to investigate greenhouse gas (GHG) and other emissions mitigation. CETC-Ottawa's ammonia fuel cell research team was one of the successful recipients. As a result, they have been developing a novel ammonia fuel cell over the past two years.

Although fuel cells were developed as early as the 19th century, the technology has not been widespread because an economically viable and steady supply of hydrogen has yet to be found. Of late, the use of hydrogen-carrying anhydrous ammonia¹ has been considered. Many of us use ammonia, which has been diluted in water for cleaning our homes; anhydrous ammonia is simply non-diluted. As a fuel, ammonia has several benefits as compared to pure hydrogen or other hydrogen carriers. Firstly, ammonia has supporting infrastructure due to its current use in the agricultural industry; its safety handling and transportation characteristics are well established. As a chemical with the second largest production volume globally, there is already a 2000-mile pipeline system for anhydrous ammonia in the United States and unlike hydrogen, ammonia is easily transported in tankers. An interesting side benefit is the routine separation of CO₂ in the production of synthetic ammonia, this would mean that ammonia fuel cells could be considered CO₂ neutral if the CO₂ separated in the manufacturing stage were sequestered using geological storage methods, such as subterranean or submarine storage, currently being developed around the world.

"Ammonia fuel cells typically consist of a proton exchange membrane (PEM) to split the hydrogen gas (H₂) into protons and a reactor to catalytically "crack" the ammonia, which produces a feed gas of 75% hydrogen and 25% nitrogen into the fuel cell. A drawback of this approach is the expense of a cracking system and the lack of opportunity to incorporate heat management between the fuel cell and ammonia cracker. The fuel cell developed at CETC-Ottawa is markedly different it this regard.

CETC-Ottawa's fuel cell is a solid oxide fuel cell (SOFC) type, which operates at a hotter temperature than a PEM fuel cell. At around 700º C, there is no need to crack the feed ammonia in an external cracker, as this occurs directly in the anode compartment. Protons are generated at the anode and transported through the solid ceramic electrolyte to the cathode. At the cathode they react with surface oxygen ions generated from the air. The only by-products are water and nitrogen (McFarlan, Pelletier and Maffel, 2004). The team has been collaborating with a sister lab, CANMET Materials Technology Laboratories, to develop the ceramic electrolyte materials.

Whereas PEM fuel cells are preferred for mobile applications, SOFCs are better suited for stationary power and combined heat and power applications. Potential SOFC applications include industrial refrigeration, uninterruptible power for large computer systems or hospitals.

CETC-Ottawa's ammonia fuel cell program is in an early development stage. Having had two papers accepted from peer-reviewed journals, CETC-Ottawa's scientists are also exploring the technology's commercial potential with support from the Technology and Innovation Initiative in Distributed Electricity Production. The lifecycle economics are also being studied with a focus on developing the business case for stationary power applications in the 10 to 200kW range. The results of a feasibility study will help with planning future stages of the project.

The possibilities for ammonia as a fuel are still being discovered. The innovative work at CETC-Ottawa is turning that possibility into a practical reality.

¹ Anhydrous means the ammonia is without water. Anhydrous ammonia is a clear, colourless gas at standard temperature and pressure conditions and has a very characteristic odour.