FUEL CELL TECHNOLOGIES FOR AN AMMONIA ECONOMY

We propose to develop a radically new system for low-temperature hydrogen fuel cells that promises a performance that can match proton-exchange membrane fuel cells but costs less and is more robust. Our system involves two new technologies, which we ourselves have developed: alkaline polymer electrolyte fuel cells (that contain alkaline anion-exchange polymer electrolytes materials that conduct hydroxide anions, and use low to zero levels of precious metal catalysts) coupled with a new effective method of hydrogen delivery based on ammonia. Our ammonia will be sourced from a low-carbon grid-balancing project that is led by Siemens AG, funded by the TSB and based at the Rutherford Appleton Laboratory. The ability of ammonia to fulfil both the role of energy buffer and energy vector (that closely mimics fossil fuel hydrocarbons such as propane and butane) indicates its potential to play a central part in a future low-carbon economy.

The proposed hydrogen store is liquid ammonia, stored at modest pressures (10 - 20 atmospheres), which is cracked at moderate temperatures (350 - 500 degC) using a novel chemical reaction mechanism that does not involve rare-metal catalysts. Our recently discovered, inexpensive approach to ammonia decomposition involves the concurrent stoichiometric decomposition and regeneration of sodium amide via sodium: it is anticipated to lead to less than a 10% loss of efficiency.

In the past decade, there has been an increased level of research into using hydroxide conducting alkaline anion-exchange polymer electrolytes in all-solid-state alkaline polymer electrolyte fuel cells. A major rationale for this is such fuel cells hold the most promise for the elimination of precious metal catalysts. Additionally, low temperature (acidic) proton-exchange membrane fuel cells are irreversibly damaged by < ppm amounts of ammonia. Alkaline fuel cells, on the other hand, can tolerate several % of ammonia in the hydrogen fuel without serious performances or durability losses. Alkaline polymer electrolyte fuel cells have even been operated with pure ammonia as the fuel.

The actively managed project (that will fully integrate into the UK's SuperGen Hydrogen and Fuel Cell Hub) will involve the development of novel amide and imide based systems for ammonia decomposition as well as the next generation of conductive and durable anion-exchange polymer electrolytes and low cost catalysts (in close partnership with Amalyst Ltd.) to produce alkaline polymer electrolyte fuel cells with improved performances over the current state-of-art. The polymer electrolyte development will include novel dual role alkaline ionomers that allows conduction of the hydroxide anions in the catalyst layers and also catalyses the decomposition of trace ammonia (to help ensure zero ammonia emissions from the fuel cell). Anode catalysts that can not only oxidise hydrogen in the presence of ammonia, but oxidise the ammonia itself (again to help eliminate ammonia emissions) will be specifically targeted. Non-precious-metal cathode catalysts will be used and ported from current and prior research programmes.

The culmination of the project will be the development of a combined system incorporating the ammonia cracker, an alkaline polymer electrolyte fuel cell incorporating developed technologies, balance-of-plant, and a control and monitoring system. Taking the systems approach beyond the test bed, a study will be performed that delivers flowsheet and device designs for a 5 kWe system to be taken forward via future projects in direct collaboration with industry.

This project will advance knowledge, understanding and readiness of technologies necessary for the use of ammonia as a fuel for fuel-cell systems. This takes a materials-to-systems approach and includes development of a low-cost, high-efficiency and compact ammonia cracker, fuel cell materials that are resilient to the slippage of ammonia from the cracker and demonstration of an integrated fuel cell system composed of fuel (ammonia) processing, hydrogen buffer storage, thermal integration and control. The technological approaches proposed offer a potential step-change in fuel cell uptake, with huge associated impact. Specifically, this research project will have impact on:

- Society and the environment: Fuel cells are the most energy efficient means of converting chemical energy to electricity and thus have great promise for the replacement of heat engine technologies. This will have great impact on quality of life and public health for people in the UK and around the world by massively reducing CO2 and pollutant emissions, particularly in the automotive sector. The technology also has added technological value for a wide range of applications, where benefits over batteries allow for longer operation and more power-hungry applications to be serviced more effectively. Reducing dependence on fossil fuels also has the potential to lessen international socio-economic and political tensions, with the prospect of improved geo-political stability.

- Economy and the commercial sector: Use of ammonia as an energy carrier overcomes the key challenge of hydrogen storage and thus accelerates the market uptake of fuel cells, with benefits for the whole supply chain. The production of ammonia using excess electricity produced by renewables will accelerate its large-scale uptake. Use of greater efficiency power generation technologies could reduce energy bills and consequently feed the economy with greater expendable income. The UK is at the forefront of commercial fuel cell development, with some of the largest and best fuel cell companies in the world. Ammonia for fuel cells stands to remove a key barrier to fuel cell uptake and therefore shortens the distance to wide-scale market penetration, with consequent economic benefit to our companies. Also, by developing the IP necessary to underpin ammonia fuel fuelled fuel cells, the UK will have a major advantage if this promising energy vector is adopted.

- People: Positive impact for the people involved in the project will be derived from the expertise developed by the research team, training and transferrable skills acquired. The people who we will work with in industry will benefit from interaction with academics and the university environment through alternative approaches and highly creative ideas. General career progression will ensue for all those involved in the project as a result of the learning, outputs and advances made.

- Knowledge and science base: The scientific and engineering base will benefit from advancements in a range of areas, including: materials, catalysts, polymers, fuel cell and reaction engineering.

- Government: Finally, the Government and policy makers will benefit from expert input into the 'ammonia as a fuel' debate and the technology delivered will provide a new option and dimension for shaping our energy future. DECC are considering ammonia as a component of their 2050 Pathways Calculator after discussions of our research.


Ultimately, we will be considering the automotive sector in the longer term. However, we will be initially targeting back-up power which is a multi-million dollar market for the telecoms sector alone. Cost is a prime concern here, while operational lifetimes need not be long. Lifetimes in the order of 500 to several 1000s hours are that is needed because only intermittent operation is required for power resilience.