Making hydrogen fuel cells cost effective

Perhaps another example of Gartner's Hype Cycle, the technology has not quite been able to keep pace with expectation and progress has seemed to slow. Today, many engineers from major European automotive OEMs will tell you that, while interested in the technology and aiding its development, they expect there to be no serious crossover in power train, at least to hydrogen fuel cells, until 2025 at the earliest. Although many of the world's largest automakers, including Hyundai, Honda and Toyota have announced plans to launch fuel cell vehicles by 2015, like many of today's electric cars they are likely to be prohibitively expensive. There may well be thousands on the road before 2025, but it is unlikely there will be millions. There are many significant technological hurdles to overcome and barriers to entry include power density, reliability and storage. In addition, the surrounding infrastructure necessary for a hydrogen-fuelled economy is currently in limbo dominated by a chicken and egg situation of what will come first, vehicles or filling stations. Much like the current trend towards hybridisation and electric cars , don't expect any sudden moves away from the internal combustion engine just yet. However, despite the roll-out of the technology being slower than many would have preferred, engineers in general like the technology and see it as a viable future technology that is undoubtedly going to become increasingly significant. Current fuel cell technology has one inherent drawback, however, that really does need to be addressed before it can make its mark; the catalyst. Currently, platinum is widely used, with an average fuel cell car needing 30g of the precious metal to function adequately. With the average price of platinum around $50 a gram, the raw material alone incurs a significant cost. Many current fuel cell developments are based around trying to reduce, and even replace platinum catalysts altogether with some kind of low-cost ubiquitous material. Last year the US National Institute of Standards and Technology said it had developed a reliable method of applying atom-thin layers of platinum that would be cheap and easy to implement. The process would allow the precise deposition of layers of platinum to be applied to a substrate to reduce, by an order of magnitude, the amount of material necessary for the catalyst and so to the associated cost. The process involves using platinum dissolved in a solution, which can then be deposited on a gold surface in single-atom layers by alternately applying positive and negative voltages. It is clever stuff, but the science is complex and will not be easily industrialised. Another exciting development, however, is happening here in the UK and comes from Cheshire start-up, ACAL Energy. The company is working on what could be a revolutionary liquid catalyst for a proton exchange membrane (PEM) fuel cell, which could reduce the required platinum by 80% or more. The technique is offering some real potential as the liquid catalyst technology known as FlowCath replaces over three-quarters of the necessary platinum with a low cost liquid catalyst. FlowCath is a method of replacing the fixed platinum catalysts on the cathode with a liquid regenerating catalyst system. The liquid is continuously pumped through the fuel cell stack into an external regenerator and then back to the stack. The technology reduces platinum content by up to 80% and actually helps to simplify the overall fuel cell system. As a consequence the technology not only radically reduces cost, it also improves durability and robustness. "In the 19th century, coal was the fuel and the steam engine was the engine of choice," says Dr Andrew Creeth, chief technology officer at ACAL Energy. "In the 20th century it was hydrocarbons and the internal combustion engine, and moving in to the 21st century we will give up hydrocarbons for hydrogen. The fuel can be made with renewable energy and the engine of choice will be the fuel cell. "Our system can get rid of much of the platinum needed in a fuel cell and we now have working fuel cells. We're targeting the automotive industry and already have a lot of interest from major OEMs." The use of a liquid catalyst dramatically improves a PEM fuel cell's durability and at the same time reduces the cost of a system. The liquid acts as both a coolant and catalyst for the cells, ensuring that they last longer by removing most of the known decay mechanisms. Importantly, ACAL Energy's technology significantly reduces the total cost and weight of a fuel cell and enables a competitive fuel cell drivetrain with a power output of 100kW approximately equivalent to a 2-litre diesel engine. By using a liquid catalyst an ordinary transition metal can be used in the system instead which can be orders of magnitude cheaper than platinum. It is fundamentally stable, which also helps durability, and by having a liquid present it prevents the fuel cell membrane from expanding and contracting as it swells with liquid and then dries. This, in a normal fuel cell, creates an undesirable mechanical stress that leads to wear, fatigue and even eventual failure. "All these factors help our system to be much more reliable," says Dr Creech. Over the last 16 months, ACAL Energy has put its proprietary catayst and fuel cell system through an automotive industry standard stress test protocol. This simulates a 40-minute car journey with a start and stop at the end of each cycle. The cycle is repeated 24 hours a day, seven days a week, and mimics vehicle journey's with frequent stops and starts as well as occasional motorway cruising. This particular test was used to accelerate the aging of components and stress on the fuel cell systems. "We have recently reached the 10,000 hour runtime on a third party automotive industry durability test," says Dr Creech. "We passed it without any signs of degradation, which is a significant milestone to pass." The 10,000 hours mark is equivalent to 300,000 driven miles and it makes the hydrogen fuel cell comparable to the best current lightweight diesel engines under such test conditions. The technology is around the Technology Readiness Level 4 (TRL4) mark and ACAL is now in the process of entering some Joint Development Agreements (JDAs) with automotive OEMs and Tier 1 companies to integrate the technology and show long term viability. The fuel cell is also being engineered for cost effectiveness to enable higher volume manufacture. "The car companies and fuel cell industry has already designed many of the parts and components we need," says Dr Creech. "So we are in the process of adapting our designs to incorporate parts that are already [available off the shelf]. But, we can only take the engineering so far. "We want to take it to a point where we can do a functional specification and then let automotive companies take it forward from there."