Why use methanol to fuel a fuel cell? It must offer significant benefits, as it has not only inspired the development of a type of fuel cell dedicated to its use – the direct methanol fuel cell (DMFC) – but is also becoming increasingly popular as a source of hydrogen for systems based on proton exchange membrane fuel cells (PEMFC).
Examples of this later, but let’s first look at the reasons for its popularity. Methanol is a convenient liquid fuel, easily handled and easily transported, eliminating many of the difficulties associated with the provision of compressed gases such as hydrogen where infrastructure is lacking. It is readily available at consistent quality as a mass-produced commodity, and in cost-per-unit-of-energy terms compares favourably with gasoline and diesel. Methanol is inherently less prone to ignition and burns more slowly than gasoline and, while it is toxic if ingested, with sensible precautions it is non-hazardous. It is stable, has low volatility, and remains liquid over a broad temperature range, covering all conditions in which fuel cells operate. Setting aside the means of production for the moment, as a substance methanol is a relatively environmentally benign liquid fuel: it mixes with water and quickly biodegrades to harmless products, with none of the severe, long-term soil and water contamination associated with petroleum spills.
Methanol can be used in two ways by fuel cells, reformed either internally or externally. DMFC use a specialised catalyst on the anode and can form hydrogen directly from methanol via internal reforming, but are best suited to small systems. They are being used in applications such as charging batteries in forklift trucks (Oorja Protonics) and camper vans (SFC Energy’s EFOY). For larger systems PEMFC are more economical, but they require pure hydrogen to function, so methanol must be reformed externally to produce hydrogen that is then fed to the fuel cell. A further advantage of methanol is that it lends itself to this process, requiring no prior clean-up and only moderate conditions for the reforming process.
Manufacturers of PEMFC systems are now capitalising on these benefits. At the 2012 Hydrogen + Fuel Cells Group Exhibit at the Hannover Messe, Danish product developer Serenergy was showing a range of solutions based on high-temperature PEMFC with integrated fuel reforming and fuelled with liquid methanol. One of these, the EcoMotion landscape maintenance vehicle (developed by Serenergy and partners) uses this technology and displaces conventional diesel- or gasoline-fuelled equipment, with numerous benefits as a result. But because the EcoMotion is intended for use in parks, zoos, cemeteries, schools, stadiums and so on, it is likely to be a one-off sale to most customers – no deploying of fleets that would make installing a hydrogen refuelling station economical. The use of methanol makes this niche application for fuel cells viable.
Another fuel cell application where methanol can be of benefit is in the provision of off-grid or grid-support power – backup power supply to telecommunications base stations is a good example. Fuel cell systems in remote locations rely on packaged or bulk hydrogen delivery (unless they have been integrated with renewable energy microgeneration and electrolysers to produce hydrogen on site). IdaTech in the USA, a prominent supplier of fuel cell systems to this market, introduced an alternative fuelling option in its product range in 2010. The ElectraGen ME System uses HydroPlus fuel, a blend of water and methanol, and is advertised as an ‘extended run’ system for telecom applications. The use of methanol instead of bottled hydrogen allows for more energy to be supplied to the site with each delivery of fuel, meaning longer runtimes with fewer deliveries. IdaTech says that its system can run for 40 hours at 5 kW output on 59 (US) gallons of HydroPlus, which would otherwise require 24 standard hydrogen cylinders. ReliOn, another well-known name in this market, has recently announced that it also intends to add the option of methanol fuel delivery for its products, and is collaborating with Hy9 to develop an integrated methanol fuel processor.
It isn’t all positive, of course. Systems that are fuelled with methanol will produce carbon dioxide emissions at the point of use (which is one of the reasons they are not being more widely used in automotive applications). Today this is fossil carbon for the most part but there is no reason it couldn’t be renewable carbon instead. Methanol is produced using synthesis gas (a mixture of carbon monoxide and hydrogen) and can thus be made from any feedstock from which syngas is created, including biomass, second generation biofuel, and waste. Another option is to use carbon dioxide captured from emissions to provide the carbon component in methanol, and this is being trialled (the hydrogen can be renewably generated by electrolysis). There is also research into the photocatalytic conversion of methane and water to produce both methanol and hydrogen; if biomethane is used the fuels could be carbon neutral.
These examples show how methanol can be used to produce efficient power with fuel cells. Similar to most of the hydrogen used today, methanol is currently fossil fuel based, but the future for both fuels is to become carbon neutral and the technology exists to do this. Having the option to use a variety of fuels such as these can only enhance the diversity and flexibility of fuel cells as a low-carbon energy solution.
Marge Ryan Market Analyst