Considerable research is focused on how to improve fuel cells, their efficiency, environmental impact and marketability. Fuel cells are very efficient: they change a large fraction of the energy in their fuel and oxidant directly into electrical energy. They are quiet and, with the right fuel/oxidant combinations, they produce little or no pollution. Still, like any technology, fuel cells present limitations of their own to be overcome.
You can get an idea of the range of possible improvements from recent research reports available from the U.S. Department of Energy (DOE) Office of Scientific and Technical Information (OSTI). Those published in just the first few months of 2012 alone address at least four topics: using different fuels in the cell, improving the fuel cell itself, avoiding adverse environmental effects, and understanding fuel-cell market needs.
Some commonly-used fuels consist of materials that can damage either the fuel cell itself or machinery used to prepare the fuel. A recent DOE report from Argonne National Laboratory, supported by the Office of Energy Efficiency and Renewable Energy (EERE) [abstract and full text in OSTI’s Information Bridge], documents how different strategies for removing fuel impurities would affect fuel-cell efficiency and the cost of electricity.
Many fuel cells oxidize hydrogen to produce energy. The DOE-funded U.S. Patent 8,101,305 (Carbon fuel particles used in direct carbon conversion fuel cells) [abstract and full text in OSTI’s Information Bridge], by inventors John F. Cooper and Nerine Cherepy of Lawrence Livermore National Laboratory, describes the use of particulate carbon as a fuel, as well as a system for preparing the carbon for use in a fuel cell. This invention would allow a given amount of energy production with less fossil fuel consumption and pollution.
The DOE-funded U.S. Patent 8,097,384 (“Solid oxide fuel cell with transitioned cross-section for improved anode gas management at the open end”) [abstract and full text in OSTI’s Information Bridge], by inventors Paolo R. Zafred and Robert Draper with support by the National Energy Technology Laboratory, describes a novel arrangement of parts in one type of fuel cell to improve this type in several ways simultaneously. These improvements include increasing the electric current per square centimeter of terminal surface and increasing the terminal surface in a fuel cell of given volume, which address one of the chief longstanding drawbacks of fuel cells: low current per terminal surface area.
Some fuel cells have their fuel and oxidant pumped through water. The water is only one possible medium for the fuel and oxidant. In one now-common type of fuel cell, the fuel ions move about on a membrane instead of through a liquid. More recently, people have recognized potential advantages of using membranes on which the oxidant moves. A workshop supported by the National Renewable Energy Laboratory was held in May 2011 in which researchers exchanged information about recent progress in this field, and the proceedings (find more conference proceedings of interest to DOE) are freely available [abstract and full text in OSTI’s Information Bridge]. While in many respects these “alkaline membrane” cells still don’t match the present capabilities of cells whose membranes conduct hydrogen ions, they are much more competitive than they were when the first such workshop was held in 2006, with alkaline membrane cells offering greater durability and peak power density than before, using membranes of greater electrical conductivity and chemical stability. Furthermore, while the terminals of many alkaline membrane (and other) fuel cells are made of precious metals like platinum, alkaline membrane cells have now been demonstrated that don’t require precious metals.
Many different means of improving fuel cells’ current output have been found over the years. Another National Energy Technology laboratory project [abstract and full text in OSTI’s Information Bridge] reports a recent step in a different approach. This project’s research team had shown earlier that nanotubes made of platinum had relatively high usable surface area per unit mass and output current per unit surface area. However, to optimize the terminals and test the fuel cells, the team needed a way to synthesize platinum nanotubes in batches roughly ten times as large as before. They report success in synthesizing the large batches, but with considerable variation in the properties of the output, indicating that they still have some challenges in controlling and optimizing the synthesis process.
Fuel cells that transport hydrogen between electrodes on a membrane are considered a serious alternative to internal combustion engines for powering automobiles. For this application, the fuel cells are made with platinum terminals and Nafion.RTM. membranes, both of which are expensive. Furthermore, cells of this type typically last about a year before pinholes’ forming in the membrane and deactivation of the platinum catalyst render them useless. Some savings have been achieved by recycling the platinum from old fuel cells, but earlier methods of separating the platinum from the membranes produce a corrosive gas and destroy the Nafion.RTM. The DOE-funded U.S. Patent No. 8,124,261 (Process for recycling components of a PEM fuel cell membrane electrode assembly) [abstract and full text in OSTI’s Information Bridge], by Englehard Corporation inventor Lawrence Shore, describes a new method of recovering both the platinum and the Nafion.RTM. that avoids both problems.
Hydrogen fuel cells for vehicles have been experimented with for some time (see also the second paragraph under “Market Needs” below). But if they ever become common on the road, they’re almost sure to be damaged sooner or later in accidents. What happens if a car’s hydrogen storage tank is breached? That subject is addressed by Savannah River National Laboratory researchers Charles James, Kyle Brinkman, Joshua Gray, Jose Cortes-Concepcion, and Donald Anton, in a study of one particular material for storing hydrogen [abstract and full text in OSTI’s Information Bridge]. Understanding what happens when materials of this kind react to air and water will be crucial for figuring out how to use them safely, and for designing appropriate safety features if such use is possible.
While much of the effort to improve fuel cells is done with future uses in mind, the existing technology is already being put to work in some industries and offers unrealized advantages in others. A Sandia National Laboratories analysis published March 2012 [abstract and full text in OSTI’s Information Bridge] identified eleven potential applications other than vehicles in which equipment could be powered by hydrogen fuel cells, and also determined what the hydrogen-storage and other requirements would be if hydrogen fuel cells were actually used. The up-front cost of switching to fuel cells from other power sources is the most common obstacle: customers surveyed generally demanded that fuel cells pay for themselves in 2 to 5 years. On the other hand, the main attractions of hydrogen fuel cells in all these applications are their zero polluting emissions and low noise. An additional advantage in the portable power generation market is that fuel cells don’t have to idle the way generators do when their power isn’t being used but needs to be available at a moment’s notice.
Whereas the Sandia National Laboratories study dealt with requirements for non-vehicular uses of fuel cells, current results of an ongoing multiyear study of fuel-cell powered vehicles, supported by the DOE EERE [abstract and full text in OSTI’s Information Bridge] were published in February 2012 that include findings from a system of vehicles and fueling stations operating under real-world conditions. The project was started to obtain data about the durability of fuel-cell vehicles, the availability of hydrogen-fueling infrastructure, the performance of both, the need for maintenance and training facilities, and experience with related codes and standards. Other objectives were to demonstrate progressive generations of vehicle fuel system technology and multiple approaches to generating and delivering the hydrogen fuel. The project found that the vehicles met all functional needs for customers’ day-to-day use, even in subfreezing cold weather, and that the fuel-cell stack durability, which was rapidly increased during the project because of rapid response to the data obtained, is expected to meet commercial vehicle requirements in the near term. The report includes recommendations to the Energy Department about things to investigate during the remaining 3-4 years of the study and about ways to commercialize the technology.
The reports mentioned above are, in the same sequence:
Prepared by Dr. William N. Watson, Physicist
DOE Office of Scientific and Technical Information