Competing or complementary technologies? It is apparent that with current technology, EVs and FCVs are both imperfect replacements for conventional vehicles in some ways, and expecting either to make the transition to the dominant transportation propulsion technology is far from a sure bet. EVs have range and recharging limitations, and while FCVs boast an efficiency that is higher than ICE vehicles, they suffer responsive performance issues and do not offer a large enough gain to overcome the higher purchase price and lack of hydrogen infrastructure. What is needed is a vehicle that blends the advantages of EVs and FCVs. Luckily, such a vehicle design is possible. A hybridized design that uses a battery as well as a fuel cell can overcome many of the disadvantages of both EVs and FCVs and compete with the ICE vehicle on performance terms. In fact, it is unlikely that FCVs will be built without energy storage. Even better, they can be designed as plug-ins that can drive on pure electricity for a portion of the range to tap into that high EV efficiency. The FCVs that come to market will likely be fuel cell hybrid electric vehicles, or FCHEVs. A battery on board to support the PEMFC provides the quick response required - and desired - by drivers. An FCV without a battery also cannot recover regenerative braking Why not reversible fuel cells? In order for a fuel cell system to be able to capture regenerative braking energy, the system would have to also work as an electrolyzer to split water into H2 and O2. This would require a source of water on board the vehicle that could be pumped through the fuel cell. This water source would take up space, could become depleted over long trips, and would also need to be replenished. Obtaining water exiting the cathode of the fuel cell would add to system complexity, and obtaining it from an off-board source requires extra plumbing. A method for eliminating the produced O2 would also be required. There is also the problem of storing the produced H2, which would be at a much lower pressure than the H2 stored in the tank, and thus would have to be pressurized - this would require time in which hydrogen exiting the tank for propulsion would not be possible. Regenerative braking performed by the fuel cell would therefore be less efficient and make the vehicle less responsive than regenerative braking by batteries.
energy (it would be theoretically possible but completely impractical to run the PEMFC in reverse and produce hydrogen gas to be stored in the on-board tank), and this is a big efficiency advantage of a vehicle with an electric motor. So having a battery paired with a PEMFC in an FCHEV makes the vehicle more responsive and more efficient. In this way, fuel cells and batteries are complementary - and not competing - technologies. Fuel cell hybrids for the masses The commercialization of FCHEVs is certainly not following the path that fuel cell advocates have been predicting. There are several reasons for this delay: • Fuel cell performance has been lacking. • The fuel cell system is too expensive. • Hydrogen storage technology performance is inadequate. • Hydrogen production pathways have not developed. • Hydrogen refueling stations have not materialized. The technological performance issues are being addressed by the industry and by a renewed interest in fuel cells and hydrogen research by the US Department of Energy. Governments at various levels are also working on the infrastructure issues. Refueling station projects are being funded in clusters to promote FCHEV adoption in certain metropolitan areas (especially in California) in advance of FCHEV deployment. And there is support for cutting-edge research into hydrogen production via algae and other biological pathways. Interest in fuel cells never waned in Asia and Europe as it did in the US, as the growing infrastructure in both regions shows. There were 17 public stations in Japan at the end of 2012, with plans to build 19 more in 2013 and hit the 100-station mark by 2015. There are currently 15 public stations in Germany, with plans for 400 by 2023. A lot of work is being done to remove roadblocks, and the industry as a whole has made considerable progress since the last failed attempt at commercialization occurred circa 2008. The automotive companies, for their part, have been forming partnerships to pool resources and reduce R&D costs. Some of these partnerships include agreements between GM and Honda, FordRenault-Nissan-Daimler, and Toyota-BMW. Several companies, including Hyundai, Toyota, Nissan, and Kia, have said that 2015 is the year for FCHEV
Published on Dec 21, 2013