The rising level of CO2 emissions is becoming more concerning for a growing population dependent on roadway mobility. Fuel cell vehicles, hereafter FCVs, can provide a significant alternative and sustainable form of transport that combines “energy efficiency<!–[if supportFields]> XE “energy efficiency” <![endif]–><!–[if supportFields]><![endif]–>, emissions reductions, and reduced petroleum use.” This paper summarizes the report of Annex XIII in 2010 by compiling “an up-to date, neutral, and comprehensive assessment of current trends in fuel cell vehicle technology and related policy.” Telias et al. (2010) include a review of the most current components of the fuel cell battery<!–[if supportFields]> XE “battery” <![endif]–><!–[if supportFields]><![endif]–> stack, batteries, and hydrogen storage with commentary on the successful results of fuel cell vehicle demonstrations projects worldwide. —Laura Silverberg
Telias, G., Day, K., Dietrich, P. 2010. RD&D Cooperation for the Development of Fuel Cell, Hybrid, and Electric Vehicles within the International Energy Agency. 2010. World Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition, 1–6.
Telias et al. assess two applications of fuel cell technology, a system that can be seen as a power converter unit providing “electricity and heat and therefore provid[ing] an analogous function in combination with an electric machine as the internal combustion engine<!–[if supportFields]> XE “engine” <![endif]–><!–[if supportFields]><![endif]–> in a conventional vehicle.” The first system functions as an energy converter, used in conjunction with an electric motor to propel the vehicle. The second application of the system analyzes its auxiliary units where power may not be needed at all times, particularly when the vehicle is not in motion. Generally with FCVs, the auxiliaries are significantly lower than that of the demands of the vehicle propulsion. In both applications of the system, the fuel cell can be directly linked with an electric motor, creating a pure fuel cell power train. It is only when the powertrain is combined with an energy storage system that the powertrain becomes a hybrid<!–[if supportFields]> XE “hybrid” <![endif]–><!–[if supportFields]><![endif]–>. Pure FCVs, systems that can manage with the dynamic power demands of the vehicle, require maximum power; the power demand of the car matches the maximum output power of the fuel cell system. The production of power from the fuel cell system has to react instantaneously since there is no energy storage system within the vehicle. This is dynamic power adaptation. In addition, the fuel cell starting time must be in the same range as an internal combustion engine or battery<!–[if supportFields]> XE “battery” <![endif]–><!–[if supportFields]><![endif]–> electric vehicle. Finally, the power output of a fuel cell system, while temperature-dependent (the power output of the fuel cell may be reduced at a lower temperatures), must not be overly-reduced at the ambient temperatures at which it is expected to operate.
Telias et al. briefly evaluate two configurations of hybrid<!–[if supportFields]> XE “hybrid” <![endif]–><!–[if supportFields]><![endif]–> FCVs. The conventional hybrid contains batteries<!–[if supportFields]>XE “battery” <![endif]–><!–[if supportFields]><![endif]–> that store collected braking energy and supply peaking power, or as an alternative, use a supercapacitor for short-term peak power demands. The plug-in hybrid system can be used with or without a connection to the electricity storage grid—it can be charged from the fuel cell system, or charged with electricity. This allows the user to drive moderate distances using grid-supplied electricity.
FCVs require technologically advanced components that are not found in conventional vehicles today. The major components of a typical FCV include: fuel cell system power electronics (consisting of a fuel cell stack offering significant potential for cost-effective production based on economy of scale, and a motor controller, DC/DC converter, and inverter), fuel processor, current inverters and conditioners, and a heat recovery system), electric machines (use alternating current to provide traction to the wheels of the vehicle, therefore enabling propulsion; an energy storage system, and a hydrogen storage system.
Polymer electrolyte fuel cells, hereafter PEFCs, are typically applied for automotive use. Low-temperature fuel cells show good performance regarding nominal power, cold temperature performance, and service life. High-temperature PEFCs have substantial advantages regarding water management and CO<!–[if supportFields]>XE “CO” <![endif]–><!–[if supportFields]><![endif]–>-tolerance, but function slightly less well under low-temperature conditions. Generally, PEFCs can be operated at low pressure with more simple auxiliaries, which result in less power demand for the air compression. In this scenario, humidity control is needed. In a high-pressure scenario, power density can be increased, allowing the water volume for humidity control to be reduced with the addition of a compressor unit. The majority of FCVs today take advantage of high power, high energy, and long cycle life energy storage devices to improve system performance. These energy storage devices can provide assistance to the fuel cell system during events in which temperature and fuel delivery to the fuel cell stack result in voltage drops during high-load demands. Currently, energy storage systems available for use in FCVs include “lithium-ion, nickel-metal hydride, and lead-acid batteries<!–[if supportFields]>XE “battery” <![endif]–><!–[if supportFields]><![endif]–>, as well as ultra capacitors.” Onboard hydrogen storage systems are also required for FCVs. The development of an onboard system to store hydrogen fuel still remains an inhibiting factor for the widespread commercialization of hydrogen. Research and development of additional technologies is still being conducted.
Worldwide, various FCV demonstration projects have been used as a basis for development of future hydrogen infrastructure performance. These demonstrations offer the opportunity to “gather valuable data—including fuel economy, and other factors—that can be used in working towards creative solutions to technical barriers facing hydrogen fuel cell technology in automobiles.” Telias et al. highlight select results of “notable passenger vehicle demonstrations” from around the world including: North America, the European Union, and Japan. Over the next decade, these project committees will focus on infrastructure development and preparing the market for the introduction of their vehicle models in the transportation sector worldwide. Additionally, the authors assess the international trends in funding for RD&D activities regarding fuel cell and hydrogen technologies for transport applications and the policies that provide the framework of development for these activities. In the United States, the Fuel Cell Technologies Program is responsible for the research and development of: hydrogen production and delivery, hydrogen storage, fuel cell stack components, as well as various aspects of the safety standards, technology, marketing, transportation, and distribution of fuel cells. In the European Union, the Multi-Annual Implementation Plan of the “Fuel Cells and Hydrogen Joint Technology Initiative” is responsible for the research and development of: transport and refueling infrastructure, hydrogen production and distribution, stationary power generation and combined heat and power<!–[if supportFields]> XE “combined heat and power (CHP)” <![endif]–><!–[if supportFields]><![endif]–>, early markets, and cross-cutting issues. In Japan, The “Cool Earth – Innovative Energy Technology Program” gives “priority to 21 technologies based on their potential to reduce CO2emissions and to deliver substantial performance improvement, cost reduction, and increased diffusion as well as technologies where Japan could have the global lead.” In this program, the development for FCVs foresees cost reduction through technology development and improvement of durability and cruising distance over the next decade.
While there has been significant development of battery<!–[if supportFields]> XE “battery” <![endif]–><!–[if supportFields]><![endif]–> electric vehicles and plug-in hybrid<!–[if supportFields]> XE “hybrid” <![endif]–><!–[if supportFields]><![endif]–> electric vehicles, manufacturers are continuing research efforts on FCVs. The list of shortcomings of FCVs has been reduced dramatically, although improvements regarding investment costs of the powertrain and installation of the proper fueling infrastructure need further development. Telias et al. suggest learning from the compressed natural gas infrastructure network for fueling stations or introducing the fuel cell system as a “range extender” in combination with a driving battery plugged or unplugged. While the authors anticipate competition over the technologies of the pure battery electric vehicle and the FCV, the favored outcome of the two systems will be based in its superior “combination of costs and convenience.”