DOE releases final report from 6-year national fuel cell vehicle demo; key targets met, with twice the efficiency of today’s gasoline vehicles
The US Department of Energy (DOE) released the final report from its National Renewable Energy Laboratory (NREL) for a technology validation project that collected data from more than 180 fuel cell electric vehicles over six years (early 2005 through September 2011). These vehicles made more than 500,000 trips and traveled 3.6 million miles, completing more than 33,000 fill-ups at hydrogen fueling stations across the country.
The project—the Controlled Hydrogen Fleet and Infrastructure Validation and Demonstration Project, also referred to as the National Fuel Cell Electric Vehicle (FCEV) Learning Demonstration—met its key technical targets, the NREL report said. NREL also found that these early fuel cell vehicles achieved more than twice the efficiency of today’s gasoline vehicles.
The NREL report said that baseline data from the demonstration teams in 2006 showed a range of net system efficiency from 51% to 58% for first-generation (Gen 1) systems, which was very close to the target. Second-generation (Gen 2) vehicles showed an efficiency of 53% to 59% at quarter-power, within one percentage point of the target.
In 2009, NREL expanded this CDP to include a comparison of the efficiency at full power, for which DOE’s target was 50% net system efficiency. The data show first-generation systems as having 30% to 54% efficiency at full power while second-generation systems have 42% to 53% efficiency, exceeding the 50% target.
...this project has exceeded the expectations established in 2003 by DOE, with all of the key targets being achieved except for on-site hydrogen production cost, which would have been difficult to demonstrate through this project because the hydrogen stations were not designed, constructed, and utilized as full scale, commercial stations.—Final Report
The Learning Demonstration project began in 2004 when DOE competitively selected four automaker and energy partner teams. (Daimler and BP; GM and Shell; Chevron, UTC Power and Hyundai-Kia; and Ford and BP.) Two of the four original OEM and energy partner teams concluded their projects on schedule (based on the original five-year planned project duration) and provided their last data at the end of 2009, while two of the vehicle OEMs and Air Products extended their projects and provided data to NREL for another two years.
The final report is the first comprehensive report to include all new or updated results (40 composite data products (CDPs)) published in the last two years; it recaps the highlights from the first five years and summarizes new results from the final two years of the project.
The three primary objectives of the project were to evaluate fuel cell durability, vehicle driving range, and on-site hydrogen production cost and compare to DOE’s targets. The three high-level DOE technical targets for hydrogen FCEVs and infrastructure were:
250-mile driving range. Second-generation vehicle driving range from the four teams was 196–254 miles, which met DOE’s 250-mile range target. In June 2009, an on-road driving range evaluation was performed in collaboration with Toyota and Savannah River National Laboratory. The results indicated a 431-mile on-road range was possible in southern California using Toyota’s FCHV-adv fuel cell vehicle.
More recently, the significant on-road data that have been obtained from second- and first-generation vehicles allowed a comparison of the real-world driving ranges of all the vehicles in the project. The data show that there has been a 45% improvement in the median distance between fueling events of second-generation vehicles (81 miles) as compared to first-generation vehicles (56 miles), based on actual distances driven between more than 25,000 fueling events.
Over the last two years, NREL saw a continuation of this trend, with a median distance between fuelings of 98 miles, which is a 75% improvement over the first-generation vehicles. The vehicles are capable of two to three times greater range than this, but the median distance travelled between fuelings is one way to measure the improvement in the vehicles’ capability, driver comfort with station location and availability, and how they are actually being driven, NREL said.
2,000-hour fuel cell durability. The maximum number of hours a first-generation fuel cell stack (2003–2005 stack technology) accumulated without repair is 2,375—the longest stack durability from a light-duty FCEV in normal use published to date of which the NREL team was aware. On average, the rate of the initial power degradation is higher in the first 200 hours and becomes much lower after that, similar to the fuel cell voltage degradation.
NREL also found that stack operation of around 1,000 hours is required to reliably determine the rate of the more gradual secondary degradation. Finally, significant drops in power were observed at 1,900–2,000 hours, providing a solid upper bound on first-generation stack durability. The maximum and average projected times until 10% voltage degradation for first-generation systems were 1,807 hours (best of the four teams) and 821 hours (average of all teams).
For second-generation fuel cell stacks (2005–2007 stack technology), the range of maximum hours accumulated by the four teams was approximately 800 to more than 1,200 hours, and the range of average hours accumulated by the four teams was approximately 300 to 1,100 hours. Relative to projected durability, the Spring 2010 results indicate that the highest single-team average projected time to 10% voltage degradation for second-generation systems was 2,521 hours, with a multi-team average projection of 1,062 hours. Therefore, DOE’s 2,000-hour target for durability has been validated.
Over the past two years, additional fuel cell durability data were acquired from updated GM and Daimler vehicles (2007–2009 stack technology) during their extended projects. Because there are only two teams, it is not possible to provide both the maximum and the average without revealing the individual results of both teams, NREL said, but reported that the average projected time to 10% voltage degradation of the two teams is 1,748 hours, a significant increase over first-generation and second-generation results.
$3/gallon gasoline equivalent (gge) hydrogen production cost (based on volume production). Cost estimates from the Learning Demonstration energy company partners were used as inputs to an H2A analysis to project the hydrogen cost for 1,500 kg/day early market fueling stations. H2A is DOE’s suite of hydrogen analysis tools, with the H2A Production model focused on calculating the costs of producing hydrogen.
Results from version 2.1 of the H2A Production model indicated that on-site natural gas reformation could lead to a cost range of roughly $8–$10/kg and on-site electrolysis could lead to a hydrogen cost of $10–$13/kg. 1 kg hydrogen is approximately equal to the energy contained in a gallon of gasoline, or gallon gasoline equivalent (gge). While these project results do not achieve the $3/gge cost target, two external independent review panels commissioned by DOE concluded that distributed natural gas reformation could lead to a cost range of $2.75–$3.50/kg and distributed electrolysis could lead to $4.90–$5.70/kg.
Therefore, NREL concluded, this objective was met outside of the Learning Demonstration project using distributed natural gas reforming.
From all of the project results that NREL has generated, it is our conclusion that FCEVs have advanced rapidly in the last seven years. As the automotive OEMs and other researchers worldwide continue to focus on the remaining challenges of balancing durability, cost, and high-throughput manufacturability, we are optimistic that improvements will result in a manageable incremental cost for fuel cell technology. We therefore expect continued progress to lead to several vehicle manufacturers introducing thousands of vehicles to the market in the 2014–2016 timeframe, at which time the hydrogen community will have its first true test of whether the technology will be embraced by the public.—Final Report
K. Wipke, S. Sprik, J. Kurtz, T. Ramsden, C. Ainscough, and G. Saur (2012) National Fuel Cell Electric Vehicle Learning Demonstration Final Report NREL/TP-5600-54860