Editor’s note: This study should be of interest to the wind community, because fuel cells will use DC voltage to electrolyzed hydrogen from water, a supply for which wind turbines are well-suited. This is the executive summary. The full report can be found here: www.nrel.gov/publications.
By Leslie Eudy, of the National Renewable Energy Laboratory, and Christina Gikakis, Federal Transit Administration
This report is the seventh in an annual series of reports that summarize the progress of fuel cell electric bus (FCEB) development in the United States and discuss the achievements and challenges of introducing fuel cell propulsion in transit. This report provides a summary of results from evaluations performed by the National Renewable Energy Laboratory (NREL) and funded by the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Office and the U.S. Department of Transportation’s (DOT) Federal Transit Administration (FTA). Summary results from August 2012 through July 2013 for these buses account for more than 241,579 miles traveled and 21,301 hours of fuel cell power system operation. The summary results are from five demonstrations at four transit agencies:
Zero Emission Bay Area (ZEBA) Demonstration Group led by Alameda-Contra Costa Transit District (AC Transit)
- Connecticut Transit (CTTRANSIT) Nutmeg Project
- SunLine Transit Agency: Advanced Technology FCEB and American Fuel Cell Bus Project
- Proterra bus demonstration at Capital Metro in Austin, Texas.
In late July 2013, NREL began working with British Columbia Transit to conduct a third-party evaluation of the FCEB fleet in Whistler, Canada. This evaluation is being funded by the California Air Resources Board. Because of that involvement, NREL is expanding the annual status report to include FCEB demonstrations in Canada. NREL is currently analyzing data on the BC Transit buses. Because the analysis is not complete, the results are not included in this report. A summary of the results will be included in the 2014 status report. With the addition of the BC Transit buses, NREL’s evaluations cover 35 of the 38 FCEBs currently operating in North America.
DOE and FTA have established performance, cost, and durability targets for FCEBs. These targets, established with industry input, include interim targets for 2016 and ultimate targets for commercialization. Table ES-1 summarizes the performance of the FCEBs in the report compared to these targets. DOE/FTA set an ultimate performance target of 4–6 years (or 25,000 hours) durability for the fuel cell propulsion system, with an interim target of 18,000 hours by 2016. Manufacturers have continued to make significant progress toward meeting the target over the last year. As of July 2013, NREL documented a single fuel cell power plant (FCPP) that has reached 13,800 hours. Two more FCPPs have reached 10,000 and 9,000 hours.
Availability continues to vary from site to site with data from the last year ranging from a low of 31% up to a high of 81%, with the overall average at 69%. There appears to be a general upward trend for availability over time, despite extensive downtime for two of the projects. The most common issue affecting the availability for the buses was general bus maintenance, followed by traction batteries, and the fuel cell system.
The targets for roadcall frequency include miles between roadcalls (MBRC) for the entire bus and MBRC for the fuel cell (FC) system only. The FC system MBRC includes any roadcalls due to issues with the FC stack or associated balance of plant. NREL tracks an additional metric of propulsion system MBRC. This category includes all roadcalls due to propulsion-related bus systems. Overall the cumulative MBRC through July 2013 was 2,728 for bus MBRC; 3,999 for propulsion MBRC; and 11,043 for FC system MBRC.
The FCEBs continue to show improved fuel economy compared to the baseline buses in similar service. FTA’s performance target for FCEB fuel economy is 8 miles per diesel gallon equivalent (mi/DGE), which is two times higher than that of diesel buses. The FCEBs showed improved fuel economy ranging from 1.8 to 2.4 times higher than that of diesel and CNG baseline buses. Fuel economy for the FCEBs ranged from 5.8 mi/DGE up to 7.3 mi/DGE for an average of 6.8 mi/DGE.
Over the past year, AC Transit successfully re-introduced the ZEBA fleet into service after a nine-month downtime while an incident at the hydrogen station was investigated and issues were resolved. The station was repaired, upgraded, and re-commissioned by the end of January 2013. During the nine-month period that the station was down, the FCEBs were parked at the depot. Once the station was back online, the agency began the start-up procedure to get the 12-bus fleet operational. The agency reports that the start-up procedure went extremely well and that anticipated problems did not occur. There have been no reported problems with the buses as a result of the downtime.
The current economic climate has resulted in changing players within the FCEB market as companies have left the market through restructuring or bankruptcy. This makes conducting long-term demonstrations a challenge when the partners no longer provide technical support or produce parts needed for repair. The primary change over the last year involved one of the fuel cell manufacturers, UTC Power. This fuel cell technology division of United Technologies was sold to ClearEdge Power, which then announced its intention to sell the transit bus power plant portion of the company. US Hybrid, a California technology development company, has taken over that portion of the business and will complete the NFCBP projects originally led by UTC Power.
While bus performance and fuel cell system durability have continued to improve, there are still challenges to overcome to move FCEB technology to a commercial product. Technical challenges include increasing reliability of components and lowering capital and operating costs. Despite the remaining challenges, FCEBs continue to show progress toward meeting the technical targets for commercialization. In the next year, several more FCEBs and operating sites are expected to begin demonstration; these will be included in next year’s status report.
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