Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
dissolution into the carbon electrodes or sulfur and CO poisoning of the fuel cells can
shorten the life of FCVs. 34 Current fuel cell stack life from on-road vehicle testing is
approximately 2,000 hours at which point fuel cell performance is only 90 percent of the
original performance (NRC, 2008), which is significantly lower than the 5,000-hour
lifespan needed to enter the light-duty vehicle market (Wipke et al., 2007).
Another obstacle is the ability to store a sufficient quantity of hydrogen for adequate (i.e.,
300-mile) driving range. The current on-road driving range (corrected for EPA drive cycle)
for a FCV test program ranged between 190 and 250 miles (NREL, 2009b). High-pressure
hydrogen storage tanks appear to be the most effective solution for onboard hydrogen
storage until a more suitable hydrogen storage material is identified.
In addition, the amount of time required to refuel hydrogen vehicles currently is higher
than the time required for conventional gasoline refueling on a gge basis. A recent NREL
study of 3,700 refueling events showed an average of about 0.8 kg/min was achieved for
350 bar (~5,000 psi) tanks, while only 0.6 kg/min was achieve for 700 bar (~ 10,000 psi)
tanks (Wipke et al., 2009). 35
Assuming the average consumer requires a 5 kg fill, waiting
six to eight minutes to refuel is not acceptable so refueling rates must be improved. Also,
the fill rates for hydrogen are nonlinear and slow down as the tank fills. Refueling rates
will likely continue to improve as onboard storage systems evolve to provide longer
driving ranges.
In addition to vehicle-related challenges, a critical component to the development of
HFCVs will be the development of a widespread hydrogen production and distribution
infrastructure. NRC (2008) estimated the government cost for hydrogen
vehicle/infrastructure development at $55 billion between 2008 and 2023 to achieve the
two million HFCV penetration target by 2020 and 5.6 billion by 2023. Greene et al., (2008)
estimated $10 billion in Federal investment is needed to achieve two million HFCVs on the
road. There are significant challenges in the development of either a centralized
infrastructure (in which hydrogen is reformed at central production facilities and
distributed to refueling facilities) or a decentralized infrastructure (in which hydrogen is
produced at numerous small-scale facilities located at the point of sale). The options and
challenges are discussed in more detail in the sidebar on page 2-87.
Finally, reporting requirements currently exist for production, transport, and dispensing of
hydrogen, and will need to be modified or minimized in order to avoid unacceptable
administrative burdens associated with large scale use within the transportation sector
(NGA, no date).
34 Both sulfur and CO are commonly present in hydrogen gas.
35 An FCV’s increased fuel economy roughly doubles their range compared to conventional gasoline
vehicles, so small capacity fuel tanks (on a gge basis) do not severely limit operational range.
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