Image: Tiger Optics
Carbon dioxide, the gas most connected to recent global warming, represented about 82% of U.S. greenhouse gas emissions (GHGs) in 2013. Transportation accounted for 27% of those emissions, with more than 90% of U.S. transportation petroleum-based, according to the latest EPA report.
As world leaders strive to finalize a climate treaty in Paris this December, the push for carbon-free transportation gains ever-greater urgency. And President Barack Obama has pledged to reduce U.S. GHG emissions by 26 to 28% in 2025 from 2005 levels.
The state of California mandates a dramatic reduction in carbon emissions by 2020; to meet this goal, use of non-internal-combustion alternatives, including both hydrogen fuel cell and conventional electric vehicles, will be important. Currently, conventionally fueled cars and light trucks represent 62% of all GHG emissions in transportation, and control or capture of emissions on the vehicle isn’t yet technically feasible.
Use of clean-burning hydrogen can curb GHG emissions and reduce dependence on oil. With “zero tailpipe” emissions, hydrogen fuel cell electric vehicles (FCEVs) emit only water vapor, warm air and some hydrogen, which don’t diminish air quality. “However, depending on the method, production of hydrogen and electricity emit varying quantities of GHGs, so those production emissions weigh in the calculus,” says Randy Bramston-Cook, Principal at Lotus Consulting, provider of instrumentation packages.
Steam-reforming natural gas is currently the most affordable way to produce hydrogen. “Utilizing fuel from that process, a FCEV represents less than half the GHG emissions of a gasoline-powered car,” says Jerry Riddle, President of Tiger Optics LLC. “However, hydrogen can also be produced from renewable energy sources, such as biomass, wind and solar, which could reduce ‘well-to-wheel’ emissions to near zero.”
The importance of testing hydrogen
Today, automobile manufacturers are shifting from the development stage of fuels cells into full commercial production. Toyota’s Mirai is now reaching California markets. And there are both legal and pragmatic reasons to monitor the quality of the fuel for these vehicles, as safety can never be compromised.
“California law, for example, requires its Div. of Measurement Standards to establish and enforce quality standards for alternative engine fuels sold there,” says Bramston-Cook.
Hydrogen purity is critical to maintaining performance of these fuel cells, as trace contaminants from the production process or from leaks in transport and storage can shorten the fuel cell’s life. “Certainly the manufacturers of FCEVs want reliable fuel, because vehicle reliability is crucial to winning consumer confidence,” says Bramston-Cook. “Indeed, FCEV manufacturers are required in California to warranty the power train for 100,000 miles, highlighting the critical need for fuel quality.”
In response to the need for pure hydrogen, the Society of Automotive Engineers (SAE) have placed stringent standards on hydrogen fuel purity. In fact, the SAE’s Fuel Cell Standards Committee has three Work Groups responsible for setting standards for safety, performance and interface requirements of fuel cell systems in motor vehicles. One resulting protocol is SAE J2719, the commodity standard for hydrogen fuel quality.
The standard was first issued in 2005, and it was revised in 2008 and 2011 to recognize the progress made by fuel cell and automotive industries to determine and verify acceptable levels of hydrogen contaminants. Today, California has adopted SAE J2719, as has ISO internationally.
In July 2014, SAE published J2601 “Fueling Protocols for Light Duty Gaseous Hydrogen Surface Vehicles” noting the protocol was developed and verified over 13 years, moving from the laboratory “to the field with automaker hydrogen storage under extreme conditions on three continents with test tanks and vehicles.”
SAE said its “J2601 standard fueling” method will enable hydrogen stations to refuel FCEVs within three to five minutes.
Analytical Equipment to promote fuel cell use
Fuel cells using a proton exchange membrane (PEM) have been widely used for many decades. The critical requirement for FCEVs is to ensure fuel cell longevity and reliability by preserving the catalysts by avoiding contamination of the hydrogen fuel.
“With the commercial introduction of hydrogen FCEVs in California, hydrogen fuel will be regularly monitored by the state’s Dept. of Food and Agriculture, Div. of Measurement Standards,” says Bramston-Cook. “They have the authority to sample the fuel at the dispenser, test it for impurities and, if required, shut down the fueling station if the fuel isn’t compliant.”
With the SAE’s fuel standards in place, they have identified many contaminants that must be monitored at very low levels, pushing the capabilities of traditional analytical equipment. “At least seven of the over-a-dozen contaminants are effectively monitored by Cavity Ring-down Spectrometers (CRDS) supplied by Tiger Optics LLC, with advantages of being very specific to the analyte, sensitive enough to measure below the mandated levels, with response time rapid enough to allow fast throughput of samples,” says Riddle.
An “absolute” technique, CRDS is drift-free, meaning it doesn’t require external calibration. “This further distinguished CRDS, as many other technologies do require calibration, often using gases that are fossil-fuel-based,” says Riddle.
The future hydrogen FCEV
The future is bright for FCEVs which are capable of traveling 300 miles on a tank of hydrogen and refueling in under five minutes. However, the public must find hydrogen fuel readily available and reliable. With suitable public-private funding, construction of hydrogen fueling stations are underway.
“Assuring the fuel’s integrity is crucial because contaminants can harm the fuel cell,” says Bramston-Cook. ”In California, state regulators are adding a second Lotus Consulting hydrogen fuel analyzer system to test hydrogen fuel samples for a dozen or more destructive contaminants.”
“To supplement such definitive tests at state laboratories, stakeholders debate the feasibility of adding analyzers at each station to test for fewer, but likely, contaminants,” says Bramston-Cook. “However, low-cost, on-site technology for measuring all required impurities isn’t currently feasible.”