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THE NATIONAL Renewable Energy Laboratory hosted attendees of Toyota’s 2012 Future Mobility Seminar at its Golden, Colorado, facilities on Oct. 17. Here are some technical take-aways from a most interesting day spent at NREL.
Do you know those little official seals certifying delivery rate on service station gasoline and diesel pumps? Compared with these liquid fuels, compressed hydrogen presents greater challenges of measurement related to temperature and pressure.
NREL researchers are developing techniques to ensure that H2 stations supporting fuel cell electric vehicles have analogous certification. Their client in this research is the California Division of Weights and Measures, which already has a fledgling FCEV infrastructure to oversee.
A second area of NREL research is a joint effort with Xcel Energy in developing an integrated system of renewable hydrogen. Its first step involves solar panels, wind turbines or a combination of the two generating electricity.
This electricity in turn produces hydrogen through one of three means: by electrolysis of water, or by operating a fuel cell, either of the Alkaline or Proton Exchange Membrane variety, essentially in reverse. (That is, we typically think of a fuel cell taking in hydrogen and oxygen and producing electricity, but this highly efficient concept can be reversed as well.)
H2 output pressures from such hardware are on the order of 100-200 psi. Cascading compression brings this to higher pressures used in FCEVs and on-site electrical generation at NREL. Also, at several stages, excess capacity can be made grid-compatible to a local electric utility.
Researchers note that 55 kWh of electric energy can produce 1 kg of H2. Perhaps 10-12 percent of the energy is consumed in the cascading process (considerably less energy than with liquefaction, for example). At this point of development, H2 would be about $8-$10/kg delivered at the 10,000 psi. used in many FCEVs.
To put this cost in perspective, on an energy basis 1 kg of H2 is equivalent to 1 gal. of gasoline. In their favor, FCEVs are more than twice as efficient in their use of this energy carrier. Thus, right now, this hydrogen is on parity with $4.00-$5.00/gal. gasoline—and it’s renewable.
NREL researchers also displayed their activities in V2G. A vehicle-to-grid linkage exploits the fact that a vehicle spends a lot of time just sitting there. Thus, why not employ a BEV’s battery pack in support of the electric utility grid? Utilities could use this incremental storage for load-leveling or to augment peak periods. BEV owners could be given monetary or other incentive for the temporary use of their vehicles’ battery packs.
Dr. Dan E. Arvizu, NREL director, offered remarks at the conclusion of our visit. He spoke highly of an active “bio space” in energy development, but perhaps not in the usual sense of the term. The bio community is no longer simply looking for exploitable biological species, but rather at investigating bio basics. It’s focusing R&D on soluble carbons, not just making things into sugar. “Corn ethanol,” Dr. Arvizu said, “is agricultural policy, not energy policy.”