| Hydrogen Offers a Helping Hand to Diesel |
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Publication Date:18-May-2006 08:00 PM US Eastern Timezone Source:Green Car Congress-Michael Millikin |
 Two
events occurred this past week that highlighted different roles--and
potential--for hydrogen used directly in a vehicle. (Hydrogen is already
indispensable to the petroleum refining industry, among others.)
In the first, Miljobil Grenland AS, a participant in and vehicle provider to the Norwegian Hydrogen Highway (HyNor), ordered 15 hydrogen-fueled Prius hybrids from Quantum Fuel Systems--the company which has provided 30 such vehicles to various cities in California for testing. In the second, Delphi used the Engine Expo in Stuttgart, Germany, to provide an update on its work in using an on-board diesel fuel reformer that generates a small amount of hydrogen to greatly enhance the NOx control on a diesel vehicle. Quantum's H2Hybrid Priuses are modified to have the combustion engine run entirely on hydrogen. The car offers extremely low tailpipe emissions: virtually no HCs, CO, CO2 and PM, and with the potential for low NOx. It's also more cost-effective than fuel cells. The car has an estimated fuel economy of 50 miles per kilogram (mpkg) of hydrogen in the city, 42 mpkg highway. But the compressed hydrogen storage system only holds 1.6 kg (stored at 5,000 psi), thereby supporting an estimated range in a combined cycle of about 74 miles. Using a metal hydride storage system increases the hydrogen storage capacity to 4 kg, with a corresponding extension in range to 184 miles. But when laden with the hydride system, the car has a payload and passenger capacity of only 252 pounds. That increases to 772 pounds with the gaseous storage. That's not a problem with Quantum’s engineering...it's simply the problem the industry faces with not having a solution to store enough hydrogen. Hydrogen storage remains one of the major barriers to more widespread adoption of hydrogen as a fuel. Delphi, on the other hand, is using hydrogen in a completely different way. The on-board reformer is part of the emissions aftertreatment system. The reformer unit takes a small amount of fuel, mixes it with air and catalytically converts it to a synthesis gas (syngas) rich in hydrogen. This hot reformate gas is injected directly into the vehicle's exhaust system to optimize the performance of a NOx control device called a Lean NOx Trap (or adsorber). The reformate is also used for diesel particulate filter regeneration. Testing results presented by Delphi at the Engine Expo on a 2004 Silverado diesel showed NOx levels about half of those specified in the Tier 2 Bin 5 standards--in other words, it works well in cleaning up diesel systems. One advantage of this system is its ability to help diesels meet increasingly stringent regulations at a lower cost than other approaches being taken. Such cost reduction, in turn, would reduce the diesel price premium over gasoline cars. Combined with the additional fuel efficiency of the diesel platform, bridging of the sticker price gap could accelerate diesel adoption in the US even faster. Delphi plans to begin production of the device in 2010. Delphi is not alone in its exploration of an on-board reformer. Other applications, especially on large trucks, use the resulting hydrogen to enhance combustion in the cylinders, or to power an auxiliary power unit. It would be somewhat ironic if the hydrogen highway gets a boost by enhancing the fuel efficiency of and reducing the emissions from petroleum-fueled vehicles. |