Gasoline, methanol or hydrogen? It's a matter of reformer technology and infrastructure. Ideally, a sulfur-free, fuel cell compatible paraffinic fuel which can be distributed by our current infrastructure AND still power today's ICEs would be the perfect solution. I still contend that the strongest potential candidates are Fischer-Tropsch (FT) naphtha and diesel. Exxon/GM/Toyota may think so too.
Fuel cell conundrum
04/13/2001
Energy Compass
2001 Energy Intelligence Group
As the oil and auto industries combine forces in the search for a replacement for the internal combustion engine, good old gasoline has taken over from methanol as the most likely intermediate fuel for fuel-cell vehicles (FCVs). But there are still problems with gasoline-powered cells, and by the time the FCVs hit the road, a breakthrough in hydrogen storage technology could allow direct hydrogen to leapfrog gasoline.
The new generation of ultra-clean FCVs will be powered by hydrogen, either directly, or via an onboard processor that converts either gasoline or natural gas-derived methanol into hydrogen. Direct hydrogen - although used in a number of FCV bus trials - has a long way to go. The problem of safely storing hydrogen onboard a vehicle is an immediate barrier - never mind the huge cost of a completely new hydrogen supply infrastructure.
In the meantime, gasoline and methanol are the two most viable options. Neither is ideal. Aside from the added cost and complexity - for car manufacturers at least - of an onboard processor, the conversion results in some greenhouse gas emissions. Experts say there is little difference between gasoline and methanol on that score, and that both would roughly halve emissions compared to conventional combustion engines.
Unsurprisingly, oil companies tend to favor gasoline as the intermediate, if not ultimate, fuel-cell fuel. BP and Norway's Statoil are exceptions - they are working on methanol with DaimlerChrysler and Canadian producer Methanex - but then they both have large natural gas reserves. BP is fairly neutral in any case, working with General Motors on gasoline, and the European Union on a hydrogen bus project at the same time.
Exxon Mobil - currently working with GM and Toyota on an onboard gasoline processor - makes no secret of its preference for gasoline, and has just joined the California fuel cell partnership (CaFCP), precisely to further gasoline's cause (EC Mar.30,p11). The CaFCP - charged with testing gasoline, methanol, and direct hydrogen by 2004 - insists that it is fuel neutral. But CaFCP membership is telling: Four oil majors are full members, while only one dedicated methanol producer, Methanex, is an associate member. The oil companies have more muscle than methanol producers in any case, since they control the fuel distribution network.
Vested interests aside, gasoline has one major advantage over both methanol in the interim and even hydrogen in the longer term: gasoline's infrastructure - production, distribution, and retail - is already in place. GM cited uncertainty over fuel supplies when it dropped its methanol project. And the chances of a dual-fuel gasoline - which can be run in FCVs and conventional engines, to even greater environmental benefit - being explored by Exxon and BP would make it even simpler to adapt to FCVs.
The chicken and egg problem with FCVs and the fuels they run on - which should come first, the fuel or the car? - is one reason for the uncharacteristic cooperation between oil and car companies. Gasoline may help FVCs get onto the roads and ultimately make investment in a new hydrogen infrastructure worthwhile.
But it's not all plain sailing for gasoline. Methanol-powered FCV prototypes are already undergoing road tests. DaimlerChrysler is forging ahead with methanol, although it's now on its own, and plans to put its NECAR 5 prototype into commercial production in 2004. Gasoline processors have still to leave the laboratory. Exxon and GM have so far only managed to test a 12 kilowatt gasoline unit, much less than the 70-100 kW needed to power an actual FCV. GM says it will have a gasoline powered fuel cell in a prototype vehicle early next year. Already running nearly four years behind DaimlerChrysler's methanol project, gasoline powered FCVs are unlikely to be in commercial production for another six years.
And gasoline is not as easy to convert into hydrogen as methanol. The onboard processor can't cope with sulfur at all and works best if the feed is homogenous - it contains molecules of the same structure. Refined gasoline is a wild mix of hydrocarbons and other components - like benzene and sulfur - which have no hydrogen content. Most analysts expect FCV gasoline will have to be made from natural gas using gas-to-liquids ( GTL ) technology. But Exxon is adamant that it can produce a suitable grade of gasoline at its existing refineries. BP is also experimenting with straight-chain gasoline, taken from specific refinery cuts, but admits there are problems when it comes to dual-fuel suitability. Sulfur free, homogenous gasoline, either conventionally refined or GTL , is too low in octane to go into a combustion engine.
Neither type of gasoline is likely to be available in commercial quantities for another five to 10 years, when direct hydrogen's problems could have been solved. Aside from GM and DaimlerChrysler - who are also looking at hydrogen in the longer term - most other car manufacturers have ditched their methanol prototypes and gone straight to direct hydrogen, seemingly confident that hydrogen can leapfrog gasoline.
BP is optimistic that will happen, and is hedging its bets with its involvement in the EU's hydrogen bus project. Royal Dutch/Shell set up a dedicated hydrogen business unit in 1999 and, along with Norway's Norsk Hydro and DaimlerChrysler, plans to turn Iceland into the first "hydrogen economy." Aside from recent advances in lightweight high-pressure hydrogen storage that bring the target 400 miles between refueling ever closer, BP is exploring cheap infrastructure solutions. BP will supply hydrogen gas to London buses from its nearby Coryton refinery. Ideally, it thinks hydrogen should be produced on site - using either water and electricity, or natural gas - - making use of existing infrastructures before a network is viable. Exxon is more skeptical and remains confident of a long-term role for gasoline.
By Kerry Preston, London. |
