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Hydrogen Cars vs. PHEVs

August 12, 2010

There is a possibility that hydrogen can displace gasoline for powering our vehicles and thereby lessen our use of foreign oil.

President Bush called for $1.2 billion to be spent on a Freedom Fuels initiative to replace gasoline with hydrogen.

Several books have been written about the wonders of hydrogen. One began with the sentence, “When there is no more oil” … and then touted the hydrogen economy.

As is so often the case with these so-called Green thinkers, the book was long on rhetoric and short on science. And as usual, the book hyped global warming.

It’s possible that hydrogen could play a role in cutting our use of foreign oil. Eventually it could be the winner in a competition with Plug-in Electric Vehicles.

The four major problems with using hydrogen are: storage on the vehicle; producing hydrogen; transporting hydrogen to service stations; and the extremely high cost of fuel cells.

Storage of hydrogen on a vehicle currently requires large and unwieldy high-pressure containers rated 5,000 or 10,000 psi for storing compressed hydrogen; or bulky “thermos bottle” containers for storing liquid hydrogen. Metal hydrides might be an alternative for on-board storage, providing refueling can be accomplished quickly and the hydrogen can be released on demand.

A distributed system of fueling stations, similar to gasoline stations, could be established to supply fuel cell vehicles with hydrogen. A few demonstration stations have been installed around major cities such as Washington D.C.

One type of fueling station would use electrolysis to separate hydrogen from oxygen in water at the point of use; however, the amount of electricity required for this approach is prohibitive.

A second type of fueling station would use natural gas and a process called reforming to separate hydrogen from methane, also at the point of use. This approach uses the existing natural gas pipeline distribution system and would use abundantly available natural gas.

Producing hydrogen centrally requires transporting it to fueling stations. One transportation approach is to use cryogenic trucks to transport the hydrogen from the central production facility; however, cooling the hydrogen in preparation for shipment by truck, results in a very large loss of energy.  A second approach is to build a new network of special pipelines for transporting hydrogen. The existing network of natural gas pipelines cannot be used as hydrogen attacks the piping. A new pipeline network for hydrogen would cost billions.

An alternative to on-board storage of hydrogen is reforming gasoline on the vehicle. On-board reforming would eliminate three problems: the need for pipelines; new fueling stations; and transporting hydrogen by cryogenic truck.

While the cost of reforming equipment adds to the cost of the vehicle, it can use gasoline that is readily available without investing in a new system of fueling stations.

It’s unclear how much fuel-cell vehicles, using gasoline with reforming, could reduce the consumption of foreign oil.  (Modern internal combustion engine powered vehicles have an efficiency of around 30%, while the efficiency of fuel cells using gasoline and reforming is 45%, according to an Argonne National Laboratory study. With these relative efficiencies, gasoline usage might be reduced by about one-third.)

Fuel cells are several times more costly than internal combustion engines or batteries. Until the cost of fuel cells is cut by as much as 90%, fuel-cell vehicles using hydrogen are impractical.

There is a rumor that automobile manufacturers have developed fuel-cells that cost little more than an internal combustion engine. If the rumor is false we will have to wait a long while, possibly decades, until low-cost fuel cells suitable for automotive use are developed.

If this rumor is true, it might be possible to produce hydrogen powered vehicles with fuel cells using gasoline as the source of hydrogen. While this approach would only partially reduce the use of foreign oil, it could be an alternative to Plug-in Electric Vehicles.

It would be interesting to watch a free market competition between hydrogen fuel cell vehicles and Plug-in Electric Vehicles.

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