Tuesday, September 05, 2006

Fueling the Future

Nobel Prize-winning chemist George Olah has an idea which could save the world. It's not often I use such a hyperbole in describing a singular idea, but the issue of energy is, as I've said before, the chief technical problem of our day and the underlying reason for our current era of terror. Olah is 1994 winner of the chemistry award for his solution to the problem of 'non-classical' carbocations. His idea is that we re-orient ourselves away from illusory visions of a hydrogen economy, and become a methanol economy instead.

Why go against the gleaming hydrogen economy paradigm? Well there are a few inherent flaws making the jump from our current fossil fuel infrastructure to hydro-mobiles zipping along our
streets as big a jump as landing a lunar slam dunk.

Hydrogen is an explosive gas that, decades after the Hindenburg disaster, still causes technical problems in our storage and transport of it. Although molecular hydrogen has excellent energy density on a mass basis, as a gas at ambient conditions it has poor energy density per volume. As a result, if it is to be stored and used as fuel onboard the vehicle, molecular hydrogen must be pressurized or liquefied to provide sufficient driving range. Greater energy is thus needed to keep hydrogen compressed into a liquid state. The mass of the tanks needed for compressed hydrogen reduces the fuel economy of the vehicle.

Because it is a small energetic molecule, hydrogen tends to diffuse through any liner material intended to contain it, leading to the embrittlement, or weakening of its container. Since hydrogen causes embrittlement of steel, it is not clear that hydrogen can simply be put into today's natural gas transmission systems. Li-On batteries, as seen in laptop computers of today, would be a far more efficient onboard energy platform.

The storage and transport issues would necessitate an alteration in industry which is unprecedented in human history, requiring trillions of dollars. Hydrogen pipelines are more expensive than even long-distance electric lines. It is far more efficient to increase the voltage in these wires, than to strengthen a pipeline. Hydrogen also is about three times bulkier in volume than natural gas for the same energy delivered. Added to that is the grueling maintenance costs from the aforementioned embrittlement. Ultimately, since hydrogen is likely to be produced with the same sources as electricity , it is less economical than a pure electricity economy.
In The Hype about Hydrogen, author Joseph J. Romm argues that a major effort to introduce hydrogen cars before 2030 would actually undermine efforts to reduce emissions of heat-trapping greenhouse gases such as carbon dioxide. As Romm states, "Neither government policy nor business investment should be based on the belief that hydrogen cars will have meaningful commercial success in the near or medium term."

It is also requires more than a bit of energy to extract. The production problem is a combination of two different problems: producing hydrogen efficiently from energy sources, and locating suitable (renewable or at least less polluting) energy sources to do it. We can either milk hydrogen from fossil fuels or use electrolysis to crack water into oxygen and hydrogen. Usually, the electricity consumed is more valuable than the hydrogen produced, which is why only a tiny fraction of hydrogen is currently produced this way.

Liquefying would require 40% of the energy content of the hydrogen. Liquid hydrogen would evaporate at the rate of 4%/day. Just generating the electricity to liquefy 1 kg (2.2 lb) of hydrogen would release 8 to 9.5 kg (17.6 to 20.9 lb) of CO2 into the atmosphere. By comparison, burning a U.S. gallon of gasoline, which has a similar energy content, would release about 9 kg (19.8 lb) of CO2. Compressing hydrogen to 10,000 psi (70 MPa) would require about 10% to 15% of its energy content, and take about 7 to 8 times as much volume as the same energy in a gasoline tank. At 8,000 psi (55 MPa), a pressure tank would cost $2100 per kilogram of hydrogen. In brief, the electricity required to generate enough hydrogen to replace all the gasoline in the U.S. would be more than all the electricity currently produced.

Methanol can be used directly as fuel (including in hybrids) or in a direct methanol fuel cell. It can be made from hydrogen in a greenhouse neutral process and used in place of hydrogen, without construction of new hydrogen infrastructure.

What are the arguments against methanol? Well there are a few. We would need at least some hydrogen to be generated in order to synthesize methanol. At present, methanol is generated from syngas, the most popular source of which is fossil-based (although this would be altered in a methanol economy). Methanol is half as energy-dense as gasoline and has a few other chemical problems: it would be corrosive to aluminum or some plastic parts in a fuel-intake system; it attracts water, creating possible engine obstructions; it has low volatility in cold weather; it is still toxic and a fire risk, but so is gasoline.

Petroleum is, to paraphrase Churchill's comment on democracy, the worst energy system in the world, except for all the other energy systems. Almost our entire infrastructure runs exculsively on fossil fuels taken from volatile and long downtrodden regions of the world. Sustainable and renweable fuels woudl ameliorate this and avoid a 'peak oil' crash of the petro-economy. It would take decades and cost trillions for the dubious benefits of a hydrogen economy. It is hard to see the hydrogen economy idea as anything other than a bait-and-switch to prevent dealing with the deeper issue of moving towards renewable energy.

Compared to hydrogen, methanol offers a few significant advantages: as it is a liquid, storage by volume and weight is more efficient and by far, safer for smaller vehicles; it can be directly incorporated in existing gas stations and tanker trucks, even blended with gasoline; it is less explosive than hydrogen and can be used to fill the tank of someone without a degree in chemical engineering; it can be made from any organic material using the Fischer-Tropsch synthesis method; and it can be used with ethanol in a diversified biofuel marketplace.

Biofuel itself has been used since the early days of the car industry. Nikolaus August Otto, the German inventor of the combustion engine, conceived his invention to run on ethanol. While Rudolf Diesel, inventor of the Diesel engine, conceived it to run on peanut oil. The Ford Model T, produced between 1903 and 1926 used ethanol. Hydrogen's role in ths new economy would be to help produce these renewable liquid fuels. This would extend the 'reach' of biofuels, which require large amounts of cultivated land to convert photosynthetic plants into chemical energy.

Switching from petroleum-based fuels extracted from ever-deeper wells and refined in energy-intensive and polluting processes, to cleaner, greener bioalcohols like methanol, avoids both the pipe dreams of a purely hydrogen future of pipelines and pressure tanks and the do-nothingism of our SUV present. With greater knowledge of micro-organisms and how plants create bioalcholic fuel, it may be possible that we can genetically engineer a plant whose pure sap can power our daily travels. The gasoline tree will be something to watch for in the front yard of tomorrow.

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