07/21/2004
Hydrogen in Our Future?
Following up on last week’s column, I tried Edy’s Grand Light vanilla ice cream, made by the ultra low temperature extrusion process discussed in the column. It’s truly creamy, to my taste even creamier than Edy’s Grand ice cream, with over twice the fat (8 vs. 3.5 grams per half cup) and 40 percent more calories (140 vs. 100) than the Grand Light. If you missed the column, the “slow-churned” (Edy’s phrase) Grand Light’s creaminess derives from the finely divided ice crystals and fat aggregates formed in the low temperature extrusion. (Correction - last week I quoted the article that prompted the column as saying the process eliminates the need for additives. However, both the Grand Light and Grand labels list the same additives. The quote should be that the process “doesn’t rely on additives.”)
So much for ice cream. Another consumer product that I tested recently was the Toyota Prius. OK, it wasn’t much of a test – a friend allowed me to drive her Prius around the block. I was quite impressed with this hybrid vehicle, which decides on its own whether to use its battery or its internal combustion engine to power its journey and, when stopped, there’s no idling of its engine. With many more miles per gallon, widespread use of hybrid vehicles would significantly reduce oil consumption and greenhouse gas emissions. While the hybrid is here today, vehicles powered by fuel cells have been touted as the way of the future leading to a “hydrogen economy”, the subject that I’ve been putting aside in favor of ice cream and space weather.
The optimistic outlook for the future of fuel cells is exemplified by President Bush’s 2003 state of the union proposal of a $1.7 billion R&D program to develop a practical vehicle powered by fuel cells. I’ve written about fuel cells earlier (columns posted 4/18/2000 and 5/2/2000) but let’s review the fundamentals. In a typical battery, all the active ingredients are packaged in the battery. These materials react to produce the voltage and current the battery delivers. One exception is the small zinc-air hearing aid battery, in which one ingredient is oxygen in the air that enters the battery when the customer tears open a protective seal.
In the hydrogen-oxygen fuel cell, oxygen from the air is also one of the ingredients, while hydrogen is the other. Hydrogen is fed to one electrode and oxygen is fed to the other electrode. As long as you keep feeding in the hydrogen and oxygen, the fuel cell supplies the power to run your vehicle. The hydrogen reacts with the oxygen to form water, H2O - an environmentalist’s dream. No carbon monoxide, carbon dioxide or nitrogen oxides pollute our atmosphere and contribute to global warming. In a future “hydrogen economy”, you drive to your “gas” station, fill your tank with a real gas, hydrogen and proceed on your way.
This sounds wonderful, but I’m reminded of the period from 1972 to 1989, when I worked in the Battery Development Department at Bell Labs. During that period, it was the battery- powered electric vehicle that was to be our salvation. Vast sums of money were spent on projects to develop new battery systems and California passed laws mandating low- or zero-emission vehicles, expecting that electric vehicles would soon be mass produced. It isn’t going to happen, at least in my lifetime.
Is a hydrogen economy any more likely? How does the hybrid vehicle, available today, fit into the picture? The article “Questions about a Hydrogen Economy” in the May issue of Scientific American gives some answers. The article is by Matthew Wald, a reporter for the New York Times who has specialized in energy-related issues for the past 25 years. Wald does a good job of getting to the heart of the matter, the true costs and environmental aspects of a hydrogen economy. The Department of Energy Web site also provides a wealth of information. However, as the agency charged with pushing through the fuel cell program, it’s more optimistic in its outlook.
The problem with a hydrogen economy is that hydrogen is not like oxygen, which is present as pure oxygen molecules in our air. Hydrogen is tied up in compounds such water (lots of that), petroleum, natural gas, etc. So, in effect, you have to “mine” hydrogen from these compounds for shipping to your “gas” stations. While the fuel cell, emitting only water, is truly “green”, the production of its hydrogen fuel is a different matter.
How to generate hydrogen most cleanly? If you’ve had any chemistry, chances are you’d say to electrolyze water. We’ve had plenty of water from the skies in New Jersey this past week! You just hook up a couple electrodes to an appropriate power supply, stick them in water, pass current through the cell and collect hydrogen. All neat and clean, right? But wait, where did the electricity come from and how was it generated? To get a true picture of the total monetary and environmental costs, you have to consider both the “fuel chain” and the fuel cell together.
We have to sum up the greenhouse gas emissions from the power generating company and from the electrolytic production of hydrogen (the fuel chain emissions) plus the vehicle emissions. According to Wald’s article, the greenhouse emissions per mile of driving turn out to be higher for the fuel cell than for the internal combustion engine! Why? Coal is the cheapest fuel for power generating plants; however, burning coal feeds lots of carbon dioxide and other pollutants into the atmosphere.
With fuel cells, all the greenhouse gases are emitted in forming the hydrogen, essentially none in running the car. On the other hand, our gasoline-fueled cars emit a lot more greenhouse gases than are emitted during the production the gasoline. What about our hybrid car? Surprisingly, the total emissions for the hybrid are quite a bit less than for the fuel cell car fueled with hydrogen from electrolysis of water.
Actually, about half of the world’s hydrogen is produced by a process known as steam reforming of natural gas. If we fuel our fuel cell car with this hydrogen, the total greenhouse emissions go down markedly and the fuel cell car becomes the cleaner alternative. The downside is that natural gas is a fossil fuel and as it becomes depleted the monetary costs will rise. The use of solar or wind power or other alternative energy sources to generate the electricity to electrolyze water is the ideal solution, but widespread use of these sources is far in the future.
Other kinds of fuel cells are in the research or developmental stage as, for example, fuel cells in which gasoline, methanol or ethanol are used instead of pure hydrogen. Wald’s article gives the total emissions for the methanol and gasoline fuel cells as about half the total greenhouse emissions of the conventional hydrogen fuel cell. I was shocked to see that the ethanol fuel cell is cited as having almost no total emission of greenhouse gases! How can this be? The Department of Energy figures that ethanol comes from corn and that most of the emissions from the production of the ethanol (especially carbon dioxide) will be reabsorbed by the growth of more corn to make more ethanol! Nothing is simple when it comes to the environment.
Here, I’ve stressed the environmental aspects of a hydrogen economy. There remain daunting scientific and engineering challenges, not to mention the problem of money. Today, the cost of a watt of power from an internal combustion engine is about 5 cents. To produce that same watt of power in a fuel cell costs about $4! Obviously, the cost must come down. Wald notes that fuel cell cars and NASA’s manned trip to Mars are on roughly the same time schedule and suggests that both are about equally likely. While I tend to agree, and would love to see men and women on Mars, I think the fuel cell-powered car is much more feasible.
Meanwhile, in keeping with my profound disgust with SUVs, I suggest you SUV owners consider a small hybrid vehicle. OK, in a spirit of complete disclosure and even more disgust, I admit that I know there’s already a hybrid SUV on the market!
Allen F. Bortrum
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