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The Hydrogen Economy
While fossil fuels have played an important role in getting society to the point it is at today, there are four big problems that fossil fuels create.
Air pollution-When cars burn gasoline, they would ideally burn it perfectly and create nothing but carbon dioxide and water in their exhaust. Unfortunately, the internal combustion(燃烧)engine is not perfect. In the process of burning the gasoline, it also produces carbon monoxide, a poisonous gas; nitrogen oxides, the main source of urban smog; and unburned hydrocarbons, the main source of urban ozone .
Catalytic converters (催化式排气净化器) eliminate much of this pollution, but they aren't perfect. Air pollution from cars and power plants is a real problem in big cities.
It is bad enough now that, in the summer, many cities have dangerous levels of ozone in the air.
Environmental pollution-The process of transporting and storing oil has a big impact on the environment whenever something goes wrong. An oil spill, pipeline explosion or well fire can create a huge mess.
Global warming-When you burn a gallon of gas in your car, you emit about 5 pounds (2.3 kg) of carbon into the atmosphere. If it were solid carbon, it would be extremely noticeable-it would be like throwing a 5-pound bag of sugar out the window of your car for every gallon of gas burned. But because the 5 pounds of carbon comes out as an invisible gas, carbon dioxide, most of us are oblivious (不注意的)to it. The carbon dioxide coming out of every car's tailpipe is a greenhouse gas that is slowly raising the temperature of the planet. The ultimate effects are unknown, but it is a strong possibility that, eventually, there will be dramatic climate changes that affect everyone on the planet. For example, if the ice caps melt, sea level will rise significantly, flooding and destroying all coastal cities in existence today. That's a big side effect.
Dependence-The United States, and most other countries, cannot produce enough oil to meet demand, so they import it from oil-rich countries. That creates an economic dependence. When Middle East oil producers decide to raise the price of oil , the rest of the world has little choice but to pay the higher price.
Advantages of the hydrogen economy
In the previous section we saw the significant, worldwide problems created by fossil fuels. The hydrogen economy promises to eliminate all of the problems that the fossil fuel economy creates. Therefore, the advantages of the hydrogen economy include:
The elimination of pollution caused by fossil fuels-When hydrogen is used in a fuel cell to create power, it is a completely clean technology. The only byproduct is water. There are also no environmental dangers like oil spills to worry about with hydrogen.
The elimination of greenhouse gases-If the hydrogen comes from the electrolysis (电解) of water, then hydrogen adds no greenhouse gases to the environment. There is a perfect cycle-electrolysis produces hydrogen from water, and the hydrogen recombines with oxygen to create water and power in a fuel cell.
The elimination of economic dependence-The elimination of oil means no dependence on the Middle East and its oil reserves.
Distributed production-Hydrogen can be produced anywhere that you have electricity and water. People can even produce it in their homes with relatively simple technology.
The problems with the fossil fuel economy are so great, and the environmental advantages of the hydrogen economy so significant, that the push toward the hydrogen economy is very strong.
Where does the hydrogen come from?
In the hydrogen economy, there is no storehouse to tap into. We have to actually create the energy in real time. There are two possible sources for the hydrogen.
Electrolysis of water-Using electricity, it is easy to split water molecules to create pure hydrogen and oxygen. One big advantage of this process is that you can do it anywhere. For example, you could have a box in your garage producing hydrogen from tap water, and you could fuel your car with that hydrogen.
Reforming fossil fuels-Oil and natural gas contain hydrocarbons-molecules consisting of hydrogen and carbon. Using a device called a fuel processor or a reformer, you can split the hydrogen off the carbon in a hydrocarbon relatively easily and then use the hydrogen. You discard the leftover carbon to the atmosphere as carbon dioxide.
The second option is, of course, slightly perverse. You are using fossil fuel as the source of hydrogen for the hydrogen economy. This approach reduces air pollution, but it doesn't solve either the greenhouse gas problem (because there is still carbon going into the atmosphere) or the dependence problem (you still need oil). However, it may be a good temporary step to take during the transition to the hydrogen economy. When you hear about "fuel-cell-powered vehicles" being developed by the car companies right now, almost all of them plan to get the hydrogen for the fuel cells from gasoline using a reformer . The reason is because gasoline is an easily available source of hydrogen. Until there are "hydrogen stations" on every corner like we have gas stations now, this is the easiest way to obtain hydrogen to power a vehicle's fuel cell.
The interesting thing about the first option is that it is the core of the real hydrogen economy. To have a pure hydrogen economy, the hydrogen must be derived from renewable sources rather than fossil fuels so that we stop releasing carbon into the atmosphere. Having enough electricity to separate hydrogen from water, and generating that electricity without using fossil fuels, will be the biggest change that we see in creating the hydrogen economy.
How do you store and transport the hydrogen?
At this moment, the problem with putting pure-hydrogen vehicles on the road is the storage/transportation problem. Hydrogen is a bulky gas, and it is not nearly as easy to work with as gasoline. Compressing the gas requires energy, and compressed hydrogen contains far less energy than the same volume of gasoline. However, solutions to the hydrogen storage problem are surfacing.
For example, hydrogen can be stored in a solid form in a chemical called sodium borohydride (硼氢化物), and this technology has appeared in the news recently because Chrysler is testing it. This chemical is created from borax (硼砂). As sodium borohydride releases its hydrogen, it turns back into borax (硼砂) so it can be recycled.
Once the storage problem is solved and standardized, then a network of hydrogen stations and the transportation infrastructure will have to develop around it. The main barrier to this might be the technological sorting-out process. Stations will not develop quickly until there is a storage technology that clearly dominates the marketplace. For instance, if all hydrogen-powered cars from all manufacturers used sodium borohydride, then a station network could develop quickly; that sort of standardization is unlikely to happen rapidly, if history is any guide.
There might also be a technological breakthrough that could rapidly change the playing field. For example, if someone could develop an inexpensive rechargeable battery with high capacity and a quick recharge time, electric cars would not need fuel cells and there would be no need for hydrogen on the road. Cars would recharge using electricity directly.
Prospects for the future
You will hear more and more about the hydrogen economy in the news in the coming months, because the drumbeat is growing louder. The environmental problems of the fossil fuel economy are combining with breakthroughs in fuel-cell technology, and the pairing will allow us to take the first steps.
The most obvious step we will see is the marketing of fuel-cell-powered vehicles. Although they will be powered initially by gasoline and reformers, fuel cells embody two major improvements over the internal combustion engine: they are about twice as efficient; they can significantly reduce air pollution in cities. Gasoline-powered fuel-cell vehicles are an excellent transitional step because of those advantages.
Moving to a pure hydrogen economy will be harder. The power-generating plants will have to switch over to renewable sources of energy, and the marketplace will have to agree on ways to store and transport hydrogen. These hurdles will likely cause the transition to the hydrogen economy to be a rather long process.