What are the Different Methods for Hydrogen Generation?
The different methods for hydrogen generation are numerous, depending on the source matter, whether the final product is to be pure hydrogen or some sort of hydrogen compound, and what its intended uses are. Producing hydrogen fuel for rockets or compressed liquid fuel cell cars can be done by the relatively simple and well-known process of electrolysis, splitting water into charged oxygen and hydrogen atoms by running an electrical current through it. Other forms of hydrogen generation with a water-based medium include hydrolysis using ammonia borane, and modified thermochemical thermolysis, where sulfur-iodine is introduced to produce hydrogen in a nuclear reactor and the sulfur-iodine compound is retained afterward for further use.
Solid oxide fuel cells (SOFC) that produce electricity are another alternative-energy option that both uses and produces hydrogen compounds in the process, without requiring liquid water. They operate like a battery, except their input can be natural gas and output carbon dioxide and electricity. Many variations on solid fuel cells exist, most involving the use of high temperatures and some sort of expensive heavy metal like platinum. A new form of hydrogen fuel cell uses water and substitutes a much less expensive molybdenum compound metal for the platinum, and is 70 times cheaper than using platinum while capable of operating using sea water.
Much slower methods of generating hydrogen in bulk include using biological processes such as fermentation, and dark fermentation, which does not require the presence of light to operate. Microbial reactions, termed electrohydrogenesis, can generate hydrogen from waste water. The use of plants such as algae for hydrogen generation are also in development. In 2005, algae researchers at the National Renewable Energy Laboratory (NREL) in the US project their hydrogen generation project will bring the cost down to $2.80 US Dollars (USD) per kilogram, making it competitive with gasoline.
Another novel method for generating hydrogen is to use solar cell electrical power. Solar concentrator cells channel electrical energy to a solid oxide that operates at high temperature, in excess of 2,012° Fahrenheit (1,100° Celsius). The expectation is that 50% of the solar energy would be converted to an equivalent value in hydrogen energy. This is being researched for hydrogen generation as the costs could be as low as $0.85 US Dollars (USD) per watt, which is comparable to the efficiency of wind generated power systems. Hydrogen generation can be done by many low-cost, low-tech, or high-cost, high-tech means, with current research making it a practical alternative energy today, not in the distant future.
@Fiorite: Using pure hydrogen as a fuel source does present some technological hurdles despite its abundance, but hydrogen compounds are easily used as fuel with present day technology, and are abundant. They can also be clean and renewable resources.
We can create hydrogen based biofuels from many types of crop wastes now, ranging from beet waste to sugarcane, to corn.
I suggest picking up a book titled "The Hydrogen Age, Empowering a Clean Energy Future" by Geoffrey B. Holland.
The barrier to switching to a hydrogen fuel economy based on renewable bio sources is really more one of inertia and politics than it is science.
As well, if we ever develop practical fusion power, that will most likely be fueled by deuterium derived from sea water. It will be clean, safe and virtually limitless.
@Fiorite- There are six well known hydrogen production pathways, and a couple in the research phase, but like Glasshouse stated, they always take more energy to produce than the energy that is created.
The most common form of hydrogen production is through heat reforming of a fossil fuel. This technique involves separating hydrogen from methane with high temperature steam at an efficiency of about 67%. This is currently the least expensive method, but it produces carbon dioxide and carbon monoxide as a by-product. Carbon dioxide is not as potent a greenhouse gas as methane, but it is the most worrisome because the atmospheric concentrations of carbon dioxide are so high.
In essence, all of the hydrogen produced for the few hydrogen vehicles on the road today produces as much carbon dioxide as if it were using power form a natural gas turbine. This is still better than gasoline, but it is not a complete reduction of GHGs. Hydrogen should not be discredited, but it is still a ways away from being a "green" energy source.
@fiorite- Hydrogen is the most abundant known element, but it is not freely available like many other resources. Hydrogen always occurs in combination with some other element, so it is not a fuel source. Rather, hydrogen is an energy carrier.
Hydrogen must be extracted from the environment through energy intensive methods, and because of the laws of thermodynamics, it will always take more energy to extract hydrogen than it can produce. The only way that hydrogen can be seen as a truly sustainable energy source is through the use of renewable generation, i.e. a solar hydrogen generator. In this sense, hydrogen is as dirty as the fuel that is used to create it.
Maybe one day, hydrogen will be produced at solar or wind plants located near the ocean that also operate as desalination plants. This type of co-generation of usable resources would be the perfect way to market hydrogen as a competitive energy carrier. It will not be economically viable however, until the cost of production becomes competitive with other fuel energy sources.
I learned in my chemistry class that hydrogen is the most abundant element in the known universe. This would make me think that it would be the ideal energy source. Why is hydrogen not the main source of fuel yet? What is holding hydrogen back from becoming the solution to energy demand? I know it has been known to be a fuel at least since the Hindenburg so it cannot be because it has not been developed yet. Industry also uses a lot of hydrogen. What is preventing hydrogen from being used as a fuel source for cars and hydrogen power generator plants? From what I understand, the only emissions from hydrogen combustion are water.
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