- Questions:
- What are some of the sources of hydrogen?
- Doesn't it take energy to create hydrogen?
- If we use water to obtain the hydrogen, will there be enough?
- How safe is hydrogen?
- How is hydrogen stored?
- How is hydrogen transported?
What are some of the sources of hydrogen?
Although abundant on earth, hydrogen combines readily with other elements and is usually found as part of some other substance, such as water, or in hydrocarbons, including those that make up all plants and animals.
Any hydrogen-rich material can serve as a possible fuel source for fuel cells. Hydrocarbon fuels – methanol, ethanol, natural gas, petroleum distillates, liquid propane and gasified coal – can yield hydrogen in a process called reforming. Hydrogen can be extracted from novel feed stocks such as landfill gas or anaerobic digester gas from wastewater treatment plants, from biomass technologies, or from hydrogen compounds containing no carbon, such as ammonia or borohydride.
Hydrogen can also be produced from water via electrolysis.
Doesn't it take energy to create hydrogen?
Extracting any fuel takes energy – even getting gasoline from well to pump costs the equivalent of 20% of the energy of the gasoline. It takes more energy to generate hydrogen than gasoline, but since a fuel cell is more efficient than conventional energy devices, fuel cell vehicles – even today's prototypes – offer attractive overall efficiencies, even using hydrogen.
Looking at the whole picture is important. Well-to-Wheel analyses compare the entire pathway of producing, storing, distributing and utilizing any number of fuels. They can compare efficiencies and energy needs for the many different hydrogen production methods as compared to different fuels and vehicle technologies.
Michael Wang, from Argonne National Laboratory, found that most, but not all of the fuel-cell vehicle/fuel combinations being considered achieve significant energy and greenhouse gas (GHG) emission benefits over existing and other advanced technologies.
http://www.transportation.anl.gov/pdfs/TA/260.pdf
If we use water to obtain the hydrogen, will there be enough?
Putting aside the fact that a byproduct of fuel cells is water, there is more than enough water to sustain a hydrogen economy.
The Delft Institute for Sustainable Energy calculates –
Global energy demand: 4x10^20 J/year
H2 from water: 1 GJ per 90 liters H2O
Water needed: 3.6x10^13 liters
Oceans: 1.45x10^21 liters
Annual rain fall: 3.63x10^17 liters
How safe is hydrogen?
Hydrogen, like any flammable fuel such as gasoline, requires certain safety precautions to ensure safe transport, distribution and handling. There are many codes and standards already in place, and hydrogen as a fuel source already has an impressive record. Also, certain properties of hydrogen make it safer than convention combustibles.
Hydrogen is much lighter than air and has a rapid diffusivity, which means that when released in an open environment is rises upwards and dilutes more quickly into a non-flammable concentration. Hydrogen, if to catch on fire, would burn at a lower radiant temperature than a gasoline fire, significantly lowering the risks of secondary fires by ignition other combustibles in the vicinity. Finally, hydrogen will not contaminate groundwater, nor will a release of hydrogen contribute to atmospheric or water pollution.
For more information on hydrogen safety, see the following presentation:
http://www.fuelcells.org/info/HydrogenandtheLaw.pdf
How is hydrogen stored?
Hydrogen storage is similar to gasoline or propane, but proper containment requires tanks that can sustain increased internal pressure due to the properties of hydrogen.
Hydrogen can be stored either as a liquid or a gas. To store hydrogen in liquid form, hydrogen must be cooled to -423 oF, requiring a significant portion of the energy hydrogen is supposed to provide just to reach those temperatures. Therefore hydrogen is much better stored as a gas, which uses less energy than liquid storage.
Hydrides are chemical compounds of hydrogen and other materials and are a third storage alternative. Metal alloys such as magnesium nickel, copper, and iron titanium absorb then slowly re-release hydrogen gas. The energy per unit weight is small though, making this less efficient.
How is hydrogen transported?
There are two methods of delivery. Hydrogen can be shipped in pipelines or trucks from production plants to distribution centers, and onwards to the final consumer. Hydrogen can also be produced in large quantities and then pressurized. It is then stored in caverns, gas fields, or mines ready to be piped into individual homes as natural gas is today.
Still necessary is the delivery infrastructure, which will likely include a number of technologies working in combination with each other. Support from the government in both infrastructure funding and research is necessary to assess needs and resources of a particular market and the region in which it resides. Many hydrogen stations in place today generate the hydrogen on-site.
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