"Hydrogen is one of two natural elements that combine to make water. Hydrogen is not an energy source, but an energy carrier because it takes a great deal of energy to extract it from water. It is useful as a compact energy source in fuel cells and batteries. Many companies are working hard to develop technologies that can efficiently exploit the potential of hydrogen energy." Source

The Attributes of Hydrogen
Hydrogen is considered an alternative fuel for two reasons: It is renewable, and it is the most abundant element on the earth. Hydrogen comprises more than 75 percent of the environment; so if it became a primary fuel, dependence on foreign sources of fuel would be eliminated. However, hydrogen in nature exists primarily in combination with other elements. For hydrogen to be useful as a fuel, it must exist as free hydrogen (H2). One common source of hydrogen is water, which is 11.2 percent hydrogen by weight. Hydrogen also can be produced from biomass. Biomass is essentially plant matter, so the vast agricultural resources of the United States could be used to "grow" the fuel required by AAN platforms.
Hydrogen's Characteristics
Hydrogen's physical and chemical properties make it a good candidate for a fuel. At normal atmospheric conditions, hydrogen is a colorless and odorless gas. It is stable and coexists harmlessly with free oxygen until an input of energy drives the exothermic (heat releasing) reaction that forms water. Fuel cells also may use hydrogen as a fuel. A fuel cell is an electrochemical engine that converts the chemical energy contained in the hydrogen molecule into electrical energy. Hydrogen can react with oxygen to produce electricity in a fuel cell.
Hydrogen is the lightest element occurring in nature and contains a large amount of energy in its chemical bond. Because of its low density, liquid hydrogen weighs less than petroleum-based fuels. The density of gaseous hydrogen is 0.0899 grams per liter (g/l). (Air is 1.4 times as dense.) Liquid hydrogen boils at -252.77 degrees Celsius, and it has a density of 70.99 g/l. With these properties, hydrogen has the highest energy-to-weight ratio of all fuels: 1 kilogram (kg) of hydrogen has the same amount of energy as 2.1 kg of natural gas or 2.8 kg of gasoline. Hydrogen burns in air at concentrations in the range of 4 to 75 percent by volume (methane burns at 5.3 to 15 percent concentrations by volume). The highest burning temperature of hydrogen is 2,318 degrees Celsius and is reached at 29-percent concentration by volume in air.
These data give hydrogen both advantages and disadvantages. The major advantage is that hydrogen stores approximately 2.8 times the energy per unit mass as gasoline. The disadvantage is that it needs four times the volume for a given amount of energy. For example, a 15-gallon tank of gasoline contains 90 pounds of gasoline; a 60-gallon tank of gaseous hydrogen would weigh only 34 pounds. Source


Hydrogen as a Fuel

Hydrogen burns cleanly, producing little or no harmful emissions or CO2. According to the Fact SheetHydrogen Fuel: a Clean and Secure Energy Future produced by the White House Press Office in February 2006:
  • It has the highest energy content per unit of weight of any known fuel.
  • When burned in an engine, hydrogen produces effectively zero emissions; when powering a fuel cell, its only waste is water.
  • Hydrogen can be produced from abundant domestic resources including natural gas, coal, biomass, and even water.Source

Due to the increasing price of gasoline and the heightened awareness of the dangers of greenhouse gases, there are more hydrogen fueled automobiles being produced now than ever before.
  • In a report carried in the Greenwich Time, Dave Buchko, spokesman for BMW North America said, "We're close to a point where if the fuel (hydrogen) became (widely) available tomorrow, we would be able to make the cars available".
  • The Los Angeles Times, in a report titled “Stars test the waters with Hydrogen cars” on June 15, 2008 reported that Honda has produced the FCX Clarity which can get 270 miles to the tank. It also says that GM has developed its hydrogen car, the Chevy Equinox. Source

Marking Hydrogen a Renewable Fuel
To make hydrogen a renewable fuel it should use renewable energy, such as wind power or solar power, for production. A report carried on Solar Today by Susan Hock, Carolyn Elam and Debra Sandor, titled “Can We Get There” states, “Due to the relatively low cost of wind power, along with recent dramatic growth in wind energy, wind/electrolysis is well positioned to become the first economical renewable hydrogen production system.”
Another example of using wind to make hydrogen was reported in the UK Daily Telegraph of June 21 2008. The Isle of Unst, Britain’s most northerly settlement, uses two wind turbines to “create hydrogen gas to run a hydrogen-powered car and cooking facilities while the rest is captured as hydrogen fuel cells to provide back-up when the wind dies.”
As an alternative fuel hydrogen is ideal, producing little or no emissions, with a plentiful supply available. But hydrogen produced by conventional means is not renewable or carbon neutral. Wind power is a totally renewable energy source with no greenhouse gas emissions, but due to its unpredictability, has problems integrating with national grids. Combined together, wind and hydrogen can cancel out their inherent defects and be an effective tool in the battle against carbon dioxide and global warming. Source

Honda engine converted to run on Hydrogen
So I was browsing the web the other day and I found an interesting tid bit. A few student from the Los Altos Academy of Engineering in california built a vehicle that utilizes a hydrogen combusion engine using a four stroke engine from Honda. They converted the consumer engine design to run entirely of Hydrogen.

This actually was posted only a week ago. So the news is recent. You guys should definitely check it out here . Their is also a video posted on that link of the car at work. It does not use a single drop of gasoline to run.