What is hydrogen?

The sun is essentially a giant ball of hydrogen gas undergoing fusion into helium gas. This process causes the sun to produce vast amounts of energy.

Source: NASA (public domain)

Hydrogen is the simplest element. Each atom of hydrogen has only one proton. Hydrogen is also the most plentiful gas in the universe. Stars like the sun consist primarily of hydrogen.

The sun is essentially a giant ball of hydrogen and helium gases. In the sun's core, hydrogen atoms combine to form helium atoms. This process—called fusion—gives off radiant energy.

The radiant energy from the sun gives earth light and helps plants grow. Radiant energy is stored as chemical energy in fossil fuels. Most of the energy that people use today originally came from the sun's radiant energy.

Hydrogen as a gas (H2) is not found by itself on earth. Hydrogen gas is found only in compound form with other elements. Hydrogen combined with oxygen is water (H2O). Hydrogen combined with carbon forms different compounds like methane (CH4), coal, and petroleum. Hydrogen is found in all growing things and is an abundant element in the earth's crust.

Hydrogen has the highest energy content of any common fuel by weight (about three times more than gasoline), but it has the lowest energy content by volume (about four times less than gasoline).

Hydrogen is an energy carrier

Energy carriers move energy in a useable form from one place to another. Electricity is the most well-known energy carrier. Hydrogen is an energy carrier like electricity, and it must be produced from another substance. Hydrogen can be produced from a variety of sources—water, fossil fuels, or biomass—and it is a byproduct of other chemical processes. Hydrogen is not widely used as a fuel now, but it has the potential for greater use in the future.