Hydrogen
Like electricity, hydrogen is a secondary source of energy. It stores and carries energy produced from other resources (fossil fuels, water, and biomass).
Hydrogen Basics
What Is Hydrogen?
The sun is basically a giant ball of hydrogen gas undergoing fusion into helium gas and giving off vast amounts of energy in the process.
Source: NASA (Public Domain)
Hydrogen is the simplest element. Each atom of hydrogen has only one proton. It is also the most plentiful gas in the universe. Stars like the sun are made primarily of hydrogen.
The sun is basically 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.
This radiant energy sustains life on Earth. It gives us light and makes plants grow. It makes the wind blow and rain fall. It is stored as chemical energy in fossil fuels. Most of the energy we use today originally came from the sun's radiant energy.
Hydrogen gas is so much lighter than air that it rises fast and is quickly ejected from the atmosphere. This is why hydrogen as a gas (H2) is not found by itself on Earth. It is found only in compound form with other elements. Hydrogen combined with oxygen, is water (H2O). Hydrogen combined with carbon forms different compounds, including methane (CH4), coal, and petroleum. Hydrogen is also found in all growing things — for example, biomass. It is also 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 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. We use electricity to move the energy in coal, uranium, and other energy sources from power plants to homes and businesses. We also use electricity to move the energy in flowing water from hydropower dams to consumers. For many energy needs, it is much easier to use electricity than the energy sources themselves.
Like electricity, hydrogen is an energy carrier and must be produced from another substance. Hydrogen is not currently widely used, but it has potential as an energy carrier in the future. Hydrogen can be produced from a variety of resources (water, fossil fuels, or biomass) and is a byproduct of other chemical processes.
How Is Hydrogen Made?
Source: The National Energy Education Project (Public Domain)
Because hydrogen doesn't exist on Earth as a gas, it must be separated from other elements. Hydrogen atoms can be separated from water, biomass, or natural gas molecules. The two most common methods for producing hydrogen are steam reforming and electrolysis (water splitting). Scientists have discovered that even some algae and bacteria give off hydrogen.
Steam Reforming Is a Widely-Used Method of Hydrogen Production
Steam reforming is currently the least expensive method of producing hydrogen and accounts for about 95% of the hydrogen produced in the United States. This method is used in industries to separate hydrogen atoms from carbon atoms in methane (CH4). But the steam reforming process results in greenhouse gas emissions that are linked with global warming.1
Electrolysis Creates No Emissions but Is Costly
Electrolysis is a process that splits hydrogen from water. It results in no emissions, but it is currently an expensive process. New technologies are currently being developed.
Hydrogen can be produced at large central facilities or at small plants for local use.
How Much Hydrogen Is Produced in the United States?
About 9 million metric tons of hydrogen are produced in the United States annually, enough to power 20-30 million cars or 5-8 million homes. Most of this hydrogen is produced in three States: California, Louisiana, and Texas.
1. U.S. Environmental Protection Agency, Climate Change State of Knowledge.
The Space Shuttle
Source: NASA (Public Domain)
Hydrogen Fuel Cell Public Bus in Use in Perth, Western Australia
Source: Hax0rw4ng, Wikimedia Commons author (GNU Free Documentation License) (Public Domain)
Hydrogen Fuel Cell Hybrid Vehicle
Source: Gnsin, Wikimedia Commons author (GNU Free Documentation License) (Public Domain)
Most Hydrogen Is Used in Refining, Treating Metals, and Processing Foods
Nearly all of hydrogen consumed in the United States is used by industry for refining, treating metals, and processing foods.
The National Aeronautics and Space Administration (NASA) is the primary user of hydrogen as an energy fuel; it has used hydrogen for years in the space program. Liquid hydrogen fuel lifts NASA's space shuttles into orbit. Hydrogen batteries, called fuel cells, power the shuttle’s electrical systems. The only by-product is pure water, which the crew uses as drinking water.
Hydrogen Fuel Cells Produce Electricity
Hydrogen fuel cells make electricity. They are very efficient, but expensive to build. Small fuel cells can power electric cars. Large fuel cells can provide electricity in remote places with no power lines.
Because of the high cost to build fuel cells, large hydrogen power plants won't be built for a while. However, fuel cells are being used in some places as a source of emergency power, from hospitals to wilderness locations.
Portable fuel cells are being sold to provide longer power for laptop computers, cell phones, and military applications.
Hydrogen Use in Vehicles
Today, there are an estimated 200 to 300 hydrogen-fueled vehicles in the United States. Most of these vehicles are buses and automobiles powered by electric motors. They store hydrogen gas or liquid on board and convert the hydrogen into electricity for the motor using a fuel cell. Only a few of these vehicles burn the hydrogen directly (producing almost no pollution).
The present cost of fuel cell vehicles greatly exceeds that of conventional vehicles in large part due to the expense of producing fuel cells.
From the Laboratory to the Road
Hydrogen vehicles are starting to move from the laboratory to the road. Hydrogen vehicles are in use by a few state agencies and a few private entities.
The Refueling Challenge
Currently, there are 56 hydrogen refueling stations in the United States, about half of which are located in California. There are so-called “chicken and egg” questions that hydrogen developers are working hard to solve, including: who will buy hydrogen cars if there are no refueling stations? And who will pay to build a refueling station if there are no cars and customers?
