The four nonrenewable energy sources used most often are:
- Oil and petroleum products — including gasoline, diesel fuel, and propane
- Natural gas
- Uranium (nuclear energy)
Nonrenewable energy sources come out of the ground as liquids, gases, and solids. Crude oil (petroleum) is the only commercial nonrenewable fuel that is naturally in liquid form. Natural gas and propane are normally gases, and coal is a solid.
Fossil Fuels Are Nonrenewable, but Not All Nonrenewable Energy Sources Are Fossil Fuels
Coal, petroleum, natural gas, and propane are all considered fossil fuels because they were formed from the buried remains of plants and animals that lived millions of years ago.
Uranium ore, a solid, is mined and converted to a fuel used at nuclear power plants. Uranium is not a fossil fuel, but is a nonrenewable fuel.
Electricity Is a Secondary Energy Source
Electricity is the flow of electrical power or charge. It is both a basic part of nature and one of our most widely used forms of energy.
Electricity is actually a secondary energy source, also referred to as an energy carrier. That means that we get electricity from the conversion of other sources of energy, such as coal, nuclear, or solar energy. These are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or nonrenewable.
Electricity Use Has Dramatically Changed Our Daily Lives
Before electricity became available over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves.
Many scientists and inventors have worked to decipher the principles of electricity since the 1600s. Some notable accomplishments were made by Benjamin Franklin, Thomas Edison, and Nikola Tesla.
Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the late 1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current (AC) electricity, which can be transmitted over much greater distances than direct current. Tesla's inventions used electricity to bring indoor lighting to our homes and to power industrial machines.
Despite its great importance in our daily lives, few of us probably stop to think what life would be like without electricity. Like air and water, we tend to take electricity for granted. But we use electricity to do many jobs for us every day — from lighting, heating, and cooling our homes to powering our televisions and computers.
What Is Renewable Energy?
Renewable energy sources can be replenished in a short period of time. The five renewable sources used most often are:
- Biomass — including wood and wood waste, municipal solid waste, landfill gas, and biogas, ethanol, and biodiesel
- Water (hydropower)
What Role Does Renewable Energy Play in the United States?
The use of renewable energy is not new. More than 150 years ago, wood, which is one form of biomass, supplied up to 90% of our energy needs. As the use of coal, petroleum, and natural gas expanded, the United States became less reliant on wood as an energy source. Today, we are looking again at renewable sources to find new ways to use them to help meet our energy needs.
In 2008, consumption of renewable sources in the United States totaled 7.3 quadrillion Btu — 1 quadrillion is the number 1 followed by 15 zeros — or about 7% of all energy used nationally.
Over half of renewable energy goes to producing electricity. About 9% of U.S. electricity was generated from renewable sources in 2008. The next largest use of renewable energy is the production of heat and steam for industrial purposes. Renewable fuels, such as ethanol, are also used for transportation and to provide heat for homes and businesses.
Renewable energy plays an important role in the supply of energy. When renewable energy sources are used, the demand for fossil fuels is reduced. Unlike fossil fuels, non-biomass renewable sources of energy (hydropower, geothermal, wind, and solar) do not directly emit greenhouse gases.
Why Don’t We Use More Renewable Energy?
In the past, renewable energy has generally been more expensive to produce and use than fossil fuels. Renewable resources are often located in remote areas, and it is expensive to build power lines to the cities where the electricity they produce is needed. The use of renewable sources is also limited by the fact that they are not always available — cloudy days reduce solar power; calm days reduce wind power; and droughts reduce the water available for hydropower.
The production and use of renewable fuels has grown more quickly in recent years as a result of higher prices for oil and natural gas, and a number of State and Federal Government incentives, including the Energy Policy Acts of 2002 and 2005. The use of renewable fuels is expected to continue to grow over the next 30 years, although we will still rely on non-renewable fuels to meet most of our energy needs.
How Do We Measure Renewable Energy?
Each of the energy sources we use is measured, purchased, and sold in a different form. Many units of measurement are used to measure the energy we use. Learn more about converting energy units in the Units and Calculators section.
What Is Hydrogen?
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?
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.
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 (batteries) 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.
Hydrogen vehicles are starting to move from the laboratory to the road. The U.S. Postal Service, a package delivery company, a few park rangers, and a few private utility companies are also using hydrogen vehicles.
The Refueling Challenge
Currently, there are 58 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?