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2 Tutorials that teach Energy
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Author: Sophia Tutorial

Determine the key characteristics of renewable sources, non-renewable sources, and fossil fuels.

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what's covered
This tutorial will cover the topic of energy, through the definition and discussion of energy and its sources. We will cover the two main categories of energy sources -- renewable and non-renewable -- including an exploration of fossil fuels and the global carbon footprint. Finally, we will explore how energy use has changed over time.

Our discussion breaks down as follows:

  1. What Is Energy?
  2. Sources of Energy
    1. RenewableEnergy
    2. Non-Renewable Energy
    3. Fossil Fuels
  3. Carbon Footprint
  4. Evolution of Energy Use

1. What Is Energy?

Energy is used in almost every facet of modern life: to run our cars, heat our homes, clean and transport water, light our buildings, power our electronics, and manufacture our products. Energy is defined as work that can be done by a fuel source. Fuel sources can vary and the form of energy they take can as well.

Energy can be thermal, mechanical, or even chemical, though a large portion of what is used by humans is in the form of electric energy which powers houses, businesses, and various industries. Different fuel sources provide different amounts of energy in their various forms.

Electric Discharge from a Tesla Coil

2. Sources of Energy

Energy sources are split into two main categories: renewable and non-renewable. 88.5% of energy used by humans comes from non-renewable sources, while renewable ones take up the remaining 11.5%.

2a. Renewable Energy

Renewable energy is considered renewable because it can be replaced in a reasonable human lifespan -- meaning months, years, or decades -- or it is simply an unlimited supply.

U.S. renewable sources break out as follows:

Energy Source
Percent of Total Generated
Biomass and ethanol 50%
Hydroelectric 27.5%
Wind 17%
Photovoltaics 3%
Geothermal 2.5%
Total 100%

2b. Non-Renewable Energy

At 88.5%, non-renewable sources provide the vast majority of energy used in the United States. Non-renewable energy sources are those that cannot be replaced in the normal human lifespan. Most non-renewables take thousands to millions of years to form, so for human purposes, there is a finite supply.

Non-renewable energy sources break out as follows:

Energy Source
Percent of Total Generated
Natural gas 39%
Oil 21.5%
Coal 27.5%
Nuclear 12%
Total 100%

Both natural gas and oil are used for heating and transportation, while coal and nuclear power plants (which uses a rare form of uranium) are used for electricity in the home and industry.

did you know
The United States is the largest global producer of natural gas. Also, oil is the largest source of energy in the United States, even though it is not the largest utilized.

2c. Fossil Fuels

The majority of U.S. energy and, therefore, non-renewable energy, comes from fossil fuels, which are most often oil, natural gas, and coal. Fossil fuels are sought after for their energy-dense nature and their accessibility -- hence, once discovered, they quickly became the world's prime energy sources.

They provide energy for transportation in cars, buses, trucks, boats, and airplanes, as well as electricity to power homes, industries, and businesses -- and heating for the same end uses.


Despite being only 5% of the world's population, the United States consumes approximately 20% of the world's energy. This graph illustrates energy intensity globally through kilograms of oil equivalent -- a standard measure of the amount of energy that can be extracted from one kilogram of crude oil. The lighter the country's color, the higher the energy intensity.

Energy Intensity

As you can see, while the United States is one of the highest in energy intensity, its population is only 5% of the world.

3. Carbon Footprint

Carbon footprint is a tool used to measure the amount of greenhouse gases produced by a source, whether it is a person, a product, a company, or a country. Carbon footprint assessments are tools used to increase awareness of impacts at an individual, organizational, or product level.

Greenhouse gases are of interest because of their capacity to accelerate and exacerbate climate change. Carbon footprint is actually just a part of ecological footprint calculations and can be used as an indicator of sustainable energy use. The map below shows the average amount of carbon dioxide emissions by country per year. Notice that the United States and China are by far the biggest producers.

Average Tonnes of CO2 Annually

4. Evolution of Energy Use

When talking about energy, it is important to highlight how its use has changed in quantity over time. In the graph below, you can see that U.S. energy use has dramatically increased since the 1700s. The graph follows the rise of the Industrial Revolution. As technology use has increased, so has the need for electricity and other forms of energy.

Energy Consumption

The graph of global energy consumption looks quite similar. It also follows the rise of the Industrial Revolution, which caused increased technology use and electric energy needs, resulting in increased energy consumption.

Global Primary Energy

Today we learned about energy -- we discussed an overview of energy and its different sources. We learned about energy's two main categories of renewable and non-renewable sources, including the energy mixes of each. We learned about the nature of fossil fuels, carbon footprint, and how energy use has changed over time in the United States and worldwide.