1.2.2 Energy basics
Helpful prior knowledge and learning objectives
Helpful prior learning:
Section 1.1.1 The economy and you, which explains what an economy is and how it is relevant to students’ lives
Section 1.1.2 The embedded economy, which explains the relationship between the economy and society and Earth’s systems.
Section S.1 Systems thinking, which explains what a system is and why systems thinking is useful. (coming soon)
Learning objectives:
outline different forms and sources of energy
explain the role of energy in the economy
distinguish between renewable and nonrenewable energy resources
All life on Earth requires energy, and humans are no exception. Everything we do needs energy - breathing, working, playing, driving, watching Tik Tok videos - all of it! But what is energy, and how have we come to be so dependent on it?
What is energy?
Energy is the ability to do work or cause change. Energy makes things happen, like moving objects or producing heat and light. Energy is essential for all life and comes in different forms.
Kinetic energy: energy of motion
Radiant energy
Energy from electromagnetic waves.
Electrical energy
Energy produced by the movement of electrons; powers electronic devices.
Thermal energy
Energy related to heat; it increases as things get hotter.
Potential energy: stored energy
Nuclear energy
Energy released from the nucleus of atoms.
Chemical energy
Energy stored in the bonds of chemical compounds and released during chemical reactions
Gravitational energy
Energy stored in an object's position or height
Elastic energy
Energy stored in objects when they are stretched or compressed
The First Law of Thermodynamics says that energy cannot be created or destroyed in the universe. The Earth is a closed system, which means that no new matter enters Earth’s systems, but radiant energy of the sun can enter. Earth is constantly bathed in solar radiation, which has an impact on most other energy sources, as you will see later in this text.
How do we measure energy?
Energy is measured in different units: Joules (J), kilowatts (kW), and kilowatt-hours (kWh).
Joule (J): a measure of the amount of work done or energy transferred. For example, lifting a 100-gram (think apple or chocolate bar) 1 metre high takes about 1 Joule of energy.
watt (W): a unit of energy transfer equal to 1 Joule/second. 1 kilowatt (kW) = 1000 watts
watt-hours (wh) or kilowatt-hours (kWh): a measure of how much energy is used or produced over time.
For example, using a 100-watt light bulb for 1 hour consumes 100 watt-hours or 0.1 kilowatt-hour (kWh) of energy. Using a 100-watt light bulb for 10 hours consumes 1 kilowatt-hour (kWh) of energy.
For comparison, 1 litre of petrol (gasoline) contains about 32,000,000 Joules or roughly (a little under) 10 kWh. That is a lot of energy! To understand this in human terms, a healthy adult male labourer can perform manual work (Figure 1) such as moving and laying bricks in an eight-hour work day equal to about 0.5 kWh. So, to match the energy in 1 litre of petrol, a person would have to work for 8 hours per day for 20 days. These numbers are approximate, but give you an idea of the energy associated with fossil fuels relative to human labour.
Figure 1. Even hard manual labour like moving and laying bricks is only the equivalent of 0.5 kWh for an 8-hour workday, far less than the energy from 1 litre of petrol
(Credit: M Mahbub A Alahi, CC0)
You may hear people complain about how expensive petrol is. But considering the amount of energy petrol contains and the work it does for us, it is incredibly inexpensive. This is especially true considering rises in incomes that have made fuel more affordable and the improvements in machine efficiency that enable us to do more with less fuel.
Because we pay so little for energy, the products we produce and buy are also much less expensive. These low energy costs and low product prices contribute to the high consumption of both energy and material resources, which is discussed in Section 1.2.3 and Section 1.2.4.
What sources of energy do we have?
Most of the energy on Earth comes from the sun. The sun is the source of:
energy in food chains: Plants use sunlight to make food in a process called photosynthesis. Plants are the foundation of food chains in ecosystems, providing energy for all life on Earth.
wind energy: The sun heats the Earth, creating wind used to generate electricity with wind turbines (Figures 1a and 1b)
solar energy: The sun provides solar energy used to generate electricity with solar panels.
hydropower: The sun evaporates water, forming clouds and rain that flows in rivers that power turbines.
fossil fuels: Over millions of years, sunlight helped grow the plants and animals that later turned into coal, oil and natural gas. These fuels store millions of years of the sun’s energy in chemical form.
Figure 2a. Windmills of Nashtifan, Iran are used for milling grain. Wind has been used for centuries as an energy source.
(Credit: Hasanahmadifard CC BY-SA 4.0)
Figure 2b. Windmills in Denmark are used for electricity.
(Credit: Dirk Goldhahn CC BY-SA 2.5)
Other sources of energy include geothermal and tidal. Geothermal energy comes from the Earth's internal heat. Below the surface, the Earth is very hot. Pipes deep in the ground bring up hot water or steam, which is then used to generate power. Geothermal energy is used around the world, but is a particularly large source of energy in Kenya, El Salvadore, Iceland, New Zealand, Nicaragua, and Costa Rica.
Tidal energy, which comes from changing tides along coastlines, is caused by the gravitational pull of the moon and the sun on the Earth’s oceans. Tides move enormous amounts of water, particularly in places where there is a big difference between high and low tide. So in some places, we use this water movement to generate power.
What is the difference between renewable and nonrenewable energy sources?
Renewable energy comes from sources that are continuously available or regenerate quickly. For example, solar, wind, geothermal and tidal energy are always flowing from their sources and will not run out. On the other hand, biomass, like wood or crops that can be burned for energy, regenerates as plants grow back. Renewable energy sources are sustainable only if we use them at slower rates than they replenish and if their surrounding ecosystems remain healthy.
Figure 2 shows a stock and flow diagram (Section S.x) for a stock of wood biomass in a forest. If inflows from tree growth and outflows from tree death and human harvesting are in balance, then one of the conditions for biomass to be renewable is met.
Figure 2. Stock and flow diagram for biomass, a renewable energy resource if inflows and outflows are in balance
Figure 3 shows the share of electricity production from renewable energy by country. Which countries use more renewable energy? What could explain that?
Figure 3. Share of electricity production from renewable energy, by country (Credit: Our World in Data)
Nonrenewable energy comes from sources that do not replenish quickly or are finite. This includes coal, oil, natural gas, and uranium for nuclear power. These materials took millions of years to form and, once used, cannot be replaced within a human lifetime.
Figure 4 shows a stock and flow diagram (Section S.x), where coal stocks have a mining outflow, but no inflow.
Figure 4. Stock and flow diagram for coal, a non-renewable energy source with outflows, but no inflows
Today, we use a wide mix of energy sources including non-renewable coal, oil, gas, nuclear power, and renewable hydropower, solar, wind, and biomass. Until the mid-1800s, most of the world's energy came from burning biomass such as wood, crop waste or charcoal. Coal then became a major energy source in the Industrial Revolution. By the early 1900s, coal provided about half of all energy, with biomass providing the other half (Figure 5).
Figure 5. Global primary energy consumption by source since 1800 (Credit: Our World in Data)
During the 1900s, we began using more energy types. Oil and gas came first, followed by hydropower and then nuclear energy starting in the 1950s. Looking at the last 200 years, changing from one dominant energy source to another has been slow, often taking decades. But this transition can happen more rapidly. In the UK, the share of electricity powered by coal declined from nearly two-thirds in 1990 to about one-third by 2010, and then to around 1% in the following decade.
Renewable energy production, especially for electricity, is increasing very rapidly. However, while some countries have been able to replace fossil fuels with renewable energy sources, globally we still use fossil fuels for about 80% of our energy. It is difficult to lower that percentage because our economies and the demand for energy are growing so quickly that in many places renewable energy is simply being added to fossil fuel energy sources, rather than replacing them. This will be discussed more in the next Section 1.2.3.
This optional short video below is a nice summary of energy information from this section.
Activity 1.2.2
Concept: Systems
Skills: Research skills (information literacy)
Time: varies (see below)
Type: Individual, pairs or group (option-dependent)
Option 1 - Comparing energy use of various devices
30 minutes
Select some common electrical devices in your school, or at home and figure out how many watts they use. If you have them on hand, you may be able to find the information on the device. If not, do some quick research on the internet to find some rough estimates.
Make a table to compare the items, listing the item, the kilowatts, and a guess of the amount of time the device is used each day.
Note: electrical devices that are connected to the internet use more energy than what is listed on the energy label. This is because of the computing power and networks needed to store data and connect devices. You may find it interesting to learn more about how much energy our use of computers, cloud storage and streaming uses - it’s a lot!
Device / machine Kilowatts Time used per day (hours)
Option 2 - Using an energy calculator to determine the cost of electricity for various devices
30 minutes
There are many energy calculators online that can help you estimate how much it costs per month or per year to use various devices. See if you can find such a calculator for your country. If not, you can choose one for another country, but the assumptions in the calculator may be different from your region. You may need to find the cost of electricity per kWh to input into the calculator.
Select various devices and compare the cost of the energy used. You could add a column for this in the table from Option 1.
Option 3 - Understanding your home or school energy use
40 minutes for initial research if energy bills are ready for analysis, longer if a plan for energy reduction is developed
Ask your family/household to see the monthly or annual energy bill (electricity, gas, or other). This bill summarises your energy use at home for a period of time. You can also ask your family/household to show you an energy (electricity, gas, or other) metre, which documents the flow of energy into your home.
Try to find information on how your energy use compares to similar households in your country. Your energy bill may already have this information. Informing people about how they compare with others can be an effective way to get people to conserve energy.
You can also look at past energy bills to see how your household energy use has changed over time. What might account for these changes?
You can combine this research about home energy use, with information about the energy needed by particular devices to develop a plan for reducing energy use in your home.
You can take the same steps to start an investigation into energy use in your school. Energy bills for larger institutions are not always easy to read, so you may want to invite someone from the school administration or the building manager to come to the class to explain them.
Option 4 - Calculating the difference between human labour and petrol
20 minutes
Find out how much 1 litre of petrol or diesel fuel costs in your area.
Find out what the per hour minimum wage, living wage, or average wage is in your area, just to get a sense of how much money it takes to pay human workers.
Using the information from this section, can you figure out the difference between the cost of energy provided by 1 litre of petrol / diesel and 1 worker doing hard manual labour for one day? What insight does that give you into why our economies try to mechanise so much production?
Ideas for longer activities, deeper engagement, and projects are listed in Subtopic 1.5 Taking action
Checking for understanding
Further exploration
A Guide to the Energy of the Earth - A short TED-Ed video about energy basics. Difficulty level: easy.
Our World in Data: Energy - Many interesting interactive graphs, sometimes with short informative text. A great source to practise data interpretation skills. Difficulty level: medium
These 8 Countries Are Scaling Up Renewable Energy the Fastest - Article from the World Resources Institute with short case studies on Denmark, Uruguay, and Namibia to illustrate what the renewable energy transition looks like in three different contexts. Difficulty level: medium.
Sources
Blain, C., Jancovici, J. (2021). Welt Ohne Ende. Berlin: Reprodukt.
Daly, H., Farley, J. (2011). Ecological Economics (2nd ed.). Washington, D.C.: Island Press.
Ritchie, H. et al. (2023). Energy. Our World in Data. https://ourworldindata.org/energy.
Sneideman, J. (n.d.). A guide to the energy of the Earth. TED-Ed. https://ed.ted.com/lessons/a-guide-to-the-energy-of-the-earth-joshua-m-sneideman.
Terminology (in order of appearance)
Link to Quizlet interactive flashcards and terminology games for Section 1.2.2 Energy basics
energy: the ability to do work or cause change
kinetic energy: energy of motion
radiant energy: energy from electromagnetic waves
electrical energy: energy produced by the movement of electrons; powers electronic devices
thermal energy: energy related to heat; it increases as things get hotter
potential energy: stored energy
nuclear energy: energy released from the nucleus of atoms.
chemical energy: energy stored in the bonds of chemical compounds and released during chemical reactions
gravitational energy: energy stored in an object's position or height
elastic energy: energy stored in objects when they are stretched or compressed
First Law of Thermodynamics: energy cannot be created or destroyed in the universe
joule (J): a measure of the amount of work done or energy transferred
watt (W): a unit of energy transfer equal to 1 Joule/second
kilowatt (kW): 1000 watts, where each watt is a unit of energy transfer equal to 1 Joule/second
kilowatt-hour (kWh): a measure of how much energy is used or produced over time.
food chain: a series of organisms, each one dependent on the one before it as food; shows the transfer and transformation of energy and matter through living organisms in an ecosystem
hydropower: a renewable energy source that uses falling or running water
fossil fuel: a non renewable energy source including coal, oil, and natural gas, formed over millions of years in the Earth's crust from decomposed plants and animals
geothermal energy: a renewable energy source that uses the heat produced inside the Earth's crust
tidal energy: a renewable energy source that uses the movement of water from changing tides
renewable energy: energy from sources that are continuously available or regenerate quickly
biomass: organic matter that is burned for energy
stock and flow diagram: a diagram showing the accumulations of energy, matter, information or other things (stocks) and the movement (flow) of those things
nonrenewable energy: energy from sources that cannot be regenerated in a human timescale, such as coal, natural gas and oil