1.2.2 Energy basics

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?

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

Potential energy: stored energy

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.

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.

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.

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.

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.

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 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)

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.

Concept: Systems

Skills: Research skills (information literacy)

Time: varies (see below)

Type: Individual, pairs or group (option-dependent)

Ideas for longer activities, deeper engagement, and projects are listed in Subtopic 1.5 Taking action

• 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.

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.

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