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Energy for All

The Sustainable Development Goals are a group of 17 goals created by the United Nations to make our world a sustainable place to live. Sustainable Development Goal 7 (SDG 7) is named “Affordable and Clean Energy” and it aims for countries to provide access to affordable, reliable, sustainable, and modern energy for all people [1]. But before exploring how we might meet this goal with the help of science, we need to define some of its complex ideas.

First, what is energy? Energy can be defined as the amount of work that can be done by a force. The rate at which energy is used is what we call power. Energy can take many forms, like heat, light, work, and a more particular form that links matter, called chemical bonds. As living beings, we change energy from one form to another all the time. We eat food that is filled with energy, and we transform it into heat to keep our bodies warm, or to do physical tasks. When you kick a ball, you give energy from your body to the ball. But if you are not eating food, you will not have enough energy to keep playing until the end of the game! This applies to many vital actions of societies, like cooking, traveling, or heating.

One of the keywords of SDG 7 is “all”. It means that energy must reach every person on the planet, to improve lives and reduce poverty. The Industrial Revolution, during which modern industry was created, is a great example of how using energy to power things like trains, cars, and stoves made life much better for lots of people. However, according to the United Nations, more than 675 million people still did not have access to electricity in 2021 [2]. So, we need to make sure we provide energy for all eight billion human beings currently on Earth, and the people who will come next.

Transitioning From “Bad” to “Good” Energy Sources

Not all energy sources are good for humans and for the planet. A “good” energy source needs to fulfill three criteria. It needs to be affordable, reliable, and sustainable. Affordable means that it must be cheap enough that everyone can afford to buy it. Reliable means that it should always be safe and accessible. Sustainable is a tricky one. On one hand, it means energy should not damage the environment, but it also means that the world should not run out of the energy source.

To simplify, we can say that there are two main sources of energy and three big “actions” by which people use most of the energy. The first source is fossil energy such as coal, oil, or gas. The second source is renewable energy, such as wind, solar, or tidal energy. The three actions are heat, electricity, and transport. Today, most of the world’s energy comes from fossil fuels, which power 90% of our heating, 79% of our electricity, and 96% of our transport [2]. But fossil fuels do not meet two of the three criteria for a good energy source—they are not sustainable or reliable. The use of fossil fuels leads to global warming and air pollution. Fossil fuels are also finite, meaning that they will eventually run out. Renewable energies, on the other hand, use the natural power of the environment. They are sustainable but often not as affordable or reliable. For example, solar panels transform light from the sun into electricity, but they cannot work at night. Also, installing solar panels often comes with a cost that the poorest people cannot afford.

Renewable energies are promising, but they will need time to be developed. In the future, societies must be adapted around renewable energies. Actions need to be taken starting today. We must improve the use of fossil energies while we still depend on them.

How can Science Help?

Most fossil fuels are used through combustion. To understand how combustion works, we will compare it to cooking food using a very strict recipe. For example, to burn one cup of fuel (CH₄), you need two cups of oxygen (O₂). If you follow the recipe, you will have energy. But you will also have some waste products: carbon dioxide (CO₂) and water (H₂O). We can now write the cooking recipe in one line, called an equation:

$\begin{array}{l}1{\text{ cup of CH}}_4+{\text{2 cups of O}}_2\text{= Energy}+\text{Waste (}1{\text{ cup of CO}}_2+2\text{ cups}\\ {\text{of H}}_2\text{O)}\end{array}$

Combustion creates energy in the form of heat by burning fossil fuels. But there are two major problems that need fixing. The fuel CH₄ is not renewable and will be totally depleted soon. And the waste generated, CO₂, contributes to global warming. There is a need to supply the same amount of energy, but by using less fuel and generating less waste. What if we told you that we could fix the two issues with a simple trick? To do this, we need plasma! But what is plasma, and how does it work?

Matter is made of tiny molecules that store energy in the form of chemical bonds. There are three well-known states of matter: solid, liquid, and gas (Figure 1). Let us take the example of ice. When you heat (add energy to) ice, it melts into liquid water. If you continue to add energy to the liquid, you get water vapor or steam. If you add even more energy, you will transform the steam into plasma. Plasma is like a gas with very high-energy molecules that are perfect for combustion [3].

It is possible to turn a gas into plasma with just a bit of electricity. Think of this as an investment. You invest a little bit of electrical energy at the start to get a lot more energy at the end. If we go back to the cooking recipe example, when we add plasma, it is like chopping the ingredients. It is easier to cook when everything is well-chopped! With this trick, we can save fuel and reduce waste!

Making More Energy with Super-Flames

So how can we use plasma to improve regular combustion? We can create super-flames! Super flames, or plasma-assisted flames, are powerful types of fires that use a bit of electricity to create plasma, making the flames burn much hotter and more efficiently than regular flames. One of the best types of super-flames is called a detonation. A detonation is a very strong and fast flame, moving faster than the speed of sound! Detonations are more energetic than normal flames for the same amount of fuel. This is great, but tricky, because it is very hard to create and control a detonation. To start a detonation, plasma can be used on a flame (Figure 2). When plasma is added, the flame quickly accelerates and becomes a detonation [4]. The detonation generates a very large amount of useful energy because the particles are compressed in a small region called the shockwave. Close to this region, the temperature and the pressure are so high that the combustion process is stronger than in a normal flame.

Using Less Fuel with Super-Flames

Another way to improve the combustion process is to simply use less fuel. But what happens if not enough fuel is provided to a flame? It becomes lean. A lean flame becomes more and more unstable until it disappears, or blows out. However, if we use plasma, we can force the flame to stabilize and be sustained for longer, even if we use a very small amount of fuel. This is called extending the blow-off limits of lean flames (Figure 3). By using plasma on a lean flame, it is possible to save a lot of fuel and produce less waste [5].

What is Left to Do?

Plasma-assisted combustion is a very recent area of research. There is still a lot to do! The number of people looking at the interaction between flames and plasmas is growing. But there are questions that still need to be solved. For example, what is the best way to use plasma technology in modern engines? Or why does plasma work so well for some conditions but not so well for others? How can we make plasma-assisted combustion safe for global use?

Despite these questions, we now know that super-flames may be a reliable way of generating large amounts of energy with the least amount of fuel consumption and waste generation. This is important for SDG 7, as it may be a quick solution to the sustainability issues of classical combustion of fossil fuels. It will help us make better use of fossil fuels while we transition to more sustainable energy sources. Finally, plasma technology is not limited to traditional fossil fuels, it can also enhance the combustion of alternative and more sustainable fuel sources. These might include hydrogen, biofuels, or synthetic fuels made from renewable resources. The more we know about these new fuels, the faster we can achieve SDG 7.

Glossary

Sustainable: ↑ Using resources wisely to protect the planet for the future. It is about saving energy, reducing waste, and caring for nature so it lasts a long time.

Fossil Energy: ↑ Energy coming from the combustion of oil, gas or coal. Often associated with large emissions of carbon dioxide.

Renewable Energy: ↑ Energy coming from various sources such as the wind, the sunlight, the water flows and that are not directly producing carbon dioxide.

Combustion: ↑ A process where materials like wood or fuel are burning creating heat. For example a campfire or the flame of a candle.

Plasma: ↑ Electrified gas, in which some of the molecules have been cut into extremely energetic atoms. Plasmas transfer a lot of energy into chemical bonds very efficiently.

Molecules: ↑ Components of all matter, which are composed of atoms that represent different elements, like oxygen (O) or hydrogen (H).

Detonation: ↑ A flame that spreads at speeds faster than the speed of sound. Detonations are powerful and very effective at generating energy.

Lean Flames: ↑ Flames that are very unstable and can vanish easily due to lack of fuel. A lean flame can be stabilized by plasma addition.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank Ruben Costa and Nicki Talbot at KAUST for their invaluable support during the initial writing stage and review process, without which this collection would not have been possible. We also extend our gratitude to the KAUST Office of Sustainability and the UNDP Saudi Arabia Country Office for their dedication to raising awareness of the UN SDGs in our journey toward a more sustainable world.