What is an Energy System?

Today’s lecture is an important milestone in this course, an important turning point, because so far we’ve been mostly looking at the problems of human-induced climate change. But today, good news, we’re going to start looking at some of the solutions.

Up until now you might think that the picture looked quite grim, and you would have a point because indeed the potential consequences of uncontrolled climate change are very severe, very threatening.

And the challenge of avoiding dangerous climate change is also very significant. It requires very deep reductions in greenhouse gases emissions to eventually as we discussed in the previous lectures, net zero emissions by the second half of the century.

We also mentioned that it, in turn, requires a profound transformation of the way we grow our economies and in particular, a fundamental transformation of our energy systems.

But the good news is that this is feasible. This is certainly not easy, but this is feasible. And today we’re going to start looking at some of the possible solutions to the deep decarbonization of our energy systems.

We’re going to do so first at a pretty high level, looking at the solutions at the global level first, but for each of the key sectors of the economy, the energy supply, the industry, the buildings, the transport sector. But in the next lectures we will take a closer look at these solutions by looking in detail at country-specific case studies and also by looking in detail at some of the most important technological challenges such as carbon capture and sequestration, or new generation of nuclear power, or the challenge of having smart grids and energy storage to be able to operate our power system with a high share of intimate and renewable energies, or the challenge of having long-range electric vehicles.

But before we do that, we need to have a good understanding of how our energy systems function. And this is what this first chapter is about. I want you to understand how energy is produced. I want you to understand how it is transformed and how it is consumed because we need that to understand how we can decarbonize our energy systems. The truth is that energy is everywhere in our daily lives.  We use for example energy to transport ourselves. We use energy to light, to heat, to cool our homes. We use energy also to power our TVs or our computers or our washing machines and fridges. But energy is also absolutely central to the process of economic growth and development because we need energy to produce all the goods we consume. We need even more energy to be frank, to produce the kind of construction materials such as cement or steel that we use to build the infrastructures that support our economic growth and our development. And we also need a lot of energy to ship all these products from where they’re produced to where they are consumed.

There are many different sources of energy. Let me make a short list. We have coal. We have oil. We have gas. We have hydro energy, nuclear energy. And also all different sorts of renewable energies such as solar, wind, or biofuels. We call these different sources of energy the primary energy.

And the table you can see is what we call an energy balance. And the different sources of primary energy can be read in the columns to this table. The primary sources of energy can either be used for direct, final energy consumption or they can be transformed into another form of energy, because before their final energy use in energy end use sectors such as transport, buildings, or industry.

Let me take an example to illustrate that point. Coal can either directly be used to produce heat for buildings or different types of industrial processes or it can be used to produce electricity which in turn is used for lighting or to power any electrical equipment. There are also many different types of energy transformation processes which you can read in the lines in the middle of the table.

Again, let me pick just three examples:

• Power plants, very important type of energy transformation process. The power plants use all different sorts of primary sources of energy such a coal, gas, hydro, uranium, all different sorts of renewable energies to produce electricity.
• Second example, the oil refineries that transform crude oil into oil products that can be used by ars or by planes.
• Heat plants that use coal, gas or biofuels to produce heat for buildings or industrial processes.

There are energy losses happening during these transformation processes. And these losses represent the difference between primary energy, and final energy. You can see the final energy end use sectors at the bottom of the table.

You see the names of the different sectors, industry, transport and on the graph, other, which in particular includes buildings. The transformation and the consumption of some forms of energy, not all of them, leads to CO2 emissions and therefore contributes to global warming. Some types of energy have no direct emissions such as nuclear power, hydropower, or renewable energy such as solar or wind.

And it’s important to mention in, they might induce some emissions through their life cycle, but they have no direct emissions. To the contrary, the burning of fossil fuels, the coal, the oil, the gas emits CO2 through the burning process. And of the three fossil fuels, coal has the highest CO2 emissions content per unit of energy. Its carbon content is on average across the different forms of coal, 22% highest than oil and 68% higher than gas. So to summarize this chapter, the ultimate objective of the deep transformation of our energy system really is the phasing out of freely emitting fossil fuels. I underline “freely emitting” here because fossil fuels could continue to be used with some technologies and in particular with carbon capture and sequestration. But the uncapped fossil fuels must go, they must be phased out. And we’re going to see in the next chapter that this is a major challenge because fossil fuels still represent the lion’s share of our energy consumption. And in fact an ever-growing share.

---

---