The pie chart shows what proportion of each method of energy generation contributed to world energy generation in 2015. Oil contributed 33 percent. Coal contributed 30 percent. Natural gas contributed 24 percent. Hydroelectric power contributed seven percent. Nuclear power contributed four percent. And the remaining two percent came from other renewables.
This question has two parts. What proportion of the world energy supply came from nonrenewable sources in 2015? And what proportion of the world’s energy supply came from renewable sources in 2015? Okay, so in order to answer this question, we first need to be clear on what the terms nonrenewable and renewable mean when we’re talking about energy sources. Then, we need to identify whether each of these options counts as a renewable or a nonrenewable energy source.
When we say that an energy source is renewable, what this means is that it can’t be depleted. A nonrenewable energy source, on the other hand, is the opposite. It’s an energy source that can be depleted. Let’s look at our list and decide which of these are renewable and which ones are nonrenewable.
First on the list is oil. Now, oil is a natural fuel, which is formed when plants and other organic material are subjected to high pressures and temperatures over long periods of time. To get the energy out of oil, we burn it. While oil is formed naturally, this process takes place over millions of years. And oil is being formed at a much slower rate than the rate that we’re using it. This makes oil a nonrenewable resource. So, let’s write NR for nonrenewable next to oil.
Next on the list is coal. Coal is formed in essentially the same way as oil. And actually, natural gas is formed in the same way as well. The type of organic matter that we start with, as well as the temperatures and pressures that they’re exposed to, determine whether oil, coal, or natural gas is formed. But all three are formed over similar periods of time. And all three are being used for energy production much more quickly than they’re being formed. So, coal and natural gas are nonrenewable energy sources as well.
Next on the list is hydroelectric power. Hydroelectric power is when the flow of water is used to turn turbines, which are connected to generators which generate electricity. Hydroelectric power often involves the construction of a dam to block a river. This causes a reservoir of water to build up on one side of the dam, and we can then control the flow of water through turbines in the dam. You could even think of water as being the fuel for a hydroelectric power station.
However, it’s a fuel that’s not burnt or used up in the process. The water that flows through a hydroelectric power station is part of the water cycle. And the reservoir will eventually always be replenished by rain. This makes hydroelectric power a renewable energy source.
Next on the list is nuclear power. This is a form of energy generation which uses radioactive materials such as uranium to generate electricity. Nuclear fuel gives off heat energy, which can be used to heat water so that it turns into steam. In a nuclear power station, the steam is used to turn turbines, which are connected to generators, which then produce electricity. When radioactive materials give off energy in this manner, we call it nuclear decay.
Nuclear decay is a nonreversible process, which means that once we’ve extracted all the energy that we can from a piece of nuclear fuel, we can never use it again. Nuclear power depends on the use of radioactive elements as fuel. These elements can only be created in astrophysical processes such a supernovas, which is when a star explodes at the end of its life cycle. This means that all the uranium on earth must have been there since the Earth formed, which was around four and a half billion years ago. So, even though we don’t burn nuclear fuel, it can still be used up, which makes it a nonrenewable energy source.
The last power source on our list is other renewables, which, of course, counts as renewable energy sources, which may include things like solar power and geothermal power. So, now we know which of these power sources are renewable and which are nonrenewable. We can answer these questions.
First, we want to find the proportion of the world energy supply that came from nonrenewable sources in 2015. The nonrenewable energy sources here are oil, which contributed 33 percent of world energy generation in 2015, coal, which contributed 30 percent, natural gas, which contributed 24 percent, and nuclear power, which contributed four percent. Adding these up gives us 91 percent, which is our answer to the first question. The proportion of the world energy supply that came from nonrenewable sources in 2015 is 91 percent.
For the second question, we want to add up the proportions that come from renewable energy sources. These are hydroelectric power, which contributed seven percent, and other renewables, which together contributed two percent. Adding these together gives us nine percent, which is our answer to the second question. The proportion of the world energy supply that came from renewable sources in 2015 was nine percent.