Introduction
Of particular interest in the topic of energy is the use of energy by humans. Much has been written and spoken on this subject. Each individual approaches the vast topic of “energy” from a different angle, having various life experiences and preconceived notions. In this post I will take the “30,000-foot” view. That is, I will look at the entire subject objectively from a far-removed viewpoint from which I can see the entire scope of the topic. Of course, it is impossible to consider a subject entirely objectively, for I have my own background and experiences that color my view of the world. But I will do my best.
To start with, since humans were humans, they have always used some form of energy to support human life. Obviously (or perhaps not so obviously today when we are so connected to and reliant on various forms of energy-dependent technology), the energy of primary concern for humans is biological metabolic processes. Each and every human being must eat to survive. With very few exceptions, you can be assured that every human being you see each day has had something to eat within the past week (most people just don’t go that long without eating, though most people can actually survive 4-6 weeks without food), and likely within the past day, and probably within the past six hours (the exception being in the morning because there are quite a few people who don’t eat breakfast, as shown in this survey as one source among many).
This is, to me, a remarkable thing. Each and every day, there are over seven and a half billion people that need to get enough food into their body to provide the energy their bodies need for the day’s activities. For those of us connected to modern economies, there is a massive behind-the-scenes effort going on every day to support our food needs, providing edible products to us from far-flung places around the globe which are processed in many locations far and near. Those living in subsistence economies are usually much more closely connected to their food sources and frequently grow much of their own food needs.
Energy Use by Human Society
While the topics of human metabolism and food production certainly deserve additional attention, it is to the more obvious aspects of the use of the word “energy” in connection with humans upon which we will place our focus. That is, the use of energy in human society external to the human body itself. So for the rest of this blog post, the word “energy” will mean energy used by humans not as part of the metabolic cycle (that is, not related to food).
In this context, the vast majority of energy used by humans throughout history has been used within the past few hundred years. Throughout early human history, energy use was limited to what people could find around them (mostly wood) to burn for purposes of cooking and staying warm. This is certainly a form of energy use.
I must here interject to distinguish between energy in general and useful energy. In an open fire there may be a significant amount of “chemical energy” stored in the chemical bonds of the burnable material that gets converted to heat energy. However, it is likely that not much of that energy is actually useful. On a hot day (when the heat energy of the fire is not needed to warm up the people standing around the fire), perhaps only 5% of the heat from the fire actually goes into cooking the food. On a cold day, the efficiency is slightly better (maybe 10%) because some of the energy is useful in providing warmth to people nearby. The rest of the 90-95% of the energy of the open fire just escapes as heat into the atmosphere.
Energy use has slowly grown more efficient over human history, and the number of people on the earth has increased dramatically in recent centuries, and the average energy used per person has also increased dramatically. So, it really is no exaggeration to say that the vast majority of (useful) energy consumed by humans has been within the past few hundred years.
Fossil Fuels Dominate Energy Use
And what has been the major source of that energy? Fossil fuels. Whether in solid (coal), liquid (petroleum), or gas (natural gas) form, fossil fuels have dominated the worldwide energy scene for over a hundred years.
At this point in this post, I am tempted to include a bunch of charts, tables, and graphs to best paint the picture of energy use by humans. However, this has already been performed by a number of parties far more thoroughly and compellingly than I could ever hope to do. There are entire government agencies dedicated to compiling, analyzing, and presenting energy statistics, including the United States Energy Information Administration. The International Energy Agency has a staff of over 200 dedicated to worldwide energy issues. Even other individuals (such as Vaclav Smil) have produced more energy charts than I could hope to reproduce.
I found two articles that do a pretty good job of showing energy use over the past few hundred years in chart form if you are interested:
For my purposes here, I will include just two charts and some commentary. First, let me note that there are many ways of categorizing energy production and use. Probably the most popular way to categorize energy use is by primary supply, that is, the source from whence the energy was harvested (for example, oil, coal, natural gas, nuclear, solar, wind, geothermal, biofuel, etc.). Other ways of categorizing energy include by economy sector (industrial, commercial, residential, and transportation) or by end use (building heating/cooling, different forms of transportation, etc.). Sometimes you can even find charts with multiple categorization schemes in the same chart, such as these from Lawrence Livermore National Laboratory. This chart gets even more detailed (as explained in this article, since the website itself doesn’t explain much).
Because there are so many ways to think about and categorize energy, one must be careful looking at these charts to make sure it is saying what one thinks it is saying. For example, one might say something like “nuclear energy provides 20% of the total energy consumed in the United States”, when in reality, nuclear energy is only 20% of the electricity consumed in the United States, which only makes up only about 40% of energy used in the United States, so the correct statement should be “nuclear energy provides about 8% of the total energy consumed in the United States”. So just be careful when looking at energy statistics because there are a lot of ways to get them wrong.
Now, the two charts I am choosing to include are the worldwide total primary energy supply in 1960 and again 50 years later in 2010. I think these tell the story of worldwide energy use as well as any. Data source is Our World in Data.
Obviously, the total energy used in 2010 (about 140,000 terawatt-hours, or about 510 exajoules) is more than the energy used in 1960 (about 40,000 terawatt-hours, or about 150 exajoules). In fact, over that 50-year period, worldwide energy use increased by a factor of 3.5.
In 1960, the top two worldwide energy sources were coal (at 38%) and oil (at 27%). In 2010, the top two worldwide energy sources were oil (at 35%) and coal (at 30%). Those two sources together accounted for 65% of worldwide energy in 1960 and in 2010. Natural gas and traditional biofuels switched places, with natural gas going from 11% of energy in 1960 to 23% of energy in 2010 and biofuels going from 22% in 1960 to 8% in 2010. From 1960 to 2010, biofuel use increased by about 30%, while natural gas use increased by a factor of seven. Hydropower has maintained its position as a minor player in energy at about 2%. Nuclear-generated electricity has grown to provide about 2% of global energy. Renewables such as wind and solar made up about half of a percent of global energy in 2010.
One story these pie charts do not tell is the disparity in energy use around the world. For example, the average person in the United States uses about 20 times more energy than the average person in Ghana. And energy use within the United States isn’t equal either, as the rich use many times more energy per person than the poor. So, obviously, looking at entire world energy use alone is insufficient. If everyone in the world used as much energy as the average American, energy use would be drastically different.
We hear a lot about renewable energy these days. Energy produced by wind and solar has grown dramatically in recent years. However, wind and solar combined still only account for less than two percent of total world energy use. That is a lot of energy, and a lot of rapid growth in renewables, but it is still only a very small piece of the whole pie.
Nuclear energy has been proclaimed by various people at various times to be the solution to the world’s energy needs. Nuclear energy today is also only a very small piece of the pie. Abundant resources (uranium and thorium in ores) exist in the world to provide a lot of nuclear fission energy for the future, but there are political and economic challenges for wide expansion of nuclear energy. Nuclear fusion energy has been a hopeful subject in the energy picture for many years, but anyone who follows nuclear fusion knows that for about the past fifty years, the technology has always been about thirty years away from being a commercially viable energy source that can transform the way energy is generated for worldwide use.
The Worldwide Energy Future
So what will our energy future look like? Will earth’s population be able to shift from reliance on fossil fuels to some other alternative energy source? I can’t answer those questions, but I can point out a few thoughts for consideration.
First, the inherent difficulty in predicting the future. I always find it humorous to look at projections for future energy use right after data from past energy use (as in page 13 of this report). The past is rough and pointy, with ups and downs, while the future projections are smooth curves in predictable patterns. Of course, those that produce the projections know (or at least I hope they know) that the future will not be as smooth as their projections show. The future will be messy just like the past. We must continue to attempt to predict the future in order to plan for it, but at the same time we must realize that we will not be successful in attempting to predict the future and we will get a lot of things wrong.
There are many different visions for the future of energy, including rapid growth of renewables, rapid growth of nuclear power, curbing energy demand, etc. A central debate in considering the future of energy is whether energy will continue to be mass-produced or whether it will be more distributed. Should energy be produced on a large scale (big power plants for electricity and big oil wells and refineries for petroleum products) or by each individual user (small wind mills, solar panels, and even possibly “Mr. Fusion” units, or perhaps a more realistic alternative, home biogas reactors)? Can the production of energy be distributed in a similar manner to how the Internet has distributed information to every corner of the globe?
As we consider these questions, we need to keep in mind that energy is not like information. There have been rapid advances over the past few decades with information storage and transfer. Computers have revolutionized how information is produced, distributed, and stored. Can a similar revolution take place to revolutionize the energy economy? In reality, probably not. Energy is physically different from information and the laws of physics that apply are different. Energy storage and transfer simply involves more physical materials. So we can’t necessarily expect a revolution to occur in energy technology as has occurred in information technology. That doesn’t mean we shouldn’t try, though.
Climate Change
I simply can’t finish this post without making mention of climate change, which is probably the elephant in the “room” of this topic. Obviously, there is much discussion on this topic today and it can be difficult to go for long without hearing something about it. I, for one, feel it is a topic that should not be ignored. Of course, this topic has become, unfortunately, political. It can be difficult to get into this topic without alienating one side or the other of the political spectrum, but I will attempt to do so.
My coverage of this topic here will be short and completely insufficient. In short, whether or not one “believes” in climate change, there should be some things we can agree on:
- We need to keep studying this topic. There are constantly arguments about whether or not the science on this topic is “settled” or “decided” or “beyond doubt”. The fact is, we don’t know everything about climate change but we do know enough that we know we need to figure out more about it.
- Human action is causing significant changes to the “natural” state of the world. The fact is, humans are putting a lot of products into the atmosphere that have not been there in the past history of the earth.
- Since we really don’t know for sure what all the stuff (often simplified to “carbon”) we are putting in the atmosphere does to the future climate of the earth (though we do have some pretty good ideas based on some science), we should take steps (recognizing other priorities and limitations) to limit our emissions.
I personally think there is a lot more we can be doing to limit emissions than we are currently doing. Everything we do now to understand climate change and limit its impact is an investment in the future of humanity.
Conclusion
Societal energy use has been dominated so far in human history by fossil fuels. The future of energy use in the world is uncertain.