Energy in General – Thoughts on Energy

Measuring Energy

How is energy measured? This is a great question, and deserves our attention in this post. As we consider how energy is measured, we will run into the most commonly used units of measurement for energy, joules (J), British thermal units (Btu), and watt-hours (Wh).

It turns out that measuring energy is difficult. Energy is not something that is readily accessible to our five senses. We can’t see, hear, touch, smell, or taste energy, at least not directly. Some properties of the world around us are readily available to our five senses, such as distance, mass and temperature. We can see physical dimensions that something has and can easily compare the size of one object to another. We can feel whether something is hot or cold.

Though we may not be able to see or touch something and immediately convert it to an exact dimension (as in, “I can see that this smartphone is exactly 15.3 centimeters long” or “I just walked outside and I can feel that the air temperature out here is exactly 10.7 degrees Celsius”), we can usually get pretty close (“this smartphone is between 10 and 20 centimeters long” or “the outside temperature is between 5 and 15 degrees Celsius”), and can almost always compare things like distance, mass, and temperature to know what things are bigger or hotter.

The same is not true of energy. We do not have an intuitive sense for energy like we do for other properties. Energy takes higher-level thinking. Consider these three examples:

What takes more energy, lifting a 20-pound bag of potatoes from the floor to the kitchen counter or heating a small pot of water to boiling temperature?
What takes more energy, driving your car to the grocery store or vacuuming the floors in your entire house?
What releases more usable energy: one pellet of nuclear fuel (the size of an average marble) in a reactor in a nuclear power plant or 1,000 pounds of coal in a coal power plant?

Did you come up with the answers right away? How confident are you in your answers? Maybe you didn’t even hazard a guess because you just have no idea. I will share the answer to the first question later in this post (and the other two in a future post), but for now, let us consider why these questions may seem so difficult.

As mentioned, energy is not intuitively accessible to our immediate observations of the world around us. Thus, it wasn’t until the 1800s that the word “energy” was actually used in its modern sense of meaning, as a physical characteristic of an object or system that can actually be calculated and quantified. While it would be fascinating to dig into the history of the concept of energy, that is not my purpose here.

In order to understand how energy is measured, calculated, and quantified, it will be instructive to look at the meaning of some of the most widely used units of energy.

Units of Energy

The most widely-used unit of energy worldwide is the joule, named after James Prescott Joule, an English amateur scientist who lived from 1818 to 1889. A joule is equal to one kilogram meter squared per second squared, or one newton-meter. It is the amount of energy involved in moving with a force of one newton over a distance of one meter. The joule serves brilliantly within the overall International System of Units (also known as SI units) to measure various types of energy, including mechanical energy (kinetic or potential), chemical energy, and heat energy. The use of the joule is often the simplest method for completing energy conversions and calculations.

A watt-hour is a unit of energy that is often used to describe energy that is used over some period of time. A watt is a unit of power (amount of energy used over a given time period), defined as utilizing one joule of energy every second. A watt-hour is the amount of energy required to provide one watt of power over one hour of time. Since there are 3,600 seconds in an hour, one watt-hour equals 3,600 joules.

A British thermal unit (Btu or BTU) is the amount of energy that is needed (when added as heat) to raise the temperature of one pound of water by one degree Fahrenheit. The Btu is typically used (instead of the joule) in engineering calculations involving heating or cooling in the United States.

A separate unit in the English system of units is the foot-pound. It is defined in a similar manner as the joule, with one foot-pound being equal to the energy involved in moving with a force of one pound-force over a distance of one foot. However, the use of a pound-force can create confusion because the term “pound” is utilized to describe both mass and force in the English system of units. The foot-pound is used when mechanical energy (kinetic or potential energy) or work is involved.

Let us now use the above units to solve the first energy comparison question mentioned above: what takes more energy, lifting a 20-pound bag of potatoes from the floor to the kitchen counter or heating a small pot of water to boiling temperature?

Energy Comparison: Energy in the Kitchen

In the calculations of energy below, it is important to consider what quantity of energy is actually being calculated. In almost every process where there is a conversion of energy from one form to another, there is some inefficiency in the process. When lifting a bag of potatoes, some type of energy (if a person is doing the lifting, chemical energy in the form of glucose in the muscles or if a machine is doing the lifting, stored or produced electrical energy) is converted into potential energy as the bag is lifted up against the force of gravity.

The conversion of energy is never perfectly efficient. So when we talk about energy, we need to be careful and deliberate about what quantity we are actually measuring or calculating. Are we calculating the energy to perform a task in an ideal (imaginary) system or in the real world? The examples below will help to illustrate the difference.

So, what takes more energy, lifting a 20-pound bag of potatoes from the floor to the kitchen counter or heating a small pot of water to boiling temperature? First, we will determine the energy required to lift a 20-pound bag of potatoes to the kitchen counter.

As noted above, there is some inefficiency in the human body converting chemical energy stored in food to mechanical energy (work of physically lifting the bag of potatoes). In performing this energy calculation, we are ignoring that inefficiency and just considering the ideal (minimum) amount of energy to lift the bag of potatoes. That is, if the system for lifting the potatoes was perfectly efficient at converting stored energy into work to lift the bag of potatoes, how much energy would that system use?

Considered in this way, the energy required to lift the bag of potatoes is simply the difference in potential energy of the bag of potatoes between the countertop and the floor. The equation is: the difference in potential energy equals the mass multiplied by the acceleration of gravity multiplied by the change in height:

Let us first solve this equation using English units:

The result is 2,600 pounds-mass square feet per second squared. However, this unit is somewhat unwieldy. The more customary way to represent this amount of energy in the English system of units is using the unit of foot-pound. To understand how force and mass and mechanical energy are expressed in the English system of units, one would need to delve into the details of the units of the slug, pound-mass, and pound-force. Needless to say, it gets confusing. At any rate, expressed in foot-pounds, the energy would be 80 foot-pounds.

Now let us solve this equation using SI units:

A good approximation can be determined in this case without even using a calculator. Twenty pounds is approximately ten kilograms, and four feet is approximately a meter. The acceleration of gravity in SI units is about ten meters per second squared. So it is easy to calculate the energy in your head in this case and come up with about 100 joules, which would be pretty close to the right answer.

Now, we will determine the energy required to heat a small pot of water to boiling temperature. First, we need to make some assumptions. We will assume a “small pot” is about one liter (or 1.06 quarts) of water, and the temperature of the water is 50 degrees Fahrenheit (or 10 degrees Celsius).

Similarly in this calculation, there will be some loss of efficiency. If the heat source is a burner using a fuel (natural gas or propane), the gas will not burn perfectly, so there is still some chemical energy stored that is not converted to heat. With either a burner requiring fuel or an electric burner, not all of the heat will go into the water. Much of the heat is lost to the surrounding environment. Once again, for purposes of the calculation, we will assume we have a perfect system and no energy is lost in the conversion from chemical energy (fuel in a gas burner) or electrical energy (electric burner).

Thus, under the ideal system assumption, the energy required to heat the water is simply calculated as follows: heat energy equals specific heat capacity of the water multiplied by the mass of water multiplied by the change in temperature:

We will assume that the specific heat capacity of water is constant (even though in reality it varies with temperature), which is a pretty good assumption as it doesn’t change much in the temperature range we are looking at. First, using English units:

Since the definition of the British thermal unit was made for such problems, the calculation is fairly simple and the answer is 350 Btu’s.

Now, in SI units:

With the results from each calculation, we are ready to make some conclusions.

Conclusions

Hopefully, one of the first things you notice is that the energy involved in heating the pot of water (380,000 joules) is vastly greater than the energy involved in lifting up the bag of potatoes (110 joules). In fact, the potatoes would need to be lifted up to the countertop about 3,500 times to equal the amount of energy required to heat the pot of water. It sure is a good thing we have a burner to add that energy for us so we don’t have to add the energy mechanically. That would be a lot of lifting to get that water to boil!

Another item to notice is that we could immediately compare the values when we used SI units. The joule is an effective unit of energy when working with both mechanical energy and thermal energy. For the English units, however, we have two different units for the different kinds of energy. In order to compare the mechanical energy (80 foot-pounds) to the heat energy (350 Btu), you would need to know that there is a conversion factor of about 788 to convert foot-pounds to Btu’s. Thus, the 350 Btu’s is equivalent to 280,000 foot-pounds, which is a 3,500 times greater than 80 foot-pounds.

So, while using Btu’s or foot-pounds works just fine in some energy calculations, both of these units were made for specific kinds of energy and don’t easily relate to one another. I believe we are generally better off thinking about joules, an international standard that is easy to compare from one form of energy to another. The joule was designed to make sense as part of the overall SI system without getting messy and confusing like English units.

Another conclusion we can make is that while energy can be converted from one form to another, it is rarely very clean. There are always losses due to inefficiency. This is why experiments performed in the 1840’s to demonstrate the mechanical equivalent of heat (principally performed by James Prescott Joule) were so important and so revolutionary. The principle now known as conservation of energy (that energy is converted from one form to another such that energy is never lost in the process) was not obvious prior to those experiments. Energy is always “lost” in energy conversions, but it is never really lost in that it always goes somewhere.

Finally, as we already discovered, it takes a whole lot more energy to cook those potatoes than to get them up on the counter to prepare them. And not just by a little bit, but by a huge amount. This isn’t necessarily intuitive to us in daily life. But now you know the secret and are aware of the relatively enormous amount of energy required to change the temperature of water. So next time you are cooking on the stove, just think, that is a lot of energy going into that water!

Picture of potatoes in boiling water in a pot on the stove.

Introduction

In full recognition that I am stating the obvious, this is the first post on this blog. Thus, it behooves me to outline the intentions and purpose of the writings herein. It is my intent in this post to describe what this blog is and what it is not.

Let me start by explaining my passion for energy. I have, as far back as I can remember, always loved the topic of energy. Energy, considered broadly, is behind the scenes for every process on the earth and in the universe, small and large. Energy comes in various forms. I have an interest in all the various forms of energy, and in the conversions between the forms, which include: mechanical energy (kinetic and potential), thermal energy, electrical energy, chemical energy, nuclear energy, and even dark energy. All of these I intend to explore further in future posts.

Perhaps the most famous scientific equation in the world today (that is, the most popular answer when randomly asking someone to state any scientific equation) is E equals M C squared:

meaning energy equals mass times the speed of light squared. This expression identifies the equivalency between energy and mass. Its popularity gives an indication that energy is a concept that is recognized as important in society as a whole, though not everyone completely understands it. In fact, I would argue that no one completely understands the concept of equivalency between mass and energy, myself definitely included.

At any rate, partly because of my interest in energy and the desire to understand the complex workings of energy in the universe, I pursued and eventually acquired a bachelor’s degree in physics. I also obtained a master’s degree in nuclear engineering and have put those degrees to good use working in a career in engineering.

I have been inspired by various scientists, engineers, and writers along the way. Besides the famous, recognizable ones and the lesser known ones that I have known personally, three figures inspirational to this particular blog are Vaclav Smil, Steven Levitt, and Stephen J. Dubner (the latter two of the Freakonomics team). I will borrow something of the writing and thinking style of these three for this blog.

So what do I intend to include about energy in this blog? What will be my topic of particular focus? How will I narrow down this vast topic into something worth reading? Well, I do not intend to limit myself. If a topic somehow relates to energy, I will include it. I may cover anything and everything about energy. This includes not only scientifically measurable energy (which is what I will devote most of my attention to) but also metaphysical (I hope I am not abusing that word too much) forms of energy (as in, “I just don’t have the energy for that now”, meaning not “I do not have the necessary stores of chemical energy in my body tissues to do that”, but rather “that is outside what I feel capable of accomplishing at this moment”).

Now, I realize that not everyone shares my passion for energy, and most people probably don’t think about it as much as I do. So how is anyone else going to get anything out of this blog? Well, it is my goal to write in an engaging style that anyone can appreciate. I will have some technical concepts and some equations and math in here, but if you don’t want those details, just skip over that part. I really enjoy taking concepts that may be technical and difficult to understand and breaking them down to where anyone can understand them. It is my plan to include charts and tables in this blog to make things more interesting and easy to understand.

The purpose of this blog is to fulfill its broad and overly vague title of “Thoughts on Energy”. I decided that was a fitting title for my intended subject for writing, energy in just about any context. When one performs an Internet search for “thoughts on energy”, the most popular results that come up are related to the (hypothesized) relationship between thoughts and energy. I don’t mean to connect the two as the main topic of my blog. That is, this isn’t a blog about how thoughts and energy are related. No, this is just a blog with my thoughts about the topic of energy.

I recognize that there are many ways to produce and absorb content these days, from audio messages (podcasts and audiobooks) to video (Youtube) to various forms of the written word. I have obviously chosen as my medium the written word. My goal is to produce content that is interesting to read and includes relevant links so that the reader can find additional information on a particular topic if they so desire. I also intend to make the content audio-friendly such that someone can listen to the content as well and benefit from it. I know I enjoy listening to a good TED talk on my commute to and from work. Perhaps someday I will branch out into other forms of content such as Youtube videos, but for now I am going to explore writing.

For most of the rest of this post I will explain the guiding principles behind my writing, which you may or may not care about. Feel free to skip to the next post at this point if you have had your fill of introductory remarks. The guiding principles, which I will explain further below, are:

Transparency
Accuracy
Relevancy
Thoroughness
Agreeableness

First, transparency. I do not have a hidden agenda, and it is never my intent to misconstrue data. I intend to be open about where I am getting my facts and am always open to being corrected. I reserve the right to be smarter tomorrow than I am today. I will probably never claim to have the final answer on any particular topic. This blog is exploratory, not authoritative.

Second, accuracy. Notwithstanding the transparency ideal in the previous paragraph and the resulting constant possibility of being corrected by new and better data, my goal is to be as accurate as possible. I want to provide content you can trust. However, obviously I can’t be an expert in every subject, and thus I may misstate some things. I might make math mistakes every once in a while (I doubt it, but it is possible).

Next, relevancy. In this blog I will provide fresh, relevant, and thought-provoking content. It is natural that content published on the Internet can have a short shelf life. What is relevant today (be it sports, pop culture, or other news) is often stale and inconsequential in the future (though they may still have some significance as historical interest). My goal is to produce content that is general enough that it will be relevant far into the future, so that when this content is found years from now it can still be interesting and useful. Also, my intent is that the content will be useful for pretty much anyone that can read. The content will be understandable by the average educated person (usually including middle and high school students) and yet still stimulating and interesting to the more advanced scientists, engineers, and mathematicians out there who have an interest in energy-related topics.

The next guiding principle is thoroughness. In reality, I wasn’t even sure that was a word until I typed it out and my word processor seems to be okay with it. What I mean is that I intend to be complete in my treatment of a topic. This is dangerous, of course, because if I attempt to be too complete, these posts will get way too long, and too long is easily ignored and thus not effective in reaching people. Thus, I will limit myself to adequate treatment of a topic and always reserve the right to bring up the topic (or a closely related topic) again in a future post. Of course I can’t be fully thorough on any topic. There are entire books and entire research careers devoted to many of the topics I intend to treat. My purpose is not to be the most definitive source in every energy topic, but to present some ideas in a broad sense for further consideration.

The last guiding principle to expound upon is agreeableness. By this I mean that I do not intend to produce any controversial material. I will stay away from politics. I do not intend to get anyone riled up. I will not intentionally write anything offensive to any particular individuals or groups.

Thus concludes my guiding principles. On a related note, I don’t intend to produce any material meant to be popular for popularity’s sake. Certainly, I would appreciate a large audience of people partaking of the content I produce and finding it to be worthwhile, but it is not my intention to seek wide acclaim for my writing. I will maintain freedom to write according to my interest and not according to what will generate the most traffic. In my opinion, too much of the content of the Internet has degraded into a contest of excessive sensationalism. Thoughtful dialogue has in many cases been replaced by “click bait” designed to elicit just enough curiosity to entice someone to click on a link, and then not provide any meaningful content. But I digress.

Next, no introduction is complete without a few disclaimers. I don’t provide any investment or tax advice in this blog. I also don’t provide relationship or psychiatric advice. I’m not a doctor. I don’t have access to secret archives or millions of dollars of research funding or special equipment. I’m just one guy with a computer and access to the Internet and a lot of passion for energy and for writing, but I think that is pretty powerful by itself.

Finally, is this really the blog you should be reading if you have an interest in energy? Maybe there is a similar blog out there that is better than this one. Certainly this type of thing has been created before. Honestly, there probably is a better blog out there for whatever you are looking for, and I hope you find it. In the meantime, I hope you will enjoy this blog.

Also, I personally couldn’t find anything similar to what I intend this blog to become; that is part of why I decided to create it. Sure, there are lots of energy blogs out there. An Internet search of the term “energy blog” yields a lot of results, but they seem to be either narrow in focus or industry-centric, that is, focused on energy as an industry and not energy for its own sake.

Some of the notable blogs I found include Energy Central dot com, which seems to have a good balance of various energy industry news items, Your Energy Blog dot com, which has a pretty good mix of content but hasn’t been updated for a few years and appears to overemphasize the sensational, and Renewable Energy World dot com, which is, as the name implies, narrowly focused on renewable energy.

But perhaps it is too much to ask of an Internet search to find something like the blog I intend to create using as broad a search as “energy blog”. Perhaps a search of the term “random thoughts about energy” would yield better results. I can tell you from my experience that that search does not yield better results. The first result in my search was a blog from someone in Australia who seems to focus these days on criticism of the government, but the blog overall seems to focus on religious content. The next result is a person in the United Kingdom focused on energy policy and that seems to be pretty boring. Other notable results include one from a gentleman in the United Kingdom who seems to have something similar to what I want, but only has four posts that appear to be pretty old. Finally, there is a blog from a gentleman in California, but it is very narrow related to energy (electricity) markets, and is heavy enough in policy that most normal people (including me) probably can’t read much of it.

So, if you find a blog out there similar to this one, let me know. I personally think this blog is pretty special. But I may be biased.

With the introduction now complete, let us get to the real content!