Big Pic Energy
The mission, the state of energy, and a magnificent pun
Our mission here is to cultivate some Big Pic Energy (BPE), henceforth to be defined as:
big pic energy
A vibe someone exudes by having confidence in knowing the big picture of our energy challenges, subtle swagger in understanding our menu of technological opportunities, and commitment to keeping both eyes open going forward.
after subscribing to Honest Energy, Pete has really developed some Big Pic Energy, I should tell all my friends to subscribe as well
Unless you’ve been living under a rock, you’re probably aware that the world has an unsustainable energy problem. Boiling through all the media hype, political noise, and bold investments is the clear message that we cannot continue our current path of voracious fossil fuel consumption. You and I know this. But how much do we really understand? What does the actual clean energy gap look like? How far are we off by? How much of our problems or solutions are hung on economics, engineering execution, political willpower, or technology readiness? Real talk—what should we focus on and what should we not?
As an engineer and entrepreneur, I am frustrated that I don’t yet have full clarity on this. I have yet to fully internalize our energy problem at the macroscopic scale, and to truly put in the work to formulate a data-driven opinion on what I think would be the most important/promising thing to focus on next— in the near, intermediate, and long term. In short, I don’t have Big Pic Energy (yet).
Whereas the scientific unknowns are not for anyone to just will their way into understanding, there is a certain degree of brute-force information-chugging one can do on the other side to “first-principles”-the-crap-out-of and formulate such an opinion based upon reasonable assumptions. In this Age of Information and Season of Social Distancing, that’s just what I plan to do. In my learning process, I don’t expect to become an expert but do anticipate being educated enough to understand what the experts are saying, and (hopefully) be able to explain my learnings digestible enough to the laymen while being technical enough for the nerds. I’d love for you to join me on my journey and to learn alongside with me. If I do make errors (and I’m bound to), please do reach out and let me know. I’d love your feedback.
Understand the magnitude of our energy demand and clean energy gap
Deep dive into our electric grid and energy distribution systems, challenges, and opportunities
Deep dive into 10–12 energy storage, power generation, alternative/intermediate fuel, or carbon sequestration technologies. Understand their technical merits, engineering, economic, and political challenges and opportunities
Develop some Big Pic Energy
Let’s get started.
The State of Energy
The first step of our mission is to get a good feel of where we are today. This includes building a fundamental understanding of where energy can be found, how we measure it, how efficiently we can put it to use, and what our current energy diet looks like. Only then can we begin identifying the magnitude of the actual clean energy gap we’re facing (TL;DR at the end if you’re in a hurry).
An energy primer
Energy is the fabric from which everything else materializes. That’s super deep. Without getting too philosophical though, energy is just the “stuff” stored in various forms that we want to convert into other forms to do useful things. Keyword: convert, as it cannot be created or destroyed. We can find it stored everywhere across every length scale, and there are many ways we have figured out how to harness it.
At the smallest practical length scale in the nucleus of an atom, we have the energy holding protons and neutrons (collectively, nucleons) together. The amount of energy here is fantastical and a million times more than the energy stored in the next length scale up. This of course is nuclear energy. The first unit of energy we’ll use in Honest Energy will be the “electronvolt”, or eV. It is the kinetic energy gained by an electron accelerating from rest in a vacuum between a potential difference of 1 volt. Sounds fancy, not very intuitive, and very small. All true. But it’s the best thing we’ve got to measure energy at such small scales. The binding energy holding each nucleon together is typically on the order of 1-10 MeV (that’s mega-electronvolts, mega = million), with the nucleons in uranium-235, the fuel for most nuclear power plants today, each at 7.6 MeV. By breaking or forming these bonds, a crapload of heat energy is generated along with some gamma-rays (0.001 - 10 MeV) that will damage your organs. We’ll deep dive into nuclear fission and fusion at a later point in Honest Energy.
At a similar length scale, we find photons or “particles of light”, where energy exists as electromagnetic radiation. Typically, we are most interested in the radiation from the sun, solar energy, which has a broad spectrum of light wavelengths that irradiate Earth. Ranging from infrared to ultraviolet light, the radiation energy spans the order of 0.01 - 100 eV, with the majority of sunlight (500 nanometer wavelength—green light) at 2.48 eV per photon. Plants reflect most of these wavelengths, notably the ~500 nm range within the visible spectrum, hence their green color. But they absorb a small bandwidth of other photons in a process known as photosynthesis. Here, they are able to harness the photon energies to power chemical manufacturing plants in their leaves, where water and carbon dioxide combine to form sugars (a reducing process). Over millions of years, these sugars eventually become the fossil fuels we love and hate. Humans obviously can’t photosynthesize, so instead we have devices that help convert a broad spectrum of solar radiation into flowing electrons. Of course, we will deep dive into solar power at a later point.
Stepping up a length scale, we look at the energy stored between bonds of individual atoms within molecules, which are really the social networks of electrons. This is by far the most common form of energy we are used to, and that is chemical energy. The fossil fuels and donuts humans crave all provide us energy via their chemical bonds that we break. Typically, we do this by a process known as combustion where we “burn stuff” by providing oxygen (oxidizing) and doing something with the heat energy released. If heat is what we need, then this process is decently efficient. But if mechanical or electrical energy is what we need, this process is not efficient due to losses in subsequent conversions, but it’s still what we do. We’ll talk about this inefficiency later on. The energies holding chemical bonds together range from 1 - 10 eV, where typical carbon-carbon and carbon-hydrogen bonds have 3.5 - 4.6 eV of energy. These bonds are where we get most of our energy from in our fossil fuels (and donuts). Fossil fuels aren’t the only kind of chemical energy useful to our energy needs, though. Hydrogen fuel, ammonia chemical energy storage, and other intermediate fuels are other examples that we’ll talk about in Honest Energy, as we’ll see that electricity may not always be the best option for everything.
There is a different type of chemical energy that is extremely important, and that is electrochemical energy. These are chemical reactions that consume or produce electricity that we can use directly, and therefore very efficiently. This is where batteries hang out, and we’ll talk about them plenty much in Honest Energy. The challenge is that electrochemical reactions must be “contained” within devices, a.k.a. batteries, in order for us to reversibly insert or extract electrons in a useful manner. Unlike chemical fuels where we don’t need to lug around the other key reaction species (oxygen) and where we annihilate the fuel in the process, batteries are like the respectful guests that BYOB and take their trash home with them. This added device packaging and infrastructure significantly hurts energy densities, or how much energy content you can pack within a given volume or weight. The rate at which you can push or pull energy into or out of these devices, known as power, tends to also be lower. These two challenges, in addition to cost and useful life, are at the crux of the battery storage race today.
Stepping up yet another length scale, the speed or intensity at which individual molecules move or vibrate within a collective system represent thermal energy. This is where molten salt storage or geothermal energy derive their utility, which we will discuss at some point. This heat is already in a useable form if heat is what we want, but we will again see significant losses if mechanical or electrical energy is what we need. As we begin talking about the energy of a collective system, the electronvolt becomes less relevant, but the kinetic energy of individual molecules due to temperature changes in the order of 100ºC is approximately 0.001 eV (as can be derived from the Boltzmann constant). Much smaller, which means much lower energy densities compared to chemical or electrochemical systems, not to mention the subsequent loss of efficiency if electricity is needed.
Finally, at the macroscopic level, we understand what goes up must come down due to gravity, and what moves fast can be hard to stop. Reservoirs of water or concrete blocks can be exploited for their potential energies, and spinning flywheels can be exploited for their kinetic energies. These fall (pun intended) into the bucket known as mechanical energy. We’ll also talk about these technologies at some point.
Building an intuition for energy
Talking about energy can be a bit elusive, and that’s because it can take on many forms, as we just saw, and therefore be measured in several different ways. Here’s a list of various units we use to measure energy and in what context they’re typically used:
Energy discussions can be hard to fully grasp not only because of the various units, but also because of the sheer size of numbers. Big prefixes or a stupid number of trailing zeroes make people’s eyes glaze over. Terawatt-hour, Petawatt-hour. Tomato, tomahto. This makes it hard to build an intuition of what energy “is”.
As an engineer, I find it incredibly important to build a strong sense of intuition for units of measure in order to truly grasp a sense of magnitude, mentally manipulate ideas in thought-experiments, and exercise creativity within a given domain. So on top of conversing in the standard and often archaic units of measure (we’ll stick with watt-hours for consistency), throughout the rest of Honest Energy I will also be using some new units of measure that we can all maybe-kinda understand and relate to. Here they are in order of increasing magnitude (check my math) 1 2 3 4 5:
Now that we’re armed with these HE-units, we are ready to build a better intuition of our energy challenges. But first, a note about efficiency.
Energy, the rambunctious child
One thing we’ll soon realize is that converting energy from one form to another can either be highly efficient or criminally inefficient. This has something to do with what’s called “entropy” and the Second Law of Thermodynamics. The premise is just that energy is like a rambunctious child, where it always wants to increase its state of chaos. It doesn’t take much effort to hype them up and bounce around a room, but you’ll exhaust yourself trying to put them to bed. In the real world, this means it can be hard to channel energy into the form you want if you’re trying to constrain it.
For example, by burning fossil fuels, you are releasing the pent-up energy stored within chemical bonds into the wild, thereby converting chemical energy into heat energy. Happy, crazy child. As long as enough oxygen is present for combustion, this can be around 85% efficient, where the loss of efficiency is carried away in gases or absorbed by moisture. However, attempting to bottle this heat energy and direct it at moving a turbine or pushing on a piston (useful mechanical work) is contrary to what it wants to do. Petulant child. Here, you may only get 18-45% efficiency depending on what kind of heat engine you have. Oof. However, once you have mechanical rotary motion, you can convert that into electrical energy (and vice versa) very efficiently because there’s not much change in entropy. This can be done with 95% efficiency. The electricity can then be transmitted to consumers down a series of transformers, cables, and transformers again with 90-95% efficiency due to heat losses in conductors. Finally if the electricity is used to charge a Tesla, you can store that energy in the battery and generally get 85-90% of the energy back out through the inverters (97-99% efficient) that feed into the motors (80-95% efficient, depending on induction or permanent magnet), which turns your wheels to get you where you want. So from chemical energy at a fossil fuel power plant to final useful mechanical motion for the consumer, we end up with approximately 29% efficiency. That’s awful. But it’s still better than a typical internal combustion engine, which is approximately 20% efficient.
Understanding efficiencies is an important part of building an intuition for energy. You may think you have a good grasp of how much energy is in a gallon of gasoline based on how far you can drive on the highway when your fuel gauge is reading below “E”. But as we’ve seen, your internal combustion engine is remarkably bad at its job and the same gallon will output ~4x more useful energy if all you’re looking for is heat.
Keeping all of this in mind, let us now turn to the real world.
Finally, a hard look at our actual energy consumption
Here is a look at how human populations around the globe have consumed energy from 1800 to 2019 in terawatt-hours (tera = trillion), TWh, broken down by primary energy source6. To keep things consistent, we’ll try to always look at datasets from 2019 in Honest Energy, since 2020 data is still being processed by some agencies and can also be considered a fluke-year due to the pandemic. Not to mention, it sucked.
Speaking of the pandemic, this graph looks reminiscent of a COVID-19 surge with a key inflection point post-WWII. Unfortunately, there’s no social-distancing or vaccine-ing our way out of this one, and there’s also no indication that we’ll flatten this curve anytime soon (energy consumption is flattening in developed countries, but emerging economies are driving global demand). Unlike a pandemic, however, the total number is not the problem. Rather, the problem is the proportion of our total energy consumed that is derived from fossil fuels, which are almost always combusted in order for us to use, releasing greenhouse gases in the process that cause climate change.
The global primary energy content consumed in 2019 was 173,340 TWh. But before we begin comparing this number with our Honest Energy units, it’s important to understand what “primary energy” means. Primary energy just refers to the energy content in the original fuels, which is the same as adding up all the electronvolts in the chemical or nuclear bonds we discussed above within our fuels. This is much more wishy-washy for renewables, though, as it can be hard to quantify the “original energy content” in a gust of wind (see this sub-post I wrote on reporting “fudginess” from the U.S. EIA). Electricity is a secondary energy since it is generated from primary energy sources. 85% of the primary energy in the above chart, or 147,872 TWh, came from fossil fuels in 2019. Does this mean we need to find a way to generate 147,872 TWh in clean energy? No. Remember our conversion efficiencies for fossil fuels into electrical or mechanical work tend to be abysmal, and we ultimately have to look at what we really need to do useful things.
Consider this: getting your compact car with 36 mpg to move you 36-miles (the useful part) may cost you one gallon of gasoline with a 20% efficient internal combustion engine. So 36.3 kWh of chemical energy is used to do ~7.26 kWh of useful mechanical work. Alternatively, it would cost you just 8.8 kWh of electrochemical energy in a Tesla Model 37 with 83% efficiency to travel the same distance, which comes out to be ~7.29 kWh of useful work. The numbers in these two examples agree, but we can also confirm with a bottoms-up calculation. The energy required to move a 3,500-lb compact car traveling at 60 mph with a drag coefficient of 0.25, cross-sectional area of 2.64 m2, a coefficient of rolling friction of 0.01, and no headwind can be calculated:
That’s 7.18 kWh, which roughly agrees with our two tops-down estimates above. Noice. You get the point. Ultimately, the energy we actually need to do useful stuff (the actual technical term is “useful exergy”) is what we should be looking at, and using input energies and conversion efficiencies is a reasonable way to derive a first-order approximation. Talking in terms of primary energy has a supply-side and fossil fuel bias, which makes it seem like the gap is bigger than it may actually be (to be clear, it’s still very big), and makes it hard to estimate what we actually need to replace with clean energy. Finally, there is also a percentage of fossil fuels that are not used for combustion purposes and instead used for things like asphalt, lubricants, and petrochemical feedstock to make plastics. In the U.S. this number was 5.8% of all fossil fuels in 2019, 99.7% of which came from petroleum products8.
In order to figure out how much energy we actually need, we need more data on how this energy is being used by the ultimate consumers, or the end-use sector. Thankfully, the U.S. Energy and Information Administration (EIA) does exactly what it sounds like and publishes a bunch of reports and raw data for public consumption. We’ll take our analysis now to focus on the U.S. only due to the availability of this information.
Focusing on 2019 data, the figure above is a summary of how energy flowed from primary energy on the left to end-use sectors on the right, with electricity generation in the middle as a secondary energy source9. In keeping with using the same units, I have converted all units to TWh. I have also made corrections to the renewables primary sector to remove the fudge-factor I wrote about separately, but here we care more about the end-use sector anyway. The primary energy consumption of the U.S. in 2019 was 28,209 TWh, or 16% of global primary energy consumption (we only comprise 4% of the world’s population). Of that, 23,557 TWh came from chemical energy that we actually burned. Using Honest Energy units, that’s the equivalent amount of chemical energy as 68 times the 2020 California Wildfires, which would also be equal to burning forestland totaling the area of California, Texas, and Maine combined in just one year. Yep, that’s a blue, red, and purple state because climate change doesn’t care. Here’s what that looks like for you visual people:
Let’s now evaluate the amount of energy actually converted into useful work within each end-use sector.
Transportation Breakdown (don’t worry we’ll just do this one in detail)
Almost all of the primary energy in the form of oil and biofuels going into the transportation sector is used for mobility purposes in vehicles. You don’t say. 53% of fuel came in the form of gasoline for internal combustion engines10, which we’ll assume 20% efficiency for all light-duty vehicles on the road in 2019. Based on this approximation, 876 TWh of useful mechanical work was needed in one year. Sanity-check: considering 3.23 trillion miles were driven in 201911 and using average vehicle weights and drag coefficients, the bottoms up work calculation comes out to 925 TWh. Close-enough (about 5% error). 22% of the fuel came in the form of diesel or distillates, which run higher efficiencies in diesel engines, which we’ll estimate 30%. 13% of the fuel was jet fuel for aviation, and turbofan engines are around 35% efficient. Most of the natural gas reported here actually refers to the turbine compressors used to run natural gas pipelines12 so we’ll assume 35% efficiency there as well. This means the entire sector is only approximately 22.8% efficient. This agrees with the math done by the EIA in years 2008-2013 (20-25%)13. Yay.
Total Useful Energy
I was going to do the same calculations for each end-use sector, but recent datasets, such as 2019, lack all of the information for the remaining sectors. The industrial sector, in particular, can be opaque and I don’t feel comfortable making all of those assumptions without more data. Also, it’s a lot of work 🙄. Thankfully, however, other smart people have done similar math before. The last set of detailed information published by Lawrence Livermore National Lab with data from the EIA was 201314. While our primary energy consumption has increased slightly since then, the efficiencies are likely still close enough to where they are today. So here’s the final breakdown of the total useful energy performed in 2019:
12,114 TWh. That’s the same amount of energy it takes to lift the entire Antarctic ice sheet by ~18 centimeters. Cold calculations.
The reason the industrial sector’s energy efficiencies tend to be high is that the majority of energy is used for process heat (furnaces, ovens, and boilers) and machine drive (electric motors) in manufacturing. These have typical efficiencies of 85% and 90%, respectively.
So all told, the U.S. was only able to convert 43% of the primary energy consumed into actual useful work at the end. It may seem like that sucks, but on the bright side, we now have a much more clear-eyed, non-(fossil fuel)-biased understanding of the energy we actually need. And we can begin replacing that with fossil-free energy.
Understanding our actual energy needs is just the first step in formulating our clean energy problem statement. The next step is figuring out how we fulfill that gap. It’s not like we can just say we need to produce 12,114 TWh of useful energy from solar, wind, and hydro in the form of electricity and call it a day, because that’s not always the most appropriate form of energy.
To give a quick example, let’s look at the transportation sector again. At this point, it’s clear that battery electrification is the most viable, practical, technologically superior, and economical way to decarbonize light-duty vehicles, not to mention the tremendous momentum already underway. In this case, the 876 TWh of useful energy for (majority) light-duty vehicle transport should be converted to rely solely on Li-ion battery storage, which means a slightly higher amount of energy (accounting for efficiency) will need to come from the electricity grid each year from clean power. For those still holding their breaths on a hydrogen fuel cell family car…maybe don’t. We’ll go into detail why in a later post about hydrogen. However, that’s not to say there’s no place for hydrogen because there very much is. While the game may have already been called in the light-duty vehicle sector for battery electrification, the jury is still out in the heavy-duty long-haul trucking and maritime industries. This is because the energy densities of electrochemical storage will hit a practical ceiling. Taking things up another notch (literally), long-range commercial aviation may never become practical with hydrogen and certainly never with electrochemical battery storage due to hard energy density limitations (sorry to burst your bubble). But that’s not to say we can’t do anything about it, because there may eventually be ways we could sequester an equal amount of carbon to offset the emissions from jet engines.
As we can see, we can’t just electrify our way out of everything, as sexy as that may sound. In cases where electricity and electrochemical storage are not the right solution, our calculus will change in terms of electric power generation and energy storage upstream. So to understand how we approach the clean energy gap, we can organize our approach into three primary buckets:
This provides us with a useful framework in thinking about the challenges ahead of us. As we begin our deep dives throughout this year into various power generation, transmission, energy storage, alternative/intermediate fuels, and carbon sequestration technologies, we’ll always keep these three buckets at top of mind. This will help us be clear about what problems they are useful (and not useful) in addressing.
Well, that’s it for today 🤓. Hope you got something out of this.
Our mission here is to develop some Big Pic Energy (BPE)
Energy can be found everywhere, and we have various ways of harnessing it. It’s also a rambunctious child, so conversion efficiencies can suck
Our primary energy looks super bloated, but what we actually converted into useful work is much less. This is what we really need to look at to understand what to replace with clean energy
We have three buckets to think about our clean energy gap going forward because we can’t electrify our way out of everything
Your pic just got bigger
Thanks for sticking with me to the end, and I look forward to continuing our jam-sesh in the next deep dive. If you want to show some real BPE, please share with your nerd friends to subscribe :)
Thanks and much love,