Last time, I introduced the gasoline reciprocating engine, which in a sense was the ultimate form.
Although the jet engine was invented two generations ago and relinquished its leading role in the skies, the gasoline reciprocating engine is still evolving and going strong.
This time, let's consider gasoline reciprocating engines and electrification, which has recently gone beyond being just a trend and has become a national policy.
Reciprocating engines from before WWII
The Dawn of the Reciprocating Engine
The prototype of the reciprocating engine was indeed the steam engine, and it was in the late 1600s that a man named Newcomen in England developed a steam engine that seemed to be of decent use.
Because its performance was not very good, James Watt of England soon improved it, achieving greater efficiency, and it spread explosively as a power source for industrial and transportation machinery.
Up until this point, coal had been the main fuel, but in 1859, a Frenchman named Renoir invented an internal combustion engine that used gas. It was a simple two-stroke single-cylinder engine.
Shortly after, I learned that Nikolaus Otto, a great figure to whom I hold a high regard, created the concept of the thermal cycle and laid the basic theory for 4-stroke and 2-stroke engines (strictly speaking, the 2-stroke is slightly different).
I have relied on an Otto Cycle for most of the past 15 years.
Then, young engineers Daimler and Maybach joined the team, and the full-scale development of the four-stroke gasoline engine began.
Both Daimler-Benz and Maybach remain top-tier companies today (though Maybach's status is debatable).
At that time, steam engines were dominant, and this technology was treated as something obscure.
The beginning of the development of the reciprocating engine
Meanwhile, a major incident occurred in America.
The Wright brothers flew through the sky.
It's a little anecdote, but it's a well-known fact that when the Wright brothers succeeded in the world's first manned powered flight in 1903, the design of the aircraft, particularly the twisting of the wings, was what made flight possible.
But the decisive factor that set them apart from previous challengers was the use of a lightweight 12-horsepower gasoline engine built by the Wright brothers themselves.
At that time (around 1900), the common power source was basically the advanced steam engine, and gasoline engines were still in a supporting role. The gasoline engine's track record was limited to Karl Benz and others putting it in automobiles in Europe.
Moreover, gasoline itself was a liquid with little use back then, mainly just for lamp fuel, so it's hard to believe, but it was only sold in pharmacies.
The Wright brothers were quick to recognize the high power output relative to weight (power-to-weight ratio) of the gasoline engine and decided to adopt it. Initially, they tried to outsource the production of the gasoline engine, but no one would do it, so they built it themselves.
That's how significant their presence was.
The real breakthrough point was actually the adoption of this gasoline engine.
Many challengers had attempted manned flight before the Wright brothers, and a fair amount of know-how had been accumulated regarding aircraft design, but the Wright brothers were almost the first to use a gasoline engine in an airplane.
As you all know, airplanes were recognized as extremely useful for the military and underwent explosive evolution, but at the same time, the usefulness of gasoline engines was also recognized, and explosive evolution began for them as well.
The technologies that emerged from this evolution led to the development of gasoline engines for civilian automobiles (their respective technological developments mutually influenced each other's progress).
At the time, the Wright brothers also started an aircraft company and developed new airplanes, but they were eventually weeded out and absorbed into Curtiss-Wright, which would go on to create the Wright R-3350 Cyclone 18, the monstrous engine used in the B-29.
However, although the company name has changed slightly, the Wright brothers' company grew from 12 horsepower to 2400 horsepower in 40 years (although horsepower alone isn't enough for a direct comparison).
That's simply 240 times more. Incredible.
Simply put, if you subtract 40 years from your current age, you'll probably find that a prime mover with 240 times the power and this level of complexity doesn't exist today, let alone one that's mass-produced.
Those were the 40 years it was all about.
Modern gasoline reciprocating engines and electrification
Let's compare a modern reciprocating gasoline engine with an electric motor that uses electricity as its energy source.
Gasoline and batteries (electricity)
Let's use some numbers to concretely demonstrate why the widely discussed goal of "achieving the electrification of most machines by the 2030s" is quite unlikely, especially for electric vehicles.
When it comes to power sources for electric vehicles, I think most people will focus on comparing gasoline engines and electric motors.
Certainly, if given the same amount of energy (fuel) as an engine, an electric motor is more efficient at generating output, and its rotational speed control and torque characteristics are easier to handle (easier to control). Moreover, its power-to-weight ratio is about the same as or even lower than that of an engine.
The key point here is that the assumption that the same amount of energy (fuel or electricity) can be supplied to both the engine and the motor is not valid.
It's easy to overlook, but while gasoline is dangerous, technologies (like fuel tanks) have been established to transport it safely, cheaply, and in large quantities.
On the other hand, at the time of writing, the most efficient way to carry electricity is with a lithium-ion battery (the kind used in smartphones and hybrid cars).
Now let's compare how much energy each of them possesses relative to its weight.
Gasoline has a specific gravity of 0.8, so about 800g per liter, which translates to 32 MJ (megajoules).
On the other hand , lithium-ion batteries have a power output of 201 Wh (watt-hours) per kilogram.
The units are all different, making comparison impossible, so let's standardize the units.
First, let's consider gasoline. Since we can't directly use the energy contained in the fuel to calculate work, let's assume that a car travels 60km in one hour at a speed of 60km/h on an empty road.
Let's assume that an average car weighs approximately 1200kg and has a 2000cc engine, requiring 30kW of power at 2500rpm to reach a speed of 60km/h.
In that case, the energy consumed is 30kW (W: watt is the energy generated per second, J: joule), so if you convert that to an hour, it's 30k × 60 × 60 = 108 MJ (megajoules). If the engine's thermal efficiency is around 35%, the energy of the fuel required will be 108M × 2.9 (100/35) = 313.3 MJ (megajoules).
Gasoline has an energy output of 32 MJ per liter, so you would need 9.8 liters, which weighs about 7.84 kg (that's pretty bad fuel economy).
Well, the average real-world fuel efficiency of a car these days is about 12 km/L, so you need 5 liters of gasoline to travel 60 km. Therefore, the calculation above assumes an engine with a fuel efficiency of approximately 6 km/L.
That 7.8 kg of gasoline was used to continuously output 30 kW for an hour, so multiplying by 30 kW × 1h [kWh] and converting to per kg, we get 30 [kWh] ÷ 7.8 [kg] = 3.8 kWh/kg.
On the other hand, looking at electricity, although it's unlikely, even if 100% of the energy in a battery were converted into work, the latest lithium-ion battery only produces 201 Wh/kg. Compared to gasoline, the ratio is 3800:201, meaning the amount of energy per kilogram is only 1/19th.
Therefore , to obtain the same output in one hour with an electric vehicle that has 100% motor efficiency, a battery weighing 19 kg (19 times the weight of gasoline) would be required for every 1 kg of gasoline.
If the motor's efficiency is 80% (a fairly good motor), the battery would need to be about 1.25 times heavier, or around 25 kg.
It's impossible to make all cars electric now, right?
Moreover, this calculation gives electric vehicles a significant advantage and gasoline-engine cars a significant disadvantage.
So, if a gasoline car can travel 400km on a full 50L tank, the weight of the gasoline would be 40kg, while the battery would need to weigh 19 times that, so it would need to weigh 760kg.
This is a fairly rough comparison of the efficiency of prime movers, including their energy sources (electricity, gasoline, etc.).
To find out the true fuel efficiency of an engine , you should use a value called BSFC (Net Fuel Consumption Rate) instead of the fuel efficiency in km/L that you are all familiar with.
The unit of BSFC is the amount of fuel (in grams) required to generate 1 kW of engine power, expressed as g/kW.
Engineers use this to compare engine fuel efficiency. This value removes as many external factors as possible (such as vehicle condition, temperature, and other standby conditions).
This is a confidential figure for car companies, so it's not widely publicized.
To be frank, this is completely useless.
Therefore, the electric vehicles currently on the market can only achieve a driving range of around 200-250km by keeping the battery weight to around 300kg and driving in the most efficient way.
Moreover, while you can simply add more gasoline when it runs out, batteries require a chemical reaction to charge, so it takes time.
Incidentally, a typical reaction equation for lithium-ion batteries is as follows.
$ Positive side MO2 +Li^++e^- → LiMO2 $
The negative side is LiC → Li + C + e^-
No matter how fast we can charge it, it doesn't seem like it will be faster than refueling with gasoline anytime soon.
Furthermore, batteries degrade with repeated charging and discharging. In today's smartphones, this can be estimated at around 800 cycles, even with a generous estimate.
Furthermore, as some of you may have noticed, the negative electrode of a lithium-ion battery is made of carbon (C).
In other words, CO2 is emitted every time a lithium-ion battery is produced, and naturally, carbon is also emitted when it is disposed of because it contains carbon.
On the other hand, while gasoline itself deteriorates, the tanks used to transport it can last almost indefinitely.
In other words, electric vehicles may have reached a point where they can be used for hobbies, but when considering them on a commercial basis or in terms of important cargo volume, they are completely unsuitable from the standpoint of efficiency and cost for things like large trucks, ships, and commercial vehicles, which are the mainstays of transportation.
Furthermore, even in passenger cars, the thermal efficiency of gasoline engines alone has started to exceed 40%, and when considering the entire system, such as hybrids, the efficiency is likely to be quite high.
Moreover, unusually for Japan, the Cabinet Office took the lead in establishing a research project called SIP (Strategic Innovation Promotion Program) through industry-academia collaboration, and in 2019, they achieved a thermal efficiency of 51.5% for gasoline engines alone and 50.5% for diesel engines.
If this becomes a reality, and considering the overall efficiency of hybrid systems, I think it will probably exceed 60%.
Furthermore, the ultra-large diesel engines used in ships, which are the mainstay of logistics, achieve a thermal efficiency of around 80% for the entire system.
The diagram shows an example of thermal energy recovery.
Even with the author's simple example of a car, the difference is 19 times, but when considering the latest engine technology, the gap widens even further.
In the automotive industry, even with the development of highly efficient motors for electric vehicles , the battery remains a bottleneck and cannot be utilized until two or three more revolutionary advancements occur.
Moreover, even if the amount of energy stored is increased 19 times, it only becomes equivalent to an inefficient car.
Furthermore, since batteries work through chemical reactions, in order to increase the amount of energy per unit mass, we need to find new, practical chemical reactions.
The lithium-ion batteries that you mainly use today took about 25 years from the start of development to widespread adoption.
This is incredibly difficult, beyond anything I can imagine.
Unlike the performance competition in areas such as personal computers and communication speeds, where performance doubles every year, this kind of fundamental technological development can only be achieved through persistent and steady progress.
Politics and technological development
The government says it will electrify most cars by 2030, but that leaves only 9 years.
We don't have much time, and this isn't a problem that can be solved simply by throwing money at it.
I wonder what the government's stance is on this matter.
I am by no means opposed to electrification, including electric vehicles; I simply hope that people will recognize the extremely difficult technical challenges involved and take on those challenges.
If we wanted to reduce CO2 emissions, we didn't necessarily have to stick to electricity. We could simply drastically improve the efficiency of existing internal combustion engines and then use the small amount of CO2 emitted by those engines to reduce emissions (regardless of the pros and cons of global warming and carbon).
This method would allow us to achieve what is known as carbon neutrality overall.
While it's true that CO2 is a fairly stable molecule and difficult to reduce, CO2 reduction devices already exist.
There's electrolysis, catalytic methods, and artificial photosynthesis.
If we could develop an ultra-high-efficiency CO2 reduction device, even without electrification, the mood of society would change in an instant.
In the worst-case scenario, it would be perfectly acceptable to bury the CO2 underground.
The ultimate goal is "CO2 reduction," and electrification is merely one means to that end. If there's an easier way to achieve this through a different means, then that should be done.
What's important is whether the chosen method was decided upon after thorough consideration from various angles.
If the goal is electrification, then I suppose there's no helping it.
Indeed, if Japan succeeds in developing a new type of ultra-high-capacity battery, it could take the world lead.
However, if a country invests heavily in batteries and neglects other areas, and then stumbles in battery development, it will suffer crushing defeats in all other fields, and as its national power declines, it will no longer be able to focus on battery development (a risk management principle).
Therefore, if you're going to use taxpayer money for investment, you should at least clearly outline the advantages, disadvantages, risks, and technical challenges (we can all figure out the solutions together).
It's unacceptable if the slogan "electrifying by 2030" is simply not achievable, and "half-hearted investments result in failure and nothing to show for it."
Because the money, resources, and time we use are finite, and furthermore, these are taxes collected from everyone, so this is unacceptable.
I think it would be extremely problematic if we don't learn from the lessons of past wars, where countries and militaries made huge mistakes in their policies and strategies.
Just slogans alone will lead to defeat, just as they did in the last war.
Even just considering the engines used in transportation equipment presents such significant challenges, so I can only imagine the immense difficulties involved in electrifying other fields as well.
If the government won't explain, then at the very least, the mass media should analyze and explain it.
When seeking to create new fields or technological innovations, it is crucial for engineers to calmly analyze the situation and clearly communicate the advantages, disadvantages, risks, and challenges. This is an important aspect of engineering ethics.
This is purely speculation on my part, but I seriously doubt whether the Comet, too, was properly informed about its disadvantages, risks, and challenges, perhaps blinded by the title of the world's first jet passenger aircraft.
The fact that development, first flight, and then the start of commercial flights all happened in about four and a half years is incredibly fast. Even today, a project of this magnitude typically takes at least six years, and up to ten years.
The speed at which Comet was developed feels abnormal. I can only assume that some mysterious pressure was at work.
The emergence of the jet engine, which dethroned the highly superior gasoline reciprocating engine in the high-altitude skies, was a truly phenomenal technological revolution.
Up to this point, the Comet's power source has been secured: a jet engine, providing the necessary propulsion for high-altitude flight.
Just as we were about to take off into the sky, the aircraft technician shouted, "Wait a minute!"
When I inquired about what was going on, it turned out that achieving high-altitude flight presented significant technical challenges for the aircraft itself.
Next time, we'll take a look at aircraft technology for high-altitude flight.
To those who found this article helpful in understanding design:
Since we're on the subject, I'd like to recommend a book that's essential for mechanical design.
To be honest, the content is extremely unhelpful, but it can be used like a dictionary when you forget the details. If you read this article, you should be able to understand the content and use it effectively. It also includes commonly used standards, making it quite useful.
If you don't already own one, I highly recommend getting one, even though it's a bit pricey. However, new ones are expensive, so if you're considering buying a used one, I strongly recommend checking that the surface roughness conforms to the new JIS standard.
Comment: