Prof. Abdennaceur Karoui

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Last Updated: Friday, 31 December 2021 16:05

Is Powering Trucks, Buses, and Cars with Batteries a Good Idea?  [1]

Some emergent electric transportation technologies are discussed in connection to future energy reality, and the need for material conservation and sustainability. While analyzing the transportation technology trends, some conclusions on future sustainable scenarios for public and fret transportation will be derived. The discussion starts with looking critically at two technologies that seem to attract savvy engineers, the automotive industry and business, as well as many informed and less-informed consumers.

Information and pictures were retrieved from popular articles [2, 3]. Many of these are selected from papers commented by professionals in LinkedIn.  The relevance of such publications is clear from the opinions of the readers, representing a diverse and large base. I must note that public opinion is important, in particular in a field where technology development is driven by consumers.

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Abstract: It appeared that the energy-transportation-sustainability triple issue brought-up by the new trends is, in fact, not fully understood by the public; thus, further clarifications are needed. This article endeavors discussing the reasons as to why i) "battery powered truck" is not at all a viable solution for heavy fret and more so for long distance transportation, ii) electric hybrid car technology could still be acceptable now and in the future, although, the vehicle will not be enough popular to survive in the form of current designs, iii) lightweight trains are the best for commuting,  iv) photovoltaics (and other alternative energy sources) integrated with lightweight vehicles is a viable solution, it will complement electric trains in urban transportation, and v) it is necessary to avoid large scale use of batteries for transportation, as this technology entails a host of insurmountable problems.

Recently, I was asked to read the debate in LinkedIn [4] and other venues on what seems to be an emerging technology “Battery powered truck”. The debate has been running for quite some time. The initiator has brought it to the table, by connecting LinkedIn community of engineers and scientists to a short paper titled “This is the Tesla Semi-Truck, 500 miles of range and more aerodynamic than a supercar”, wrote by Z. Estrada, and published in November 2017.

The paper shows a nice looking truck with a futuristic design. The author highlighted the vehicle range, the advanced aerodynamic design, and the comfort of the cabin, which look attractive, really! The vehicle range is appreciable and sufficient for an average round-trip in the USA.

The Root Problem of Battery Powered Trucks

Looking into the core energy problem of this particular technology, it is obvious to see what works and what will not work. The analysis reported here, in a simplistic way, is sourced form knowledge on batteries as well as energy and transportation technologies. For readers who don’t have time to go through the entire paper, they can be sure that the idea of powering long-courier vehicles, and heavy trucks with batteries is, at this point, wrong. At best, it has a very small market segment. Large scale use of this technology will fail for, at least, the luck of battery reliability, overall reduction of the energy efficiency, insufficient endurance, environmental issues, cost reasons, and more importantly, the non-sustainability of the key materials used to construct batteries. If the readers want to delve in the details of this statement, they are invited to continue reading this paper as well as technical papers on batteries. It is certain that they will discover the complexity and the fragility of the utilized layered materials in batteries, and how tight the design of batteries is. These facts make high energy density batteries very vulnerable, prone to damage, and a moving hazard. Also readers must look at the energy balance and the involved phases of energy utilization, from the source to the final step of discharging the battery during energy extraction. Most likely, these facts will lead the readers to conclude that “heavy vehicles powered by batteries” is not at all, or even close, to the optimum energy and materials pathway that could guarantee a sustainability. Whatever will be the conclusion, at the current horizon, this technology will not work for heavy trucks because of diverse and significant reasons. The author will try to explain the major ones.

Investors and people who believe in this technology will realize the non-practicality of batteries after wasting time and resources. It will be very unfortunate for all, the producers, the consumers, and the economy, in more general terms. As a matter of facts, it has been reported that several big companies offering electric charging services already went bankrupt. The first was Better Place, even though the company obtained large federal grants. The incentives for installing chargers are gigantic, but if using current battery technologies, they will ultimately fail.

The Popular View of Batteries Powered Vehicles

In a sense, it is surprising to see that the original paper has received 14,500 approvals and 450 Comments, in just seven months. Only among the comments, one could discover a minority of readers that saw the problems and consequently appeared skeptical, some were not so sure, and the rest defended blindly this tricky idea of “Battery powered truck”.  The author was astonished to see how could such a large community believe that batteries could run heavy duty machines? Never mind the future advances in battery technologies, utilizing them for such application will still be so wrong. Batteries for that application are not energy efficient and will not be economical as well, regardless of the low prices of energy and raw materials necessary to build these batteries, which can surge at any time and make the problem even worse. Of course, there is on-going extensive research on cheaper and abundant materials to make non-Lithium based batteries. That may give hope for some; but, still, the material quantity and the energy spent to fabricate these batteries will remain a decisive barrier. Indeed, in scaling-up that technology one must consider the massive volume of batteries needed to power one truck. If we factor that by the large number of trucks running now on highways, we obtain an astronomic quantities of batteries. Moreover, combined with the already massive utilization of batteries in critical technology areas is going to hurt badly the environment, and will work against the long term sustainability, both are dear to human survival.

The author is still puzzled as why, really, the mass of the readers applauded the use of batteries to power a truck! Didn’t they remember how much they suffer from a failing remote control, when they enjoy family gathering watching TV,… How about a computer or cell phone running out of batteries, how many embarrassments, how many missed meetings,...  , don’t these small amenities require just a tiny electric charge to work and yet they fail? Aren’t they lower power devices?  Shouldn’t they work all the time? Problems caused by batteries are not unusual to each of us!  Didn’t the readers forget that the frequent battery problems re-educated us, as they have put us in continuous alert of not forgetting to charge the precious smart phone, or else the next day we lose quite a bit in our meetings, and our business …. How can we then rely on batteries to power extremely heavy vehicles? Come on!

The only explanation of the overwhelming “blind support” is that readers have accepted this new idea, mostly to encourage the inventor(s) and for eagerness to see new emergent technologies. Scientists and engineers do need all kind of support. The author has done research on photovoltaics and knows how that research depended on taxpayer opinions and federal supports. At any rate, one can’t close the door to innovation, as a bright idea could one day sparkle from nowhere. While the core of the problem for this particular application is not the battery itself, but it is the way they are used, truly defies the energy sustainability we have been looking for. Energy storage has been addressed for many decades by a very large scientific community. For instance, the much respected Electro-Chemical Society (ECS) has an entire section on batteries and semi-annual symposia. The extent of that scientific community and produced papers just show how complex batteries are, and how true progress is very slow. These facts alone support the critical views discussed in this paper. There is no doubt that we badly need better and robust batteries for many applications, from nanodevices to large scale systems, and from medicine, to portable consumer electronics, to space technologies… you name it. But, having good batteries on the market, with prospects of further improvement and cost reduction, does not imply that they could be used haphazardly; no! Also, one must not forget the possible surge of prices, for the basic elements and the raw materials.

The Magnitude of the Battery Issue, as related to using them for Powering Heavy Duty Vehicles

Here are two essential questions that are critical to the “Battery powered truck” technology: How many batteries one would need to power common trucks (40 tons)? How to get rid of them once they wear off?

For comparison purpose, it is worthwhile looking at other battery applications that, like the “battery powered truck” technology, draw high energy amounts from such very large assembly of fragile and sensitive devices (tiny electrochemical cells). Many utility companies have installed huge and costly energy storage systems. They have chosen to utilize batteries as back-ups, the easier existing options, for entire city electric utilities. Maybe such solution could be economic (in current market), but surely it is a short term solution, and would be a wrong one for the long run.

Likewise, huge battery packs for similar purposes have been put in the market. Today, it is not certain how successful that technology is on the ground. It does not seem to have received much attention except in some cases. There is a limited number of projects for storing renewable energy excess, like that of Ta’u Island, the Kauai (Hawaii) , which consists of a 52 megawatt-hour battery pack [5], the  Dubai Electricity and Water Authority project, which has ten sections of 7.2 MWh each.

Note that supporting utility infrastructure with batteries, leads to preserving legacy technologies, which are aging, often oversized, and are energy inefficient. It turns out that the legacy infrastructure (for example, the electric grid) requires large budget to maintain it, which is a huge burden on consumers and taxpayers [6]. Now, compare “the legacy electric infrastructure” to a system that produces energy right where the need is; would one ever require in that case a grid to transport it? Absolutely not! That's the case of photovoltaic (PV) systems; one can have a power source just few meters away, or maybe less, from the DC powered amenities. As a result, in such simple energy configuration, there is an absolute minimum of wasted energy! This is an example that shows that we cannot scarify the future of nascent and modern technologies to save the legacy technologies and to promote unjustifiable business. And that's what, in a sense, the “Battery powered truck” project is doing, because the public is sticking to the old idea of trucks in highways!

It is necessary to stress that ill-designed technologies must not go out from the laboratories to the market. A decade ago, many ill-designed products powered with small PV cells were put on the market. They have disappointed the buyers, as they performed much below expectation. It was a set-back to PV, a nascent technology. Such reckless business has tarnished the image of PV in the eyes of the general public, and had surely contributed in the setback of the technology.

Car-Caused Environmental Disasters

Used parts from cars, including batteries, produce enormous waste that is difficult to recycle or get-rid of it without impact on the environment and loss of materials. Let’s find out about the amount of needed batteries for a 36 ton semi-truck. This can be evaluated from the energy consumption. It was reported that the truck energy consumption is 2.0 kWh/mile, which seems too optimistic [7]. Such an extremely high performance might have been obtained in ideal laboratory conditions without any load [8]. But let's assume that the 2.0 kWh/mile has been achieved; then, the 500 miles autonomy requires batteries that have an energy capacity of ~1,000 kWh. This leads to believe that the battery pack should weigh 7.5 tons, or so. Now, imagine the quantity of lithium (expensive and dangerous material) that is going to be put in these batteries?  Also imagine, how lithium (the hard to extract material) is going to be recycled from a complex and polluting device? Reclaiming lithium from batteries seems to be mastered and industry is waiting to reach a critical mass to make it economic. Unfortunately, the recycled portion will not suffice. At any rate, frankly, I believe that it will be too hard to reclaim lithium from micrometer thick sheets loaded with a certain percentage of Li particles, and economically inefficient!

What an environmental disaster would be induced, should that technology be adopted on a large scale!

The issue of generated waste by vehicles (unusable parts, large junkyards,…) is problematic. To give a picture of what we expect to see should batteries are used in every truck and car, the tire waste is given as example in Appendix I.

To finish-up, the environmental aspects alone induced by these active devices, i.e., batteries, will prevent the technology discussed here from being generalized. Besides, as the market is going to be tougher in the near future, once polluters will be billed for gas emission and other forms of pollution; the extravagant and wasteful technologies will be filtered out, batteries (at least those built with current technology) will be among them.

Risks of Transporting Massive Battery Pack

One has to note that electrochemical devices (here, chargeable batteries) are like biomaterials, they live, and they feel their environment. They have limited lifetimes, and they degrade irreversibly, to the point they die without a chance to revive them (at least for current technologies). Even rechargeable batteries have a limited number of charge-discharge cycles. If you are careful when charging your battery and you avoid heating and freezing them, you could extend their lifetime. The heart of the battery problem is the irreversible degradation of the electrode-electrolyte interfaces (Solid-gel or solid-liquid) and you cannot cure that. Inevitably, defects are created at these interfaces, the battery active elements. Also over time the electrolytes age, as they get contaminated. So, if your “battery powered truck” breaks, you could rebuild the electric motor, the transmission gearbox,... or fix the electronics, but you cannot fix the battery active elements, at least for current technology. Most likely, you would have to through the batteries away.

Damaged Lithium battery taking fire; note the magnitude of the fire as compared to the size of the battery and how it is violent.

When driving a truck, the mechanics frequently suffer abrupt and extreme loads. Also driving in cities or nearby leads to frequent accelerations, which induce additional forces that frequently vary, and the resistance torque often changes as the wheel velocity varies. The sudden variations reflect directly on the batteries. Indeed, direct mechanical coupling of the electric motor, instead of through the inertial arbor and the hydraulic gear box... propagates these variations to the batteries, unless the fluctuating energy is dissipated or recycled (with more complication, and additional efficiency factors). If these energy fluctuations were excessive and not managed, they would stress the batteries, and would lead to significantly cutting down their lifetime. It is hoped that the regenerative breaking compensates for these variations, and if so, it would protect the batteries. Furthermore, batteries cannot withstand extreme weather (both cold and hot). Heat forces inter-diffusion and contamination of active materials, while cold destroys the electrolyte and the interfaces, and induces mechanical stresses that may lead to delamination of the layers. Also, failure of the electronics (battery charger, inverter, controller) can happen by an overload, exposure to harsh environment, or the combination. These are more pathways to ultimately damage few elements, or severe the entire battery pack. One must note that for an electric car, the stress incurred by batteries is bigger, damage is more frequent, and aging is faster than for the battery of a normal car. For the latter, the battery is only used to start the motor, so it does not undergo continuous charge state variations, and the battery charging happens smoothly during the trip. When you start a gas powered car, stress on the battery is not severe, because the car is not moving, only the motor inertia is felt by the battery. Also inside the battery, the ionic exchange is driven in the way it is designed for. In light of these multiple factors, one can conclude that the batteries of that 36 ton semi-truck will die-off much quicker than your car battery.

Wouldn’t be better to Ride an Electric Train than Driving a Car: Think Energy Efficiency!

I intend to write another paper on the question of oil that is being used-up, while it is an extremely high value material that should be preserved and used in higher value applications. The paper will show the urgency of leaving oil technologies and moving quickly to renewable energy technologies. Also, the idea of fully relying on batteries for trucks (on highways or in suburbs) should be strictly abandoned, no matter how much advances batteries will have. The fact that one would waste additional energy for fret transport is a disastrous idea, using batteries for that purpose is just a non-sense!

As far as vehicle size is concerned, one can only express astonishment and even indignation over the utilization of oversized four-wheel drive SUVs, massive trucks, 20” wheel cars,… for commuting, often alone, as a single rider. These riders have choices, but they totally omit economic aspects and disregard any form of energy saving, and conservation of materials too. It is useful to estimate the required energy to move one of such massive wheels at the vehicle speed. The roll and translation motions at ordinary speed (35 miles/hours) demand enormous amount of energy, about 4000 joules for a 195/65R20 tire mounted on aluminum alloy rim of 20”. That high energy value is spent by the engine to just sustain the wheel kinetic energy at the indicated car speed, without considering the friction of the wheel with the road. Comparing that amount to what is needed to move a single wheel bicycle (unicycle), one would find only one sixteenth of that amount. A compact SUV will run on 300 times more energy than that unicycle. Can we still afford wasting our resources (both energy and materials), just to have an illusion of luxury? Isn’t it insane to still tolerate that massive waste? The unicycle needs same energy amount as the more practical Penny-Farthing Bicycle (the energy is mostly used to move the big wheel). That bicycle is a direct drive lightweight vehicle, and is the most efficient machine for ground transportation. The velomobile has a similar efficiency but is much more comfortable and faster. So, let’s convince ourselves about "efficiency and sustainability first", and let’s push industry to find true solutions to save ourselves from depredation and from unsustainable dreams.

Penny-Farthing Bicycle	Unicycle: not practical for common users.	jcshines.com
		Self-balancing one wheel motorcycle seated electric unicycle

The idea of friction-less vehicles (cars in tubes, maglev...) could be the ultimate answer to the massive issue of transportation. Here, I applaud the company Tesla for digging out in 2013 that old idea of vehicles in tubes [16]. The idea appeared in the mid-seventies (possibly earlier) as a large tube, either pressurized or vacuumed, in which vehicles move friction-less at high speed. The two approaches were based on different concepts and technologies. Both provide means to minimize the contacts of the vehicles with the tube walls. There was nothing better than that dream transport system; unfortunately, it was plagued with technical difficulties.  In theory, the hyper-loop project should succeed, provided that some technicalities are solved. However, the engineering work remains challenging, namely, the mechanical elements of the loop, entry and exit devices, collision control... . Most likely the engineering aspects have been mastered since then [17]. It is possible that Tesla engineers have already come up with viable solutions for these challenges.

Conclusion

Before recapitulating let me point out, once more, that electric batteries are not primary energy sources; they are just storage devices that fulfill an intermittent charge-discharge function. The hurdle of transportation is and will always be, the energy generation, conservation, and sustainability; it is never been about storage, or offsetting the energy use, or articulating the technology in a way to capture new investments. The latter risks to drive the transportation technology development into catastrophic pathways, which could be also fatal for associated technologies.

Put in the larger scope of future transportation, batteries alone cannot be the answer, whatever vehicle spectrum one may think of. Let's face it, batteries and associated electronics that feed energy-intensive machinery, severely reduce the overall energy efficiency. Hence, as supplementary components they are detrimental for energy intensive applications. Such applications require the most direct coupling of the electric load to the primary energy source, which is not the case of technologies relying on batteries. Therefore, we must continue to use electricity storage devices, only, to power devices with limited capacity and limited function.

While the development of electric cars is something to encourage, the electric trucks running on batteries is the thing that will not survive large scale demand. How is it possible to fill highways with trucks running on batteries, when we know that semi-trucks need 5 to 7.5 ton batteries? What to do with these tons of batteries (per truck) once they become inefficient? Unfortunately, recycling portion of the lithium and other metals, some of which are not abundant, others are literally rare, will not suffice.

Contrary to trucks, electric cars represent an acceptable platform laboratory for developing future technologies focusing on more conscious transportation vehicles and systems. At any development phase of the electric car, engineers will be able to deal with the limiting factors of the day. For instance, when energy sources and materials shrinkage will be more visible to the market and the consumer, the size and the weight of the car will be shrunk to accommodate any of such situations. For instance, lightweight small cars running on combined photovoltaics, pedaling, and small battery will be adopted. In my opinion, that technology will be one of the future transportation components for transits, the primary transport problem for cities and suburbs. If so, the small hybrid car should be used as connectors (gap bridging vehicles) that enable going from one train/metro stop to another, or shopping,… while the heavy duty transport must be left to electric trains, metros,... The connectors loaded with artificial intelligence management systems can be owned and operated by the city. Therefore, hybrid electric cars can be considered as prelude to a viable and robust technology. Contrary to cars, electric trucks have an intrinsic limiting factor, which is the fret tonnage, which means electricity consumption remains high. As a consequence, considering current technology, a gigantic battery pack per truck is needed, no matter what we will do, and that’s the problem! As such batteries are an overload to the system it powers. In addition to their own problems, they degrade the overall efficiency inherent to energy loss, both during the storage and energy extraction. Hence, they are incapable of powering massive trucks or planes, or used to store energy for entire cities. In the long run, batteries will not support economic development in a sustainable fashion, in addition to the fact they are source of huge pollution, if used over a large scale. Because of these intrinsic problems and their impact on other technologies, batteries must only be used to power devices with limited capacity and thus limited functionality.

In closing, cars and trucks are central to gigantic energy and pollution problems they have created and maintained over a century. Since transportation is inevitable, it is hoped that automotive industry will start developing sustainable technologies and infrastructure, rather than bringing illusive and unsustainable options like this "battery powered truck". In addition, they need to engage in gradually breaking away from gas powered cars. Since transportation is one of the most pressing problems for humanity, to accelerate the development of sustainable and clean technologies, consumers must arrive at a clearer understanding of the underlying problems and the viable options, opt for solutions that are economic, and consciously invest in viable technologies for the future.

This brief analysis of the trends of future transportation, an extremely complex problem involving many players, views, and technologies, was intentionally kept simple and mostly qualitative. It has been triggered by the widely spread public view on the emerging “battery powered truck” technology. The author’s vision stems from his research on renewable energy technologies and his knowledge of batteries.

Appendix I

Tire-Caused Environmental Disasters

The example of car tires is used to illustrate the environmental situation that will be created, should batteries are utilized on large scale; i.e., 7.5 tons (16,500 lb) lithium-ion batteries per truck, and 218 kg (480 lb) batteries per car (e.g., Nissan Leaf, 40 kWh). This appendix reminds us the mountains of wasted tires [21] that industry does not entirely recycle [22], because the process is technically difficult and not economic [23]. It has been preferred to pile the tires to ultimately burn them. The process produces heavy smoke and other pollutants [24] while it, in fact, leads to loss of very precious materials.

Because current batteries are not easily recyclable, it is likely that we are going to pile mountains of wasted batteries, just like the tires. Currently, only few % of the active materials are put back in battery production lines, because of processing difficulties. Very unfortunately, some companies do that to just obtain extra funds through "green initiatives" and tax breaks. Practically they are not capable of extracting the spent materials for reuse, and the technology is not lucrative enough. The reality is, many industrial sectors care less about the environment and the sustainability, and at the moment, “Green batteries” is way under expectation, even though there seem to be a strong interest in re-using lithium.  The recycling business in that area might one day work, but not before strong incentives are put in place, and battery producers contribute in the effort.

Tire cemetery (Courtesy of Environmental Waste International, Http://www.ewi.ca/products/tires/)

The reclaimed materials from car tires can find many applications such as production of liquid hydrocarbons, raw rubber, rubber mats, tiles for playgrounds and sport fields, paves for sidewalks, rubber pellets mixed with asphalt for roads, ... Also, tires can be rejuvenated and put in refurbished wheels for low speed vehicles. The last resort to get rid of wasted and un-refurbishable tires is, to simply use them as solid fuel for powering plants.

Because of the structure of tires and the materials composition, technically, they are easy to recycle [25]. Though the economic reasons and incentives for recycling car tires are countless, yet, the industry is not recycling them all!  Therefore, it is forecast, that recycling batteries will face the same fate or worse, being active devices. Ultimately, feasibility obstacles and difficult economics will lead to formation of mountains of wasted batteries.

Appendix II

The paper has received several comments from readers who were essentially engineers in automotive industry and some from scientists, the responses are given below.

Comment 1:  This article has received an interesting comment; in response, I have written a paper titled: ... very large scale battery for storing harvested solar energy??? Are we forbade from dreaming of the "free energy era"?  [26]

Comment 2: One of the readers argued that the idea of electric cars and trucks is great and the technology will have a bright future, and we need it badly; thus, it must be allowed to develop.  There is no doubt that the reader’s comment has a lot of truth. The engineers of the company that have designed and built the truck must have developed modern electric motors, drive-train, gearbox... as well as electronics that instantly accommodate the power negotiation (electric demand/availability and mechanical resistance/push) and vice-versa…  Even though the details of the technology were not published, it is likely that the engineers have used reversible motor-alternator that recycles the excess of energy during breaking (regenerative breaking,...), or along a descendant slope…  It is conceivable that one can solve these power electronic problems with modern electronics combined with AI.

However, one must realize that the technology has already given the most (or almost) it could.  Also, the important point of not much improvement expected at the level of batteries in the near future, must be considered. Add to that, a 35 ton truck negotiating of turns, banked roads, ramps… running in highways and mountains generates huge challenges for current batteries, which severely degrade the batteries. That is a real problem more stringent than the case of battery powered cars.

So the essential problem is not really at the level of engineering the electric truck, but it is about using (current) batteries for powering such huge vehicle.

Comment 3: Small electric trains can be used in cities and suburbs. These vehicles are proven to be the most efficient for urban transportation (2.6 times more efficient than electric cars). Also, they can connect hubs and large railway stations, ports, airports… and will not pollute the cities. Moreover, they are quite, comfortable, safe...

In the city, passengers can "jump" in and off the tramway car. With good technologies, tramways would make easier transits, would smooth the traffic, and would enable a flexible and economic transportation.

The author believes that it has become urgent to target proper technologies, and only those that are sustainable and have greater chance to become the technologies of the future. The efficiency and practicality of these technologies will tell if we should build more of that legacy infrastructure, which is constraining new developments. For instance, we would know if building highways is justified or not. Today highways do not appear to enable efficient transportation, there is a risk they will become soon a useless burden. Tens of miles around cities get easily and often jammed with single rider cars. That proves that the efficiency per rider is very low. In the contrary, lightweight Trains/tramways don't cause such traffic difficulties, and they can take tens or hundred times the capacity of a highway cluster (in a given region).

These small trains don't need batteries, as they can be energized with electricity through their rails, which can be connected to small photovoltaic power plants.

Comment 4: It is clear why we must be very much concerned with the transportation problem. Currently most energy consumption and pollution are done by cars and trucks. They induce dangerous polluting materials, namely, toxic gases, soot, chemicals that modify the stratosphere… as well as heat, and noise, all of which are severing our environment. The worst part of that pollution is the fact that the emitted gases are spread in the air, naturally, because cars and trucks move. Sadly, today, there is nothing we can do about it, unless there is a radical change in transportation concepts.

Zero-emission cars and trucks are utopia. The only way to alleviate the problem is through the development of public transportation (based on good technologies) fed by renewable energy. In the meantime hydrocarbon power plants can be used to produce electricity; the fact that these are centralized allows processing the gases and the soot they produce. In the contrary, burning that same hydrocarbon through cars and trucks would not allow processing the emitted gases.

Comment 5: If we put that advanced technology (mentioned by the reader) in small electric trains, we will have something dependable and viable, now, and in the long run. Small electric trains can be used for transits of both passengers and fret. Evidently, vehicles always work to overcome friction and air resistance, and trains are made to minimize friction (that’s why usually railways are horizontal, and the contact wheel-rail is really minimum) and to have low aerodynamic profile. Trains have the smallest air resistance (cross section area) per ton of transported merchandise, and they are longer than any other vehicle.  Trains spend relatively (per ton) less energy to do that than any other vehicle. It is not possible to avoid trains over the long term. One mist put the up-coming 10billions in perspective, there energy and transportation needs is one of the biggest challenge.

Comment 6:  In response to a manger in a French company installing Chargers for Vehicles and Electric Signals.  Battery charging systems for consumers (on the road) and for many other applications, is a good technology. Photovoltaics needs your technology. However, it is hard to believe there will be a need for installing in highways large charging plugs for trucks, but possibly for small cars.

Comment 7: In connection to the discussion about future cars, which are expected to be lighter and energy efficient, a reader brought my attention to the two smallest cars ever built [27],[28],[29]. The reader added, it is absolutely conceivable to ride much lighter and economic cars, if we just accept to move at lower speed and ride on less comfortable seats. I could not agree more! As we will be facing soon more difficult situations with energy, materials sustainability, and pollution as well as tougher economic realities, we will ultimately be forced to adopt slower mobility and lighter cars. Certainly, we will develop much better and faster cars than the P50. To compensate for the loss of "high mobility", I envision that we will have better urbanization plans and many supporting solutions. Don't forget that the increased communication, virtual meetings, remote services,... drastically reduce the need for transportation. So we must not be so alarmed, as our extremely high knowledge level will allow finding proper solutions.

Comment 8:  Inspired by an article published in a popular online venue [30], based on data reported in that paper, a reader has quickly compared efficiency

The contrast in health of a car driver and constant bicycle rider is more than evident to each of us. While cars degrade the health of the riders, bicycles directly improve it. Moreover, a car does induce a lot of pollution, during its fabrication and more so during the decade(s) of operation. That strongly effects public health. The reader also compared efficiency of other means of transportation, which I found in [16] in a chart (shown on the left) that relates machine type to its efficiency. 

A "Walking Bicycle", a cool concept, but the least efficient [Courtesy of 31]. It is certainly healthier than riding a car.

References

[1] The intention behind this article is mainly education, as well as enhancing the public awareness to the question of renewable energy and sustainability as related to transportation. There is no any commercial purpose and cannot be used so or to challenge or oppose the technology developers. 

[2] https://www.daimler.com/products/trucks/fuso/ecanter.html

[3] https://www.theverge.com/2017/11/16/16667366/tesla-semi-truck-announced-price-release-date-electric-self-driving

     https://www.extremetech.com/extreme/259195-tesla-semi-500-mile-range-cheaper-diesel-quick-charge

[4] https://www.linkedin.com/feed/update/urn:li:activity:6420469520820944896/

[5] Jordan Golson Tesla built a huge solar energy plant on the island of Kauai, The Verge, Mar 8, 2017 https://www.theverge.com/2017/3/8/14854858/tesla-solar-hawaii-kauai-kiuc-powerpack-battery-generator

[6]  The cost is hidden to the public as it is not talked about.

[7]  Compare that value to the energy needed by an economic small car, you will find it too optimistic even when considering the regenerative break technology that, seemingly, the truck has. A 132 hp small car running on gas performs on average 31 miles/gal, thus consumes 1.17 kWh/mile (considering that a gallon of gas produces 36 kWh).

[8] One cannot confirm these hypothesis for luck of information.

[9] David Tracy, Here's What Firefighters Do To Extinguish A Battery Fire On A Tesla Model S
Oct. 2017,  https://jalopnik.com/watch-volunteer-firefighters-in-austria-extinguish-a-fi-1819665352

[10]  The literature is full of articles showing that oil reserves are shrinking at alarming pace.

[11] D Banister, S Watson, C Wood, Sustainable Cities: Transport, Energy, and Urban Form, 24 (1), pp 125-143 (1997), doi: 10.1068/b240125.

[12] M.J.Maher, P.C.Hughes, A probit-based stochastic user equilibrium assignment model Transportation Research Part B: Methodological, 31 (4), pp 341-355, (1997) doi: 10.1016/S0191-2615(96)00028-8

[13] Stephen Graham, Simon Marvin, Splintering Urbanism, networked infrastructures, technological mobilities and the urban condition, ISBN 0–415–18964–0 Taylor & Francis e-Library, 2002.

[14] O.Y.Edelenbosch, D.L.McCollum, D.P.van Vuuren, C.Bertram, S.Carrarae, H.Daly, S.Fujimori, A.Kitous, P.Kyle, E.Ó Broin, P.Karkatsoulis, F.Sanol, Decomposing passenger transport futures: Comparing results of global integrated assessment models, Transportation Research Part D: Transport and Environment, 55, pp 281-293, (2017), doi: 10.1016/j.trd.2016.07.003

[15] "Airbus A350: is the Xtra making the difference?", Aspire Aviation. 8 June 2015.

[16]  Kate Baggaley,  Elon Musk's hyperloop dream may come true,  MACH NBCNEWS,  March 2018  https://www.nbcnews.com/mach/science/elon-musk-s-hyperloop-dream-may-come-true-soon-ncna855041

^[17] There are no convincing news about hyperloop projects in Virgina (by Tesla), California, and in Europe. It is said that they are moving slowly, and there is a risk of cancellation. https://www.nbcnews.com/mach/science/elon-musk-s-hyperloop-dream-may-come-true-soon-ncna855041

  It is hoped that complete pilot projects will see the light to enable essential tests.

[18]  Thanks to the latency of dissipation of stored heat during the day. The technology allows for at least 6 hour heat storage, depending on the design. This is excellent for powering a city at night. That cancels the need for large electric batteries. The salt and other compounds used for heat storage are not dangerous, and do not represent pollution risks; CSP is another reliable technology for the future.

[19]   N. Lia, Z. Chena, W. Rena, F. Lia , and H. M. Chenga , Flexible graphene-based lithium ion batteries with ultrafast charge and discharge rates, PNAS, 109 (43) ,  17360–17365 ,  (2012).

[20]  H. Wang, X. Li, M. Baker-Fales, and P. B Amama, 3D graphene-based anode materials for Li-ion batteries, Current Opinion in Chemical Engineering, 13, 124–132 (2016).

[21] Stephen K. Ritter, Tire Inferno, Chemical and engineering News, 91 (43), pp. 10-15 (2013) https://cen.acs.org/articles/91/i43/Tire-Inferno.html

[22] https://paulscrap.wordpress.com/2016/07/27/simpsons-tire-fire-episode/

[23] http://cen.acs.org/articles/93/i16/Elusive-Dream-Tire-Recycling.html

[24] James C. Peterson, David F. Clark, Peggy S. Sleevi, Monitoring a New Environmental Pollutant, Anal. Chem., 1986, 58 (1), pp 70A–74A, (1986) DOI: 10.1021/ac00292a771

[25] microwave polymerization http://ewi.ca/products/tires/ 

[26] A. Karoui, ... very large scale battery for storing harvested solar energy ??? Will it forbid us from dreaming of a "free energy era"? published in https://www.linkedin.com/pulse/very-large-scale-battery-storing-harvested-solar-energy-karoui/

[27] The first car mentioned by the reader is the Peel P50 car that weighed 56 kg and had a top speed of 60 km/h, 1.34m length, 1m width, and 1.34m height.

[28] The second is even lighter, the car was constructed a century ago by Louis Borsi; it weighed 9.5 kg and could drive up to 25 km per hour.

[29] Craig Glenday (ed.). Guinness World Records 2010 (56 Ed.). Guinness World Records Limited. p. 162. ISBN 1904994490.

[30] Chris Woodford, The science of bicycles, May 27, 2018. 

https://www.explainthatstuff.com/bicycles.html

[31] https://www.youtube.com/watch?v=4ZCa4fbr6Zo