# Zero Emission Tanks

When we look at the future with our sci-fi glasses on, most new weapons are electrically powered, such as coil guns, railguns, laserguns. But what about vehicles?

In 2014, Tesla released all patents making them available to everyone; so why not take that in to military use?

The M1 Abrams tank has a 1,120 kW motor and in comparison the Tesla Model S has a 568 kW motor, so it wouldn't be unrealistic to up-scale the motors and batteries. The Tesla has an effective range of 265 miles (426 km) and the Abrams tank has an effective range of 265 miles (426 km), so there isn't much difference there either.

What would be the main reason not to convert armored tanks into electric, zero-emission vehicles? What challenges would the R/D Facility have to overcome?

Assume the R/D department will use the patent to develop their own product rather than retrofit existing Tesla hardware, thus making motors and batteries more "war"-friendly.

Petition:

We already got a lot of good answers regarding the lack of good batteries, I think we can stop beating the dead horse, and move the debate from the question "Are there any good batteries?" to "What challenges do you need to solve to make a next-gen-tank?"

• Google says the Tesla Model S masses around 2.1 metric tons and the M1 Abrams masses 62 metric tons. The effective range of the Tesla would likely go way down if you added 60 tons of armor, transmission, tracks and ammunition to it. – Scott Whitlock Oct 5 '16 at 16:35
• Also consider that energy density of a Li-ion battery is max ~0.8 MJ/kg and diesel is 48 MJ/kg. You'd be better off with a ham and cheese sandwich powered tank at 10 MJ/kg. :) – Scott Whitlock Oct 5 '16 at 16:43
• That's right, this new generation of tanks doesn't burn coal or fossil fuels, but runs on electricity that was generated by burning coal or fossil fuels! Buy now! – Devsman Oct 5 '16 at 19:30
• @iAdjunct If Samsung were manufacturing the tanks in question, the batteries would serve as both. – Crashworks Oct 6 '16 at 5:57
• Another point, the American military uses the same diesel in it's tanks, APCs, humvees, generators, and even motorbikes. Makes the logistics of fuel easy. "We need some generic everything fuel moved over there". The moment one vehicle needs something else, you lose that – Grimm The Opiner Oct 7 '16 at 10:29

# Time

It takes few minutes to load fuel into a tank. 150 US gallons (570 L) per minute is possible. So 3–4 minutes from empty to full for an M1 Abrams (not sure if that's the system installed in it, but it's just a glimpse on possibilities). On the other hand, it takes 15–30 minutes to charge Tesla. Doubling it for double power, and you have it: 4 minutes wins with an hour when it comes to be up and running again.

# Reliability

Diesel engines are old, well tested, reliable and sturdy. To some extent, you can still ride if one of the cylinders fails. You can still ride if your fuel is leaking a bit. Lost one cable in accumulator battery? One coil in electrical motor, and you're toast.

Gas turbines are also old and true. Not as old and reliable as diesel, maybe, but older and more tested than electric ones.

Tesla engines are built to be replaced, not repaired in common shop. Personally, I would prefer to take more rounds and more fuel, and engine that can be repaired, than to have to load spare motor.

Note: I'm talking about modern Tesla motors, not good old heavy, bulky, energy inefficient but sturdy and easy to maintain submarine electric motors. And I'm talking about modern energy dense batteries, not old, heavy lead-acid batteries. Old electric tech was just too heavy and bulky for land vehicles, but indeed it was reliable all right.

# Personnel

Think how many guys with years of experience with gas engines you have in army. A lot. And many have experience longer than Tesla cars even exists. You can't replace that by some classes. When it comes to battlefield, you want equipment your people will be able to use, maintain and fix.

Don't forget that railguns are simple. Knowing how to use one and even how to make simple fixes is by far not enough to also know how to fix a coil in electric engines or re-wire battery pack to go around a broken unit. Especially when fixing gun can wait, and fixing engine cannot and you have to do it, even if the bullets are flying.

# Logistics

Electric lines are natural target. You can move fuel quite easily. Not so with electricity. You can't just load electricity on a truck and move it where it's needed.

For many diesel engines, you can use things like frying oil, moonshine, etc. to make them run. It's not good for the engine, but who cares if this allows you to save your life or to go to position and defend a city full of civilians?

# Storage

You can store fuel a long time without losses. Accumulators, on the other hand, discharge when not used, slowly but significantly. You do not want to be surprised by empty battery.

# Ease of checking

You can just knock on the fuel tank to hear if it's full, empty or in between. You need device to test if battery is full or empty. Surprises are bad. Knowledge is life.

Of course you can have a chip to monitor cells. Worked great for Samsung Galaxy Note 7, right? Well, nope. At least empty fuel tank will not explode in your face.

# Safety

As fr13d points out, lithium-ion batteries tend to explode violently. Fuel tanks do not—still not exactly safe, but diesel can't be ignited by simple puncture, and requires air to burn. Same for natural gas, gasoline, jet fuel and other burnable fuels. Batteries burn well on their own.

• About refueling - if you can swap batteries, the time is reduced to a few seconds. – T. Sar - Reinstate Monica Oct 5 '16 at 14:05
• Why would you even need double the charge time for double the batteries? Couldn't you just run double the power and charge in the same time? It wouldn't take twice as long to change two separate battery packs assuming ample power supply. – Alexander O'Mara Oct 5 '16 at 15:08
• Tesla didn’t reinvent the electric motor. It’s still the same “old heavy, bulky” motor that drives submarines or any other industrial appliance. The same motor that was already present in cars one hundred years ago. Simply, because the motor never was the problem, it’s even older and more reliable than Diesel motors; it’s all about the batteries. – Holger Oct 5 '16 at 15:34
• You missed the most important part where batteries to store enough energy are really really really big and heavy. – user253751 Oct 5 '16 at 21:59
• M1 Abrams use a turbine, not a diesel engine. Also the range issues on an electric tank are nullified if you have a small Auxiliary Power Unit fed off a fuel tank, a-la the Chevy Volt. The APU doesn't have to do anything complicated except spin at constant speed/load. Battlewise, the question is whether you realistically expect to advance 200 miles in a day. That's a LOT. – Harper - Reinstate Monica Oct 6 '16 at 3:12

# Availability and portability of energy

When you are fighting a war, emissions and the environment is not really on your mind. What you care most about is that your weapons work when you need them.

Now granted electricity is very portable and available, when you have a working infrastructure, which makes peace-time use of electricity to power vehicles a splendid idea.

In war however, you can expect that electricity will most likely not be available, even in urban environments. And when it comes to having electricity available out in non-urban environments, well then you are expecting a bit much.

Fossil fuels come in handy in war because those you can move about in tanker trucks. And even if one or a few of your trucks take a hit, those are easy to replace, plus they are mobile and not all that easy to hunt down.

The power grid on the other hand is static and immobile. So blowing up a power switching station is very easy, and whoever was depending on it is pretty much screwed for several days, if not weeks or months.

Fossil fuels have stuck around because they are available, portable and work well enough when we need them.

• If the recent stories abut the skunk works small fusion reactor becomes reality you could certainty have MBT with final electric drive hell if the suggested power outputs are achieved you'd have a "Panzer" not a MBT. – Neuromancer Mar 29 '18 at 19:38

Currently humanity has no means to efficiently store electrical power in big volumes

Batteries is the first and largest problem to solve, before making tanks fully electrically-powered. Tesla uses lithium-ion batteries:

• They are costly to produce
• They lose capacity naturally, even without being in use.
• They lose stored power, even without being in use. (Those two make them pretty unfitting for war use - 2 years old tank will need a full battery change before going to combat, unless you want it to be only 30% effective).
• Their effectiveness depends on environment conditions (reccomended use/store temperature is ~25C).
• They shouldn't be discharged fully (meaning you will have to bring some "useless" weight with you).

There are even more "cons", which can be discovered by surfing internet/wikipedia.

P.S.: This problem can be avoided on larger vehicles by removing the battery completely:

However, making a huge tank or a "walking citadel" with nuclear engine seems to be too dangerous/costly.

Sci-fi writers use the idea of "portable nuclear reactor" to make such things happen.

• I present to you the Ratte! – SMS von der Tann Oct 4 '16 at 23:28
• Die Ratte is an interesting concept indeed, however when you want to actually make ratte-like tank nuclear-propelled, you'll need to take in account safety and "power-generator-onboard" factors: you will need to at least double the operating personnel, hence doubling(?trippling?) the size of ALREADY not-too-mobile, easy-to-hit and too-heavy-for-current-roads vehicle. – haldagan Oct 5 '16 at 15:57

Expanding on my comment:

Electric engines and electric systems in general have many advantages (an electric engine potentially needs no transmission, for example), but overall, the real killer is that battery technology is nowhere near as energy dense as hydrocarbon fuels. Other issues like the length of time to charge batteries (a commenter named GoatGuy on NextBigFuture has rebutted this on numerous threads, providing detailed calculations involving energy, voltage, heat etc. Sadly, since these are comments and not the articles it is hard to look up), battery weight and shelf life all factor into this. Even environmental factors like outside temperature affect battery performance (ever try to start a car in the dead of winter, when the temperature is well below zero?).

Now we can go partway there, by combining the energy density of hydrocarbon fuels and electrical energy. The chemical energy of the fuel needs to be extracted by fuel cells, rather than burning them in an engine them tapping the engine power through a generator. Fuel cells are very efficient on their own (estimated maximum efficiency is @ 60%, depending on the type), and direct conversion to electrical energy eliminates multiple "step possess losses" of going through different systems.

For military vehicles using hydrocarbon fuels like JP-8 (the NATO standard diesel and helicopter fuel), you would want a Solid Oxide Fuel Cell (SOFC). These fuel cells run at elevated temperatures which "crack" the fuel into hydrogen and carbon monoxide, both of which can be oxidized across the membrane and converted into electrical energy:

Most SOFC's today are built to run on natural gas, but there have been demonstrators using diesel fuel, and there is no conceptual reason not to have a diesel powered SOFC. If you notice the diagram there is also a lot of heat energy being released, and a bottoming cycle like a turbogenerator or even a small steam generator could be added to the loop to harvest some of that energy. The turbogenerator would resemble a turbocharger, with the turbine in the hot exhaust stream spinning a generator, and BMW has experimented with micro steam turbines which use engine exhaust heat, so the concepts have been tested in the real world.

The primary disadvantages of an SOFC is it needs to be brought up to operating temperature to work (@ 800 C), so no "instant on"; and current versions are made of brittle ceramic materials (mostly because research is on stationary power generation applications). An insulated container will assist in the former problem (once it is running, the reaction is exothermic, so the SOFC remains hot), and material science can be used to find better materials for the fuel cell stack.

Vehicle powered this way will have the range and logistical advantages of a diesel powered counterpart, but are potentially lighter and have a great deal of electrical power to run the engines, sensors and even laser or railgun weapons.

• As a technical note, the CO2 and water produced are emissions, and CO2 is considered a greenhouse gas (although a weaker one). Therefore a SOFC tank would produce emissions, just less deadly ones and possibly less overall. – PipperChip Oct 6 '16 at 0:42

There is a difference between car and tank. The Tesla Model S rarely utilises more than 5% of that 568 kW motor. The tank, on the other hand, has to move its 60+ tons on unpaved terrain. To provide the same effective range up-scaled Tesla battery pack is going to be at least 10 ton. Maybe 20. 10-20 ton of fragile, flammable potential disaster. Add to that up-scaled recharge time (many hours at best). The end result is of no interest to the military...

• So, you consider lithium-ion battery more dangerous than explosives and a tank of jet fuel? – Agent_L Oct 4 '16 at 15:31
• @Agent_L In comparable usable energy capacity, sure. 20 tons of solid chemical fuel & oxidant that will burn from random thermal runaway compared to partitioned ammo & (relatively) smaller fuel tank. – Martheen Oct 5 '16 at 7:56
• @Agent_L You do know that fuel tanks have been used as armor, right? upload.wikimedia.org/wikipedia/commons/d/d5/… A fuel tank on the outside of the tank may burn, but the inside of the tank do not care much about that. Compared to taking the molten metal jet of a shape-charge, a fuel fire on the outside of the tank is a minor thing. Also the preferred fuel of tanks — diesel — do not burn easily unless you manage to aerosolize it. Same with jet fuel: it is not that the fuel is particularly explosive, it is that a crash makes a mist of it that is bad. – MichaelK Oct 5 '16 at 11:32
• @Agent_L a 2 ton fuel tank is much easier to protect than the literal 100 tons of batteries (~50 times more) required to carry the same amount of energy around. A 10-20 ton battery pack would mean decreasing the tank's range multiple times from the current one. – Peteris Oct 5 '16 at 17:21
• Since the batteries are going to be so heavy, maybe they can be arranged outside of the tank to act as armor themselves - maybe lead acid would be better than LiIon for this (though at about 1/3 the energy density by weight, maybe not). The batteries can be wired such that losing individual batteries doesn't cut off power entirely. If a burning LiIon cell can be contained and not spread, then exploding cells is less of a problem outside of the tank. – Johnny Oct 5 '16 at 23:31

Handling large amounts of electrical power is non-trivial. Pushing large amounts of power into batteries is decidedly non-trivial. Any battery-powered electrical vehicle will need to recharge the batteries on a regular basis, just like a diesel-powered vehicle needs to refuel on a regular basis. The difference here is that diesel is just a liquid that can, absent some relatively trivial engineering problems, be poured at huge (almost arbitrary) rates. You can't readily do that with batteries.

Cem Kalyoncu mentioned solar panels (and in fact, this answer started out as a comment to that answer), which is a decent way to get power in an off-grid scenario. The odds that electrical networks continue working perfectly in a war scenario seem low, to put it mildly. Not only that, but to get any reasonable recharging time, you'd be drawing on the order of megawatts. That's a small power plant.

Let's say you build the tank around an 1,100 kW (1.1 MW) engine.

Insolation is 1 kW/m$^2$ or less in most parts of the world, and you might get 8-10 hours per day of good insolation at best. Solar panels generally achieve something like a 30% conversion efficiency, up from early ones which were more like 10% efficient.

Say you have 400 m$^2$ (20x20 meters) of solar panels. That gets you somewhere on the order of 120 kW of electrical power.

Consequently, to a first order approximation, with good assumptions about what time of day it is needed, to match the energy requirements for driving the tank around, you would need somewhere on the order of 4,000 m$^2$ of solar panels. The more reasonable 400 m$^2$ will give you one hour of driving time per day of charging.

Add to this that many military operations are performed during nighttime to help conceal the activities against the enemy.

A large pack of solar cells might be enough to recharge the tank's batteries sufficiently to move it from one place to another, but it won't be enough for actually having the tank perform useful (in a military, combat sense) work.

For this reason, an electrically-powered battle tank would be completely dependent on huge amounts of infrastructure.

Transporting diesel by tanker vehicle is far, far easier.

• Could this be solved by an exchangeable battery-pack? – Magic-Mouse Oct 4 '16 at 13:06
• @Magic-Mouse Possibly, but you still have to get the battery pack to the tank, and I suspect that simply providing means to replace it could introduce vulnerabilities. – a CVn Oct 4 '16 at 13:15
• @Magic-Mouse A battery pack big enough to power a tank is going to absolutely massive, probably comparable to or bigger than the engine bay of a tank, so we're basically talking about doing an engine-swap every time you need to refuel. A flatbed truck could hold two or three of these at best, and that's only to refuel two or three tanks a single time. A diesel tanker, on the other hand, could refuel and entire armored company. – UIDAlexD Oct 4 '16 at 13:34
• Also, 400-4000 sq.m. of solar panel isn't exactly stealthy It would be like setting up a sign saying "Bomb here!". – Stig Hemmer Oct 5 '16 at 7:25
• @Magic-Mouse That's a really generous figure. I just googled "M1A1 Cross Section" and to me it looks like 40% engine by-length. While having a giant engine-sized battery pack is ridiculous enough, at least it could be swapped out in an hour or two, provided you have a crane to help you. Each of your battery slices is still going to be so heavy it requires a crane, and since there's dozens of them that have to be individually installed, connected, and secured, you now have a much more complicated procedure. You just made a couple-hour job take a couple days. Batteries are a non-starter. – UIDAlexD Oct 5 '16 at 13:19

I have read many good answers for this question. Let me explain some points that may also come into consideration:

Redox Flow Batteries

A comparatively new approach to batteries and recharging, where you'd use a liquid electrolyte storing the power, which can be quickly replaced with fresh ones. This way you''d get rid of the land lines for recharging. They are also quite cheap.

Liquid Anode Batteries

Molten Salt Batteries. Uh, those... they have a relatively high energy density, but are filled with stuff you don't want to have inside of your tank. If one of those ruptures, you're toast. They are pretty cheap though...

Fuel Cells

Well, this one is old. Really old. The technology was already available during world war 2, although not quite exploited to the point it could have been. Can be refilled with oxidant and fuel in a similar way to combustion engines.

Energy Density/Specific Energy Considerations

Other answers have pointed out the logistic problems batteries. I would add that there is a general problem with the energy density and Specific Energy of batteries when compared to fossile fuels. Most batteries don't even come close to the amount of energy that is stored in a Liter of Diesel or jet fuel, let alone the part of it that is actually usable. I would think that this is the problem generlaly with electrical vehicles that don't have an auxilary power supply.

While hybrid machines could be used, like back when they tried them on the King Tiger, using combustion generators to produce the elctricity, such combined systems seemed to be far too complicated for a military application.

TL:DR

The main problem is energy density and logistics. The logistics side could be solved if those Redox Flow Batteries work. Secondly, energy density. I don't know how large the energy content of the liquid electrolytes are, but they'd have to match the 46-48 MJ/kg (specific energy) / 26-40 MJ/L (density). Li-Po batteries have around 1 MJ/kg and 3 MJ/L. Thats not nearly enough...

• I like your answer. Something to add as interesting thing is that there are submarines which use fuel cells so they can be incredibly stealthy. – WalyKu Oct 5 '16 at 9:11
• All the time while reading the other answers I was trying to remember the name of this relatively new tech I've recently read about… Thanks for mentioning redox flow batteries, since that's what i had in mind! – MvG Oct 5 '16 at 15:55

If your aim is to kill people and destroy stuff, emission control becomes irrelevant.

Bombing Bagdad – and later rebuilding it! – caused more air pollution and excess heat than all the air planes and tanks in that operation. If you want clean air, you do not make war.

An emission-free tank is like putting vitamins in cigarettes. The little good that does stands in no relation to the harm of smoking, and the only way to make cigarettes healthy is to not smoke them.

• The question was not about zero-emission bombing, it was about zero emission vehicles used in warfare. – Magic-Mouse Oct 5 '16 at 10:23
• the question was pointed towards the vehicle, verbatim: "most new weapons are electrically powered, such as coil guns, railguns, laserguns" why use laser, well to make more precise shots so you don't need to destroy buildings. Just the target ;) But please provide an answer for the entire context not just 14 words. – Magic-Mouse Oct 5 '16 at 10:50
• "Why not do X?" "Because Y is worse!" This is effectively your answer, but it isn't a solution to the problem; it's an excuse to avoid the problem. You haven't identified a reason why X shouldn't be done. – Frostfyre Oct 5 '16 at 12:18
• Because it would be like asking "Why catch a thief if you cannot remove all crime in the world?", "Why build a windmill/solar-panels, since the world is using coal burners anyway", it says nowhere that those who commission the tanks don't care, actually it "between the lines" say they do because they are in fact ordering a Zero-emission tank. It is called taking baby steps in the right direction. – Magic-Mouse Oct 5 '16 at 12:39
• Zero emission tanks tend to be stealthier... – Efialtes Sep 17 at 12:20

Full electric system might have advantages, aside from the glaring problems. So this is on top of other, rather grim, answers.

• A full electric system will probably use multiple electric motors. This will serve as redundancy and will allow tank to go on even if one is blown.

• A full electric system can have disjoint batteries leading to motors. If one block develops a fault, rest will go on.

• If necessary, every tank can be equipped with foldable solar panels, thus if you fail to find electricity you may continue next day.

• Not within zero emission spec but you could have portable diesel engines to generate power if it comes to that.

• In hostile lands, mobile thermonuclear power station can have double use: as a scare tactic and power station. At home, you can have power stations seeded. If zero emission warfare is considered, probably countryside would be littered with renewable energy generators.

• Electric systems have less mechanical peripherals and easier to do repairs.

That said, it is not very good idea with the current technology. Better batteries and widely used renewable energy is necessary to take advantage of this technology.

• The amount of solar panels required to power a tank would be ridiculous. – Yakk Oct 4 '16 at 13:29
• I need to do the maths, wait for it .... – Cem Kalyoncu Oct 4 '16 at 13:43
• @CemKalyoncu 1120 kW for M1 engine, while a square meter of solar panel could produce 200W under good sunlight. Even if they can unfurl the stadium sized panel, with the weight of the panel it's tyranny of rocket equation all over again. – Martheen Oct 5 '16 at 8:12
• Oh I forgot to do the math thx for help, you won't need to run the tank over sunlight. Have 10 sq-m panels and say with the losses it does 1120kW for 6 hours. You could charge the tank during the day to run an assault during night. Obviously this won't be your first choice but it is better than running out of diesel in the middle of the desert. – Cem Kalyoncu Oct 5 '16 at 8:15
• An electric drivetrain is possible even when the source of power is a combustion engine - many rail locomotives are diesel-electric (diesel runs a generator, wheels are driven by electricity) and there have been functioning armored vehicled designs with the same concept at least since WW2 (e.g. en.wikipedia.org/wiki/Elefant) having electricity replace the mechanical transmission. – Peteris Oct 6 '16 at 0:22

Its about energy density. A vehicle needs to carry enough energy (stored in batteries or fuel to move it) A Tessla can afford to have most of its mass (less than 2 tons) dedicated to storing energy. But a tanks has lots of mass that has to be dedicated to armor and weapons.

according to Wikipedia
Lithium ion Batteries have a energy density of 0.5 - 8.75 MJ / KG and the less expensive lead acid batteries are .17 MJ/KG Where fuel has a density of 46.4 MJ / KG Which means if you switch to using batteries to store your power you need 53 - 272 times as much weight dedicated to energy storage.

It is true that electric motors are more efficient but the ratio is closer to a factor of 2 -4.

Even with higher engine efficacy you need to spend 50 times as much weight on fuel which is huge think a 60 ton tank suddenly going from 2 tons of fuel to 100 tons of batteries. The extra 100 tons of weight increase the energy requirements to move the tank which require still more batteries and a stronger engine which in turn weighs more and so on.

• If you had unobtanium batteries which can serve a dual purpose as both energy storage and armor plating it could be possible. It would require very specific properties for the materials used, so it's probably not feasible though. – WalyKu Oct 5 '16 at 9:13
• Even if you had tankshell resistant batteries it would increase the volume of the tank significantly making it a bigger target – sdrawkcabdear Oct 5 '16 at 17:09
• An MBT like Abrams has nearly 2 tons of fuel - to replace that (keeping the range) means that you need 100 tons of batteries, which is simply not possible on a 60 ton vehicle. – Peteris Oct 5 '16 at 17:13
• Yes, it's only possible with unobtanium as of now. The volume of unobtanium batteries is whatever the author decides it should be. So we aren't bound by definiton when using these non-existent materials. – WalyKu Oct 5 '16 at 17:17

One thing that's not been considered here is that a large main battle tank might become just as irrelevant on the future battlefield as a cavalry charge* in 1939.

When its possible for the adversary to employ huge swarms of drones both in the air and land a tank might just be a slow lulling deathtrap.

Creating armour capable of stopping a rail gun projectile moving at 2km/s is also much bigger technological hurdle than scaling up an electrical motor and battery technology.

We already have electrical powered unmanned flying aircraft and ground vehicles that have been used in combat.

• * The polish cavalry thing is largely a myth. – papirtiger Oct 4 '16 at 19:55
• Though the first battle of the Afgan War (Mazar-i-Sharif) began with a cavalry charge. – jamesqf Oct 5 '16 at 4:13
• Actually several types of swarmed antitank weapons have existed for quite awhile and are highly effective on tanks with engines. OP's proposal for an electric tank would defeat this weapon because there'd be no engine heat signature to lock onto. abcnews.go.com/Technology/story?id=97677 – Harper - Reinstate Monica Oct 6 '16 at 3:24
• The future in fighting vehicles is active defense, not armor. Swarm weapons are highly susceptible to lightweight counter-measures. They'll be zapped by DEW or some computerized shotgun. – TechZen Oct 6 '16 at 19:20
• @Harper: You must have misunderstood something, you will always have the heat signature, much higher than background if you have enough energy in any form concentrated in the volume of a tank. – TechZen Oct 6 '16 at 19:21

Since electric motors produce much more torque than internal combustion ones for the same size occupy less space, have less weight, easier to maintain, less complicated + lost of other advantages, tanks will surely be 0 emission in the future.

It's just a question of when a fast rechargeable battery will be produced. Electricity is available anywhere you have a socket. Diesel or gasoline you can only find at pump stations/your own army supply.

Otherwise, "All is fair in war and love", so 0 emissions will never be a priority for the army, it will only be a question of electric tanks being straight upgrades compared to internal combustion ones.

P.S. Tesla P100D is the quickest production car in the world, 0-62 in 2,5 seconds, so electric cars have already beaten the internal combustion ones in terms of power, space, weight, maintenance etc.

The only problem is the slow charging/poor energy density batteries.

• There are sockets in the battlefield? – JDługosz Oct 10 '16 at 12:26
• Well, if you conquer any village or even a house anywhere, it's bound to have electricity. It's not guaranteed to have a gas station. – DariusDare Oct 10 '16 at 14:40
• When it come to tanks I picture Rommel in the desert. – JDługosz Oct 10 '16 at 17:52
• Somewhere within the same lines: The GCV is propelled by an Hybrid Electric Drive (HED) developed by the partnership. It puts out 1,100 kW of electricity, has fewer components, and lower volume and weight than current power plants. Being an electric drive, it generates high torque at start, smoother low-speed operation and can run silently – an advantage in night operations. newatlas.com/bae-gcv-hybrid-tank/25113 – DariusDare Jun 23 '17 at 8:27
• The destruction of infrastructure during wartime suggests that there will be no working electrical outlets in a village or town under battlefield conditions. – Thucydides Mar 29 '18 at 15:27

Availability of fuel

Tank motors are not normal diesel engines, but multifuel engines; modified diesels or gas turbines which can use nearly anything combustible (oil, ethanol, gas, diesel, petroleum) and even in bad quality. This allows tanks to use already existing infrastructure for refuelling and makes logistics much easier if you do not depend on a single fuel with good quality.

This also raises the question: How exactly electric energy should be transported for refuelling tanks ?

sdrawkcabdear's answer put out nicely how shoddingly bad lithium batteries are in comparison of energy density against fuels (Unfortunately people are still unaware how bad it is because the Tesla hype). High voltage transmission lines are easily disrupted (even without the intention of pulling them out) and you need a non-movable distribution substation to convert them into anything usable and they can be easily destroyed or sabotaged.

The only thing already mentioned in the other answer are fuel cells; if they finally made a breakthrough invention like LEDs which allows us to convert fuel reliably, they will in fact replace emission engines.

Their advantage is that they do not need gears, an electrical engine is much more simple and robust and they are much, much harder to detect (Emission engines have strong infrared signatures, emit carbon dioxide and are loud; tank engines are even detectable after a cooling period of hours). Electrical engines and fuel cells have also a much better efficiency, comparably something in the 70% range while emission engines have only 30%.

So if your sci-fi story has this breakthrough, electric tank are very persuasive.

Actually the army does care about the environment. Yes, they are "green". But even more, tactically, emissions give you away!

Visible smoke has been a huge deal for centuries. The navy able to distribute clean-burning coal to its outposts got to sneak up on the other guys.

Engines are dreadfully inefficient. The waste heat makes a huge heat signature for weapons to lock on. The futurists talk about swarmed weapons, but for decades there have been cluster bombs which will make short work of a tank division because each bomblet seeks out a tank's engine compartment. They only work on tanks with engines. They can't tell an electric tank from a pile of pipe (or a decoy tank). Identifying tanks visually (especially from decoys) is a much harder problem.

Engines and turbines make a lot of noise. Whereas an electric drive is spooky quiet! That would allow them to "sneak" in ways currently infeasible.

So yes, an electric tank is definitely a potential winner. Just beware the blunder of comparing an automobile's peak horsepower with an industrial engine's continuous horsepower.

Recharge is easier than it sounds. You just need a small diesel APU (or hey, three of them for resiliency) such as the units made by Thermo King. This engine will be efficient and durable since it is optimized for one continuous load. A small fuel tank could be kept onboard, with larger fuel tanks mounted outside or in a trailer. The trailer could be dropped in combat. I'm not even sure I would bother with plug-in recharging, since that would motivate the enemy to destroy electricity infrastructure, which would hurt civilians.

Solar panels which unfold and cover the tank would be awesome. The extra battery charging; masking heat emissions from APUs; and making decoys very effective. (the decoy could be a plain truck with the exact same solar array, charging itself and the tank too.)

Tanks are not that fast, and they spend a lot of time idling while the combat engineers clear obstacles. A 200-mile tank charge would be one long, slow, miserable day.

Armies have long had a problem with the tanks outrunning the support infrastructure. Several times in the North Africa campaign, tanks had to suspend a very successful advance, or allow the enemy to escape, because the fuel bowsers couldn't keep up. The efficiency of an electric drive would really help.

• And while idling they don't spend that much power where as diesel tanks spends fuel just being turned on – Magic-Mouse Oct 6 '16 at 13:33

Forget Batteries

If the world has got to the stage where armored warfare is conducted using electrically powered vehicles, I'm assuming someone cracked the wireless power issue. That's right, no more having to refuel! Buy the newest M1E Abrams MBT with satellite power link!

The technology has already been demonstrated, powering a light bulb through, afair, 1ft lead. Combine it with solar collector satellites, LFTR reactors or what ever other energy source you can come up with and you've got a battle force that just keeps running.

This is actually something in development, and something I keep getting excited for, only, it's taking a while to become a commercial possibility.

• Got a name for those: Wardenclyffe tanks. – Michael Schumacher Oct 6 '16 at 21:12
• However if someone takes out your satellite networks you are toast. – Efialtes Sep 17 at 12:21

One of the primary objectives in designing military hardware is ruggedness. You don't want to your military hardware to break easily, compare military grade radios with your smartphone. Apart from tolerating harsh physical conditions, military hardware also needs to deal with a huge range on operating conditions. If your smartphone is designed to be paired with a 5 V battery, it might not tolerate a 9 V one.

Tanks often use multifuel engines, which can run ony virtually anything. This really comes in handy if you manage to come across fuel sources, be it a civilian gas station, an enemy jet fuel dump or some trucks transporting diesel fuel. Whatever you find, fill up and carry on.

With battery based tanks you impede you armored forces, unless the economy as a whole has moved away from oil-based fuel (for trains, ships, airfraft, ...).

In a post-oil society, there might still be fuel around that is chemically stored energy, e.g. compressed hydrogen gas or other forms of hydrogen storage for use in fuels cells. So even in a post-oil scenario batteries might not be your first choice.

I also would split your question into two parts, or two questions, since the issue of electric mobility is independent of electric weaponry. If global oil production stops, you might need a different source of energy to move your Abrams around, but why replace chemical explosives? There might be reasons, but mobility and weaponry are independent from each other.

A Tesla with a gun, or rocket launcher is still a zero-emission vehicle. As others pointed out, waging war is never zero-emission. Thus, I wouldn't bother to make the weaponry zero-emission. If you set a chemical plant on fire with a laser weapon or conventional bombs, the total amount of pollution dwarfs the pollution from the weapons themselves.

## What will warfare look like if we can't use petroleum/fossil fuels to power our (military) vehicles?

I'll rephrase the question such, to narrow down the answer, hopefully keeping to the intent of your question. It leads to a question of why, which I won't address here.

It will depend greatly on the timeframe of the transition. When, but more importantly how long. The shorter the transition time, the less radical the changes will be.

In the shortest timeframes, you have to use the engines already in place, so one will simply have to use/invent fuels that can be used in place of diesel/gas in the same engines. I believe we have ways to do this already, but it is not economically viable to do so compared to pumping oil. Already at this point we could achieve carbon-neutral.

In longer timeframes, we can start to replace engines. This opens for other forms of liquid fuel like ethanol, but most logistical systems (transport and delivery in particular) will be unaffected.

If we have at least several decades, lots of money to spend on this "modernization", and the prerequisite technologies exist already, we can start moving the bulk of active deployed forces onto other paradigms. The consensus of the answers here is the techs do not exist in the case of electric, and that there are several pieces currently missing. Between that research and several decades to deploy, we're unlikely to see a wholly electric military in our lifetimes, if ever.

There's another factor that didn't get mentioned:

Fuel is a lot more available than electricity in a war environment. You very well might capture fuel stocks (and the M1 can run on quite a variety of different fuels) but capturing an operating source of electric power is rare.

Depends where you're fighting. The original tank concept was designed during world war one as a way to counteract trenches. The modern tank to a large extent was designed around conventional warfare of the sort that was projected towards the end of the cold war.

That said, most modern wars seem to be fought in urban or post urban areas. Rather than an electric Abrams, a different sort of armoured vehicle might make sense.

Lets start with the issues of a electrical tank - You would have limited range, need to spend time recharging it (and that electricity needs fuel anyway) and the energy density of batteries is a bit naff. The tesla S has a range of say 500km. Assuming the same range, you're basically limited to staging areas roughly 250km or less.

Modern Lithium Batteries are also gloriously inflammable. Its actually pretty hard to set diesel or even petrol alight.

Tanks are also much bigger vehicles, with a less efficient drive system (even if treads have their own advantages),

That said, we have modern fighting vehicles that run off electricity anyway - submarines. And many of them use a combination of fossil fuels and batteries. A hybrid tank might have the option of using batteries, topping them off with periodically run, smaller engines, and use electrical motors for a simplified drive train.

That said, the modern MBT isn't really the best sort of vehicle for urban combat. They might make good command vehicles but many modern armed forces are moving off it.

Now a swarm of technical type vehicles, completely noiseless until they start firing... that would be scary.

So what if we had a tank with a ten wheel tracked with all-wheel drive and each wheel had a permanent magnet electric motor on each wheel which is somewhat quiet and super duper rugged. Each of these wheels would have an alternator on them allowing the tank the chance to recharge itself on the move. Including the motors to power the turret and gun traverse. Also you could mount thin nanoscale pieszoelectric generators all over the hull, they would basically be like thin films that convert ultra and and ambient sonic frequencies into electricity allowing it to recharge itself from the noisy battlefield environment. It also could have every lense or viewport be a trnsparent solar panel allowing you to generate more electricity, so even if you had crappy batteries you could last longer without needing toswap batteries or recharge...

• And what challenges are there in creating such a tank? – Mithrandir24601 Jan 19 '18 at 21:15
• most likely in configuring the tank to accept all of these changes. – Efialtes Mar 29 '18 at 12:37

My previous answer was not good enough, I did not give enough thought to it...

To create an electirc tank, we can't just use an old platform we have to start from the ground.

http://iopscience.iop.org/article/10.1088/1361-6528/aa8948 If you read the link's abstract you can see that graphene supercapacitors might be the energy storage device you need. They have really high density and can be made paper thin.