Li-metal batteries [edit: still an immature tech] are at around 14 MJ / kg, and gasoline is at 47.5 MJ / kg.
Moreover, suppose that you are really "off-grid". Meaning, you are off any fuel supply network!! In this case precisely, you would be saved by electric-related techs, such as photovoltaic.
Do you have a link to back this number? Are these batteries rechargeable? Does the measurement include wiring, cooling, cell connections and overall structure of the battery pack?
For comparison, Tesla's (Li-ion) battery pack energy density is 160 Wh/kg, which is 0.576 MJ/kg:
At that point you need to consider the whole car. The engine needed to extract energy from that fuel is much bigger in the ICE car. And it also needs cooling, etc.
Comparing just the gas tank to several subsystems of a battery electric vehicle is not really an interesting comparison. The closest comparison at that level is just gas vs just cells.
Overall electric is still lower energy density per weight, but is also far more efficient. The whole Tesla pack has the energy of just a couple gallons of gas but can go 400 miles.
I used that, and actually I may have missed the bit where they explain that "lithium metal as an anode were suggested for future high-energy-density batteries", implying that it's still an immature tech.
I have driven through parts of the western US where it is 100 miles to the next gas/petrol station. There are farms and ranches in these areas but they are connected to the electrical grid with wires. It seems like having an electric tractor and charging at the farm would be more convenient than transporting hundreds of gallons of diesel fuel from 100 miles away.
Tractors are bursty. They are heavily used at planting and harvesting. Farmers can't spend long periods of time recharging in the middle of planting season. And it would be too expensive to buy 12 hours of battery capacity for a couple times a year.
Actually, batteries win on refuel time. Swapping batteries is much faster than filling a tank. Gas wins on meantime between refuels and in other categories. Farmers can and happily will spend super long periods of time recharging if they can operate during the recharge.
My own initial experiences have been mixed. Overall advantage still goes to gas. But I think we're very close to getting this battery thing figured out. Just a few years away. When we look back it will seem like it happened overnight.
>>Actually, batteries win on refuel time. Swapping batteries is much faster than filling a tank
By that logic, you could say that there is absolutely no difference, because if you can imagine a car where the battery can be swapped, you should be able to imagine a car where the entire fuel tank is swapped. A tractor arrives at a station, and instead of filling up 500 litres of diesel, the entire tank is simply replaced with a full one. It wins again since fuel tanks are cheap - they are just metal and plastic after all, you can have several just sitting there, full or empty.
The fact that no one has done it yet suggests that this really isn't an issue - commercial diesel filling stations usually run at much higher pressure than your regular pumps, a truck/tractor tank fills in minutes because of a much higher flow rate.
That is very silly and disingenuous argument to make and a total straw man.
Swapping gas tanks provides no advantage and you conveniently ignore the whole point of the batteries which is that you don't need any fuel infrastructure to fill your tanks!
Swapping 2000 lbs+ of batteries is faster than filling tank? When is the last time you hauled thousands of pounds? It ain’t fast, let me tell you that.
Perhaps you've never seen a 1500 lbs steer get its hooves trimmed. Or a 1 ton bail get loaded and unloaded in seconds. Or somebody change the tire on a tractor.
Farmers have machines and equipment for almost everything. Swapping out a flat pack? POC
> Actually, batteries win on refuel time. Swapping batteries is much faster than filling a tank.
Swapping batteries implies either having multiple batteries, which adds to you costs significantly, or it implies adding yet another proprietary service company putting the screws to you in your supply chain.
Tractors use a lot of horsepower constantly. Cars are burst. Put the pedal to the floor on a Tesla and you are up to the speed limit in seconds at which time you back off. Take your Tesla to an infinite straight track and put the pedal to the floor and the battery will be dead in a few minutes. (though probably something else will break first)
A tractor will go through fuel faster than you can imagine if you've never worked with one. Plowing a field or running some powered attachment while you have the creeper gears engaged will cause a nice little vortex in your fuel tank.
It depends. Electric motors also have losses in their controllers, which removes another 5% or 10%. If you want mechanical power output and have 1kg of pre-charged batteries and 1kg of liquid fuel, the efficiency of electric motors might close the density gap. Lets assume 95% efficient controller+motor (slightly optimistic) and 30% efficient ICE (somewhat pessimistic).
1kg * 14 MJ/kg * 95% = 13 MJ mechanical
1kg * 47 MJ/kg * 30% = 14 MJ mechanical
It comes out pretty close!
If you want mechanical power and also heat (for keeping people, animals, or equipment warm, decreasing the viscosity of fluids, etc), ICE is definitely the way to go.
-- edit --
/u/ash points out Tesla's energy density is is 0.576 MJ/kg
One can't really charge a battery with power spikes from randomly hitting the brakes. Only part of the braking energy is recoverable, for example when braking to reduce speed while descending a long slope. Braking strategy should also be different in this case: similar to engine braking in regular vehicles. Since most EVs rarely have a multi speed gearbox, regenerative braking should be built into the brake pedal.
I was using off-grid in the most straightforward of senses - off the electricity grid. That doesn't necessary mean stationary or without weight limits (as solar would require) - it could mean long distance trucking, or logging, construction, or even the maintenance of electricity pylons (which probably can't be turned on during that process).
All those require huge amounts of energy, and batteries are not yet nearly there (as others point out, your numbers for battery energy density are out by a factor of 30).
> Moreover, suppose that you are really "off-grid". Meaning, you are off any fuel supply network!! In this case precisely, you would be saved by electric-related techs, such as photovoltaic.
Albeit in theory true, here in the outskirts of the Sahara, I have yet to find a village where I can get an electrician to fix my solar panels, though a few bottles of gasoline can be found everywhere.
If I run off to start a farm, and I buy an existing OTS used tractor, it will have a tank that I can pour almost any flammable liquid into to make it run. If I want to plug the tractor in... well, that'll get the engine to turn over, but it won't get it moving anywhere.
If I build myself a cabin in the woods, I can burn wood or wood pellets to keep cook food, or keep warm during the winter. Alternatively, I could purchase batteries, PV panels, and the necessary charge control electronics, in order to run an electric heater.
Burning recently-alive biomass does release carbon, but it's carbon that was in the atmosphere as recently as a few months ago. It isn't zero emission, but it doesn't contribute a long-term increase to the amount of carbon in the atmosphere.
Other emissions like particulates can be worse from wood burning. And most of the CO2 is likely to have been collected over a much longer period than a few months. Without a significant tree planting effort it is likely to increase CO2 levels.
A forest is a carbon store. Burning trees puts carbon from this store to the atmosphere.
To count it as carbon neutral is an accounting mistake, that could be very costly...
Burn the dead leaves and you shrink humus (or annihilate it, depending on how much you do it), another huge carbon store. So that makes it yet another accounting mistake.
More generally, it is good practice to separate well atmospheric carbon (CO2) and captive carbone (anything in solid/liquid state). Just show that faithfully in the accounting method, and a lot of good will follow.
Would you then just unnoticingly burn them for energy, and keep telling the customers that you just captured a net amount of carbon?
PS: oh you are jacquesm! :) didn't notice. How are you?
PPS: some critic about the link you sent me ("wood-energy.extension"): I disagree with what they say, in that fallen wood too is a carbon store, and in a forest at equilibrium the amount decomposed by fungi/bacteria is roughly compensated by the newly fallen wood. So that's just a carbon store, and if you begin to burn it you shrink this store.
Hydrogen tops out at 142 MJ / kg. Disappointing that so few here are aware of this basic fact.
It seems obvious that if you want the density of liquid fuels, hydrogen is the answer. Compromising yourself with a lower energy density substance stands as a very difficult problem to solve.
If there was a Nobel Prize for understatement, this comment would take it hands down.
New "breakthroughs" in battery energy density are a dime a dozen. They're proving incredibly difficult to bring to commercial viability, and there's no evidence that that's going to change.
It's not quite that bad. Solar panels that point directly at the sun during the summer solstice will still receive 91% the density of light during the winter solstice. ( cos(24deg) ~= 0.91 ) Where I live (about 40deg north), the winter solstice is 63% as long (9.5 hours) as the summer solstice (15 hours). Even a thick blanket of snow, or 100% cloud cover, will only reduce power by about 50%.
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Under the worst possible conditions (not considering temperature), on the shortest day of the year, with 100% clouds and a thick layer of snow, PV panels would produce 14% as much power per day as on the longest day of the year with 0 cloud cover.
Not at all, except if you mean arctic winter (when it's technically night all the day).
Also, electric offers you the plethora of choices in methods to produce your energy. If it's not photovoltaic, you still have many solutions. Could as well be eolian, or a dam, or hundred of people riding generator-bikes (half-kidding), or etc.
It's funny to think about, but if you do the math even dozens of humans riding bikes contribute so little energy compared to what a building requires it is totally negligible and would never be worth the cost beyond a gimmick.
Li-metal batteries [edit: still an immature tech] are at around 14 MJ / kg, and gasoline is at 47.5 MJ / kg.
Moreover, suppose that you are really "off-grid". Meaning, you are off any fuel supply network!! In this case precisely, you would be saved by electric-related techs, such as photovoltaic.