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Post like these always make me go into the rabbit hole of how energy dense gasoline is. The energy density of gasoline is higher than liquid hydrogen! It does
by mattfrommars 3y ago
Post like these always make me go into the rabbit hole of how energy dense gasoline is.
The energy density of gasoline is higher than liquid hydrogen! It does not need to be super cooled and is liquid state at atmospheric pressure and ambient temperature.
Gasoline is an absolute miracle fuel. Sort of feels under appreciated to casually pump it at the gas station ha.
- boromi 3y agoYes per volume gasoline is impressive. You would need a tank 4 times the size of a gasoline tank for liquid hydrogen, not to mention the high pressure tank that is needed to store the liquid hydrogen .
- BHSPitMonkey 3y agoDo those comparisons take into account their respective engine technologies and how much useful work they are able to extract from each fuel in practice?
- dzhiurgis 3y agoHow come fuel cell cars have tanks holding like 10kg of liquid hydrogen?
- salty_biscuits 3y agoBecause fuel cells are very efficient at turning fuel to electricity, especially compared to an ICE.
- TylerE 3y agoThat's not ICE.
- anonymouskimmer 3y agoNitpick: It's typically compressed hydrogen for cars.
- imtringued 3y agoBecause hydrogen is the energy densest fuel by mass, but not by volume.
- AYBABTME 3y agoEnergy density of diesel is higher but it emits more crap. Renewably producible combustibles like methane would be a cool alternative.
- kijin 3y agoEthanol fits your bill perfectly. It is liquid like gasoline, easy to produce, easy to transport, and burns cleanly. It doesn't release any carbon into the atmosphere that wasn't already there, assuming you got it by fermenting plant matter and used renewable energy for distillation. Only problem with ethanol is that it directly competes with human food production.
- coderenegade 3y agoMethanol also works, and doesn't compete with food production. You can make ethanol catalytically if you want, but you have to make methanol first.
- xedrac 3y agoAnd it gums up your engine more than gasoline does. Although this problem can be mitigated somewhat.
- hcarvalhoalves 3y agoIt's the opposite – it's gasoline that causes carbon deposits on the engine, and ethanol acts as a detergent.
- hcarvalhoalves 3y agoEthanol has some issues: - If large areas are deforested for sugar cane plantation, not only CO2 is released but the capacity of fixing future CO2 as well. - Large scale sugar cane plantations demand synthetic fertilisers, which come from fossil fuels. - Ethanol burning still produces toxic gases like NOX.
- AYBABTME 3y agoCan you make ethanol from thin air, such as with the Sabatier reaction? I like the fact that you can take electrical energy input, atmosphere, and get methane. This means I could convert excess solar into a mass and volume dense combustible, and then retrieve some of the store energy back later. Personally I'm principally nerding out about energy storage for sailing cruising yachts. But I have by no means done an exhaustive search of the space.
- Retric 3y agoEnergy density of gasoline is deceptive because of how inefficient ICE engines are in practice. A Prius getting 50mpg is only the equivalent of 1.5 miles per kWh when many EV’s get ~4 miles per kWh. Where gas really shines is ultra cold temperatures where you can make use of the waste heat. But even here it’s still not very efficient.
- coderenegade 3y agoDo the EV measurements take into account the energy used to thermoregulate the battery during charging? They should, because there are conditions under which the battery won't charge at all, in which case the efficiency goes to zero.
- mort96 3y agoI can't imagine there's a lot of extra energy going to heat up the battery while charging? I'd guess the waste heat does the job everywhere except the very coldest climates.
- Rebelgecko 3y agoIt can be an issue if you're charging at like 6amps and it's way below freezing
- imtringued 3y agoThat doesn't result in zero energy efficiency. The energy efficiency is only zero when the heating is insufficient and then it is not the energy that you are putting into he battery that is the problem but the energy needed to keep it warm.
- coderenegade 3y agoThe energy required for charging is the energy input required to fill the battery, plus whatever additional energy is needed to condition the battery. If 50% of the energy you use for charging (which you pay for) goes towards conditioning the battery, then then the energy efficiency of the vehicle is 50% times whatever efficiency you get through the drivetrain. When it gets cold enough, all of the energy draw goes towards conditioning the battery, so the car doesn't charge at all. Since none of the input energy goes towards moving the vehicle, the efficiency is zero, though if you wait long enough it'll take a low value as the temperature increases and the vehicle begins to take charge. It's probably more correct to say that the energy efficiency of the vehicle approaches zero as the temperature drops. This is different to a standard car, because losses during refueling are negligible, but losses in the drivetrain obviously aren't. And of course for both types of vehicle you have additional upstream effects, e.g. production and transportation of fuel versus production of electricity, production of the vehicle, etc. The reason I raised the issue is because I hear a lot about well-to-wheels efficiency of BEVs, but I've never heard anyone take into account the effect that conditioning the battery has in certain climates. It's one thing to say that the well-to-wheels efficiency of a BEV is around 60% compared to 16% for ICEVs, but if you're neglecting a large multiplicative efficiency hit in your chain, things like hybrid electric vehicles suddenly compare a lot more favorably. And if you're comparing mileage on the basis of miles per gallon using energy input at a pump or cable that you paid for, it seems like a reasonable question to ask. Is that mpg figure calculated using the energy of the battery, or the energy that was paid for?
- yazaddaruvala 3y agoOne thing to keep in mind is that the energy density of gasoline is a chemistry measurement. The energy density of a gasoline power train is a different measurement taking into account chemistry and physics. Specifically car engines can only turn 33% of gasoline’s stored energy into motion. Which still puts gasoline ahead in terms of efficiency relative to hydrogen or battery powertrains but reduces the difference a lot.
- agumonkey 3y agoI remember people saying that hybrid vehicle used ICE not to generate car scale torque, thus being build differently to improve the efficiency (mostly due to better control of thermal constraints ensuring better chemical reaction, higher conversion and less pollution). Do you know how true that is ?
- schiffern 3y agoThey might be referring to the Atkinson cycle engine, which is really just adjusting the valve timing. Lower power but higher efficiency. https://www.autoweek.com/news/green-cars/a1832081/atkinson-cycle-explained/ https://www.autoweek.com/news/green-cars/a1832081/atkinson-c...
- etrautmann 3y agoNo, it means that you can leverage a more efficient part of an engine’s torque curve by supplementing with electric power at the low and high end (since motors have a flatter torque curve).
- sharpneli 3y agoNot just that. It does require Atkinson cycle to reach the efficiencies they have. It just means that the compression stroke is shorter than the power stroke. Basically with that cycle they can get massive compression ratios. As an example newer Toyotas are at 14:1 ratio with 41% thermal efficiency. That’s close to diesel territory on a gasoline car. Naturally when you floor it it goes to Otto cycle and efficiency drops.
- seanmcdirmid 3y agoOil leads to geopolitical destabilization since where it is found just happens to be a very volatile region. Even if the Americans somehow detached from the world market for oil (considering they have enough their own), the Chinese definitely aren't willing to forgo energy security by stopping their much more aggressive EV development programs. Gasoline got us this far for a hundred years, now we can pursue a different path?
- nwellnhof 3y agoI'd argue that these regions only became politically volatile because oil was found there.
- namaria 3y agoThan we can rephrase original claim to: "oil leads to geopolitical instability because it's only found in economically viable deposits in very specific areas of the planet." This create strong asymmetries and strong incentives to project power.
- some_random 3y agoIt's not though, not in terms of oil production or reserves. Extractable resources can exacerbate instability by providing funding to warring groups and giving a reason for outside entities to interfere but none of this is even remotely set in stone. https://en.wikipedia.org/wiki/List_of_countries_by_proven_oil_reserves https://en.wikipedia.org/wiki/List_of_countries_by_proven_oi...
- zilti 3y agoYes, I mean, just look at Norway! Or the USA! Or Saudi Arabia! All constantly on the brink of political collapse!
- brohee 3y agoSaudi Arabia had to crank up the execution rate quite a bit to keep opposition in check recently. That only can work so long. "Owning the wrong books, posting a critical tweet, speaking to a journalist or disagreeing with the Crown Prince can earn you a death sentence." (https://reprieve.org/uk/2024/01/02/saudi-arabia-executed-at-least-172-people-in-2023/ https://reprieve.org/uk/2024/01/02/saudi-arabia-executed-at-...)
- thelastgallon 3y ago> Gasoline is an absolute miracle fuel. Yes, it is a 'miracle' fuel, if you ignore these factors: (a) Global oil, gas, and coal supply chains. The resulting complex network has 6.09mn nodes and 15.70mn edges: https://github.com/Lkruitwagen/global-fossil-fuel-supply-chain https://github.com/Lkruitwagen/global-fossil-fuel-supply-cha.... And the defense budgets of all the countries protecting these assets and supply lines. (b) Trillions of dollars in subsidies every year: https://www.bloomberg.com/opinion/articles/2023-10-16/climate-change-why-are-governments-still-subsidizing-fossil-fuels https://www.bloomberg.com/opinion/articles/2023-10-16/climat... (c) 10 million air pollution deaths/year: https://www.nytimes.com/2022/07/08/opinion/environment/air-pollution-deaths-climate-change.html https://www.nytimes.com/2022/07/08/opinion/environment/air-p...
- p1mrx 3y ago> (c) 10 million air pollution deaths/year That's a drop in the bucket compared to the plausible future deaths from climate change. Burning gasoline moves carbon from the ground into the air, and we basically have no idea how to undo that operation at an appropriate scale.
- 4hg4ufxhy 3y agoIf we ran out of oil today billions would die.
- jauntywundrkind 3y agoEnergy density of gasoline by weight is >3x worse. We just haven't been good about putting that to use. RIP VentureStar. Personally I'm just tired of this discussion around energy density being brought up every time transportation is mentioned. These conversations almost never surface interesting new points.
- osigurdson 3y agoGasoline may have been a miracle fuel but once affordable EVs have 1000km range with fast charge times we won't use it anymore.
- chii 3y ago> once affordable EVs have 1000km range with fast charge times we won't use it anymore and how long will that take to eventuate tho?
- ben_w 3y agoExtrapolating the current rate of change, early 2030s.
- osigurdson 3y agoThey also have to be price competitive. I'm convinced they will be much cheaper than ICE cars eventually. Engines, transmissions, etc. are very complicated things. We've just gotten incredibly good at making them.
- ben_w 3y ago> They also have to be price competitive. Yes, that's why I said early to mid 2030s: extrapolating current trends, that's when a 200kWh battery will cost $US 10k-15k.
- pmarreck 3y agoYou are right. And honestly, if someone came up with a way to "perfectly" burn it, we wouldn't have this problem. The biggest thing about EV cars IMHO though is the responsiveness. There's no way a gas engine will ever keep up with that.
- audunw 3y agoThere are so many aspects of modern EVs that gas engine cars have no way of keeping up with. Like, 220V AC outlets are becoming pretty standard on newer EVs. In you can pre-heat or pre-cool the car no matter where it's parked. It's possible and now common to build EVs with a skateboard-like architecture which gives way more interior space than a gasoline car ever could. You can build cars with 2, 3 or even 4 motors, with super fast torque vectoring. It's feasible to have steering on the rear wheels. And we're not even done with the innovations. Look at Hyundai's recently announced Uni Wheel design which frees up even more interior space.
- vjk800 3y agoIndeed. For all the shit fossil fuels (rightfully) get, they are pretty damn good for storing energy. When you look into this, it really isn't a wonder that it's so difficult to transition away from them.
- jnsaff2 3y agoEnergy density of liquid hydrogen is about 4x more than gasoline. https://en.m.wikipedia.org/wiki/Energy_density https://en.m.wikipedia.org/wiki/Energy_density
- audunw 3y agoI'm guessing the parent post means volumetric energy density, and you're referring to gravimetric energy density. It's frankly inexcusable to not be specific when you're citing an article where both figures are clearly visible. You must have seen it, and consciously chosen to ignore it, causing unnecessary confusion.
- mpweiher 3y agoIf you think the energy density of gasoline is miraculous, and it is, you should try uranium. Its energy density is a million times higher. https://xkcd.com/1162/ https://xkcd.com/1162/
- textbookrental 3y agoIt seems like battery technology hasn't improved much since the model s was introduced. A 2012 Toyota Camry was rated around 28 mpg combined. A 2025 is rated at 46 mpg combined. That's a 60 percent improvement. I don't think the model s has seen anywhere near a 60 percent improvement in range or efficiency during the same time span.
- jackmott42 3y agoDon't forget that you can only extract about 30-35% of that energy via combustion, though. Whereas a battery with an electric motor you get more like 90% Another knock against gasoline is that you spend about 1 EV battery pack of energy to refine a cars tank of gasoline from crude oil in the first place.