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Comment by samdung | Hacker News Reader

Battery noob here: Will this achieve the energy density of fossil fuels? In other words, a 50 litre tank of petrol gets me around 500 km. What will a similar volume of these batteries get me?

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Not even close, but that's not so bad. ICEs will probably always have their place but most people can go without, especially in Europe (Americans are very loud about how they need to drive 3000 miles to work everyday so I won't bother arguing that)

You can fit an entire Italian town in the size of a freeway interchange in Houston:

https://www.texasmonthly.com/politics/highway-interchange-ho...

Our cities were designed to be spread out to make them less susceptible to atomic weapons in the 1950's (not a joke).

So... Yes, we need cars. It really is a long way for many of us.

Granted, not to take away from the point of different use cases, however Sienna is a very small medieval-era town that one can walk across at leisure and the Houston interchange is one of the most complex in the US. So it is somewhat of a hyperbolic comparison.

I agree that very common suburban and rural vehicles, respectively, are SUVs and pickup trucks. But I am curious what portion of urban drivers use a vehicle that most of the time far outclasses their average use case. I would like to find data on this but it seems to me like often people own a vehicle for the extreme outlier use case.

Why would you want a vehicle that only covered 95% of your use cases?

It's like condoms - better to have it and not need it than need it and not have it.

It certainly makes sense on a personal level but when one multiplies this thought process by a given population there starts to be a compounded issue of excess material going into the construction of the vehicles, excess fuel being used to move them, and excess parking space used to store them, to name a few.

Redunancy and efficiency are common tradeoffs we are constantly trying to balance. It's only a question of how important the effects of downsides are.

Sometimes someone dies as an immediate result, and for some it means waiting for another 5 minutes.

> Will this achieve the energy density of fossil fuels?

I think non-fossil-derived synthetic fuels have the potential to become a major player in the overall transportation picture.

Liquid fuels have significant energy density advantages. Producing them synthetically should allow for removal of various impurities that cause pollution issues today. And not pulling them out of the ground would get around the non-renewable angle.

To be clear though, I think this situation is different from the big Ethanol push we've had in the Midwest the past 20 years.

Everything I've seen about Ethanol is that it is ridiculously inefficient in terms of inputs vs outputs and basically just exists as a subsidy program for farmers to ensure we have enough food supply to avoid ever having shortages.

But I think synthetic fuel could be a big thing in the coming years, particularly since all automobile infrastructure already centers around easily refillable liquid fuels.

I think a fairer comparison might be to compare weight of IC Engine + fuel tank vs electric motor + battery.

IC and Fossil fuels still win out (particularly if you swap to gas turbine) but the numbers are much closer.

No, current batteries have about 1 percent the energy density of gasoline.

Note that most of the energy in gasoline gets wasted as heat in a car, only a part gets used in winter to heat the cabin. So there's a factor of ~3 that you get back in that comparison. So the more comparable number is more like 3-4%. Still very low of course. The electric motors are also lighter than what creates equivalent power for gasoline so there's another small amount you recover there. ~5% is probably reasonable.

There are additional factors that are application dependent. I'm not sure how much if affects road vehicles, but for aircraft that fact that fuel burns off, making the aircraft lighter as the tanks empty is a huge contributor to total range, so you would need to subtract some factor to account for the fact that batteries have a constant mass.

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