141–150 of 399 posts
This seems like an interesting solution to the "what to do if my battery runs out in the middle of nowhere" problem. Normally, you'd either have to have to call a tow truck or have someone with a generator come along and recharge. However, towing for awhile (probably at much less than 70 mph for safety reasons) to recharge the battery enough to get to the next town is something that could presumably be done by just a…
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Show HN: lapetitejort goes hiking, discovers perpetual motion
+3 miles hopefully didn’t include the energy spent going up, or the law of energy conservation would have been broken.
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Teslas will switch to friction brakes when regeneration limits (peak current or battery SOC) are exceeded. I’ve sustained constant 50kw regen while downhill through Appalachia passes, no issues, with the caveat that regen current is limited if the pack is cold until it approaches operating temperature (yellow dashed lines on the regen current display indicate your reduced regen capability).
Does this mean that when the battery is full you must use the brake pedal? Or does the software automatically apply the friction brakes when you back off the accelerator?
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Show HN: lapetitejort goes hiking, discovers perpetual motion
+3 miles hopefully didn’t include the energy spent going up, or the law of energy conservation would have been broken.
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Show HN: lapetitejort goes hiking, discovers perpetual motion
That would be a neat test. Find a steep hill, preferably as straight as possible, and test how many times an electric car can traverse it before running out of batteries. Would the distance traveled exceed that on a flat road with no generation? By how much? I'm sure someone in San Fran has already tested this.
It’s actually very interesting to me that while driving that car, I developed a sort of feel for how trading potential and kinetic energy affected my available range, and I had an imaginary boundary drawn in my head that defined all the places where I’d be able to make it home “for free” that was kind of like a topo map. In particular, if I managed to crest the hill where Canlis sits on highway 99, I knew that despite all the ups and downs in between me and home, I’d be able to make it there without having to fire up the gas engine. :D
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The heavy iron ore is essentially a large battery storing gravitational energy. In a way it's just another natural energy source. Maybe in the future clean power can be generated from pulling down mountains.
Apparently there is already the concept of rail train batteries: https://www.vox.com/2016/4/28/11524958/energy-storage-rail You run the trains up the hill when energy is cheap or, for example, when the sun is out and solar works. Then when you need it, you run the trains down hill to generate electricity. Similar to pumped hydro where they do the same by pumping water up hill and then draining it downhill later. Supe…
Suppose you wanted to run a normal electric train up a mountain. It would certainly take a decent amount of power but not so much that it would be a big challenge for a city-scale power grid. So far you're not yet talking the scale of power where storing it would really be interesting to a grid.
One option to store more power would be to make the train much, much heavier. Sounds simple enough -- fill all of the cars with concrete and now hauling it up the mountain will store a lot more power. However now the rails and the trains themselves will need to be far sturdier than a normal railway, and will wear out quickly.
The other option will be to simply scale up -- start the day with a hundred trains in a rail yard at the bottom of the mountain and over the course of a day move them all to a rail yard at the top. Now you have successfully stored a decent amount of juice.
But hold on a minute... you've now built two large rail yards, meaning you'll need a lot of relatively flat real estate at both altitudes. How about instead you just dig a hole on each side, called it a reservoir, and put a pipe between the two? Certainly it must be a lot easier to store and move mass in the form of water than it is in the form of trains!
That is why I don't see much potential in rail-based storage: if you have the geography to build one at-scale, probably you could build pumped hydro there cheaper. Even if you were in a water-scarce area where you would need to enclose both reservoirs to avoid evaporation loss it still sounds simpler to me than building and maintaining a hundred heavy trains would be. Also, routing a pipe between two reservoirs is a lot more flexible than building a railway.
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Maybe this could be applied to water towers? That's a lot of potential energy just sitting there.
Water towers are already used that way- water is pumped in during off-peak time and used during peak time.
They would clearly have been better off putting a diesel generator on a trailer behind the tesla, for fuel efficiency. 4 gal in 20 minutes the video said? That's about a 160kW generator https://www.hardydiesel.com/resources/diesel-generator-fuel-... I wonder how diesel generator + tesla compares to an actual diesel car.
I've sometimes wondered if it would be viable to build a "range extender" for electric cars which is basically a generator which is designed to integrate with the vehicle, but can be easily removed. Then people could fit them when they were going on longer trips converting the car to a plug-in serial hybrid. Car dealerships could perhaps rent them out and do the install/removal.
https://www.autobytel.com/car-ownership/technology/what-is-t...
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+3 miles hopefully didn’t include the energy spent going up, or the law of energy conservation would have been broken.
I imagine there might also be an effect in play, in which the available miles are calculated using the energy used in the past x miles. Although it should usually take a fairly long distance to change that approximation... I think. Maybe something about using negative energy though regenerative braking skews the approximation.
New EV users often forget that unlike 'gallons of gasoline' or 'kWh', 'estimated miles of travel' are not a true unit of energy.
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Hah, don't try it in Europe either, max towing speed in Europe is 40km/h or 25mph. I guess a tow truck with a bed that has a rolling road would be an idea, prop up the car so the weight of the car isn't actually exerting force that makes the wheels harder to turn/cause extra wear. Or the "rolling road" can be replaced be a contraption that attaches to the wheels by e.g. its rims, and spins it.
Plus in Europe it's forbidden to tow with a rope like he does. You must use a rigid link, like a bar or a tube.
But like speeding as long as you show decent discretion when doing it you'll be fine.