Post #410,723
6/5/16 10:11:01 PM
6/5/16 10:11:01 PM
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I think that's harder than going to the moon.
There are simple calculations that can be done to figure out how much electricity would be needed for a car to go 300 miles. Let's see, let's be aggressive and say it only weighs 2000 pounds. My Jetta needs 20 HP to cruise at 50 MPH, if I recall correctly. It weighs about 4000 pounds (with me). Let's say 10 HP to cruise at 50 MPH for our electric supercar. 1 HP = 745.7 watts Let's be very aggressive and assume no losses, and 1000 V electrical system. So 1 HP at 1000V = 0.75 amps, 10 HP = 7.5 A. 300 mile range at 50 MPH = 6 hours. 6 h x 7.5 A = 45.0 Ah = 2700 A min of battery capacity. Neglecting the falloff in battery voltage with discharge time, so probably even more battery capacity would be required. To charge in 2 minutes we would need to supply 1350 A. That's a boatload of current, even at 1000V. (And this is why electric cars are pushing the technology to higher and higher voltages.) I don't know of any way to overcome those intrinsic limitations. Going to the moon was "easy". Figuring out how to build a large enough rocket. Figuring out how to protect people outside the atmosphere. Figuring out how to do the navigation and docking. It's something that sensible project management with good people can accomplish in a reasonable amount of time. No physical or chemical laws had to be violated. ;-) If fast charging is required, then something like a hydrogen fuel cell would probably make more sense, but it only has about half the required range. Otherwise, I don't see how one gets around the need for ~ 10+ HP for a very long tome, and how that necessitates a very large amount of electrical power in a short charging time. There are lots of potential "moon-shot" projects that would take a decade to make substantial progress. Figuring out cancer. Creating new antibiotics. Creating new batteries with much higher total energy density. Getting started on a national high-speed rail system (let's remember that it took about 35 years to build-out the Interstate Highway system - HSR will probably take at least that long). We know how to attack these problems and make substantial progress. We just need to elect leaders that will make it happen. Like you say, easy peasy! :-( My $0.02. Cheers, Scott.
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Post #410,730
6/6/16 7:34:24 AM
6/6/16 7:34:24 AM
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Replaceable batteries gets you the charge time
And Musk has talked about building exchange stations.
I thought about high speed rail but the issue there isn't technology, it's getting the right-of-way for it.
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Post #410,732
6/6/16 8:50:56 AM
6/6/16 8:50:56 AM
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In the real world, people aren't going to be swapping 1000# of batteries in 2 minutes. ;-)
I can't see it happening. Batteries need to be customized to the car (form factors) and they aren't just going to be a an easily-swappable cube in the trunk. Maybe with new battery materials fast swapping will become an option, but as long as batteries are big and heavy, I can't see it happening.
There are still advancements to be done in HSR - e.g. what Acela tried to do running kinda fast trains on "normal" tracks via fancy suspensions and leaning and so forth; control systems to maximize packing on the tracks while maintaining safety; new track, road bed, power distribution materials to minimize maintenance costs; figuring out the most efficient ways to get people on and off the cars with their luggage, etc., while maintaining security; etc.
They're interesting problems.
Cheers,
Scott.
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Post #410,741
6/6/16 10:47:20 AM
6/6/16 10:47:20 AM
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you need to go to a better place
always look out for number one and don't step in number two
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Post #410,744
6/6/16 11:22:41 AM
6/6/16 11:22:41 AM
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Interesting.
https://en.wikipedia.org/wiki/Better_PlaceBetter Place filed for bankruptcy in Israel in May 2013. The company's financial difficulties were caused by mismanagement, wasteful efforts to establish toeholds and run pilots in too many countries, the high investment required to develop the charging and swapping infrastructure, and a market penetration far lower than originally predicted by Shai Agassi. Less than 1,000 Fluence Z.E. cars were deployed in Israel and around 400 units in Denmark, after spending about US$850 million in private capital. [4][5][6] After two failed post-bankruptcy acquisition attempts,[7][8][9] the bankruptcy receivers sold off the remaining assets in November 2013 to Grngy for only $450,000.[10] It's a tough way to try to make a living. Cheers, Scott.
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Post #410,746
6/6/16 11:24:32 AM
6/6/16 11:24:32 AM
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can be done doesnt mean it will be done
always look out for number one and don't step in number two
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Post #410,756
6/6/16 12:29:54 PM
6/6/16 12:29:54 PM
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So maybe getting battery weight down / energy density up is step 1
And that's a technical problem. That's comparable to putting someone on the moon.
Fighting the current car manufacturers and gas companies is the political problem that you'd have to overcome to even start the project in the US.
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Post #410,758
6/6/16 12:59:42 PM
6/6/16 12:59:42 PM
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It's not clear how much more can be done with current technology.
Making a bigger rocket is "easy". Just keep adding motors if necessary. Look at Soyuz:  Putting more electrical energy in a fixed volume is hard. Foreseeable batteries probably aren't the best solution for transport.  The performances of ECs can be compared in the Ragone chart plotting their respective energy and power densities as illustrated in Fig.2 [above] for different electrical energy storage devices. Due to their physical charge storage, capacitors feature very large power densities compared with batteries and fuel cells but low energy densities. On the other hand, batteries and fuel cells have large energy densities but low power densities due to their slow reaction kinetics. Electrochemical capacitors bridge the gap between capacitors and batteries/fuel cells. They offer the prospect of maintaining the high energy density of batteries without compromising the high power density of capacitors. Our hypothetical 10 HP 300 mile, 6 hour, range car would need 45Ah x 1000V x 6 hours = 270 kWh in energy. At 200 Wh/kg, that's 1350 kg of advanced batteries. Ouch. Maybe some combination of fuel cells for endurance and batteries for quick acceleration is the way to go. Dunno. A paper on R&D considerations: Electrochemical capacitors (especially double-layer capacitors) are intrinsically high power devices of limited energy storage capability and long cycle life; batteries are basically energy storage devices, which can be designed and used as relatively high power devices with a sacrifice in useable energy storage capacity. Both electrochemical capacitors and high power batteries are designed with thin electrodes, materials having nano-scale characteristics, and a minimum resistance. Much of the research on electrochemical capacitors is concerned with increasing their energy density with the minimum sacrifice in power capability and cycle life for deep discharges. Of special interest has been the development of advanced carbons with specific capacitance (F/g) significantly greater than the present values of 150–200 F/g in aqueous electrolytes and 80–120 F/g in organic electrolytes. Cost continues to be a major obstacle to the development of large markets for electrochemical capacitors particularly for vehicle applications. The development of lower cost carbons appropriate for use in electrochemical capacitors is underway by several speciality carbon suppliers. The goal is to reduce the cost of the carbon to $10–15/kg. Ultimately, anything developed for a real market has to be cheap enough. That wasn't a consideration in going to the Moon. ;-) Note that there may be some error in my calculations - don't be betting money on them! Cheers, Scott.
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Post #410,759
6/6/16 1:09:00 PM
6/6/16 1:09:00 PM
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The top end for fuel cells shows 1,000 Wh/kg, that's 1.35 kg
That's a bit under 3 pounds. Manage a third of that and you've got ~10 lb unit that would need to be swapped out. That's self-service light. Half again and you need two units, which would be a better idea anyway.
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Post #410,763
6/6/16 1:26:38 PM
6/6/16 1:28:06 PM
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But like the paper says, fuel cells are slow.
And refilling fuel cells with hydrogen is fast, so they wouldn't need to be swapped out. As I understand it, fuel cells are good for providing lots of energy (Wh) but can't do it quickly (because it works via chemical reactions - atoms moving across membranes and such). So if you want to cruise at 50 mph on flat ground for 6 hours, they're probably great for that. If you want to accelerate from 0-60 in < 10 s, they're probably not at all great for that due to the low power density (energy provided per unit time). Just to see what batteries and fuel cells are up against, see where they are compared to gasoline and diesel fuel below:  Powering trackless transportation affordably a tough problem... Cheers, Scott.
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Post #410,764
6/6/16 1:40:42 PM
6/6/16 1:40:42 PM
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Hybrid is is, then
Take today's gas/electric hybrid and swap out the gasoline engine for a fuel cell.
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Post #410,841
6/7/16 5:28:20 PM
6/7/16 5:28:20 PM
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Bitchin Soyuz pic, also brief energy-density graph..
Rocket "engines" (as shown here analogous to the sizes of organ pipes!)
All they are is: an Infrasound Organ!
(Think: "Asleep in the Deep" on Rocket ... not a mere tuba.)
{{chortle}}
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