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.

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.

Post #410,758 by Another Scott 6/6/16 12:59:42 PM 6/6/16 12:59:42 PM Reply	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.
Post #410,759 by drook 6/6/16 1:09:00 PM 6/6/16 1:09:00 PM Reply	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. -- Drew
Post #410,763 by Another Scott 6/6/16 1:26:38 PM 6/6/16 1:28:06 PM Reply	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. Edited by Another Scott June 6, 2016, 01:28:06 PM EDT Expand All History
Post #410,764 by drook 6/6/16 1:40:42 PM 6/6/16 1:40:42 PM Reply	Hybrid is is, then Take today's gas/electric hybrid and swap out the gasoline engine for a fuel cell. -- Drew
Post #410,841 by Ashton 6/7/16 5:28:20 PM 6/7/16 5:28:20 PM Reply	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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