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Comment: Re:Can't say I'm surprised (Score 1) 47

by wagnerrp (#48602373) Attached to: Sir Richard Branson Quietly Shelves Virgin Submarine Plan

Branson has a track record of seriously underestimating the difficulty of the challenges he picks. Plus he seems to believe he can replicate serious engineering achievements - eg space flight - on a shoestring budget.

You're overestimating the capability of SpaceShipOne/Two. It goes to space for all of a couple minutes. It does not go to orbit. The engineering requirements aren't nearly as tough. We've been sending unmanned vehicles up there since the early 40's, and manned ones up since the late 50's, back when NASA was still called NACA.

Comment: Re:Oh Carbon (Score 1) 80

by wagnerrp (#48559751) Attached to: High Temperature Superconductivity Record Smashed By Sulfur Hydride

There's even a type of energy storage system you can make with superconductors - one of the highest power density and efficiency energy storage methods known to man.

The ultimate capacity of one of these systems is on the par with supercapacitors, and an order of magnitude lower than traditional chemical batteries. Their high power, low capacity, and functionally unlimited cycle life make them useful as a transient power filter, rather than a meaningful energy storage mechanism. Their sudden and nearly instantaneous quench makes them downright frightening as a sizable energy storage mechanism.

Comment: Re:Use the money you save (Score 1) 488

by wagnerrp (#48408801) Attached to: Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

Like I use energy to lift a stone, and I get 100% of that energy back if the stone drops.

No body is fully elastic. You will have infinitesimally small energy losses due to changing internal stresses in the two bodies. You get very very close to 100% recovery, but not 100% recovery. The energy is still there. It hasn't escaped your hypothetical closed system. It is simply not recoverable in a useful form. It is disordered. Reversible processes are those "special cases".

Comment: Re: so why specifically target drivers? (Score 1) 554

by wagnerrp (#48392855) Attached to: The Downside to Low Gas Prices
Those numbers already take into account the difference in traffic volume. An individual loaded tractor trailer causes several thousand times the damage as a single sedan. In other words, there would have to be 80x the volume of passenger traffic on the road to cause the same amount of damage as present truck traffic.

Comment: Re: so why specifically target drivers? (Score 2) 554

by wagnerrp (#48392829) Attached to: The Downside to Low Gas Prices

Doesn't matter much, it's the same people that drive their cars that also buy supplies that require trucking.

So what? You're artificially buoying up industries that perhaps shouldn't be. Nearly all of our shipping is done over the road, due to cost and convenience. Make roadway shipping pay to repair its fair share of damage done to the roadway. Initially, shipping costs will rise. Costs for all products would rise across the board as those increased operating costs trickle down to consumers. Over time, those companies will find new ways to reduce costs. Money would be pumped into the rail system, expanding and modernizing it to improve speed and throughput. Manufacturing would become more regionally diverse so less has to be shipped across the country. Fewer vehicles on the road means lower traffic congestion. Less roadway maintenance further means lower traffic congestion. Locomotives are more efficient per unit of shipped material are more easily managed in terms of emissions. Fixed, limited access railways can be more easily converted to electric.

The trucking industry would suffer, unquestionably, but it's a much more complicated issue than you give it credit for, and perhaps the advantages in other areas outweigh those effects.

Comment: Re:Use the money you save (Score 1) 488

by wagnerrp (#48375999) Attached to: Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

Electrolysis has nothing to do with thermodynamics

By that, you actually mean everything has to do with thermodynamics. You're adding energy to disassociate a molecule. Thermodynamics dictates that you cannot recover that same amount of energy by letting the constituent elements recombine. Tyr07's uncertain belief coincides with one of the fundamental principles at play in any real world system.

Fuel cell efficiency varies greatly, it goes up to 85% for current marketed high temperature hydrogen fuel cells.

No it doesn't. The only way you could hope to achieve anywhere near that is through some combined cycle process that scavenges waste heat from the fuel cell. You might find some experimental units pushing 70%, but anything commercially available is going to be under 60%.

Total cycle efficiency is going to be under 25%. That is complete nonsense, you must be bad in math.

Assuming realistic values for electrolysis and fuel cells, you're already well under 40%. Depending on your compression ratio, you're only likely to recover 50-60% of the energy spent compressing the hydrogen for storage, so that's either higher losses, or higher capital costs for storage volume. Tack on a couple percent for leakage, and 25% is very reasonable.

Comment: Re:Use the money you save (Score 1) 488

by wagnerrp (#48367489) Attached to: Denmark Faces a Tricky Transition To 100 Percent Renewable Energy

conversion ratio wise I believe it takes more power to produce the hydrogen than it returns so there is a loss

Yes. Electrolysis does not violate the laws of thermodynamics. What I assume you were getting at, electrolysis usually runs around 50-60% efficiency and fuel cells range from 30-70% depending on the chemistry, and in practice since you have to store it, you also have to factor in compression losses, hydrogen leakage, and burners to bring your decompressed gas back up to the operating temperature of your fuel cell. Total cycle efficiency is going to be under 25%.

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