Flywheel energy storage

gadget_lover

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It would appear you have purposefully misquoted me. What I actually wrote is still there for anyone to read. I wrote exergy not energy. They are two completely different things. Please correct your misquotes of my post or take them down.

LOL! No offense intended.

For those who are late to the thread, I had misquoted him as follows: "To propel a vehicle requires a huge amount of energy. It matters little whether the energy comes from gasoline or steam or a flywheel spinning at high rpms."

The spell check on my system flagged exergy as mis spelled, and since we were talking about stored energy, I assumed that it was a typo, so corrected it as a courtesy to others. It's so hard to read when things are mis-spelled. It seems that my error was a good thing to do, since now you can explain the fundamental difference between the sentence "To propel a vehicle requires a huge amount of energy." and "To propel a vehicle requires a huge amount of exergy."

As far as I can tell, the first is perfectly valid, and the second one is too. A quick search turned up the phrase "Exergy is the energy that is available to be used." which leads one to believe that one is a subset of the other. Would you mind explaining why was that an important distinction? I learned about a new word, but I'd be interested to find what makes it useful in this context.

As far as I can tell, the concept of a frangible flywheel is that it will destroy it's container (and possibly anything nearby) rather thoroughly but will contain the damage to a smaller area due to the small pieces. It's akin to the shotgun shell that fires a slug through a rail road tie, yet the equivalent weight in 100 pellets will damage a wider area with far less penetration.

Daniel
 

Sub_Umbra

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Thanks for the response.

I like the term exergy because its more accurate in many uses than the word energy.

In a nutshell, we have no energy crisis, we have an exergy crisis. If one wants energy it is literally everywhere. One can not get away from it. As an example the residual heat from the Big Bang is ~2 D above Absolute Zero...and its everywhere, which is to say there is a lot of it out there. The problem is that we would have a hard time scraping together the technology to reheat a cup of coffee with it because it lacks exergy. Its the same reason why there is so much confusion in the public mind about why its so hard to substitute hydrogen or methane for gasoline as a portable fuel or why we can't just tweak the settings on a refinery designed to process Sweet Brent Crude when we may only purchase crudes bearing less exergy. That's part of why we are losing refining capacity.

Another example would be if you had two round boulders that were identical in mass -- with one perched on the rim of the Grand Canyon and the other sitting on flat land a mile away but exactly the same distance from the center of the Earth. Both boulders have the exact same potential energy as they are of the same mass and and the same distance from the center of the Earth. The difference is that the boulders have different amounts of exergy because the one poised on the rim of the Grand Canyon may easily be pushed over the edge and thus be made to do meaningful work. (Maybe to crush butternuts) :D

I thought the word was appropriate in the post because in general, it takes so much exergy to to power a car. It takes ~ a ton of standard car batteries to store the exergy held in one gallon of gas. Their exergy requirements make all cars, whatever their fuel type, both interesting and challenging from a safety standpoint.

Anyway, I like the word so I tend to use it.

As a side note, I did also note the spell checker flagged exergy in my post and I had to look it up again.

I'm not particularly pleased with the tone of my post where I mentioned the misquote. In my defense I've had a couple of misquoted posts in the last year or so that were very flip and ticked me off to no end. Even though my spell checker flagged the word when I used it it never occurred to me that that you were responding to the spell checker.

Thanks again for the response. It makes perfect sense. I appreciate it.
 
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Steve K

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"exergy".... who knew??

I'll have to use it and impress all of my friends. :) It's always good to learn something new!
 

gadget_lover

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"exergy".... who knew??

That's one of the things I love about the internet. I see new phrases, words and ideas every day.


The description of exergy reminds me of a point my third (or was it forth?) grade teacher made in class. One student was instructed to push against the wall while the other was told to lift a piece of paper. Thus he explained that student #1 was exerting force, and #2 was performing work.


Daniel
 

Steve K

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That's a nice design.... store short bursts of power in the onboard supercaps, and larger, longer power surges can go into the batteries attached to the system's power bus.

The graphic showing how fuel cells, batteries, supercaps, and regular caps all had their place in the world of energy storage was good too.

Going back to the theme of the OP, does this mean that flywheels have faded again? Or are they just waiting for the right application to come along? For systems that are primarily mechanical, I can see value in storing energy in mechanical devices like a flywheel. I vaguely recall someone coming up with a flywheel for bicycles in city traffic, so that energy wasn't thrown away every time the bike had to stop at an intersection.

edit: info on bicycle with flywheel...
http://www.gizmag.com/flywheel-bicycle-regenerative-braking/19532/
Adding a 15 pound flywheel to a 25 pound bike.... probably not a solution for hilly places, but perhaps fine for a flat city.
 
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alpg88

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>>>>> The amount of energy that could be harvested from freight train braking systems using flywheels could be huge,,,
someone should put their thinking cap on for that <<<<<




^^

lol, do you realize the size and weight of such wheels that need to be installed on board freight train, it would take how much from its engines\motors just to get that weight going, not to mention traction issues.
this idea reminds me of installing huge fan on a sailing ship to blow its sails.
 

orbital

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^

The thought was harvesting energy from train braking,, not so much even a wheel at all
I understand the flywheel would too huge

...it's the braking concept w/ trains here


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