Caps for Short Term Mobil Energy Storage

The question becomes: "How much power did it take to pump it up there in the first place?" If we can only get back 25 percent of what we had originally, it wouldn't be worth it.

--=20

Densa International=C2=A9 'Think tanks cleaned cheap'

Due to the insane amount of spam and garbage, I block all postings with a Gmail, Google Mail, Google Groups or HOTMAIL address. I also filter everything from a .cn server.

m II wrote

Depends on where the energy comes from. It can be with nukes particularly.

I'm still not a big fan of nukes, but I'm not totally opposed. Maybe steam can be created from passive solar, and it can power a combination of electrical generator and pump to store any excess energy during the day, which can then be recouped at night or during periods of low insolation. All components of such a system are inexpensive, safe, and proven.

Paul

Paul E. Schoen wrote

And solar in spades.

More fool you. They make a hell of a lot of sense in the first world.

and it can power a combination of

can then be recouped at night or during

Nukes make a hell of a lot more sense.

And can produce hydrogen when the cost of crude oil is high enough for long enough to make that economic.

Like hell they are.

Like hell the production of steam is.

Nukes are proven too. The French generate 80% of their electricity that way and havent had a serious accident.

True, nanowires can improve the exposed 'area' that is so crucial in capacitors. But there is a limit to what you can obtain with enlarging the 'area' of capacitors' contacts : The dielectric determines that limit : The MAXIMUM energy per (cubic meter) volume of capacitors is simply :

U = epsilon * Ebreak ^ 2

where epsilon is the permittivity of the material used as insulator in the capacitor, and Ebreak is the maximum electric field (volt per meter) of the same material (before is 'breaks down (shorts out)' under electric stress). One of the best capacitor insulators is Aluminum Oxide (Al2O3), with epsilon of about 10*(epsilon0)=10*8.8E-12 = 8.8E-11 and a breakdown electric field of about 1E9 V/m (amazing but true : 1000 V/um) if deposited correctly.

That brings the theoretical maximum storage capacity of Al2O3 capacitors to about 88 MJ/m^3 or 88kJ/liter or about 24Wh/liter or about 6Wh/kg. Incidentally, that is about the maximum storage capacity of the best ultracapacitors of Maxwell Technologies (leading ultracap manufacturer). This compares to 30Wh/kg for lead-acid batteries, and 180Wh/kg for Li-polymer batteries.

There is a company called EEstor that claims to have a capacitor that stores

1MJ/kg (277Wh/kg), using a ceramic (Barium titanate) dielectric with an epsilon of 38,000 or so. However, there are strong indications that EEstor is talking out of their a..s, since they seemed to have completely ignored an effect called dielectric saturation in barium titanate that has long been verified and known to be a limiting factor in such high-permittivity dielectrics. Also they claim a much higher breakdown voltage than what was previously found in barium titanate. When that is taken into consideration for their dielectric, then the storage capacity goes down to the level of Al2O3, around 5Wh/kg. We'll see if EEstor can actually get even close to their claimed 277Wh/kg. So far, they are a no-show.

Long story short : Unless there is a real breakthrough, Ultracaps have a way to go before they will replace batteries.

I agree. Especially for short-term storage (topic of this thread) flywheels might actually be a pretty darn good competitor of ultracaps. A flywheel with a motor-generator could actually get close to 50 Wh/kg, which is comparable with lead-acid batteries, but has the advantage of huge power density. Here is an example (which gets 27Wh/kg) :

In fact, I think that for regenerative braking (or battery peak unloaders in electric vehicles), ultracapacitors and small flywheel systems (with a motor-generator) will be competing with each other. Flywheels are not bad at all, and as safe (or unsafe) as ultracapacitors.

to

30 - 60 W hr/kg is all that is necessary to get a tractor across a field.

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Supposedly EEStor isn't a really good capacitor, but a hybrid between a battery and a capacitor and ordinary cap calculations do not apply. Supposedly the theory behind EEStor was well settled for decades but only EEStor managed to get it to work.

None of the above means EEStor has anything that will work, just that it cannot be summarily ruled out with cap calculations.

way

trolly

a fair

So there's still a wire at the edge of the field. It just powers the flywheel motor.

That's all that's necessary.

ge

ca/~fesi/

Then the flywheel tractor is the way to go.

in

New alternators are efficient over a broad rpm range.

Two counter rotating rotors will eliminate any undesirable external torques on the tractor. The bearings between the two rotors may need to be beefed up, however.

Bret Cahill

My great-grandfather was not a big fan of illuminating gas, but every room in his home contained multiple gaslights.

My grandfather was terrified by the lethal potential of alternating current electricity, but his home was completely wired for it, and he owned numerous electrical appliances.

My father believed that television sets radiatiated x-rays plus were fire hazards, still he owned three of them.

People in general were afraid of the consequences of a leak in a live steam line (death by scalding), but many buildings in large cities have it piped in for heating.

Many people today fear the electrogmagnetic fields produced by cell phone, but this does no appear to diminish the number that you see in everyday use. (I'm personally more concerned with working in a building with a multi-megawatt TV transmitter sitting two floor above my office, but I'd still work in one anyway.)

No new technology is without some level of risk/benefit tradeoff, and today the focus is on nuclear power generation. My guess is that when people become more familiar with it, it will be fully accepted as just another form of technology that provides great benefits, but requires caution in both its use and the locations chosen for the reactors. Spent fuel is not a problem, because that vast bulk of it is reprocessed, The dark side is that the reprocessing concentrates the plutonium content, so that requires careful monitoring to preclude any possiblity of it becoming available to make nuclear weapons. Pure profit motives on the part of nuclear fuel reprocessors would appear to assure that this is unlikely to happen, because the peaceful applications of plutonium make it more valuable than gold or platinum.

Just some of my thoughts on this subject.

Harry C.

The difference with nukes is the cost-benefit risk analysis is more complicated than an individualist deciding to wire his own home.

A individual doesn't decide where to put the nukes.

_Society_ decides where to locate the nukes.

The French can go nuke for the exact same reason railroads are straight in France.

If any French landowner or other rich induhvidualist objects to enlightened egalitarian public policy out comes the guillotine.

That just ain't gonna happen in the U. S. with the current disparity in wealth. If the rich try to locate a nuke in a poor area, everyone will immediately understand the scam.

If the space elevator ever becomes reality, send the waste into the sun.

Bret Cahill

Fine; show your calculations.

John

00 ton

lly

Only an idiot such as yourself would do all those calculations when excel is available.

Bret Cahill

Only an idiot such as yourself would not know Excel does "calculations" among other things.

So post the spreadsheet(s).

--
If you\'re _that_ interested, do your own legwork.

JF

--- Hope?

Instead of helping in the quest, technically, it seems that all you want to do is sit on the sidelines, puff yourself up as being an authority, and poo-poo everyone else's work even though you haven't the technical acumen to do so.

To what end?

JF

Obvious troll.

No, it's not different at all. Back shortly after the turn of the

19th century, most people did no understand even the basics of electricity, and thus feared it could and would kill them. The general publics today is equally afraid of nuclear generated electricity, and are equally ignorant of how it can be safely handled. The anti-nuclear media hype, generated by people whose education is primarily limited to the liberal arts did not help, because they fear anything new that they cannot understand.

This a a major part of the problem. If we were were to allow the competent engineering people to choose the generation sites, and not put it up to a popular vote by uneducated member of society, mistakes of the past would be avoided in the future.

Actually, they are anything but. Don't ask me how I know this, but from past employment, have some knowledge of the French transit systems and railways. Their civil designs have the identical problems of anywhere else.

Sounds more like China in your words.

What scam? I'm a physicist, and when I lived in the Rochester, NY area, I welcomed the Ginna nuclear plant as a neighbor. It in my opinion was situated on an ideal site, close to cooling water from lake Ontario, in a region relatively free of major faults.

659C8B63

The problem today is not the placement of the nuclear facilities, but legislative involvement on that subject, rather than leaving it up to competent, engineering professionals.

Today's resistance to nuclear is identical to earlier resistance to gas, and then electricity, because of public ignorance on the subjects.

Again, any technology advance is a trade-off between risks and benefits. 50 years of operation have statistically generated that nuclear power generation is the safest of all of the existing power technologies, and the most environmentally clean.

Then consider how many members of the consuming public have modern nuclear power plants ever injured on killed during over 50 years of operation. The answer is not one. During that time, how many deaths have coal, oil, and natural gas fueled resulted in as a result of the pollution they create? Likely the count is measured in the thousands.

Now if you are an open minded person, think about the many deaths you have seen documented on CNN from coal mining alone, and compare that with the deaths resulting from the production of nuclear fuels. Then too, how many people die on oil or gas rigs? That subject doesn't get much press attention, but is significant. How about when a trans- continental gas line running though an urban area bursts and destroys half the neighborhood?

So if you truly believe that nuclear is dangerous, consider the annual death rates resulting from the alternatives.

Harry C.

p.s. Just for the record, I have no holdings in any energy company, but I occasionaly do a few weeks of consulting a year for some of them I trust that you do know why major firms like Humble Oil and others changed their names to "energy". It's wasn't just for PR purposes; it accompanied a change in their corporate charters to allow them to purchase and invest in nuclear and other energy sources. But, Dhuh, I suppose you knew that already.

On the subject of the the original thread, I've had the opportunity to work with LARGE, energy storage capacitors. Trust me in telling you that if their energy storage capacity were sufficent to drive a truck for 15 miles, it could not carry the capacitors. They're heavy and large.

I've been waiting for major breakthoughs on this suubject, but advancement in battery technology seems to be making the greatest advancements. That little NiMH battery on my electric drill seems to do wonders, but after about a month of repeated use, it no longer is able to hold a charge. Same with my 3 spare batteries.

I'm no authority on the subject, but it seems to me like NiMH batteries are very similar to lead acid batteries in that they are limited in their deep cycle number of recharge cycles. Wonderful when they work, but cost roughly $25 when you need a new one for your electric drill!

Harry C.

Thats obvious.

Nope, NiMH does that fine with the right charging.

Not if you know where to get the replacements.

I agree. Many advances have been made when people have ignored those who said something would never work, or laughed when initial attempts failed. All ideas should be "on the table", even "obviously" unworkable ones, to be subject to analysis and debate. Sometimes factors change over time, and an idea that is impractical one day might be usable a year later.

Paul

Kris Krieger wrote

But arent as viable as replacing the batterys as required.

You're the one doing that.

Dont need to invent anything for perfectly viable solar lights.

Thats already been done and you can buy them anywhere for peanuts.

Pointless if some basic calculations show that it isnt a viable alternative.