RE without batteries or the grid?

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RE without batteries or the grid?

 Does anyone know if there is a way to use a RE home system off grid and without batteries?

One thought I had was to simply use the power when you have it and not when you don't. But no systems seem to be designed that way. 

Another thought was about alternative ways of storing the energy produced. For example, a PV system could pump water uphill while the sun is out, perhaps to a tank. When power is needed later, the tank would release water that would flow through a hydro generator.

I've got a stack of pv books, but they don't cover this. The assume that we will be either be tied to a working grid and/or have a supply of batteries.

Thanks for ANY help or links!

David

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Re: RE without batteries or the grid?

Not sure what you mean with the "RE home system" statement, David. But I am glad to explain some science to those so interested.

One would be much better off to just store the PV energy in batteries and use it directly. Since 100% efficiency is never achieved in any system and introducing two stystems, pumping the water up, then running it back down hill through a hydro generator is really two systems, one would halve the efficiency of that system.

If you want to use the power when you have it and also when you don't, you have to store it.

Storing that energy within the same system that creates it is much more efficient.

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Re: RE without batteries or the grid?

In a word.....  NO!  It can't be done.  Why?  Renewable Energy, whether wind or solar, varies CONSTANTLY.  So when the sun first rises, no energy will be generated until enough light can produce the 12V the panel is designed to produce, but the current (Amps) will be negligible.  As the sun gets stronger, the A will rise, but eventually so will the V, up to as much as 14V or more.  Wind turbines are even more erratic, they won't produce anything at all until the wind reaches a design minimum speed.  Then, the power output increases with the cube of the wind speed!  Any gusts, and the V and A coming out the machine will be all over the place.

When the A are insignificant, you won't be able to run anything, but once they ARE significant, you might even fry what it is you want to run.  Basically you need a BUFFER between the vagaries of the PV/turbine output and the appliance(s) you wish to run.  Other wise they may not run at all, or you might fry them!

Battery storage is REGULATED by "white man's magic" gizmos, such that if you want 100W, no more no less, then the grid, or your batteries will provide 100W (Watts, BTW are V x A), and UNREGULATED solar panels/wind turbines cannot do this.

So I' afraid, you have no choice in the matter.  Some things, like lights, will run unregulated.  They'll just go dim when there's not enough juice, and go really bright when there's too much, but they will blow if you overdo it.  CFLs will NOT do this.  Some motors will either speed up or down, but they won't like it and you will shorten their life.

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Re: RE without batteries or the grid?

Thanks DtM. I have never understood electricity and appreciate the expanded answer. I have a couple follow ups, if you don't mind...

In a grid tied RE system, isn't there some way that current is controlled, so that the right amount of juice gets to the house panel and the rest goes to the grid? Couldn't the same method be used, except that the excess would go to somewhere else other than the grid? Perhaps even to a motor (pump) designed to run with variable current, or even to someone else's house. How about some kind of regulator that would stop (divert) the flow if there is too much, or not enough?

Thanks also Jerry for your reply. The issue I'm trying to solve is how to use renewable energy in the home at a time when the grid is down and batteries are not available (these 2 things would likely coincide). And in any event, an energy system that needs a bank of new batteries every 5 to 10 years is not very useful over the long term. 

David

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Re: RE without batteries or the grid?

That's what the grid connect inverter does.  It turns the mish mash of variable DC (Direct Current, ie one that ONLY flows in one direction) into a steady flow of 110 or 240V AC (Alternating Current, power that changes direction 50 or 60 times a second - depending on which part of the planet you live on!)

Generally, in a grid tied system, ALL the renewable energy goes to the grid, measured through a meter.  Then, if you need some at the time it's being generated, some of this current will do a U turn back into your house via another meter that measures your consumption.  At least that's how our system works.  Some utilities will make you fit just one meter, so that when you are putting out more than you use the meter runs backwards.  Which is kinda cool actually!

If you need MORE than what you're generating, like running a 2000W electric kettle with a 1200W solar array, ALL of the renewable energy does the U turn, PLUS the extra 800W supplied by the grid.  Once you turn the kettle off, all of the solar power goes back to the grid again...

If you are using less than what you generate, then indeed your neighbours will have access to your excess.

It IS possible to have BOTH grid tied and batteries, that's what we do.  Of course it costs more, our batteries are worth $1500, and that was cheap through eBay.  The inverter we use is no longer available.  So it's highly likely that if you want to use backup batteries, you'll need TWO inverters, one to feed the grid, and one to feed the house from the batteries.  Then you need a special switch (ours is automatic/instantaneous so that the only way you know there's grid failure is if you hear the switch go klunk or the lights on the inverter tells you you're in stand alone mode).  Utilities will not allow you to feed into the grid during a blackout in case you kill the guy trying to fix the blackout!  Two inverters gets expensive....

Your comment re batteries is totally correct, I worry constantly that one day all this hi tech stuff will not be able to be replaced.  Welcome to the end of the world as we know it....!

Mike

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Re: RE without batteries or the grid?

Thanks, Mike. That explanation (that all the power goes to the grid first) clears up some of it.

The batteries are certainly the weakness in RE. As we come down the backside of the peak, energy prices will shoot up, and there may likely be shortages. Demand for RE will shoot up, and batteries may become hard to get. It seems a shame that a system intended to be renewable depends on a non renewable element like batteries.

It makes me wonder how power is no managed on the commercial grid. What happens to extra power when it is not called for? I know it keeps getting distributed over a wide network, but there must be some extra somewhere. What I'm really driving at is the possibility of a local grid. There's got to be some way to generate usable power without replying on expendable batteries or FF supplied commercial grids.

David

 

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Re: RE without batteries or the grid?

 David,

 The telecom industry is testing a centrifuge for remote location backup power. The results so far are promising, as they have provided reliable backup for several years.  The plan is to make them available sometime in the near future.

 Permanent magnet and brushed D.C. motors are not harmed operating on variable voltage ( P.V. direct). They just slow down and speed up with the variation in voltage. I have several in operation for a decade now.

 Batteries are the weak link in an off grid system. The best options are nickel-iron deep cycle which have an indefinite life span, if taken care of. Some of your large lead-calcium and lead-antimony batteries have a design life of 25-30 years, again if taken care of. Electronic desulfation may extend that.

 I have a 3800 amp-hour bank of GNB lead-calcium batteries. With a 1.215 specific gravity, I only water them once per year and that is the only maintenance. Quality design and assembly is important. Check out the archives of Homepower magazine for an abundance of battery and related information.

 Having just spent the last six weeks TIG welding boiler tubes in the local coal fired power plant, I can tell you there is NOTHING sustainable about our current electricity grid. In order to maintain a grid of any size, you must have a constant source of energy. There are many alternatives to storing energy, we must develope them on a small, sustainable scale.

 Spencer 

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Re: RE without batteries or the grid?

I think the only way to go without batteries is to use power while you make it. The downside with commercial PV systems is that the voltage your panel produces most likeley wont be a usuable voltage. The current systems run real high voltage strings, anywhere from 50 up to 500 volts. Usually for efficiency reasons. Lower gauge wire since less amperage with higher voltage, also the battery chargers are more efficient running at higher voltages, vs lower, the ones with Maximum Power Point Tracking (MPPT) specifically.

My opinion, if you bought a gird tie system, and the grid fails. Your system is basically useless. Try running a 12 VDC motor off 250 volts, see what happens. The other downside, the inverters are meant to run off batteries, usually a voltage of around 12 to 14 volts. If you tried to hook your panel directly into the inverter, it will shutdown on over-volatge, or maybe fry the inverter. I have only come across one inverter that is meant to run off panels directly, but only panels up to 25 volts.

If you are getting a PV system as a hedge against grid failure, you really need to pay attention to what you are getting, and getting into.

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Re: RE without batteries or the grid?

SPM wrote "My opinion, if you bought a gird tie system, and the grid fails. Your system is basically useless."

Only if it's set up this way......

http://www.solarelectricsupply.com/Inverters/inverters.html

The Trace SWPV, UT and microsine, AEI GC and Omnion 2400 inverters are examples of an intertie inverter. Using a multifunction inverter allows you to sell excess power to the utility, and also maintain a battery bank for standby power in the event of a utility power failure.

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Re: RE without batteries or the grid?

Utility-Intertie Inverters
Intertie inverters convert DC power from PV modules into AC power to be fed into the utility grid.  There are two major types of utility inverters; string inverters and low voltage input inverters.

The SMA Sunny Boy, Fronius and Xantrex GT-3 inverters are string inverters.  The name "string" comes from the way the PC modules are wired together, in series to achieve a higher voltage.  These inverters are designed to run at voltages up to 600 VDC.  String wiring is faster to install, more efficient and allows the use of smaller gauge wire.  DC voltage this high can be deadly, so string inverters should be installed and serviced by qualified electricians.

A utility-tie PV system uses the utility company as a storage battery.  When the sun is shining, your electricity comes from the PV array, via the inverter.  If the PV array is making more power than you are using, the excess can be sold to the utility (power company) through your electric meter.  If you use more power than the PV array can supply, the utility makes up the difference.  This type of system makes the most sense if you have utility power, because there are no batteries to maintain or replace.  Unfortunately, if the utility power goes down, this type of inverter will go off, too.

Multifunction Inverters
Using a multi-function inverter allows you to sell excess power to the utility, and also maintain a battery bank for standby power in the event of a utility power failure.  the Outback GFX and Xantrex SW series are primarily stand-alone inverters that can function as an intertie inverter at the same time but with a slight lower efficiency than an inverter designed for intertie only.  The new Beacon Power M5 is an intertie inverter that is designed to provide batter backup when the utility fails.  The SMA Sunny Island inverter is designed to work with a Sunny Boy inverter to provide utility intertie with battery backup.

In a typical installation, the inverter is connected to a batter bank, the utility power lines, a standby generator and the house load center.  If the utility is available, the inverter will supply the house loads from the utility.  If the utility fails, the inverter will supply power to the loads from the battery.

When the utility is available again, the inverter will switch the loads back to the utility, and recharge the batteries.  If the batteries become fully charged by another power source, such as photovoltaic modules or a wind or hydroelectric generator, excess power may be sold back to the utility.

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Re: RE without batteries or the grid?

"In a typical installation, the inverter is connected to a batter bank, the utility power lines, a standby generator and the house load center.  If the utility is available, the inverter will supply the house loads from the utility.  If the utility fails, the inverter will supply power to the loads from the battery."

What happens when we run out of batteries, or they get too expensive?

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Re: RE without batteries or the grid?

Well, I think there could be several ways to "bank" your RE production for later use without batteries if you're willing to accept a lossy application. Using a solar or wind pump to transport water uphill and then power a small hydro generator via the fall downhill is one way. Diverting your extra power to an electric water heater and then doing a geo-thermal thing with it is also viable (although making heat with electricity is very inefficient and you'd do better to use solar thermal collectors -- but an electric water heater does make an excellent and useful power sink to keep from overloading your system). A similar scenario could be used to heat an anaerobic digester to create biogas that could power a combustion generator or be used for cooking/heating. You could also use all your sunny PV electricty to run a chainsaw and log splitter, then use that wood to generate heat... possibly in conjunction with a steam generator for power. You could use your electricity to power a distillation pump, then use the produced ethanol in a combustion generator or vehicle. Using a single lightbulb in your root cellar to keep it from freezing preserves your food energy.

All these uses are inefficient and lossy -- but it's better to lose some of the energy produced than all of it, right? Batteries are the best way to store electricity, yes; but electricity isn't the only definition of power. If we consider that 50% of the electricty in our homes is used for heating and cooling... even if we only use 10% to facilitate another heating/cooling method and lose 40% to inefficiency, we're still breaking even. The key to an effective system is to determine what you actually need electricity for and whether an application really needs some other form of power to truly be efficient. I think we focus too much on electricity sometimes, and often overlook that mechanical and/or thermal power may actually be more useful and efficient in a given application. I guess it's because electricity is "universal", whereas mechanical and thermal are more site and application specific.

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Re: RE without batteries or the grid?

"What happens when we run out of batteries, or they get too expensive?"

THAT, SPM is called an epiphany.....  Welcome to the end of the world as we know it.  The world has limits, and we have hit the limits.

Mike

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Re: RE without batteries or the grid?
Damnthematrix wrote:
Quote:

"What happens when we run out of batteries, or they get too expensive?"

THAT, SPM is called an epiphany.....  Welcome to the end of the world as we know it.  The world has limits, and we have hit the limits.

Mike

You know I wonder how we all survived for the hundreds of thousands of years before electricity. It's seems like people think we sprang spontaneously into existence when the lightbulb was created.

 

 

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Re: RE without batteries or the grid?

Amen Gungnir! There are so many things that used be done with different mechanics and different power sources just fine... but we've all been spoiled by those traveling electrons.  But as I was saying the other day, until they find a way to plug an electrical appliance into a steak or a potato and have it work, I'll "take my chances" and continue using mechanical methods powered by food energy!

(and if that was a little too indirect for people to follow - I prefer to collect the majority of my "solar power" by growing and raising food to generate animal and human power, and utilizing the stored "solar power" in trees and other vegetation for heat, light and even a bit of electricity when it's needed)

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Re: RE without batteries or the grid?

Long term, a pumped water storage system ( properly designed ) could be the most "sustainable", maintainable with very low tech gear.

The efficiency of a small system may not be as good as a battery system, but if long term operation life is your goal it is probably the best bet.

However it will rely on a conveniently placed hill

 

Off the top of my head ( and late at night ) and ignoring losses...

100 amp hour 12 v battery will store 1.2 Kw hrs

10,000 Liter  tank 10 m in the air ( if you live in a flat area  ) will store 0.27 Kw hrs

But a conveniently placed hill 100 m high would push this to 2.7 Kw hrs

 

 

Cheers Hamish

 

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Re: RE without batteries or the grid?

If your water source is moving, you might look at a hydraulic ram pump to get your water up the hill. These pumps are powered by the flowing water only and they work.

Also, transpirational pull (the way trees move water up from the roots to the leaves) and it's coupled 'capillary action' power supply can be employed to move water up hill. Wicking actions are also being developed:

http://www3.telus.net/farallon/

And of course, farmers have been using wind powered water pumps to pump water from well to tank for at least a couple of centuries.

If you then want to store some of that as energy, one might look at water electrolysis. This might be set up by running the wires from a solar panel into a vat of water. When the panel begins producing electricity, oxygen will bubble from one wire and hydrogen the other.

The hydrogen can then be tanked to use however you wish.

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Re: RE without batteries or the grid?

I think if you have a good hydro setup, meaning a stream and water wheel, or something like that, I think you can generate your electrical needs the most efficiently this way. I imagine only a small percentage of people actually have access to a stream or river on their property though. Alternators are your best bet. They have integral voltage regulators from 13 to 14 VDC.

You could also hand pump water uphill. I think you would need a good pump for that though. I also thought if you dont have access to a hill to move water, but maybe have access to large trees, you can setup a weight and pulley system. You have to pull the weight up the tree yourself to be the most efficient, but you can use the force of gravity to generate the electricity. Gravity is free. I think you can setup some type of Ferris Wheel, with water tanks instead of seats, set the tanks to dump at certain flow rates and intervals and it will generate rotational force, and you can then generate electricity. The larger it is, the more energy you can generate. Turning it to refill would be a challenge, but maybe a hand crank and gear ratios you could do it. Also try and save the water, for refill. A closed system would work best to fight evaporation. You would need to know industrial automation to do a lot of it though, programmable logic controllers (PLC) and ladder logic. At least relay logic, and a lot of relays. I/O can also be done through a peripheral component interconnect (PCI) to rs-232 card, but those setups are still expensive and you need a lot of different components: I/O and different function cards, PCI card, cables.... The DIY kits are coming down in price, but still you would have to power a desktop to run it, versus a small independant PLC, or you can try some type of cam or gear setup, and be even more efficient.

I think people will be limited by their own abilities. I guess why in my mind, community is important.

 

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Re: RE without batteries or the grid?

Actually, I just thought of this, you can also store energy in a flywheel. This setup is extremely dangerous if you have no clue what you are doing, but it has great potential to store energy.

Pick up some flywheels from some old back geared OBI presses. Those would actually work perfectly, and they are already flywheels.

Tying in to what I wrote in the previous post, you could pull 4 weights up a tree and have them drop consecutively to spin a flywheel.

Just trying to throw out ideas.

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Re: RE without batteries or the grid?

I think whatever we can do under our own power will be the most benefit. Besides, us Americans need more exercise anyways.

A mountain bike and a flywheel might be a good idea. I would want the flywheel secured to a quite a few tons of concrete though if I'm pedaling my heart out right in front of it.

Maybe have it reverse directions through one pulley, that way if it takes off, it should go the other direction as you. You would need a real heavy support structure, but I think its a good idea. The heavier, better balanced, and least amount of friction through bearings, it should stay spinning for quite a long time depending on how fast you can spin it. I have seen some on presses that can take 20 minutes to a few hours to completely stop spinning, and they are up to full speed by electric motor in a minute or less. I think gears may be better than belts though, that way you can disconnect, and lose the friction incurred from the bicycle, or a clutch, but you need more stuff for a clutch, so gears would probably be the most simple.

We had a small 2.5 ton with a hundred pound flywheel that the last company threw away. I should have grabbed it but I wasnt thinking of this stuff at that time. One from a 75 ton or larger would be nice though, but you would need a forklift to move it around.

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Re: RE without batteries or the grid?

OK, I have to do the math for this one, and I'm not sure that I will cause I don't know it all off the top of my head, but if I do I'll let everyone know. It would only be in theory, unless I have specifications from the parts I would use. All in a days work for a janitor. Sorry to hijack the thread.

If you had a small DC motor, but higher RPM range, maybe a 1/4, 1/8, or 1/16th horsepower. If you got the flywheel up to speed by hand or bike, and then used the small motor to keep the rpm, as long as the inertia of the flywheel can overcome the resistance from the generator and load, and the motor could keep the inertia at a stable level, does anyone think it would work?

I guess it could serve as perpetual motion, maybe not permanently, but I think it could function for quite a few hours.

 

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Re: RE without batteries or the grid?

Sorry, repost. I'm done now.

 

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Re: RE without batteries or the grid?

Supposedly, I should be able to recharge my laptop battery with an alternator hooked up to a bicycle. (some guy did it, I'll try to find the link again)  If that's the case, then I'd essentially be getting 3+ hours of computer use for an hour of pedaling... not a bad exchange. A little tweaking of the gear ratio, and you might even be able to get more with less. You wouldn't be able to generate enough juice pedaling to use your computer from the power supply, but plenty to recharge the battery... I think I'd get motion sick trying to do both at once anyway LOL.

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Re: RE without batteries or the grid?

Create hydrogen and oxygen through electrolysis.

Pipe the hydrogen up the hill. This will not require any extra energy as the gas is lighter than air. the oxygen you just release or collect it for some other use.

Combust the hydrogen on the top of the hill creating steam to drive a turbine, The result is water which can be collected and stored in a basin.

The water can be release from the basin and drive another turbine creating electricity when needed.

I just made that up so i have no idea about its efficiency. :)

 

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Re: RE without batteries or the grid?

SPM, I hate to say this.....  but you don't seem to iunderstand energy at all....

It doesn't matter how you pump the water up hill or spin a flywheel up to speed, IF you do it with human power, the most LEG power you're likely to get is 100W, and probably half that with your arms, simply because the arm muscles are considerably less powerful than the leg ones.

NOW....  if you pump water up hill for say five hours, all the ENERGY you will have stored is 100W x 5 hours = 500Whrs or 1/2 kWhr.  If you do it by hand, then you'll likely only have 1/4 kWhr. At 100% efficiency too!

That's bugger all energy.  Our very efficient household only consumes 5 kWhrs a day, which is TEN TIMES your legs pumping water uphill.  TWENTY times using your arms.....

Now of course you COULD do some work with 1/2 kWhr, but certainly not enough to run a fridge...  you'd end up spending an awful lot of time pedaling or pumping, time which I would suggest to you would be better spent ensuring you had enough food growing in the garden...

Mike

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Re: RE without batteries or the grid?

Damnthematrix, what possible function can the first sentence of your latest post serve, other than to efficiently and effectively create bad feeling?

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Re: RE without batteries or the grid?

 Ok, here is another idea on storing the energy from a RE system without batteries. Let me preface it with the fact that it might not be a very energy efficient method, but then again, what method of energy storage is?

What if you powered an air compressor(s) with your inverter and stored the energy via compressed air tanks?

You could then convert the compressed air back into electricity via the Green Steam Engine.

Or maybe just skip the whole RE system side of the equation and just use a steam engine to power a generator. 

Granted, this idea may be a bit premature in its development, but it might have potential, and its low-tech.

Feel free to bash it now. Thanks

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Re: RE without batteries or the grid?

LOL, sorry, repost

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Re: RE without batteries or the grid?

Sorry, Repost

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Re: RE without batteries or the grid?

LOL, you really are ignorant Damnthematrix. In your constant quest to upstage me, you ignore comon principles of engineering. I'll let you figure them out, you're the smart guy, what do I know. But, you can get much more than 100 watts through your personal ability. Blatantly incorrect. People like you are why I don't like posting here.

Also, I am never really talking to you, I'm not sure what your issue is with me, but you have never been pleasant, so if you could please take the initiative to ignore what I say, I would tremendously appreciate it. Also chiming in with false information doesn't help get any messages out there.

100 watts isn't very desciptive. Where did you get that figure? Is it 100 watts per hour, or one push, 100 watts your arm is done for the day?

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Re: RE without batteries or the grid?

Here is a quote from Wikipedia on Flywheels, I guess they use them in UPS now.

"Flywheel power storage systems in current production (2001) have storage capacities comparable to batteries and faster discharge rates. They are mainly used to provide load leveling for large battery systems, such as an uninterruptible power supply for data centers.[9]

Flywheel maintenance in general runs about one-half the cost of traditional battery UPS systems. The only maintenance is a basic annual preventive maintenance routine and replacing the bearings every three years, which takes about four hours.[5]" http://en.wikipedia.org/wiki/Flywheel_energy_storage

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