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Energy Storage discussion (critical for Renewable to work).

MontyFloyd

Member
Aug 9, 2021
233
141
Houston
One of the messages that narrow minded detractors of renewable energy keep espousing against renewable energy is the cyclical and unreliable nature of renewable generation.
For there to be any chance for people to be 100% renewable energy humans must find ways to store extra energy from the sun (safely) to use when the collectors (PV or turbines) cannot collect.
Storing excess energy during surplus renewable energy production is critical, and subject of this post.

Batteries are the WORST method of energy storage in terms of cost of production, lifespan, and simply cost.
Yes, they certainly are ideal in a short list of specific uses, but when it comes to large fixed location, they are awful (basically, inappropriate use of technology).
I would rather have the limited production of batteries all go to EV's.

Option 1 for energy storage: "g"

One of the easiest and oldest forms of energy storage is Gravity (gravity "battery"). There is hints of such devices in ancient times, but the most familiar use today is the clock (typically a pendulum clock), invented in 1656 by Christiaan Huygens. On aside, Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), has been in grid scale usage since 1907 (small scale various uses for centuries). Simply pumping water uphill into a reservoir, then releasing stored water to generate power when needed.

Taking the pendulum clock idea to a grid scale we have companies like:
Gravitricity is one such pioneering company in Scotland designing "gravity battery" (battery usually denotes chemical, however is a commonly used term).
"Gravitricity’s existing 12 meter (39.4ft), £1million test tower in Leith, the firm have generated 250 kWh from lowering two 25 tonne weights in combination."
That is not the only concept, but one that was built as working prototype.

(There are other ideas, including one (what I think is insanely complex and destined to fail) idea by EnergyVault. )

Mass lifted up a great distance vertically to store energy.
Reminded me of an elevator.
No, an elevator is not a good energy storage, as it is a balanced mass.
WHAT IF one elevator shaft of building was converted to an gravity battery?
A tiny 36sq-ft area (smaller than typical office cubical) is used to lift a several ton weight during surplus energy.
During peak times (running AC for instance) the mass dropped to balance demand.
Something that would be incredibly easy for building designers to ad to any design.

Even better:
Retrofitting a little used existing elevator shaft as a "gravity battery" would be super easy as well.

Is there an energy storage system easier to build, operate, and have as long life as G battery?
 
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MontyFloyd

Member
Aug 9, 2021
233
141
Houston
Here is a YT video talking about the exact same ideas (first half).
I swore I found this a few days after she posted hers (2 days before I started this thread)

 

RubberToe

Supporting the greater good
Jun 28, 2012
3,159
7,977
El Lay
As much as I would like Energy Vault to succeed, I suspect that it might not be a good investment. They are going the SPAC route and will be NYSE listed. Long term energy storage is indeed the holy grail. We should have an indication in a few years which horse is leading the race.

RT
 

MontyFloyd

Member
Aug 9, 2021
233
141
Houston
As much as I would like Energy Vault to succeed, I suspect that it might not be a good investment. They are going the SPAC route and will be NYSE listed. Long term energy storage is indeed the holy grail. We should have an indication in a few years which horse is leading the race.

RT
Why EVault and not the simpler Gravitricity?
 

RubberToe

Supporting the greater good
Jun 28, 2012
3,159
7,977
El Lay
Why EVault and not the simpler Gravitricity?

I haven't studied the numbers, so the following may be not much more than guessing on my part, but having said that...

It takes a lot of weight falling quite a distance to generate a reasonable amount of power. Someone on this forum did a simple test and my recollection from that was that I was astonished at how little power was able to be stored. The Gravitricity system uses a single long excavated shaft, which somewhat limits the amount of weight you can use unless you dig deeper or wider shafts, which gets expensive. The EVault system is all above ground, so no digging required. While you might not be able to stack weights up as far as say a 1km deep mine shaft, you could easily have 500 separate stacks each 100 meters high. It seemed to me that the EVault system was much more scalable and therefore able to store much more energy. But the mechanism that EVault uses would also have to be very reliable and complicated, which is my primary concern.

I worked with a lot of mechanical engineers over the years, and their favorite saying was always "The best mechanism is no mechanism". Which could be why pumped hydro was developed long before anyone thought to use weights and mechanisms.

And don't forget that ARES is doing a similar thing too. Their scaled back Nevada site is supposed to be ready late this year per their news story from October 2020:


RT
 
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MontyFloyd

Member
Aug 9, 2021
233
141
Houston
I haven't studied the numbers, so the following may be not much more than guessing on my part, but having said that...

It takes a lot of weight falling quite a distance to generate a reasonable amount of power. Someone on this forum did a simple test and my recollection from that was that I was astonished at how little power was able to be stored. The Gravitricity system uses a single long excavated shaft, which somewhat limits the amount of weight you can use unless you dig deeper or wider shafts, which gets expensive. The EVault system is all above ground, so no digging required. While you might not be able to stack weights up as far as say a 1km deep mine shaft, you could easily have 500 separate stacks each 100 meters high. It seemed to me that the EVault system was much more scalable and therefore able to store much more energy. But the mechanism that EVault uses would also have to be very reliable and complicated, which is my primary concern.

I worked with a lot of mechanical engineers over the years, and their favorite saying was always "The best mechanism is no mechanism". Which could be why pumped hydro was developed long before anyone thought to use weights and mechanisms.

And don't forget that ARES is doing a similar thing too. Their scaled back Nevada site is supposed to be ready late this year per their news story from October 2020:


RT

An excellent response! My replies

The Gravitricity system is proof of concept. A utility scale one would need to have a much longer shaft, and have a much bigger mass. Note it can extend above and below the surface, depending on the location. A building could be a viable shaft too, so intra-urban storage is easily possible.
I agree there is limits with mass size, but building another shaft will solve that (and add redundancy.

Sure EnergyVault smaller mass units reduces the equipment requirements, but I just see failure points everywhere. Even a stiff breeze could make picking up the blocks a impossible. I wonder how much power it will consume to make this work, too.
Like you I have serious concerns about reliability (let me say, I doubt it will work)

Did not know of the ARES project, AND I LIKE IT! Sure there is loss due to being at an angle, but it is far more scalable (provided other limit, land). Mechanically very simple, likely uses common rail parts, probably cheap to build and simple to operate. I far prefer that over EVault.
 

MontyFloyd

Member
Aug 9, 2021
233
141
Houston
Option 3: Chemical via electrolysis mainly H2O.

While easy and inexpensive to split and keep as gas, it becomes much more expensive and complex if density is needed either by compression or by cryogenic liquification.
And what about the "waste product", O2?

While there are many downsides, in certain niche situations electrolysis has clear advantages.
Perhaps the best example is hospitals (as I forwarded here).
Hospitals needed large quantities of O2, so on site electrolysis will produce the needed O2 (zero transportation costs, unlimited supply)
Hospitals often have broad roofs and large parking areas, space for PV array.
The H2 collected will be used to power Fuel Cells or generators at night, or to fill H2 tanks on ambulances.

Such on-site electrolysis can be used by any industry that needs O, the H being used for other energy production.
The key advantage in this is reducing transportation costs saving stored fuels for other uses.
 
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MontyFloyd

Member
Aug 9, 2021
233
141
Houston
Option 4
Kinetic energy.
This actually an ancient technology too, the prime example is the flywheel, more accurately as Flywheel Energy Storage.
FES is actually a very good storage system in storage and extraction, its weaknesses is mechanical (that is care is needed to prevent unscheduled rapid disassembly).
While magnetic bearings can nearly eliminate a source of energy drain, a bigger issue is the gyroscopic effect. The earth rotates, rotating mass react to movement. There are ways to reduce that too, without adding too much to cost and energy loss.

Perhaps one ideal use for FES is with a PV arrays to even out fluctuations of output due to clouds and other shadows.
 

EVEnergy

Member
Sep 2, 2021
24
20
Wyoming
I've spent a career in energy and all are good options but the devil is in the details. Pumped storage is awesome but needs a wide pricing spread between peak and off-peak power prices. You need to pump at off-peak prices and release at peak. The difference in prices has to be enough to cover operating costs and give a good return on investment. To make things harder, it's locational specific (you need the elevation difference plus the ability to environmentally permit a dam). There are few in the U.S. but when I was looking to buy one about 10 or so years ago, the price differential was quickly evaporating.

Thermal is used today for heating and cooling applications. I did a project in New Orleans where we chilled glycol at night (made ice) which melted during the day and created the air conditioning for hospitals. The thermal conversion efficiency isn't that great but it can work in the right place.

Chemical - sure, Bloom Energy does that. Not exactly utility scale but it can be used to basically take something like a Home Depot "off grid".

Flywheel is pretty good and there are some operational examples. Frictional losses are a big problem so they put the flywheel in a vacuum. A company built a facility for the NY grid (NYISO) to provide ancillary services and from what I know, it works pretty good. The company later went bankrupt, however. It's expensive to operate and maintain - pulling a vacuum in vessels large enough for the flywheel is pretty hard.
 
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MontyFloyd

Member
Aug 9, 2021
233
141
Houston
I've spent a career in energy and all are good options but the devil is in the details.
Yes!
To be clear I was not putting one over other, just listing techniques.
As the title suggests, its about addressing the main weakness with renewables with a variety of proven technologies that are not just battery.
If anything, I hope almost all batteries are reserved for vehicles only. Be smart about resources.

Please post your experiences in the industry, hopefully it will help someone with decision making.
 

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