Donate to Remove ads

Got a credit card? use our Credit Card & Finance Calculators

Thanks to eyeball08,Wondergirly,bofh,johnstevens77,Bhoddhisatva, for Donating to support the site

Sand batteries

Scientific discovery and discussion
GoSeigen
Lemon Quarter
Posts: 4399
Joined: November 8th, 2016, 11:14 pm
Has thanked: 1599 times
Been thanked: 1590 times

Re: Sand batteries

#657461

Postby GoSeigen » April 2nd, 2024, 2:20 pm

odysseus2000 wrote:
You are misunderstanding what heat is & the mechanisms of transfer within materials.


No sir, it is you who are misunderstanding. My mistake is answering your posts.


GS

odysseus2000
Lemon Half
Posts: 6413
Joined: November 8th, 2016, 11:33 pm
Has thanked: 1555 times
Been thanked: 969 times

Re: Sand batteries

#657464

Postby odysseus2000 » April 2nd, 2024, 2:32 pm

GoSeigen wrote:
Bubblesofearth wrote:
Check out the diagram 19s into the video in the OP. You want a balance between rate of heat release and heat storage. You don't want the reservoir to lose all its heat quickly but you want to be able to access the heat as quickly as is required. The design in the diagram shows how this is achieved.

BoE


If you insulate it the reservoir will not release (waste) heat. You cannot access heat as quickly as required if you use an insulating material. Imagine using polystyrene. How good a battery would that make? LOL

GS


You have this entirely wrong.

In a heat transfer system you have a high temperature reservoir & into this you put an extractor that will remove some of the heat. The main requirements are that the reservoir retains its heat & that the extraction system can take a little out.

Regards,

odysseus2000
Lemon Half
Posts: 6413
Joined: November 8th, 2016, 11:33 pm
Has thanked: 1555 times
Been thanked: 969 times

Re: Sand batteries

#657466

Postby odysseus2000 » April 2nd, 2024, 2:35 pm

GoSeigen wrote:
odysseus2000 wrote:
You are misunderstanding what heat is & the mechanisms of transfer within materials.


No sir, it is you who are misunderstanding. My mistake is answering your posts.


GS


Well I have a PhD in physics and decades of experience as a professional physicist, worked as a project manager for an NASA project & including years of teaching undergraduates at Oxford.

Regards,

tjh290633
Lemon Half
Posts: 8257
Joined: November 4th, 2016, 11:20 am
Has thanked: 917 times
Been thanked: 4124 times

Re: Sand batteries

#657468

Postby tjh290633 » April 2nd, 2024, 2:40 pm

Mike4 wrote:
Hallucigenia wrote:
Except in this district scheme they are heating the sand to 600C.

How does water perform at that temperature?

https://www.bbc.com/future/article/2022 ... ean-energy



Given the specific heat of sand is only 1/5 that of water, I'd say the water performs five time better. The box containing it might need to be a bit stronger though.

You then have superheated steam, which means the latent heat of vaporization comes into play. From memory 840 kcal/kg. I think that trumps the sand argument.

TJH

odysseus2000
Lemon Half
Posts: 6413
Joined: November 8th, 2016, 11:33 pm
Has thanked: 1555 times
Been thanked: 969 times

Re: Sand batteries

#657473

Postby odysseus2000 » April 2nd, 2024, 3:10 pm

tjh290633 wrote:
Mike4 wrote:

Given the specific heat of sand is only 1/5 that of water, I'd say the water performs five time better. The box containing it might need to be a bit stronger though.

You then have superheated steam, which means the latent heat of vaporization comes into play. From memory 840 kcal/kg. I think that trumps the sand argument.

TJH


Do you want a low cost efficient system or a very high cost system?

Most folk just want to be warm at the lowest cost possible.

Regards,

tjh290633
Lemon Half
Posts: 8257
Joined: November 4th, 2016, 11:20 am
Has thanked: 917 times
Been thanked: 4124 times

Re: Sand batteries

#657480

Postby tjh290633 » April 2nd, 2024, 3:25 pm

odysseus2000 wrote:
tjh290633 wrote:You then have superheated steam, which means the latent heat of vaporization comes into play. From memory 840 kcal/kg. I think that trumps the sand argument.

TJH


Do you want a low cost efficient system or a very high cost system?

Most folk just want to be warm at the lowest cost possible.

Regards,

This isn't most folk, though. It's the most efficient means of storing energy. Superheated steam may be the best way of releasing the stored energy.

TJH

odysseus2000
Lemon Half
Posts: 6413
Joined: November 8th, 2016, 11:33 pm
Has thanked: 1555 times
Been thanked: 969 times

Re: Sand batteries

#657486

Postby odysseus2000 » April 2nd, 2024, 3:44 pm

tjh290633 wrote:
odysseus2000 wrote:
Do you want a low cost efficient system or a very high cost system?

Most folk just want to be warm at the lowest cost possible.

Regards,

This isn't most folk, though. It's the most efficient means of storing energy. Superheated steam may be the best way of releasing the stored energy.

TJH



It is often noted that perfection is the enemy of good.

Regards,

tjh290633
Lemon Half
Posts: 8257
Joined: November 4th, 2016, 11:20 am
Has thanked: 917 times
Been thanked: 4124 times

Re: Sand batteries

#657488

Postby tjh290633 » April 2nd, 2024, 3:50 pm

odysseus2000 wrote:
tjh290633 wrote:This isn't most folk, though. It's the most efficient means of storing energy. Superheated steam may be the best way of releasing the stored energy.

TJH



It is often noted that perfection is the enemy of good.

Regards,

This is not about perfection, it is about the best way of storing and releasing energy. There are time scales involved.

TJH

odysseus2000
Lemon Half
Posts: 6413
Joined: November 8th, 2016, 11:33 pm
Has thanked: 1555 times
Been thanked: 969 times

Re: Sand batteries

#657492

Postby odysseus2000 » April 2nd, 2024, 4:06 pm

tjh290633 wrote:
odysseus2000 wrote:

It is often noted that perfection is the enemy of good.

Regards,

This is not about perfection, it is about the best way of storing and releasing energy. There are time scales involved.

TJH


Yes, but it is also about economics. If the best way is orders of magnitude more expensive than a good way, most will choose good.

Regards,

Bubblesofearth
Lemon Quarter
Posts: 1095
Joined: November 8th, 2016, 7:32 am
Has thanked: 10 times
Been thanked: 443 times

Re: Sand batteries

#657494

Postby Bubblesofearth » April 2nd, 2024, 4:10 pm

GoSeigen wrote:
If you insulate it the reservoir will not release (waste) heat. You cannot access heat as quickly as required if you use an insulating material.

GS


Depends how much heat you want and how quickly you want it. I have a microwaveable bag of wheat that I put on my feet at night that is very effective both in terms of speed and longevity :D

Clearly heat is released quickly enough by a sand battery for the purposes described in the video.

Polystyrene would be hopeless as it has such a low density. The density of dry sand is some 1.6x that of water which at least partly offsets the lower SHC when thinking in terms of volume required.

BoE

9873210
Lemon Quarter
Posts: 1010
Joined: December 9th, 2016, 6:44 am
Has thanked: 230 times
Been thanked: 306 times

Re: Sand batteries

#657495

Postby 9873210 » April 2nd, 2024, 4:26 pm

odysseus2000 wrote:
tjh290633 wrote:This is not about perfection, it is about the best way of storing and releasing energy. There are time scales involved.

TJH


Yes, but it is also about economics. If the best way is orders of magnitude more expensive than a good way, most will choose good.

Regards,


An alternative way to put odysseus's point is that if you end up choosing "good" over "best" it was "best" by the wrong metric.

In engineering almost any metric that does not include cost is the wrong metric. Even in emergency cost-be-damned projects cost still matters. If it costs more than the GDP of Earth (or some smaller area) it isn't going to work.

9873210
Lemon Quarter
Posts: 1010
Joined: December 9th, 2016, 6:44 am
Has thanked: 230 times
Been thanked: 306 times

Re: Sand batteries

#657496

Postby 9873210 » April 2nd, 2024, 4:27 pm

Mike4 wrote:Given the specific heat of sand is only 1/5 that of water, I'd say the water performs five time better. The box containing it might need to be a bit stronger though.


You probably* want the capacity by volume rather than the capacity by mass. Since sand is 60% denser than water that helps a bit so water is only 3 times better by reasonable metrics.

If the storage media is on or in the ground you won't care about the mass for reasonable materials. If it's in a tenth floor flat the mass may matter, but in that case hundreds of kg of near boiling water would have a different set of problems that sand might avoid. There's several reasons storage radiators don't use water, ceramic plates are, thermally, not that different from sand, but are less messy to install indoors.

GoSeigen
Lemon Quarter
Posts: 4399
Joined: November 8th, 2016, 11:14 pm
Has thanked: 1599 times
Been thanked: 1590 times

Re: Sand batteries

#657500

Postby GoSeigen » April 2nd, 2024, 4:31 pm

Bubblesofearth wrote:Check out the diagram 19s into the video in the OP. You want a balance between rate of heat release and heat storage. You don't want the reservoir to lose all its heat quickly but you want to be able to access the heat as quickly as is required. The design in the diagram shows how this is achieved.


That diagram shows effectively a sand-and-air system. As I noted in another post, I agree that is an interesting proposition. Heat is being extracted quickly because of the air being forced through the sand (mechanical transfer of heat) NOT because of the thermal conductivity of the sand itself, which is poor.

GS

Bubblesofearth
Lemon Quarter
Posts: 1095
Joined: November 8th, 2016, 7:32 am
Has thanked: 10 times
Been thanked: 443 times

Re: Sand batteries

#657506

Postby Bubblesofearth » April 2nd, 2024, 4:48 pm

GoSeigen wrote:
That diagram shows effectively a sand-and-air system. As I noted in another post, I agree that is an interesting proposition. Heat is being extracted quickly because of the air being forced through the sand (mechanical transfer of heat) NOT because of the thermal conductivity of the sand itself, which is poor.

GS


Yes and that's why its heat storage is so good.

BoE

servodude
Lemon Half
Posts: 8349
Joined: November 8th, 2016, 5:56 am
Has thanked: 4468 times
Been thanked: 3594 times

Re: Sand batteries

#657576

Postby servodude » April 2nd, 2024, 10:31 pm

GoSeigen wrote:
servodude wrote:
Some batteries are...
... but sometimes I want a battery designed to hold energy/charge for a long time, and go months between charges.
It's always a tradeoff


IIUC you are discussing a different trade-off here. It's the problem that there is a correlation between the rate at which energy can be withdrawn and leakage/waste of that energy. If you don't require rapid withdrawal of the energy but you do need to minimise losses then of necessity you may have to reduce the energy withdrawal rate [or possibly the same could be forced by safety requirements].

Agreed.

But I don't think that equates to saying that batteries in general are best designed to release their energy slowly which is the implication if a highly insulating material is to be used for storing the energy. A slower release rate would be indicated by other factors.


GS
P.S. All interesting discussion for me as I am considering various upgrades to our commercial property.


I think my point could probably be distilled down to the fact that, in my world model, it's the storage property that makes a battery a battery.
Or more correctly it's storage that makes a cell a cell (whether you are storing charge, heat or counts from Monte Christo)
... having more than one cell makes it a battery.

How quickly you can get your "stuff" in and out of storage, how much you can store and how well it stores or retains it while it's there, are just all parameters you have to balance for the specific storage job at hand

kempiejon
Lemon Quarter
Posts: 3547
Joined: November 5th, 2016, 10:30 am
Has thanked: 1 time
Been thanked: 1171 times

Re: Sand batteries

#657577

Postby kempiejon » April 2nd, 2024, 10:34 pm

servodude wrote:or counts from Monte Christo)
... having more than one cell makes it a battery.
Thanks, that had been bothering me.

GrahamPlatt
Lemon Quarter
Posts: 2075
Joined: November 4th, 2016, 9:40 am
Has thanked: 1038 times
Been thanked: 840 times

Re: Sand batteries

#658850

Postby GrahamPlatt » April 10th, 2024, 9:23 pm

Mike4 wrote:
tjh290633 wrote:If you are looking for heat capacity, surely water is the optimum medium. It has a higher specific heat than the alternatives however you measure it.

TJH



Yes. Remarkably having just looked it up, the specific heat of water is almost exactly five times that of sand.

The slight advantage sand has over water as the thermal store medium is that it doesn't boil away when heated far above 100 C (at atmospheric pressure).

https://en.wikipedia.org/wiki/Table_of_ ... capacities



They’re using water for this one: https://www.pv-magazine.com/2024/04/09/ ... ge-system/

“ Vantaa Energy plans to construct a 90 GWh thermal energy storage facility in underground caverns in Vantaa, near Helsinki. It says it will be the world’s largest seasonal energy storage site by all standards upon completion in 2028”

Mike4
Lemon Half
Posts: 7153
Joined: November 24th, 2016, 3:29 am
Has thanked: 1650 times
Been thanked: 3808 times

Re: Sand batteries

#658858

Postby Mike4 » April 10th, 2024, 10:25 pm

GrahamPlatt wrote:
Mike4 wrote:

Yes. Remarkably having just looked it up, the specific heat of water is almost exactly five times that of sand.

The slight advantage sand has over water as the thermal store medium is that it doesn't boil away when heated far above 100 C (at atmospheric pressure).

https://en.wikipedia.org/wiki/Table_of_ ... capacities



They’re using water for this one: https://www.pv-magazine.com/2024/04/09/ ... ge-system/

“ Vantaa Energy plans to construct a 90 GWh thermal energy storage facility in underground caverns in Vantaa, near Helsinki. It says it will be the world’s largest seasonal energy storage site by all standards upon completion in 2028”


Hmmm water-filled underground cavern, pressurised so they can heat the water to 140C!

servodude
Lemon Half
Posts: 8349
Joined: November 8th, 2016, 5:56 am
Has thanked: 4468 times
Been thanked: 3594 times

Re: Sand batteries

#658868

Postby servodude » April 11th, 2024, 12:34 am

Mike4 wrote:
GrahamPlatt wrote:

They’re using water for this one: https://www.pv-magazine.com/2024/04/09/ ... ge-system/

“ Vantaa Energy plans to construct a 90 GWh thermal energy storage facility in underground caverns in Vantaa, near Helsinki. It says it will be the world’s largest seasonal energy storage site by all standards upon completion in 2028”


Hmmm water-filled underground cavern, pressurised so they can heat the water to 140C!


Sounds a bit dodgy geezer?

Mike4
Lemon Half
Posts: 7153
Joined: November 24th, 2016, 3:29 am
Has thanked: 1650 times
Been thanked: 3808 times

Re: Sand batteries

#658869

Postby Mike4 » April 11th, 2024, 12:39 am

servodude wrote:
Mike4 wrote:
Hmmm water-filled underground cavern, pressurised so they can heat the water to 140C!


Sounds a bit dodgy geezer?


Dunnit just!!!

Getting a cavern of 0.1 cubic kilometres in volume totally pressure-tight sounds like quite a project.

Out of interest, can you or anyone post up the calcs to work out the pressure required for the boiling point of water to reach 140C?


Return to “Science”

Who is online

Users browsing this forum: No registered users and 20 guests