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odysseus2000 wrote:
You are misunderstanding what heat is & the mechanisms of transfer within materials.
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
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
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.
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
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,
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
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,
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
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
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,
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.
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.
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
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.
Thanks, that had been bothering me.servodude wrote:or counts from Monte Christo)
... having more than one cell makes it a battery.
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
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”
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!
servodude wrote:Mike4 wrote:
Hmmm water-filled underground cavern, pressurised so they can heat the water to 140C!
Sounds a bit dodgy geezer?