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PostPosted: Sep 13, 2018 6:00 pm 
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One of my soon to begin PhD research proposal concept is to underground mine limestone for aggregates, pressurise with nitrogen and then use thin walled tanks of pressurised water to store heat.
The tanks can be insulated to avoid overheating the walls.

Net costs of a few US dollars per cubic metre for pressure vessel volume are going to be very hard for conventionally engineered vessels to beat.


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PostPosted: Sep 13, 2018 6:27 pm 
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E Ireland wrote:
One of my soon to begin PhD research proposal concept is to underground mine limestone for aggregates, pressurise with nitrogen and then use thin walled tanks of pressurised water to store heat.
The tanks can be insulated to avoid overheating the walls.

Net costs of a few US dollars per cubic metre for pressure vessel volume are going to be very hard for conventionally engineered vessels to beat.


It's neat that you are pursuing publishable research on interesting thermal storage techniques. What kind of cavern pressures are you envisioning? Are you considering bag/bladder type tankage, or only fixed hard shell tanks?

Though this topic probably should be in another thread, such as the thermal pit one.


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PostPosted: Sep 14, 2018 5:13 am 
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Asteroza wrote:
It's neat that you are pursuing publishable research on interesting thermal storage techniques. What kind of cavern pressures are you envisioning? Are you considering bag/bladder type tankage, or only fixed hard shell tanks?


Currently my concept (we shall see how it stands up when I get started on the actual detailed research!) is to pressurise to about 45 bar and use hard-shell tanks with a steam blanket inside the tanks.
The plant would use the pressurised water in a modified triple flash geothermal unit, which will be simplified and more efficient since the fluid won't contain anything dissolved in it.

Heat would be stored using the feedwater heating train of a PWR/CANDU or other reactor above ground, drawing high temp feedwater out of the system, transfering the heat into the fluid to be put into the tank and then reinjecting [the feedwater] into the low temp heaters.


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PostPosted: Sep 20, 2018 7:16 pm 
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A tower with multiple uses could make it economical.
High towers for wind energy could be modified, to store the compressed air produced by it.
Higher sunny side areas could be used for photovoltaic panels.
Compressed air could be used for mechanical work at low cost with pneumatic motors without going through electrification at lower cost
Compressed air cooled naturally could be used for air conditioning at low cost.
The focus could be on using wind power optimally via compressed air
The heat of compression could be used to heat water if a use is available and more compressed air stored at ambient temperature in an isothermal use pattern.


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PostPosted: Sep 27, 2018 7:06 pm 
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Flexible container for air storage at ocean depth. Depth of the storage container determines pressure. Pressure does not drop as storage is depleted which should simplify the turbines for the generators. The external water pressure keeps the pressure constant. Since the majority of the population is near the coast, it should be able to be widely implemented. The greater the depth the greater energy storage per given volume.

http://www.thin-red-line.com/140714_ThinRedLine_OSES2014.pdf


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PostPosted: Sep 27, 2018 8:23 pm 
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Joined: Feb 25, 2011 1:55 am
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jagdish wrote:
A tower with multiple uses could make it economical.
High towers for wind energy could be modified, to store the compressed air produced by it.
Higher sunny side areas could be used for photovoltaic panels.
Compressed air could be used for mechanical work at low cost with pneumatic motors without going through electrification at lower cost
Compressed air cooled naturally could be used for air conditioning at low cost.
The focus could be on using wind power optimally via compressed air
The heat of compression could be used to heat water if a use is available and more compressed air stored at ambient temperature in an isothermal use pattern.


So, turning the towers into pressure vessels is not entirely insane. You can get substantial mass saving with what are effectively structural balloon tanks (see Atlas rockets for an extreme example), which is starting to become a cost issue for the megaturbines. There is the issue of failure mode if pressurization fails however (if you design for strength sufficient only for initial erection and not subsequent loads with turbine installed). There's also the heat loss through the tank to consider plus you can't put the heat store close to the compressor since that's located at the top of the tower.


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PostPosted: Sep 27, 2018 8:28 pm 
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michaelw wrote:
Flexible container for air storage at ocean depth. Depth of the storage container determines pressure. Pressure does not drop as storage is depleted which should simplify the turbines for the generators. The external water pressure keeps the pressure constant. Since the majority of the population is near the coast, it should be able to be widely implemented. The greater the depth the greater energy storage per given volume.

http://www.thin-red-line.com/140714_ThinRedLine_OSES2014.pdf


Energy Bags like this are workable, provided you extract heat from the water when extracting air from the bags as well. Since in most cases you will lose all your compression heat to the ocean unless you do compression onshore and store the heat there, though most systems proposed use an offshore compressor (and some measure of ocean heat recovery when the chilled product air passes through the air pipeline to the onshore generator facility).


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PostPosted: Sep 28, 2018 6:59 am 
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The option of underwater compressed air storage is open only to floating or shore wind power installations. Towers are natural inland choice, for power produced by it. Many other uses of tower remain open.


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