Electronics > Power/Renewable Energy/EV's

EnergyVault gravitational energy storage

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voltsandjolts:

--- Quote from: rob77 on February 07, 2022, 07:54:13 am ---compressing natural gas can't be compared to pumping sea water at 75atmospheres of pressure.

--- End quote ---

Correct, it can't. Subsea natural gas compression is much more complex.

Hydrocarbon reservoirs don't produce nice clean gas ready to pipe to consumers. If you’re lucky it's a condensate mix with minimal hydrogen sulphide, so hydrogen metal embrittlement isn't a big problem over the long term. Regardless, the multi-phase flow needs to be separated into gas and liquid before the compressors. The gas passes through the turbine compressor while the liquid goes through a centrifugal pump. Then they are mixed again into the export line. All these pressure and temperature changes means hydrate formation can spoil the fun, so mitigations for that need to be designed in. Then throw in some magnetically levitated bearings because you’re aiming for decades long operational life in harsh media. So, yeah, pumping some sea water is much simpler.


--- Quote ---what was the cost of the pump assembly ?

--- End quote ---
Subsea gas compression is a relatively new technology with only a handful in actual operation. The complexity and costs are high.


--- Quote --- it sure makes economical sense when pumping natural gas, but let's be realistic.. we're talking about 5MW of pumped hydro with similar cost for the pump assembly (of course manufacturing at large scale would bring the cost down a bit).

--- End quote ---
The cost of a water turbine, relatively well understood technology would be much less. Is it economically viable? Neither you nor I know at this time.


--- Quote ---btw.. the numbers from that reality you linked are terrifying...

--- End quote ---
Ah, your terrified. That explains the lack of logical thought :P


--- Quote ---lifetime 20 years... what ?? why ? concrete lasts much longer ! why only 20 years then ??? probably the maintenance issues i'm talking about are the reason of the short lifetime ?

--- End quote ---
Calm down and think logically. The document did not say 20 year life for the concrete. You're right, concrete can and does last many decades in sea water, particularly in benign seabed conditions.
The pump/generator and controls package would likely need replaced several times in that timespan.


--- Quote ---concrete structures is definitely not "green".

--- End quote ---
Humans have produced a horrific amount of concrete, and with it a horrific climate-changing amount of carbon dioxide. The question is whether the CO2 required for the production of these spheres is less than they save over their lifetime. Demand for concrete globally will continue and likely increase, so hopefully we can find new ways to produce it more sustainably.

I am just making the point that your responses are generally emotive with little to no effort in the understanding of technical detail. Please use reddit for such shallow discussions, not an engineering forum. Subsea pumped hydro may or may not be a viable solution for grid energy balancing. There may be better solutions, but it has enough merit to warrant investigation.

rob77:

--- Quote from: voltsandjolts on February 07, 2022, 10:51:36 am ---

--- Quote ---btw.. the numbers from that reality you linked are terrifying...

--- End quote ---
Ah, your terrified. That explains the lack of logical thought :P

--- End quote ---
yes i'm illogical irrational so we must support this impractical startup and let the governments waste taxpayer money. abandoning investment after 20 years and creating negative impact is terrifying...



--- Quote from: voltsandjolts on February 07, 2022, 10:51:36 am ---

--- Quote ---lifetime 20 years... what ?? why ? concrete lasts much longer ! why only 20 years then ??? probably the maintenance issues i'm talking about are the reason of the short lifetime ?

--- End quote ---
Calm down and think logically. The document did not say 20 year life for the concrete. You're right, concrete can and does last many decades in sea water, particularly in benign seabed conditions.
The pump/generator and controls package would likely need replaced several times in that timespan.


--- End quote ---

and we're again back to the impractical and expensive (probably even impossible) maintenance :) the very point everyone is fighting against... i was thinking logically and logic says either needs to be maintained (back to the initial problem) or abandoned after 20 years.


--- Quote from: voltsandjolts on February 07, 2022, 10:51:36 am ---

--- Quote ---concrete structures is definitely not "green".

--- End quote ---
Humans have produced a horrific amount of concrete, and with it a horrific climate-changing amount of carbon dioxide. The question is whether the CO2 required for the production of these spheres is less than they save over their lifetime. Demand for concrete globally will continue and likely increase, so hopefully we can find new ways to produce it more sustainably.

I am just making the point that your responses are generally emotive with little to no effort in the understanding of technical detail. Please use reddit for such shallow discussions, not an engineering forum. Subsea pumped hydro may or may not be a viable solution for grid energy balancing. There may be better solutions, but it has enough merit to warrant investigation.

--- End quote ---

i said "abandoning concrete structures is definitely not green" - you excluded 1 word and literally changed the whole meaning.... so you're reacting to your fabricated sentence while pretending it's mine ? ... i think you should move over to reddit ;) 

voltsandjolts:

--- Quote from: rob77 on February 07, 2022, 02:10:26 pm ---impractical and expensive (probably even impossible) maintenance :)

--- End quote ---

So, your main argument against this idea is difficulty of maintenance. I suppose I can forgive that, as my judgement is based on a career which for the most part has been in subsea and subterranean engineering. You perhaps don't have the benefit of that, I mean, seeing the difficult engineering challenges that can be overcome when the finances are viable. Sure, there are challenges in fitting a subsea turbine in a retrievable package, for maintenance or replacement from a vessel. But I've seen similar challenges end successfully. So I don't see it as unsurmountable. You do.


--- Quote ---i said "abandoning concrete structures is definitely not green" - you excluded 1 word and literally changed the whole meaning....

--- End quote ---

That was not an intentional miss quote, in fact I don't think it means much.
Neither creating or abandoning concrete structures (in the way we manufacture cement today) is sustainable.
But the point is that with maintenance of the turbine package, the concrete structure is not abandoned.

rob77:

--- Quote from: voltsandjolts on February 07, 2022, 02:48:40 pm ---
--- Quote from: rob77 on February 07, 2022, 02:10:26 pm ---impractical and expensive (probably even impossible) maintenance :)

--- End quote ---

So, your main argument against this idea is difficulty of maintenance. I suppose I can forgive that, as my judgement is based on a career which for the most part has been in subsea and subterranean engineering. You perhaps don't have the benefit of that, I mean, seeing the difficult engineering challenges that can be overcome when the finances are viable. Sure, there are challenges in fitting a subsea turbine in a retrievable package, for maintenance or replacement from a vessel. But I've seen similar challenges end successfully. So I don't see it as unsurmountable. You do.


--- Quote ---i said "abandoning concrete structures is definitely not green" - you excluded 1 word and literally changed the whole meaning....

--- End quote ---

That was not an intentional miss quote, in fact I don't think it means much.
Neither creating or abandoning concrete structures (in the way we manufacture cement today) is sustainable.
But the point is that with maintenance of the turbine package, the concrete structure is not abandoned.

--- End quote ---

i'm not saying it's impossible - i said "impractical, expensive and probably even impossible maintenance"... and the fact they're presenting the solution with a lifetime of only 20years and don't mention anything about maintenance is very trange ;)

for the maintenance you would need high accuracy in a depth of 750m. you say you have experience in sub-sea stuff... then you know you need expensive ROVs (or divers) to aid the operations.. expensive sea-cranes , insurance, weather must be good to perform such a lift. so it's definitely expensive.
you say it's not a problem, so try to get a quote for such a operation and share the results ;)   releasing ~ 20 bolts  in a depth of 750m and lifting a several ton assembly from that depth , then lowering it back down 750m while placing it accurately into the hole and fasten those bolts. and let's not forget the electrical connections as well. ( 18-20 bolts is what seems they have on the prototype, final might be even more)

i just hope the representatives of the governments considering this solution will ask the questions about maintenance and lifespan before investing into it.


voltsandjolts:

--- Quote from: rob77 on February 07, 2022, 04:52:49 pm ---you need expensive ROVs (or divers) to aid the operations.. expensive sea-cranes , insurance, weather must be good to perform such a lift. so it's definitely expensive. you say it's not a problem, so try to get a quote for such a operation and share the results

--- End quote ---
OK, it's your turn for a misquote, I said I don't see it as an unsurmountable problem.
Of course, like all grid-scale engineering, it's expensive. Like a 700km subsea interconnector or a £9Bn offshore windfarm.


--- Quote ---i just hope the representatives of the governments considering this solution will ask the questions about maintenance and lifespan before investing into it.

--- End quote ---
I am sure they will since the real question is the economic viability and that takes time to assess. Not a job for a 10min rant on eevblog like batteriser was.

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