Use gravity to store wind power?

[PowerEngineer]

Originally posted by: silverpig
When I was doing research on it the utility companies don't buy the power back at retail rates, rather at wholesale rates.

I've done some quick research (which in my case means "googling") and see that the effective rates paid for delivered power have become more complicated and varied. While there are still many utilities that do buy back at retail rates, there are others that pay a fixed rate set by tariff (presumably tied to average wholesale rates). It's also true that more utilities are moving toward "time-of-day" tariffs/metering where rates charged (or credited) are based on hourly market pricing. I even came across one tariff that required customers (not opting for time-of-day service) to give the excess power to the utility.

So I guess the bottom line is that under a "net metering" arrangement, you'll effectively get paid your retail rate for current power generated up to the amount of your current load (i.e. you are still a net taker of power from the utility). Rates established by tariffs for any excess generation (i.e. the power you deliver to the utility) can vary quite a bit.

I stand corrected (again).

 

[cheesehead]

If you could connect a constant source of power (hydroelectric for preference - it's far more constant) to a pump and a watertower, you could store loads of power. It would likely end up being an electrical connection and not mechanical (complicated variable-ratio gearboxes are very inefficient), but it's a good way to do it, especially seeing as how there are loads of watertowers already, each with its' own extremely powerful pump.

 

[deputc26]

Unfortunately electrolysis is very inefficient (23% if I recall correctly) flywheels on the other hand are capable of energy densities similar to todays li-ion batteries. Unfortunately getting this high energy density requires materials with very high strength to weight ratios (like in aircraft which is my area of expertise) which are correspondingly expensive. I don't think high speed fly wheels will ever penetrate the market due to safety concerns and the current extreme sensitivity to (physical varieties of) danger. All that energy would be released a lot faster (more catastrophically) in the event of a failure than equivalent failure modes of batteries (the technology that does and will continue to have a high degree of market penetration in energy storage) I.e. thermal runaway.

Actually certain li poly varieties of battery have equivalent levels of "boom" after relatively brief exothermic "run-ups".

edit: wow the thread has moved on, probably should have read the whole thing before replying. Apologies.

 

[spikespiegal]

Biggest problem with flywheels is gravity. At 1g you need a bearing to suspend the flywheel in a frictionless space, and this causes all kinds of engineering limits.

If you were in orbit you already have a vacuum, and you could use a much bigger object to store a huge amount of kinetic energy at a low rotational speed. An asteroid for instance.

I recall an eleborate white-paper I read on the subject about a decade ago where a physicist doing some pretty hairy math worked out the the angular energy as a spinng wheel (made from unobtanium of course) would theoretically approach relativistic rotational speeds. He than translated the whole model to a sub-atomic scale where nuclear interactions actually bumped up the efficiency.

 

[silverpig]

Originally posted by: spikespiegal
Biggest problem with flywheels is gravity. At 1g you need a bearing to suspend the flywheel in a frictionless space, and this causes all kinds of engineering limits.

If you were in orbit you already have a vacuum, and you could use a much bigger object to store a huge amount of kinetic energy at a low rotational speed. An asteroid for instance.

I recall an eleborate white-paper I read on the subject about a decade ago where a physicist doing some pretty hairy math worked out the the angular energy as a spinng wheel (made from unobtanium of course) would theoretically approach relativistic rotational speeds. He than translated the whole model to a sub-atomic scale where nuclear interactions actually bumped up the efficiency.

Which is why flywheels are excellent for short term storage but not for long term.

 

[piasabird]

Maybe if you wound up a giant pendulum as the pendulm went down by clockwork you could generate some steady current. Works for a quartz watch and a koo koo clock.

You could slowly fill up the supporting pole with water and then empty it through a small diameter pipe and create hydro power. Maybe by sectionalizing the support structure you can slow down or limit the pressure.

 

[BrownTown]

See, yet again this is the annoying part about Anandtech "highly technical". The correct answer was posted forever ago and yet people keep posting nonsensical answers to a question solved 50 years ago. Pumped storage IS the solution to the question here, it is the only one that can be done economically. This is not a theoretical discussion, there are pumped storage plants with larger capacities larger than nuclear plants that have been in service for decades.

 

[spikespiegal]

The correct answer was posted forever ago and yet people keep posting nonsensical answers to a question solved 50 years ago.

Gotta love a rhetorical critic. Makes time travel paradoxes seem plausible

Pumped storage IS the solution to the question here, it is the only one that can be done economically.

Fluid spinning across a turbine blade is far from 100% efficient, but, if you were born 50 years ago you might think it was.

So professor, how'd you fix the hole in the Minnow's hull?

 

[BrownTown]

Originally posted by: spikespiegal

The correct answer was posted forever ago and yet people keep posting nonsensical answers to a question solved 50 years ago.

Gotta love a rhetorical critic. Makes time travel paradoxes seem plausible

Pumped storage IS the solution to the question here, it is the only one that can be done economically.

Fluid spinning across a turbine blade is far from 100% efficient, but, if you were born 50 years ago you might think it was.

So professor, how'd you fix the hole in the Minnow's hull?

its 80% efficient which is better than anything else you are likely to come up with in the next few decades. Yes there are 20 other more efficient ways, but none of them are economical on a large scale. The pumped storage plant near here can produce 1600MW for 24 hours. That's enough energy storage to run a million homes for a day. IT would be one thing if people answered with "magic" as in some sort of future device. However they are answering in current generation devices like flywheels or capacitors etc. This isn't a theoretical discussion when you consider all the choices in question are used for energy storage, and the one used for grid level storage is pumped hydro.

As for selling it back to the electricity company, that works now because there are so few people doing it, but if alot of people do it then there are grid stability problems which have to be accounted for. Also, around here they buy back "green" power at like 4 times the normal market rate for electricity, so it is hugely subsidies which is again something that couldn't happen if it were done on a large scale.