Ditch the Batteries: Off-Grid Compressed Air Energy Storage • Hacker News Board

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#231

Post by jacknews » Fri, May 25, 2018, 1:38 PM UTC

This makes some sense in poor tropical nations, where rigging a mechanical system like this is quite feasible locally (instead of having to import advanced lithium batteries, along with usually exorbitant import duties etc), and some of the "inefficiency" can be used to heat, and particularly, cool spaces.

It also makes sense for oceanic wind turbines, which can use periods of high wind vs low demand to pump air into large under-sea air storage bags, using the sea as free cooling/heating towards isothermal operation.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#232

Post by paulmd » Fri, May 25, 2018, 3:13 PM UTC

throwaway5752 wrote: post #206

paulmd wrote: post #197

Earlier quoted context omitted.

> Unless you can start synthesizing utility grade quantities of well-behaved fissile material at a net energy surplus then it's not renewable even if we have decades/centuries of supply. Someday, even the Sun will run out of fuel. In the long run, we are all dead - unless someone figures out how to reverse entropy. http://www.multivax.com/last_question.html

If you listen very hard, you can hear my eyes rolling through your computer. But I enjoyed reading the story and begrudgingly admire your pedantry on the matter!

Some animes have theorized a different method for reversing entropy. Like nuclear fission, we may be able to release a tremendous amount of energy by smashing the dreams of young girls and harnessing the power of their tears.

https://wiki.puella-magi.net/Thermodynamics

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#233

Post by brimstedt » Fri, May 25, 2018, 4:56 PM UTC

mattygh wrote: post #216

vosper wrote: post #170

Earlier quoted context omitted.

Don't rule out hydrogen just yet - at least not for cars (and then using your car as a generator to power your home): http://www.thedrive.com/tech/14431/are-hydrogen-cars-the-nex...

I'd be very surprised if hydrogen vehicles work out. Hydrogen is not a source but rather a store of energy like a battery is. There's a few practical and technical issues: 1 it would require building out entirely new infrastructure, running up against severe NIMBYism at this point. It's incredibly hard to even build new power lines right now. Try a highly combustible, very leaky gas. 2 it's far cheaper to just strip…

Possibly a bit off topic,but why do we charge the batteries at stations rather than switching them with full ones?

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#234

Post by ttul » Sat, May 26, 2018, 11:35 PM UTC

romwell wrote: post #213

ttul wrote: post #199

Earlier quoted context omitted.

Given that even a small reactor still requires considerable shielding, generates waste that could be used for nuclear proliferation (if ammassed), and emits harmful radiation, I would say chances of a nuclear car for the every man are slim to none.

There's that, but on the other hand, small gasoline vapor explosions are quite harmful and require considerable shielding, and generate waste that is destroying our ecosystem. The nuclear waste problem seems to be not so severe in the age where everything is tracked every second; and it doesn't need to be solved completely - just raise the cost of (illegal) waste extraction to be considerably higher than getting it f…

Yeah, but we are talking about thousands of small reactors driving along highways... that will never scale.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#235

Post by blevin » Sun, May 27, 2018, 5:33 PM UTC

dredmorbius wrote: post #204

blevin wrote: post #178

Earlier quoted context omitted.

Are buried flywheels used in practice? Is the flywheel axis aligned with the Earth rotation axis? Do they pull a vacuum around it?

Yes, in cases, to the first two. Containment is frequently buried concrete vaults. Not AFAIK for the last, though precessional torque bearing load is a nontrivial consideration.

Thanks for this response. My untrained guess is that precessional torque would cause more loss than air friction, assuming the wheel is cleanly symmetric (ex. no bolt heads sticking out). It's fascinating how many paths there are to push something up various kinds of potential energy gradient in a way that it mostly stays there by itself but is still available to us to access in a controllable way.

Wikipedia claims flywheel loss rate circa 2013 of 5% per day. https://en.wikipedia.org/wiki/Flywheel_storage_power_system

That compares to recent estimates of Tesla li-ion loss rates at under 5% per month -- 0.16% per day.

Amber Kinetics is one company building fixed flywheel storage products. http://amberkinetics.com/

They have one 32 kWh, 5-ton, 98% steel flywheel installation on Oahu; pictures here: http://amberkinetics.com/hawaiian-electric-and-amber-kinetic...

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#236

Post by dredmorbius » Mon, May 28, 2018, 7:22 AM UTC

blevin wrote: post #235

dredmorbius wrote: post #204

Earlier quoted context omitted.

Yes, in cases, to the first two. Containment is frequently buried concrete vaults. Not AFAIK for the last, though precessional torque bearing load is a nontrivial consideration.

Thanks for this response. My untrained guess is that precessional torque would cause more loss than air friction, assuming the wheel is cleanly symmetric (ex. no bolt heads sticking out). It's fascinating how many paths there are to push something up various kinds of potential energy gradient in a way that it mostly stays there by itself but is still available to us to access in a controllable way. Wikipedia claims f…

Frictionaal losses are part of the consideration, but just plain bearing wear is a bigger one AFAIU.

Angular momentum in 100 kWh - multi MWh rotational systems is large.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#237

Post by rahulroy9202 » Mon, May 28, 2018, 12:14 PM UTC

brimstedt wrote: post #233

mattygh wrote: post #216

Earlier quoted context omitted.

I'd be very surprised if hydrogen vehicles work out. Hydrogen is not a source but rather a store of energy like a battery is. There's a few practical and technical issues: 1 it would require building out entirely new infrastructure, running up against severe NIMBYism at this point. It's incredibly hard to even build new power lines right now. Try a highly combustible, very leaky gas. 2 it's far cheaper to just strip…

Possibly a bit off topic,but why do we charge the batteries at stations rather than switching them with full ones?

probably because we park our cars, instead of giving them away when we reach our destination, and getting one when we need to go again.

Re: Ditch the Batteries: Off-Grid Compressed Air Energy Storage

#238

Post by cwkoss » Tue, May 29, 2018, 6:18 PM UTC

ChuckMcM wrote: post #221

cwkoss wrote: post #220

Earlier quoted context omitted.

If the entire contents of the data center were pressurized, would it increase the efficiency of air cooling? (Denser air -> more heat capacity?)

It would certainly increase the heat capacity of the air. Compressing air into the data center however would not be a win. During compression the air gets hot. In the system that I was pushing the compressed air tanks were outside in the wind so that they were benefiting from the cooling effects of the same wind that was pumping air into them.

Good point. Could allow for low power cooling (once pressurized, venting pressure would drop temperature of the contents without added energy), but probably not worth the trouble.