Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
(OP)
Question came up on a different "science" and energy forum about using high-speed (or verylarge) centrifuges to "store" wind or solar energy for use later in the day or at night to balance out their irregular power outputs.
1. Getting outside of the politicals/money/CAGW and usefulness of the idea at large - which is impossible in the real world, but bear with me on that - for a house-sized unit ( 1-2 kw size) what would be the needed weight (inertia) rotating at 15:00 pm to still generate power the next morning at 9:00 am?
2. Could those assumptions be "built up" to a 2-3 megawatt unit - as if one windmill running one centrifuge M-G set?
Overall, I can't see it working at anything but a government-funded Sandia-type national lab.
Problems:
Clearly balancing, bearings, lube oil system and storage and cleanliness and cooling and maintenance.
If the centrifuge were ultra-high speed, seems you be buying the reduction gear issues and problems as cost as well.
Air resistance of the rotating centrifuges and MG-Set, unless a nearly-impossible vacuum or hydrogen-cooled gas cooling system were used. And those are tough to build and maintain even on the big power generators!
Brushes and and all those DC-side problems, or could they be avoided by an AC-AC motor generator with an outlet
AC-AC frequency converter to "pickup" the slowly lowering AC output from the centrifuges as it slows down?
Thus, you'd have a transformer <-> grid connection <-> AC-AC static frequency converter <-> AC motor-generator <-> clutch/coupling <-> (optional reduction gear) <-> centrifuge.
It seems like you'd need to setup the ac-ac MG to be able to over-speed the centrifuge up past the MG set synchronous speed (to build up stored inertial energy in the centrifuge) during off-production hours, then pull that inertial energy down from centrifuge max speed though the unit's nominal speed down to the generator's cut-off speed
As a guess, I estimated a house-sized unit would be about the weight of two cars. Way too big, or way too small?
1. Getting outside of the politicals/money/CAGW and usefulness of the idea at large - which is impossible in the real world, but bear with me on that - for a house-sized unit ( 1-2 kw size) what would be the needed weight (inertia) rotating at 15:00 pm to still generate power the next morning at 9:00 am?
2. Could those assumptions be "built up" to a 2-3 megawatt unit - as if one windmill running one centrifuge M-G set?
Overall, I can't see it working at anything but a government-funded Sandia-type national lab.
Problems:
Clearly balancing, bearings, lube oil system and storage and cleanliness and cooling and maintenance.
If the centrifuge were ultra-high speed, seems you be buying the reduction gear issues and problems as cost as well.
Air resistance of the rotating centrifuges and MG-Set, unless a nearly-impossible vacuum or hydrogen-cooled gas cooling system were used. And those are tough to build and maintain even on the big power generators!
Brushes and and all those DC-side problems, or could they be avoided by an AC-AC motor generator with an outlet
AC-AC frequency converter to "pickup" the slowly lowering AC output from the centrifuges as it slows down?
Thus, you'd have a transformer <-> grid connection <-> AC-AC static frequency converter <-> AC motor-generator <-> clutch/coupling <-> (optional reduction gear) <-> centrifuge.
It seems like you'd need to setup the ac-ac MG to be able to over-speed the centrifuge up past the MG set synchronous speed (to build up stored inertial energy in the centrifuge) during off-production hours, then pull that inertial energy down from centrifuge max speed though the unit's nominal speed down to the generator's cut-off speed
As a guess, I estimated a house-sized unit would be about the weight of two cars. Way too big, or way too small?





RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
There was an article (in ME, I think, before it became a comic book) maybe a decade ago about designing safety containment structures for energy storage flywheels, based on a thick walled lead ring that absorbed the flying pieces, and rotationally accelerated itself within a steel ring, and sort of melt/extruded axially upward as it decelerated.
The accompanying photos were _very_ impressive.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
http://beaconpower.com/stephentown-new-york/
this may be more of a size that is useful
http://www.power-thru.com/industrial.html
Advantages compared with lead acids are very long life times and high round loop efficiency, the latter being remarkably unimportant in these days of cheap pV.
The energy stored is just 1/2*Izz*w^2
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
http://www.cnet.com/news/teslas-elon-musk-introduc...
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RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
http://rameznaam.com/2015/04/30/tesla-powerwall-ba...
Back to flywheels
this does half the job
http://www.calculatoredge.com/mech/flywheel.htm
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
I've used high-powered DC-AC MG sets and high-potential lead-acid batteries in the Navy's nuke plants (S1W, S6G, S5W), and serviced very powerful DC-AC MG sets with battery DC sources at several power plants; and have a smaller (625 watt) inverter with a lead-acid deep cycle battery for home backup ... And that's why I can't see a "regular" household ever being able to support hardly form of battery-inverter-backup system. People today just know enough to tighten the bolts after changing batteries.
Assuming they don't sue when they lose their eyes to to acid spilling from a broken battery that fell across their legs.
RE: Rotating Stored Energy (Centrifuge with M/G Driver): Theoretical Weight & Speed
Interesting idea = good concept.
But,m for industrial use - as a backup BEFORE the generator comes on is their criteria.
Thus,
225 kW at 30,000 to 53,000 rpm =
190 kW continuous for 10 seconds, 225 KW maximum surge, "until generator starts"
.528 KW-hr @ 190 Kw, 1900 kw-seconds at 1300 lbs, underground installation for debris containment (outdoors in the photo's at the site.)