4 ms·

Modern Flywheels (in a vacuum with magnetic bearings) have close to the same energy density as batteries. From Wikipedia: "Flywheel power storage systems in c

by proee 17y ago

Modern Flywheels (in a vacuum with magnetic bearings) have close to the same energy density as batteries. From Wikipedia: "Flywheel power storage systems in current production (2001) have storage capacities comparable to batteries and faster discharge rates." http://en.wikipedia.org/wiki/Flywheel_energy_storage http://en.wikipedia.org/wiki/Flywheel_energy_storage Also, I've heard that satellites often use flywheel's over batteries because they last longer.

ynniv 17y ago
Thats good to hear - most of the flywheel densities that I haven't been so high. I can't find any commercial wheels of that density for individual use, tho (many references to start-ups making them for central power utilities). Satellites are a special case, as they have enormous budgets, plentiful solar power (so cycle lifetime is more important than capacity), and have the additional benefit of using the flywheels as a rotational propulsion device (usually in counter-spinning pairs).
- ynniv 17y ago
  It seems that commercial flywheels are about 7 times more expensive than batteries per kWh. The article mentions 24 batteries at ~$1,500 each providing "3 days" of power at an average of 2500 watts, so 180 kWh for $36,000. A recent blog post regarding Beacon Power flywheel systems quotes them at ~$1,400 per kWh, or ~$250,000 for 180 kWh. http://neuralenergy.blogspot.com/2009/06/flywheel.html http://neuralenergy.blogspot.com/2009/06/flywheel.html
asciilifeform 17y ago
> faster discharge rates This phrase is the key to understanding why flywheels are seldom used. Read up on what happens if the wheel jams, cracks, or otherwise malfunctions.
- proee 17y ago
  I think "faster discharge" rates is being noted for their ability to dump large amounts of current very quickly. This is useful for large surges of power. It's not referring to some sort of parasitic leakage.
  - asciilifeform 17y ago
    > dump large amounts of current very quickly Consider what happens when the flywheel dumps all of its energy within a fraction of a second - a not-unlikely event in the case of almost any mechanical failure. Do I have to spell it out?

by proee 17y ago

ynniv 17y ago

Thats good to hear - most of the flywheel densities that I haven't been so high. I can't find any commercial wheels of that density for individual use, tho (many references to start-ups making them for central power utilities). Satellites are a special case, as they have enormous budgets, plentiful solar power (so cycle lifetime is more important than capacity), and have the additional benefit of using the flywheels as a rotational propulsion device (usually in counter-spinning pairs).

ynniv 17y ago
It seems that commercial flywheels are about 7 times more expensive than batteries per kWh. The article mentions 24 batteries at ~$1,500 each providing "3 days" of power at an average of 2500 watts, so 180 kWh for $36,000. A recent blog post regarding Beacon Power flywheel systems quotes them at ~$1,400 per kWh, or ~$250,000 for 180 kWh. http://neuralenergy.blogspot.com/2009/06/flywheel.html http://neuralenergy.blogspot.com/2009/06/flywheel.html

asciilifeform 17y ago

> faster discharge rates This phrase is the key to understanding why flywheels are seldom used. Read up on what happens if the wheel jams, cracks, or otherwise malfunctions.

proee 17y ago
I think "faster discharge" rates is being noted for their ability to dump large amounts of current very quickly. This is useful for large surges of power. It's not referring to some sort of parasitic leakage.
- asciilifeform 17y ago
  > dump large amounts of current very quickly Consider what happens when the flywheel dumps all of its energy within a fraction of a second - a not-unlikely event in the case of almost any mechanical failure. Do I have to spell it out?