Alternatives to storing electric energy

[BrownTown]

Originally posted by: Mark R

Originally posted by: BrownTown
OK, so I was right, there only really can source power on the seconds to minutes range? Seems pretty darn useless for any real world applications.

It depends what you want the power storage for.

For transport applications, the use of such a short term store are limited.

However, for power grid management, these stores can be useful. The vast majority of power quality problems are of short duration (transient voltage sags due to sudden short term loads - e.g. large motor start-up, or a 10s disconnect due to a breaker tripping, then auto resetting). The problem is once power to one area has been lost, it could cause cascading failures, or require a managed restart. Short term power stores (e.g. flywheels, but occasionally battery, or experimentally superconducting magnetic storage) are starting to be deployed by power companies in problem areas.

Trust me, having worked for a power company I know exactly what you are talking about, my comments were about the use of flywheels in cars, and the reason I doubted their effectiveness was precisely because I knew that they usually are only called on for a few seconds, not a 20 minute drive. Flywheels are a good source of POWER, they are not a very good source of ENERGY. I pretty much see them as the mechanical equivilent to capacitors as they serve similar roles.

 

[CTho9305]

For transport applications, the use of such a short term store are limited.

Not really... it lets you accelerate faster with a smaller engine.

 

[Rastus]

Make an LC tank out of superconductors. It can store massive amounts of power and theoretically oscillate forever.

 

[BrownTown]

Originally posted by: CTho9305

For transport applications, the use of such a short term store are limited.

Not really... it lets you accelerate faster with a smaller engine.

Yes, that is a high POWER usage, which is what htey are good at, not a high ENERGY usage like would be needed to replace batteries as per the origional question.

 

[shortylickens]

How come nobody has yet mentioned mini alchohol cells?

 

[dkozloski]

Originally posted by: shortylickens
How come nobody has yet mentioned mini alchohol cells?

Like those little bottles they give you on the airplane?

 

[f95toli]

Originally posted by: Rastus
Make an LC tank out of superconductors. It can store massive amounts of power and theoretically oscillate forever.

There is a very important difference between theory and practice. While Superconducting cavities (which is what we are talking about here) can indeed have a very large Q-value (in excess of 10^10) it is still finite. Hence in reality the energy will decay in a few seconds (at most). Moreover, the energy is in the microwave range (a few GHz) meaning it is not very usefull.

 

[wwswimming]

there used to be a company named Active Power that was publicly held and, last i
heard, specialized in using Centrifuges to store energy.

http://finance.yahoo.com/q?s=ACPW

 

[Costas]

Originally posted by: BrownTown

Originally posted by: CTho9305

For transport applications, the use of such a short term store are limited.

Not really... it lets you accelerate faster with a smaller engine.

Yes, that is a high POWER usage, which is what they are good at, not a high ENERGY usage like would be needed to replace batteries as per the origional question.

Urban buses make frequent stops and they waste a lot of energy in the form of heat dissipated in the brakes. I suspect flyweels are used in buses to temporarily store energy while the bus is braking (presumably by using generators to spin-up the flywheel) so it can be used to re-accelerate the bus after the stop.

As such, flywheels seem to be a alternative to batteries for this type of short-term energy storage need. It's not clear what, if any, advantages the flywheel has over batteries in such applications. The relevant factors probably include durability as well as power density. The longevity of batteries has increased dramatically on recent years but the flywheel may still be more durable.

BTW, the Toyota Prius uses batteries to store energy in its battery bank when the driver steps on the brake pedal.