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That is a great question. There are other people who know more about EVs than I do in this kind of capacity, but one really good proof of concept example is what MAGICC has been doing. Imagine that you have not just your EV but hundreds or thousands of them and they have the smarts to talk back to a central computer. Now you can start getting really clever with the computer calling on those EVs in series to produce frequency regulation services. You'll get paid (the figures out of MAGICC would suggest something like six dollars a day is possible - not going to make you rich, but I wouldn't say no) and the grid operator now has a very fast ramping system that could potentially aggregate up to several MW and enhance grid reliability and efficiency.

By the way, a few posters have suggested this is going to kill your battery. I'm not going to scoff at that, but the technology is getting WAY better and attending conferences like the ESA conferences will quickly give you the idea that a lot of really clever people are putting a fair chunk of research into improving the technology.

Not to gloss over the problems, but this is what being a researcher is all about, and it's really exciting.

Obviously you're not an engineer,

"By 1933 reversible pump-turbines with motor-generators were available. Adjustable speed machines are now being used to improve efficiency. Pumped hydro is available at almost any scale with discharge times ranging from several hours to a few days. Their efficiency is in the 70% to 85% range. "

Now, one must ask... why would a person make such a wild claim??

table of large pumped hydro facilities around the world..

Obviously you're not an engineer,

"By 1933 reversible pump-turbines with motor-generators were available. Adjustable speed machines are now being used to improve efficiency. Pumped hydro is available at almost any scale with discharge times ranging from several hours to a few days. Their efficiency is in the 70% to 85% range. "

Now, one must ask... why would a person make such a wild claim??

table of large pumped hydro facilities around the world..

uhm... no.

Electricity Storage Association.

Power companies in the US currently use large-scale battery arrays (think lead-acid car batteries but massively larger) for storage; there are also experiments with creating large-scale flywheel farms for the same purpose.

Well.. a better option is to use some other form of energy storage (flyweel, etc.).

  The easiest one that you can build yourself (if you are a Slashdot Hobbyst) is the water energy storage.

  Please go to http://www.electricitystorage.org/site/technologies/

And the chart http://electricity.ehclients.com/images/uploads/capital.gif

Pumped Hydro is one of the best choices, and very simple to implement.

Hydroelectric energy storage systems are between 70-85% efficient. If this superconducting power line is more efficient than that it would be cheaper to transfer power than to attempt to buffer it locally. As an added bonus if they can transfer at a higher efficiency than it can be stored at there will be energy saved overall.

1 http://www.electricitystorage.org/site/technologies/pumped_hydro/

Pumped hydro is insane. I can't imagine what your power loss is on taking water that you've run downhill and running it uphill again. Almost certainly in excess of 100%. If not, you have a perpetual motion machine on your hands. Go forth!

To pull out one cite from a quick Google search, pumped hydro is around 75-85% efficient. In other words, you get back about 75-85% of the energy you used to pump the water uphill when you let it run back down again. That's pretty decent when you realise that the wear and tear is significantly less than chemical-based storage methods (like batteries). Flywheels can get up to around 90% according to Pikiwedia.

So that takes care of the "lose too much in storage" argument. As for the loss in transfer, you build the storage close to where the energy will eventually be used. Losses in transmission will occur regardless, so it's not a major concern comparatively. It comes down, in other words, to the cost of building these things in an environment where we already have large scale coal and fission plants to provide "baseload" power - in other words, the incentive to build energy storage just isn't there at the moment. Which is a damn shame, IMO.

• Solar Thermal - The cheapest option out there at the moment. Heat up water. Keep it in an insulated tank until it's needed. Drive steam through a turbine. Works up to 16 hours a day which isn't perfect but it's better than "only when the sun's shining"
• Vanadium redox (flow) batteries - Charge a Vanadium electrolyte and pump it into tanks for storage. Pump it back the other way to release the charge. Highly scalable (just add more electrolyte and bigger tanks) to many MWh of power. Still pricey but could be competitive with more research funding and economies of scale. A great candidate for Google funding IMHO.
• Compressed air - Use surplus energy to compress air into an underground aquifer. Release it through a regular gas turbine when needed significantly boosting the turbine's efficiency. Not truly renewable as you're still burning gas but you still get the benefit of otherwise wasted wind power. The advantage of pumping water into an aquifer is that the constant hydrostatic pressure removes the need for variable regulation at the plant saving significant cost. Won't work everywhere though and the drilling cost would be significant.
• Pumped hydro - Well established and incredibly scalable (to GWh of power storage!) but not cheap to build.
• Supergrid - Spread your wind farms across a wide enough grid and the wind will be guaranteed to be blowing somewhere giving you guaranteed supply. Uses HVDC lines to minimize power loss over the large transmission distances involved.

Compressed air is an interesting idea for storing energy.

But I have to wonder how it compares to the alternatives.

How about a capacitor bank and a hand-crank generator?

If you're out of compressed gas or batteries in the middle of nowhere it's hard to replenish your cell phone. Turning a hand crank would make use of cheap, available human power.

According to http://www.electricitystorage.org/tech/technologie s_technologies_flywheels.htm Flywheels are ~90%.

Electrical Storage:
Hydrogen conversion is at presenly only 65% efficent versus 85% for a hydro storage system

http://www.electricitystorage.org/tech/technologie s_technologies_pumpedhydro.htm

and

http://www.electricitystorage.org/tech/technologie s_technologies_flywheels.htm

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04 /marine/tech_storage.htm

http://www.jet.efda.org/pages/focus/004power/

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04 /wind/content/storage%20available.html

http://www.geocities.com/dfradella/homepage.htm

Electrical Storage:
Hydrogen conversion is at presenly only 65% efficent versus 85% for a hydro storage system

http://www.electricitystorage.org/tech/technologie s_technologies_pumpedhydro.htm

and

http://www.electricitystorage.org/tech/technologie s_technologies_flywheels.htm

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04 /marine/tech_storage.htm

http://www.jet.efda.org/pages/focus/004power/

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04 /wind/content/storage%20available.html

http://www.geocities.com/dfradella/homepage.htm

Fuel cells, maybe. Ultracapacitors, maybe. Batteries are probably within a factor of two of their ultimate limits.

What happened to the super capacitors? You know, caps with such a high energy density that they could be used to replace batteries in many applications. I'm sure I read about them last on Slashdot, but a quick search on the site turned up too many hits.

The ones out there now are already pretty cool because they can be charged quickly. If the energy density gets closer to high-capacity batteries like LiIon, it would be great to have them in portable devices so recharges would be speedy. Hate to have one short out all of a sudden, tho.

- Leo