rstuart,
There may well be a lot of bottles floating around soon if electric cars (and hybrids) become plentiful. If they are largely plugged in when not driving, the batteries would represent an enormous reservoir of the same order of magnitude as "peak" consumption. So long as they are otherwise kept charged, it will hurt the commute not at all for the battery to supplement either the grid or just the home (or office) during peak loads (morning, evening and daytime aircon).
I imagine a far more advanced version of the old off-peak "ripple" controllers. Modern integrated circuitry allows the population of connected car batteries to be accessed and drained far more progressively (signals to specific ranges of serial nunbers, serial numbers ending in particular digit etc) to closely match load, to not deplete the cells past anticipated requirements for the rest of the day, to use more batteries in hi-load areas, thereby reducing peak load on main feeders and switchyards and tranformer losses, as well as on generation.

I think a national power grid helps this even more. The staggering from time zones plus power grid helps existing generators to supplement each other, so too such reservoirs as the cars.

One non-esoteric bottle you didn't list was dams and hydroelectric. There is the small one at Wivenhoe, that I know of, but surely many others store excess off-peak power by pumping back up, then generate peak power from this water. Admittedly, dams and hydro aren't cheap. The losses are greater than you specified earlier for regenerative braking, but then I don't imagine a forty year old hydro setup would be as efficient as a new one. Better magnetic fields and electronic control of power factor and eddy currents could help a lot.

Maybe one could use two tanks and a pocket hydro setup (and say an off peak or solar pump to pump back up) to act as a home-sized power storage.

Lets hope the new non-silicon solar cells keep coming. I'm not so sure there will be enough silicon for all the cells we might need.

Cheers,

Rusty.

The interesting thing about all the hydrogen generators I have investigated is that they all recommend using bicarb soda in the water as an electrolyte.
Salt water would work perfectly well, and when you apply a charge, you can see all the lovely bubbles of hydrogen.
If you use bicarb, you get heaps more bubbles, but when bicarb soda bubbles in water, guess what gas the bubbles consist of?
Hydrogen generators do produce some hydrogen, no doubt, but the gas produced does not come close to the power required to produce it.
In my solar powered home, I had a 13 hp backup generator. I fitted a 24volt, 80 amp alternator to it to charge the batteries on rainy days.
Watts = volts * amps. 24 * 80 =1920 watts. I horsepower is (roughly) 750 watts, so the alternator pulled 2.56 Hp. BUT, to get the necessary revs, I had to gear it 4 to 1. so it pulled more than 10 hp.
I had to fit an isolating switch, so I could start the motor and get it up to full revs before I switched on the alternator, otherwise the 13 hp motor would just stall.
Sorry to get so technical, but I wanted to stress the point that the electricity generated by your car isn't free.

Rusty Catheter,

As you have probably gathered, I do love crunching numbers. I crunched some here (second comment from the top):

http://ambit-gambit.nationalforum.com.au/archives/002874.html

Batteries are expensive. Lets assume we have to store 1 weeks worth of power for a typical household & car which would be approx 300 kW hr. So look at the prices at http://www.allaboutbatteries.com/Battery-Energy.html For the sort of highly efficient batters these cars use, that is $1 per watt hour, or $300,000 total. But they only last a decade at most. There are batteries that last much longer, but they are currently 2 to 3 times more expensive.

Yes, dams like Splityard Creek are fantastic - 80% efficient. But as I understand it there are stuff all places you can put these things.

Rusty Catheter: "I'm not so sure there will be enough silicon for all the cells we might need."

There are some things that will never be an issue. Silicon is the 2nd most common solid element in the earth's crust. The most common is oxygen. http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/elabund.html

rstuart: Thanks for crunching the numbers. For electric cars to do the job (as you have already argued they will), they will have the capacity already paid for at whatever price, just for moving the cars around. Having already paid for the cells, getting more use out of them seems a reasonable thing. Yes they have a service life which is a function of both age, number of cycles, depth of cycle, heat during peak current, and time spent at low charge states. Even barely used cells will degrade with time, so using them is prudent. We all reasonably anticipate better cells. Existing electrics and other applications will retrofit rather well with perhaps only software revisions to accomodate optimal management.

Perhaps we need to find more dam sites? They don't have to be huge. There are some small commercial hydro operations from quite small dams. A proliferation of such is not at odds with the original topic of this thread, and more small dams and waterholdings may have other local benefits.

rstuart, planetary composition is not the sole criterion for shortage.
Both silicon and numbers are plentiful, crunching them takes effort. Producing the clear quill in crytalline form is a star achievment. Sources of suitable silicon for producing semiconductors are becoming scarcer, and waste from the electronics industry was until recently the major source for solar. Solar cells don't need anywhere near the same purity as microprocessors, but they are a lot bigger, and a *lot* purer than in nature. The limiting factor is crystal growth rate, so more production means more individual production units, not just flogging existing ones harder. No one will build a factory just to supply a brief period of high demand, so there will be "shortage" and correspondingly high market prices. The silanes used to make the crystals are energetically expensive to produce. The energy of production is about 5% or more of the expected total output over the service life for even the best new cells.
Thin film will help and alternative materials are a major focus of research, with considerable success but...

I believe the Snowy scheme can pump up from Jyndabyne to Eucombene dams.
I don't know how much it is used.

I once suggested a storage system using a motor to raise a heavy weight
and then when power out is needed, let the weight run down using the
motor as an alternator. The efficiency would not be brilliant but
then no other like storage systems are too good.
If really good quality motors/alternator were used, say 80% that would
be 80% of 80% would be 64% efficiency, not real good but usable.
To be of much use it would have to be a very large machine.

The use of floating car batteries would probably be OK if the rate
paid for power fed back into the mains was high enough to enable
a profit sufficient to make up for the loss of life from charge cycles
plus a profit. If not why bother ?

Bazz: "The use of floating car batteries would probably be OK if the rate paid for power fed back into the mains was high enough to enable a profit sufficient to make up for the loss of life from charge cycles plus a profit."

Yes. Obviously. It is not difficult to express this numerically. Perhaps illustrating it will drive home how poor current battery technology is. By crunching the battery price, capacity and number of cycles the batter is good for, we can figure out how much it costs to store a kW hour in the battery.

Existing:

Chemistry - cycles/$ per Whr - $/kW hr
=-=-=-=-=___=-=-=-=-=-=-=-=___=-=-=-=
Lead Acid - 800/$0.17 - $0.21/kW hr [1]
Ni Cad - 1500/%1.50 - $1.00/kW hr [1]
Ni MH - 1000/$1.00 - $1.00/kW hr [1]
Li Ion - 1200/$4.17 - $3.48/kW hr [1]
LiFePO4 - 3000/$0.80 - $0.26/kW hr [2]

Future?

Li Ti - 25000/$2.00 - $0.08 [3] ($2 sounds too cheap)
Li Thin Film - 40000/Big - Big [4]

By way of comparison, in a car that gets 10 km/litre, petrol currently costs roughly $0.10/km. I always use 0.2 kW hr per km for electric cars, so divide the above by 5 to get cost of paying for the the battery to drive a car for a km. That is before you pay for the electricity to put into it. In case it isn't obvious, Lead Acid doesn't work in cars - too heavy and too bulky.

Li Thin Film is I believe used in pacemakers. Its about the only application that can withstand their cost. But if you could make them for $1/Whr the world would be your oyster.

Cycles: http://en.wikipedia.org/wiki/Rechargeable_battery
Costs per W hr:
[1] http://www.allaboutbatteries.com/Battery-Energy.html
[2] http://www.zeva.com.au/tech/LiFePO4.php
[3] http://en.wikipedia.org/wiki/Altairnano
[4] http://www.excellatron.com/advantage.htm