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[protomech]

Note that I talk specifically about the Nissan LEAF, but it could apply just as easily to our bikes with CHAdeMO or similar offboard direct-DC charging/discharging units. Think CHAdeMO on the 2013 Zeros, or (presumably) SAE J1772 Combo charging on a future Empulse.

http://protomech.wordpress.com/2013/07/31/decentralized-battery-grid-storage-and-the-13k-ev/

The charger would be somewhat less effective for our bikes, as it maxes at 30A. That would provide for 3 kW charging/discharging for the 2013 Zero/Empulse bikes @ 100V.

Still.. suppose the subsidy was halved for bikes. What would a $4k subsidy (bike) / $8k (car) and 3 kW (bike) / 6 kW (car) charging installed at home and work do to encourage adoption of electric vehicles?

[NoiseBoy]

Very interesting concept and the infrastructure is no more difficult than current on-grid PV installations.   Levelling day/night electricity demand is the biggest problem facing energy companies at the moment, this has to be worth a look.

[CliC]

I think that part about guaranteeing that the EV owner would have enough charge to take a trip on short notice would be the trick. I for one would be hesitant to allow some central, faceless organization to make that determination for me. And the first time someone gets into a discharged car when they really need to go somewhere, the power grid has permanently lost a participant.

But this idea is interesting. I'm assuming the EVSE has a grid-tied inverter in it or something to convert the battery's DC to AC. So with that cost a wash either way, let's say that when my EV battery degrades to its EV useful life (80% capacity), the patron of this system gives me an incentive discount/subsidy on my new battery in exchange for my keeping/housing my old battery and letting it be connected to the aforementioned inverter/charger as grid storage. That way, the only sacrifice I make is a little space. And the old battery gets nicely recycled. What do y'all think?

[WindRider]

This sounds interesting but there is a fair amount of lost energy in this equation.

You lose some power every time that you have to translate it from AC to DC to battery and then back again.   

[protomech]

Sure. Every form of grid storage is lossy. Pumped hydro has a round trip efficiency of around 70%; battery storage is closer to 80%.

[frodus]

But it's is lossy to generate it locally with an inverter than generate it remotely and have it go down the transmission lines.

[NoiseBoy]

The issue isnt efficiency,  the issue is capacity of power generation.    If you look at a 24 hour graph of energy demand, it peaks during the day and dips towards midnight.  There is a hole in the middle they call the 'bathtub' because of the shape of the curve.

Locally average demand during the day is around 120MW and we have a 100MW cable link to EDF in france, its nuclear generated but there is a deficit during the daytime so they have to fire up gas turbine generators to cope with demand.   At night time demand drops to 80MW or less on average.  That means if they had 20MW of storage, they could use the nuclear power from EDF to charge the storage at night and remove the need to fire up the turbines.

On a global scale companies are building power stations to cope with daytime demand which then sit idle all night.  Most forms of power generation are only close to their rated efficiency when running at their rated output.  Running them below this level makes no economic sense.