Eschew Obfuscation: Vehicle-to-Grid (V2G)

Vehicle-to-Grid (V2G)

Max Dunn — Wed, 30 Jan 2008 16:20:00 -0800

What is with this vehicle-to-grid (V2G) stuff? Why is everyone so excited about it? I already showed how using batteries to store energy at night when it is cheap and then use it during the day doesn’t make sense economically¹.

However, this is only part of the picture. It turns out that electricity generation is very complicated, in large part because there is no real storage on the electrical grid. Think about this: what happens when the power plants on the grid don’t produce enough electricity? There will be brownouts or blackouts, both of which are bad. But what happens when they produce too much electricity? Where does it go? Well, actually, since there is no real storage on the grid, it can’t go anywhere, so this is bad.

"Vehicle-to-Grid (V2G)" by Max Dunn

Fri, 01 Feb 2008 15:14:33 -0800

When a battery is only lightly discharged, it’s life is extended, sometimes greatly. For instance in a typical battery, discharging to 80% gives 500 cycles, discharging to 50% gives 1000 cycles, gives 5000 cycles. Put another way, a 10kWh battery pack would produce a total lifetime energy output of 4,000kWh at 80% depth of discharge (DoD), 5,000kWh at a 50% DoD, and 10,000kWh at 10%.

1 Battery Life

"Vehicle-to-Grid (V2G)" by Max Dunn

Fri, 01 Feb 2008 11:48:31 -0800

There are several barriers to making V2G happen:

There needs to be an aggregator for this power, since the ISO won’t want to deal with individuals
The ISO regulation signal needs to be transmitted to each car
We have to figure out a way to meter the power, no matter where the car is (home, work, shopping)
The cars needs some more electronics installed to invert the battery power to A/C and transmit it back onto the line
The ISO needs to update their software so they can deal with a zero power nominal level

"Vehicle-to-Grid (V2G)" by J.R.

Fri, 01 Feb 2008 11:44:18 -0800

This is very interesting stuff. So what are the barriers to making this happen? Is it difficult to engineer a way for the individual batteries to start outputting when necessary (I wouldn’t think so)? Or is it simply chicken and egg – there are no battery banks available, so there’s no energy program to encourageit.

Also, I’d be interested in seeing your math for this. How do you get $390 month? And how does this impact the cost of the batteries – like your earlier analysis?