Comments on: National Research Council says benefits from plug-in hybrid vehicles decades away

By: Ed Reid

Ed Reid — Mon, 21 Dec 2009 15:29:27 +0000

Tom,

Thanks for the link.

I still believe that the dependence on grid connection is blindingly obvious, as I stated above.

The net transaction between the grid and the vehicle, especially for an EV, must be G2V during each connection period and must leave the vehicle essentially fully charged at the end of the connection period, so that the vehicle is available for its intended purpose, though that does not preclude periods of V2G during the connection period.

However, it would seem that variable rate G2V would be as effective under most circumstances; and, it would tend to enhance the users’ value proposition. The rectification and battery-in losses occur on the customer side of the meter, as would any inversion and battery-out losses. Also, the customer would be adversely impacted by increased battery cycling.

The users’ value proposition is not obvious when the in/out transactions occur primarily intra-period, so that there is no rate-based spread between the multiple purchase and sale transactions. That is not to suggest that such a value proposition could not be structured, such as through a grid balancing service fee.

By: Tom

Tom — Sun, 20 Dec 2009 22:20:06 +0000

DOUG-
You’re right that “speed” was the wrong word, I should have said “constant loads”, not speeds.

As for the source of the value of V2G, the UPS study referred to above assumes otherwise.
http://www.altenergystocks.com/archives/2009/09/usps_study_ev_economics_depend_on_smartgrid_revenue_1.html

By: D.O.U.G.

D.O.U.G. — Sun, 20 Dec 2009 16:39:44 +0000

Constant *speeds*? I’m afraid you don’t understand, Tom. Generators don’t speed up or slow down (except very slightly in very short-term excursions that average to zero). You’re thinking of the plant output level, which isn’t related to the “speed” of the generator.

My guess is that Ed’s most likely correct that the real V2G value is in on-peak operation, not in smoothing short-term fluctuations in supply and demand. There are some efficiencies in consumption of energy off-peak, which do tend to keep baseload generators operating at more efficient output levels, but that’s not exactly V2G.

By: Tom

Tom — Sun, 20 Dec 2009 15:40:35 +0000

Ed- Sometimes the blindingly obvious not correct.

V2G cannot only provide power at peak, but it can also be used to help smooth fluctuations in supply and demand, allowing fossil fuel generators to operate more efficiently at nearer to constant speeds. These services are useful 24/7, and the majority of the $200/day value in the UPS study derived from these services. $200 seems high to me, but there is value there.

By: Ed Reid

Ed Reid — Sun, 20 Dec 2009 14:19:21 +0000

It is blindingly obvious that V2G requires that the vehicle be connected to the grid. The potential benefits of V2G exist only during periods of peak demand, in the afternoon of hot business days. In the afternoon of business days, delivery vehicles, such as those used by USPS are on the road, not parked and connected to the grid.

On those same hot business days, vehicles used for transportation to and from work are parked in the company lot or in a commercial parking facility. While they could conceivably be connected to the grid while parked for work, that would trigger the potential for the energy stored in the battery to be inadequate for the trip home. While that would not necessarily be a deal killer for a PHEV, it certainly would be for an EV.

Of course, business hours could also be shifted to offset the non-AC power loads from the AC peak.