Leveraging existing assets is one of our best prospects for cleaning up the air and cutting petroleum consumption. An under-appreciated possibility is using conventional hybrids, even retrofitting existing ones, to substitute a bit of grid power for petroleum fuel.
In an article on advanced lead-carbon batteries for mild hybrids at GCC
, there are these notable phrases:
The state-of-charge (SoC) of current lead-carbon batteries is typically maintained at between 30 and 50%.... Advanced lead-carbon batteries for vehicles currently under development will be capable of operating in the 30 to 70% SoC range at 12.5kW.
That's operation. What about off-line? Lead-acid likes to be held at 100% SOC, and I doubt that lead-carbon suffers at all from it. NiMH batteries also appear to prefer to be held at 100% SOC and cycled only shallowly
. Neither could accept regenerative braking power when full, but when the vehicle is starting and driving shortly after start there is no braking energy to recover.
The GCC article continues:
Future battery developments will most likely combine advanced lead-carbon electrochemistry with ... substantially reducing the size of a 1 kWh battery required for mild electrification of the powertrain.
The hybrids and mild hybrids of tomorrow will have on the order of 1 kWh (above) to 1.3 kWh (base Prius) of battery, and operate it in a SOC range centered between 40% and 50%. But if the battery was charged to 100% SOC off-line, there would be between 500 and 700 Wh of extra energy to move the car (or for other functions, like instant high-power defrost). This is enough for perhaps 2 miles of petroleum-free driving, perhaps more if the first stretch after starting is creeping in traffic for an extended distance.
How much fuel could this save? Approximately 930,000 hybrids (not plug-ins or BEVs) were sold in the USA in 2012-3. If we assume 10 battery top-offs per week 52 weeks a year, 2 miles range per top-off and 40 MPG consumption avoided, the 2012-3 fleet would avoid about 1 gallon consumption per vehicle per week, 52 gallons/vehicle/year, 48 million gallons/year for the fleet. The total for the hybrid fleet going back to the oldest Priuses on the road would be multiples of this, perhaps a good fraction of a percent of total US gasoline consumption.
What could this do for the grid? 1.2 kWh/day 5 days a week isn't much, but if you can draw it on demand it might be worth something. The J1772 Level 1 spec is 120 VAC @ 12 A, or 1440 watts. 930,000 vehicles @ 1.44 kW/vehicle is 1.34 GW of potential demand. It would take only about 25 minutes to put 600 Wh into a battery at that pace, but 25 minutes of demand equal to a large nuclear plant available twice a day (perhaps 3x, if vehicles are plugged in during after-work errands) might be very useful to ISOs for down-regulation of the grid.
This is a small possibility, not a big possibility. But there is a big push for mild hybrids (perhaps multiples of the number of conventional hybrids), and a lot of littles make a lot.