Electric-drive vehicles, whether powered by batteries, fuel cells, or gasoline hybrids, have within them the energy source and power electronics capable of producing the 60 Hz AC electricity that powers our homes and offices. When connections are added to allow this electricity to flow from cars to power lines, we call it "vehicle to grid" power, or V2G. Cars pack a lot of power. One typical electric-drive vehicle can put out over 10kW, the average draw of 10 houses. The key to realizing economic value from V2G is precise timing of its grid power production to fit within driving requirments while meeting the time-critical power "dispatch" of the electric distribution system.
The Rocky Mountain Institute has been studying this issue (and has launched The Smart Garage initiative). One of their fellows, Bryan Palmintier, recently wrote an article posted on Yahoo Green News, How Your Future Car Could Help Add Power Back to the Grid. He describes the most basic approach to the technology:
The simplest V2G strategy is to charge vehicles at night, when electricity use (and price) is lowest, and then use the batteries to provide power during the peak demand (typically in the afternoon). This way, V2G could replace the so called "peaker" power plants, which run for only a few hours to meet the highest loads, and are typically the least efficient and most polluting.
To be effective however, this peak shifting would require millions of V2G-capable vehicles on the road (or, more precisely, parked in the afternoon), which will take some time to happen. In the short run, the most promising use for V2G is to provide "ancillary services" to help stabilize the grid.
But, another smart way to implement the technology would be as a supplement to renewable sources of power where the levels of energy fluctuate frequently:
Another exciting possibility for V2G is to help compensate for (or "firm") the variable output of intermittent renewables such as wind and solar.
When the wind blows or the sun is out, vehicles could charge their batteries, while still leaving plenty of power to run other loads on the grid. Then when the wind slows, or a cloud covers the sun, power from the vehicles would be used to continue to provide the same level of power to the grid.
Many innovative solutions to our energy problems are within our grasp with a little imagination and the willingness to make some changes to the entrenched infrastructure.