A quick search revealed that the concept of cars selling energy to a grid already exists --at a wider scale, that of the electrical power grid, which makes even more sense of course!-- and is called Vehicle-to-grid (V2G):
http://en.wikipedia.org/wiki/Vehicle-to-grid << Vehicle-to-grid (V2G) describes a system in which power can be sold to the electrical power grid by an electric-drive motor of a hybrid vehicle that is connected to the grid when it is not in use for transportation.[1] Alternatively, when the car batteries need to be fully charged, the flow can be reversed and electricity can be drawn from the electrical power grid to charge the battery. Vehicle-to-grid can be used with such gridable vehicles, this is, plugin vehicles (this is, electric vehicles as Battery Electric Vehicles (BEV) or Plug-in hybrid electric vehicles), with grid capacity. Since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back, with a value to the utilities of up to $4,000 per year per car.[2] One notable V2G project in the United States is at the University of Delaware, where a V2G team headed by Dr. Willett Kempton has been conducting on-going research. Their goals are to educate about the environmental and economic benefits of V2G and enhance the product market.[3] Other investigators are the Pacific Gas and Electric Company, Xcel Energy, the National Renewable Energy Laboratory, and, in the United Kingdom, the University of Warwick.[4] ... Three versions V2G is a version of Battery-to-grid power applied to vehicles. There are three different versions of the vehicle-to-grid concept: A hybrid or Fuel cell vehicle, which generates power from storable fuel, uses its generator to produce power for a utility at peak electricity usage times. Here the vehicles serve as a distributed generation system, producing power from conventional fossil fuels or hydrogen. A battery-powered or hybrid vehicle which uses its excess rechargeable battery capacity to provide power to the electric grid during peak load times. These vehicles can then be recharged during off-peak hours at cheaper rates while helping to absorb excess night time generation. Here the vehicles serve as a distributed battery storage system to buffer power. A solar vehicle which uses its excess charging capacity to provide power to the electric grid when the battery is fully charged. Here the vehicle effectively becomes a small renewable energy power station. Such systems have been in use since the 1990s and are routinely used in the case of large vehicles, especially solar-powered boats....>> Going back to the specific EV recharging problem, in such a scheme what would be needed would be a mains socket at every possible parking spot, where a car in need of power could draw it from the grid, which would itself, especially during daytime, be mostly powered by the other EVs nearby playing the role of distributed buffers. The need for recharging stations as such disappears, as the cars interface directly with the grid. Of course, smart sockets with bidirectional power metering means and secure identification means will be needed, this seems to be the first thing to develop. Michel 2009/8/14 Michel Jullian <[email protected]>: ... > How about a grid wiring all spots on the parking lot? This way (riding > my soapbox again) the cars with extra energy could sell it back, not > to individual buyers in this variant, but to the parking lot's grid. > Wouldn't this be a nice way to implement the huge local storage > required? ...
