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Ok so, I had this great idea that a battery operated car has about 56kw, at least a Tesla does.
Why not take advantage of that power and buffer renewals during the day.

Too late:
http://en.wikipedia.org/wiki/Vehicle-to-grid

Vehicle-to-grid (V2G) describes a system in which plug-in electric vehicles, such as electric cars (BEVs) and plug-in hybrids (PHEVs), communicate with the power grid to sell demand response services by either delivering electricity into the grid or by throttling their charging rate.[1][2]
Vehicle-to-grid can be used with such gridable vehicles, that is, plug-in electric vehicles (BEVs and PHEVs), 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.[3]
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.[4] 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.[5]

And for the haters:

Poor net efficiency[edit]
Charging a fairly efficient battery system from the grid is at best 70 to 80% efficient.[citation needed] Returning that energy from the battery to the grid, which includes "inverting" the DC power back to AC with efficiencies of about 90% yields 63 - 72% energy return to the system. This needs to be factored against potential cost savings as well as the additional wear and tear on the batteries (current batteries last a few thousand cycles at maximum) and especially increased emissions if the original source of power is fossil based. The cycle of energy efficiency needs to compared with Pumped hydro which is less efficient. In addition, it is possible to take a small amount of energy from a large number of batteries if there are enough PHEV's distributed in society. 1 kW from 1000 vehicles is 1 megawatt of power and the energy is already distributed so it will not tax the existing powerlines if properly managed.
Not all skepticism is warranted. Jon Wellinghoff, from the US Federal Energy Regulatory Commission, points out that partial grid regulation (absorbing excess surges, but not supplying peak power) can be done without decreasing the life of the battery. This can be done "without affecting the charge whatsoever." [18]
 
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