Imagine turning your car to a power station when it is lying idle at the parking lot when you are off to work and actually getting paid for it. That is V2G technology for you. V2G technology or vehicle to grid technology enables an electric-drive motor vehicle to export electric power to the grid when the vehicle is not in use for transportation. It can be used with gridable vehicles, like battery operated electric vehicles (BEVs), fuel cell run vehicles and plug in hybrid vehicles (PHEVs). Figure 1 below shows the V2Gtechnology as it is envisaged when fully developed.
Fig 1: Concept of V2G
(Source: Center for carbon free integration: The University of Delaware )
The main advantage of using V2G technology is that it turns the car into a power plant which can supply electricity to the grid when required. It makes sense since most vehicles remain parked at any point of time (95% for an average vehicle in America and 90% even during peak hours) according to some estimates . It provides a way to supply electricity to the grid when it is required the most, during the peak demand hours like for instance the late afternoon hours while charging them during the off peak hours where fortunately in many places (Texas for instance), a lot of renewable power (like wind energy) is generated. This has the potential to spare the utility companies, at least partly of the need to invest in the creation of spare capacity to cater to the peak hour electricity demand.
The Center for Carbon free integration at the University of Delaware headed by Dr. Willet Kempton has created a system that uses this technology. In this video , Dr. Kempton explains about this system which has been fitted on an electric car as a prototype. Google Inc. , in collaboration with P.G and E has employed this technology on Toyota Prius cars with PHEV capacity at its headquarters at Mountain View, CA.
An additional advantage is that the car, instead of supplying electricity to the grid, can also be used to power homes directly by plugging it to the mains as explained by Dr. Kempton in the above video3. This is especially useful during times of blackouts . Using V2G technology also has environmental benefits as the cars themselves are emissions free. Provided we could generate a good percentage of our electricity from renewable sources , they could help reduce carbon emissions. It also results in cost benefits to consumers as it would be cheaper for them to utilize electricity at a lower rate while charging during off peak hours while either selling electricity to the utility companies or powering their homes during peak hours when the per unit rate of electricity is higher. It also makes sense for utility companies on account of savings arising due to lowered capital costs as they are spared of the need to invest in the creation of additional capacity .
Further research is underway on different aspects of the V2G technology , including the idea of smart charging, systems to control the amount of electricity that could be fed back to the grid, besides further trials of this system by universities, utility companies as well as car manufacturers. According to some estimates, the commercialization of this technology is at least ten years away, by which time PHEVs should have penetrated the car market to a significant extent and hence serve as the media on which this technology could potentially be deployed.
On the flip side, there is also a lot of skepticism  about this technology mainly in the areas of the compatibility of the power electronics between the system fitted in the car and the ones used for the grid, the longevity of batteries, their weight as well as the number of charge and discharge cycles they could be subject to, as well as the plug in infrastructure. Further research is needed before this technology could be deployed on a large scale and it could be some years before this becomes a reality. However, one thing is for sure, V2G technology holds great promise for the future.
1) "V2G concept", Center for Carbon free power integration, The University of Delaware.
2) J. Tomi´c, W. Kempton, J. Power Sources (2007), "Using electric fleet drive vehicles for grid support", Journal of Power sources, doi:10.1016/j.jpowsour.2007.03.010 (article in press)
4) "Power to the people: Run your house on a Prius" New York Times (09/02/2007)
5) Vehicle to grid V2G technology, www.solarnavigator.net