The concept of “vehicle-to-grid” (V2G) links two of the most critical factors of modern society – transport and electric power; both of which will need to undergo technological transitions to more renewable sources in order to achieve oil independence, increase energy security (reducing risk of shocks), and improvements in our natural environment in response to global climate change.
Electric vehicles (EVs), such as plug-in hybrid or battery electric cars, would use and also potentially supply power to the national grid, as grid-connected batteries would charge during low-demand hours and discharge when power is needed. The V2G concept could assist the transportation system by reducing petroleum use, strengthening the economy, enhancing national security, reducing strain on petroleum infrastructure, and improving the natural environment.
In order to operate in a V2G configuration there are 3 key components, namely,
A power connection to the electricity grid
1. A power connection to the electricity grid
2. A communication device to allows the grid operators access to the vehicle’s battery, and
3. Precision metering on board the vehicle to track energy flows
This two-way communication between the national grid and the vehicle presents an opportunity for more effective energy and resource management, and allows owners of EVs to earn money by selling power back to the grid during peak demand periods. EVs have the opportunity to become not only vehicles, but mobile, self-contained resources that can manage power flow and displace the need for electric utility infrastructure. V2G vehicles can reduce the lifetime cost of EVs, making them more attractive, and if V2G increases the market share of EVs, the benefits of EV use also increase. Whilst the benefits of EVs are clear, particularly in terms of running costs as electricity remains cheaper than petroleum (for equivalent distances travelled), the prospect of selling power back to the national grid could generate an additional revenue stream for owners of these vehicles in a V2G system. The batteries in electric vehicles could store electricity produced by wind turbines and other renewable sources, for example, and provide the power back to the grid when needed.
The concept may also spur efficiency gains in the electricity industry. Electricity infrastructure has been designed to meet the highest expected demand for electricity, which means that during the hours of off-peak use, enough energy is produced (and could be utilised to) power the nation’s EVs, without burdening the national grid too much to increase supply, as long as charging is targeted at off-peak times through a tariff system.
As a result, the V2G concept could provide a new demand and therefore extra revenues for electricity companies for a similar level of production. This will be especially the case at night when electricity is under-utilised during periods of low demand. As most electric cars will be plugged-in during the night for charging, the V2G link to the batteries within electric cars provides additional storage capacity for the grid (reducing the need to build extra power plants). However, there a number of social and technical barriers that require government support before any benefits can be realised.
V2G may also effectively utilise fluctuating power generated from renewable sources such as wind turbines. However, as most wind turbines produce most of their electricity at night, just when EVs would need to be recharged, a V2G strategy presents an energy storage technology, which could be part of a flexible energy system that better utilises fluctuating renewable energy sources. This would support the development and integration of such renewable sources of electricity (wind power, solar photovoltaics and others) into the grid, without the need for spinning reserves and load management. The cars could supplement existing large-scale pumped hydroelectric and compressed air energy storage systems, which have proven effective for enhancing the value of renewable-energy technologies to date.