Zero Carbon Britain - Vehicle-to-Grid Power (V2G)

Vehicle-to-Grid Power (V2G)

Description

As a form of transport, electric vehicles combine a high level of energy efficiency with the ability to use renewably generated electricity. In addition, their batteries can double as energy stores for the Grid.

Technologies have been developed to allow energy to flow in either direction between vehicle batteries and the Grid, while at the same time preventing discharge below a minimum level (set according to the owner’s anticipated requirement).

Known as vehicle-to-grid power (V2G), the concept involves harnessing the energy storage of electric vehicle batteries for load balancing. When the Grid’s supply exceeds its demand, the surplus is used to top up the batteries of all connected vehicles. When demand exceeds supply, some of those batteries are used to make up the shortfall. This effectively turns connected vehicles into additional grid storage.

One can imagine varying tariffs under such a system. From an 'always charge' tariff, most suitable for doctors and more expensive, to a 'minimum charge 20miles' which would be significantly cheaper (sometimes paying the owner) and suitable for people without an immediate need for a long journey.

The National Travel Survey (2005) found the average car in Britain travels around 25 miles per day. Thus, cars remain parked for about 23 out of every 24 hours. If they are connected to the grid, their storage capacity can be used to smooth the fluctuations of electricity supply and demand, thus reducing the necessary peak generating capacity.

The amount of energy that could be stored in this way is substantial. There are currently 27 million vehicles in Britain. The average capacity of an electric vehicle is approximately 50kWh, giving an aggregate storage of 1.65TWh – around 1.6 days of Britain’s total electricity consumption. Likewise, a single vehicle holds the equivalent of over 2 days’ supply for the average household.

Even with optimistic reductions in vehicle ownership, and with only a fraction being plugged in at any given time, it is clear that they could provide much of the extra storage necessary to the Grid for security of supply in a renewable future.

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