Electric vehicles as Energy Storage

Electric vehicles are a potential mobile storage for grid electricity. Three electric vehicle configurations have been identified to date: hybrid electric vehicles, which are not grid-connected and are entirely reliant on fossil fuels; plug-in hybrid electric vehicles, can be charged using an external power sources and can also run on fossil fuels; and battery electric vehicles that are entirely reliant on an external power sources for charging.

The majority of electric cars on the road are plug-in hybrid and thus there is not enough motivation for the rapid deployment of electric vehicle charging sites and vehicles. Electric vehicles are not price competitive with conventional cars and the lifetime of batteries is far too short. Development of the electric vehicle market is going to dependent upon adequate incentives, high oil prices and breakthroughs in battery technology.

It is highly unlikely that large numbers of battery electric vehicles will be on the road before 2020. Plug-in hybrids will still be more favourable to consumers than ‘pure’ electric vehicles due to their fuel flexibility and lower cost. In the short to mid-term the market is expected to experience significant competition from conventional vehicles and advanced cars which use cleaner versions of diesel and gasoline including biofuels. Then in the longer term electric vehicles may face serious competition from hydrogen fuel cell vehicles.

If electric vehicles were used as a storage option for the electric grid the charging infrastructure must ensure that vehicles plugged in at the required times. A situation where electric vehicles plugged in at the same time creating a large peak load is quite feasible. For example, workers finish their nine-to-five job, come home and all plug-in their vehicles at the same time. Alternatively, behavioural education programmes will need to be implemented to ensure that owners remember to charge their vehicles at times where output from intermittent renewable such as wind and solar is at its peak. Usually these times are during the daylight hours for solar and at night for wind power. Not to mention, the charging of electric vehicles must be able to adapt to seasonal changes in the generation of electricity from intermittent resources.