Battery storage technology has long been considered too costly at present to be a viable storage technology. However, recently costs for batteries have declined and are projected to fall. Vanadium Redox flow cells have been successfully used in Japan and the US for wind energy storage due to their high efficiency.
If the use of electric cars becomes more widespread, electric car batteries could be used for storage of electricity generated from wind power. At night vehicles could be connected to the grid and at times of peak demand vehicle owners could be paid for discharging their batteries.
Presently the deployment of electric vehicle charging and ‘pure’ battery technology is still in the early stages and would need significant investments in an exchange information system integrated into the grid. Large scale deployment of electric vehicles and willing participants in the scheme would be needed. It is highly unlikely that this would occur in the mid-term, if at all.
Also, hydrogen storage is in the development stages and is technically viable. Excess wind energy is used to generate hydrogen via electrolysis. Then at peak times hydrogen could be converted into electricity using a fuel cell or combustion turbine.
Magnets can also be used to store electric flow. To date, this technology has only been used for short-term storage. The two most widely developed technologies are Super capacitors and Super Conducting Magnetic Energy Storage (SMES).
One of the most interesting storage options is the use of residential water heaters. Using a smart device fitted to the water meter, the heater will switch on or off depending upon electricity load in the grid system. The stored hot water could be used at peak times to reduce overall peak load.