Batteries can store wind power accumulated at night, when people aren't using much electricity.
If the wind blows at night but nobody is consuming electricity then, what is the value of wind farms? Batteries are the answer.
Such batteries create a storage technology that breaks the link between when power is produced and when it is consumed. this article highlights the point that the price of electricity varies sharply during a day. A wise arbitrage move is to "produce low" and "sell high".
While batteries are expensive, their price is likely to fall with experience and scale of production. Increased wind farm installation will increase the demand for batteries, this will help the electric vehicle industry as improvements in battery technology take place to serve wind farms. In this sense, these different "green technology industries are all interconnected.