Data of 13 wind farms shows that there are long periods of wind power higher than average where pumping could be used and only short periods of little or no power, for example 1st July to Sept13 has a one day(8/7) and a 3 day(15,16/7,17/6) low wind period separated by 6 days and then 13 good wind days before the next low wind day(30/7).