It's also worth noting that when there is excess wind or wave power that can be used to pump water back up into the reservoirs of hydropower damns, allowing you to be able to use the power when there is low wind (not hugely efficient but works). And tidal power once fully up and running will have next to no down time,I'm a bit out of date with my info but fairly sure it was an hour or two a day, at peek high and low tide.