> There isn't much growth potential for hydro But there's significant potential in wind, particularly offshore. > That means you need to overbuild PV and wind

> There isn't much growth potential for hydro But there's significant potential in wind, particularly offshore. > That means you need to overbuild PV and wind independently, which may be an option but a costly one. Quite the opposite. Exactly because wind and solar have opposite seasonality you need to overbuild less in total with the sum of both than you would independently. See the spreadsheet. The 100% renewable scenario only requires 15% overbuild in total and it's all in solar which is now the cheapest electricity source ever. It also maintains net exports to the rest of Europe over winter which is probably when those exports are most valuable. > And you'd still need more storage, 6 days are too short, there are lulls that last longer than that. Even when in a "lull" the sources aren't at 0. 6 days of full load fills gaps much larger than 6 days. > If seasonal storage can be built then it would complement both sources and could decrease the required overbuild factor. It would have to be very cheap to be competitive with only 15% of overbuild, particularly of solar. I don't think any of the existing or proposed technologies come even close.