Comment by vrganj

Iceland is a small area, small population outlier literally sitting on two plates rubbing up against each other and a relative excess of active volcanism and large lava fields.

  About 85 percent of the total primary energy supply in Iceland is derived from domestically produced renewable energy sources. Use of abundant hydroelectric and geothermal power has made Iceland the world's largest electricity producer per capita.

~ https://en.wikipedia.org/wiki/Iceland

What works for Iceland works in few other places to the same degree (New Zealand, Yellowstone, places with thin crust and feisty caldera's).

Countries like UK, Ireland, Germany, Danmark, Netherland, Poland also have dark winters. Solar in winter is only about a fifth of production in summer months.

Iceland has geothermal, which is amazing, but won't help central Europe.

Storage of energy in the dimensions required for weeks with almost no wind is an unsolved problem. Right now, we can't store enough to make it through a single night without using fossil fuels. Most countries don't even have the capacity to store the energy for a single hour.