Depending on the location, there could be sources of geothermal energy, like Iceland. There are also various prototypical approaches at storing solar energy for the winter months, like molten salt (obviously a bit too spicy outside of industrial settings), or generating hydrogen and storing it in iron ore. The latter approach was recently pioneered by ETH Zürich.

https://ethz.ch/en/news-and-events/eth-news/news/2024/08/iro...