Non-stop energy: promising tech for long-term energy storage

To decarbonize the grid, renewable energy sources such as wind and solar power are grabbing an ever-larger share of the power mix. To balance the intermittency of electricity supply and demand large scale renewable energy storage is needed. While storage for up to one day is feasible with batteries, there are very few solutions for >100h to seasonal storage other than pumped hydro. The most promising form of electricity storage is in form of a chemical storage. However, there will be competition for these chemical agents: ammonia is a fertilizer ingredient and methanol is a base chemical for polymers and solvents.

1. What are the most promising technologies and trends in seasonal storage?
2. What are the opportunities and drawbacks of chemical energy carriers, such as hydrogen, ammonia, methanol and methane?
3. What are relevant infrastructure and supply chain synergies?