I am the cofounder at Airthium (YC S17), we make a seasonal energy storage system based on green ammonia and thermal storage (molten salts or sand). We are currently developing a low NOx ammonia burner in partnership with UC Louvain in Belgium
It seems more likely that most users will prefer to import ammonia from tropical solar farms, and keep local tankage of just a couple of weeks' worth. It is hard to imagine where seasonal storage would be needed.
Practically everyone imports what they need, at need, today. Only pipelines have lately been considered a problem. "Strategic National Reserves" are a thing, but thus far only used for economic leverage, to my knowledge. Underground storage of NG is pretty common, but again used mainly for price stability.
But this is not the only place where I see people honestly believing that seasonal storage would be desirable and important. I hope they are not, in the end, disappointed by slack demand.
We are targeting the industrial heat market first.
Our proprietary electric heat engine (=a heat pump) can generate heat up to 1000℉, and we will use it to replace industrial gas boilers and dryers with a CO2 free solution. We are in discussions with multiple potential customers for this product.
The development of the ammonia burner is done in parallel as it will be useful in a few years, when we will be ready to deploy the seasonal energy storage system.
A few companies like Form Energy are starting to deploy their first pilots at scale, let's hope they succeed!
Check us out! https://airthium.com