For solar, seasonality would be best addressed by thermal storage, which I mention here frequently.
This is being pursued most interestingly by Standard Thermal's "hot dirt" approach. They've updated their web page to include a few more technical details, which look to make sense economically (for example, they're putting the resistive heater(s) outside the dirt piles where it/they can be easily maintained).
The round trip efficiency (RTE) might be 40%, which is actually not bad since the input power (crude DC direct from solar modules) is quite cheap, not needing inverters or a grid connection sized to that DC power. Thermal losses are < 1%/month.
The technology would work down to a scale of about 100 kW average power, which is quite small all considered. Good for village-scale microgrids or individual small industrial enterprises. Scaling up, the average power would be similar to that of a large earthen dam of the same size, only the dirt would be used for to hold heat, not hold back water in a river, and could be sited almost anywhere. Heat retention improves as the size scales up; a dirt pile of the size of the largest dams, if it had been built and heated in the Bronze Age, would still be hot inside.
This is being pursued most interestingly by Standard Thermal's "hot dirt" approach. They've updated their web page to include a few more technical details, which look to make sense economically (for example, they're putting the resistive heater(s) outside the dirt piles where it/they can be easily maintained).
The round trip efficiency (RTE) might be 40%, which is actually not bad since the input power (crude DC direct from solar modules) is quite cheap, not needing inverters or a grid connection sized to that DC power. Thermal losses are < 1%/month.
The technology would work down to a scale of about 100 kW average power, which is quite small all considered. Good for village-scale microgrids or individual small industrial enterprises. Scaling up, the average power would be similar to that of a large earthen dam of the same size, only the dirt would be used for to hold heat, not hold back water in a river, and could be sited almost anywhere. Heat retention improves as the size scales up; a dirt pile of the size of the largest dams, if it had been built and heated in the Bronze Age, would still be hot inside.