- Use 100 hour battery tech, which is almost (years not decades) at commercialization. This can bridge pretty big gaps.
- Dam and fill some big valleys in the low-solar areas with water and put generation and pumps on them, to store water all summer for winter use in generation.
- Wind works most of the year. Offshore is great for that.
- HVDC lines streching from sea to shining sea.
- The BIG one: You can save 30% or more on HVAC and other specific loads, if you let software control them better. The problem is retrofitting shitty old buildings with electronics to do it, and getting building managers to repair their HVAC systems instead of letting them languish.
Instead, we need to rely on the fact that it's not winter everywhere, at least to the same degree. My house has a similar seasonal profile to yours, but an industrial plant in the Mojave desert does not get shaded by hillsides, does not have atmospheric rivers come in, can move the panels to follow the sun's angle, is at a far more southern latitude, etc. And several generation technologies like hydro and wind actually produce more in the winter than the summer, because rainy and windy days benefit them.
This is probably the biggest argument I've seen for the continued existence of the grid. My home can run indefinitely on self-supplied energy during the summer, but I still need the grid to get through the winter.
However, seasonal storage is a completely different beast. In the winter there are months without a lot of solar. For my solar panels, total energy generated in December is are about 15% of that in June.
Seasonal storage is a lot more expensive than daily storage, because you can use your battery for only 30 cycles (30 years) rather than 1000-5000, depending on the technology used. That means that storing power generated in June and using it in December costs somewhere around 1$\kWh, simply to expensive. Do you have any ideas on how to solve that problem?