There's also batteries: virtual power plants that give us the ability to arbitrage between when power is cheap and when power is needed. These can be rolled out in conjunction with residential PV systems and eventually pay for themselves. A similar approach can be used to store hot water produced during the day by PVT (photovoltaic-thermal) cells.
See:
https://en.m.wikipedia.org/wiki/Thermal_energy_storage
https://www.energy.gov/sites/prod/files/2014/01/f7/csp_revie...
Batteries, in their current form, have all sorts of issues that haven't made them economically viable either. Liquid electrolytes (liquid batteries) do show promise for grid level storage, and I am pleased to see lots of activity around them but we are still probably 5-10 years away from anything worth scaling up around.
Hot water is fine for extreme micro uses - individual buildings - but again not even remotely viable for something at scale, let alone replacing base load generation for the grid.
Base load is the real nut to crack - and so far solar is no where near being anything but a nice supplement for base load.