All solar power has to be 100% backed up by reliable power generation sources. They can’t change that.
Bulk energy storage is the future, there are a half dozen technologies that are capable of storing multiple gigawatts of power. Pumped hydro,thermal energy storage,liquid flow batteries,molten silicon, molten metal batteries.
Look up thread MIT has two technologies that can store for weeks multiple gigawatts. Bill Gates is funding one of them. He is also funding the first generation four nuclear reactor in the USA which will also have on site energy storage to not only load follow but also boost it’s output doubling it for a peaker plant role as well.
The smart way is to over build cheap solar 3x to 4x then store it right next to the panels and release it at a constant rate 24/7 this maximises the power line usage as well since they are designed to be run flat out at their max rating 24/7 it’s a myth powerlines need to cool down at night they are designed for a load point in the daytime under full solar illumination at STP only during abnormally high heat waves do you lower the total capacity that’s an environmental factor and not all that common in most of the world. If heat is forecast to be an issue in the future you increase the conductor size to compensate for higher than standard temps adding a percentage of increased costs but the payback is increased power flows which generate additional revenues.