At an fast increase of photovoltaic, it will be soon necessary to store electric power and to feed the power equable in the power grid.
There are storage power plants, but their capacity is very limited. The power plant group Kaprun can produce 330 MW electricity, but has only 113 MW for pumping the water up. This is designed to pump up all the night with excess electric power and to deliver at midday high power. At much photovoltaic, it's exactly the opposit.
The limits of electric power storage
At about 80 GW photovoltaic in Germany are the existing storage power plants not enough. Starting with this stage, additional storage capacity like batteries has to be built up. A usefull extension of battery capacity would be 5 kWh batteries per installed kW photovoltaic to create a day night balancing. The world wide resources for lead are not suitable for this task. The world market of lead becomes messed by around 60 GWh batteries for 60 million electric scooters in China. The quantity of photovoltaic to replace 50 million barrel crude oil a day requires 40,000 GWh batteries for the day night balancing. For luck 1 kWh lithium iron phosphat requires only 40 g lithium per kWh battery capacity. In the 40,000 GWh batteries will be 1.6 million tons lithium used.
Hydrogen economy + Methanol economy
Beyond a day night balancing is battery storage not usefull. Starting with 250 GW photovoltaic in Germany will be the combined hydrogen methanol economy the only usefull application for excess electricity.