Not just energy storage techniques but the material resources needed to manufacture and maintain them, the point that they will have to scale up considerably because wind, solar, and other sources have low returns, the point that they will have to scale up again to meet growing middle class demands worldwide, and the point that they will scale up once more to reverse diminishing returns affecting resource extraction, from oil to copper to uranium.
According to one study mentioned here, there is assurance that they will be able to meet a doubling in energy demand by 2050. But given the conditions of a capitalist global economy, especially with a demographic winter coupled to high per capita ecological footprints (e.g., Japan, which is one of the wealthiest countries in the world, has a footprint twice that of the global average and almost four times what global biocapacity allows), then it is very likely that at best all sources of energy combined may meet only basic needs, and that’s assuming that the world population is decoupled from that economy and works only on basic needs.
Finally, overall nuclear has the highest, then natural gas, and below that diesel and gasoline. But for various applications involving off-site equipment and transport, it’s diesel and gasoline:
www.eia.gov
That’s why they’ve been critical for industrial civilization during the past century, especially in a world where much of infrastructure needed for electric cars, electric grids, and mining and manufacturing sites are sorely lacking.
Put simply, in order to transition to fossil-free resources plus maintain high resource consumption in developed economies plus ensure the same for developing ones, all of which will create the concern that a global demographic winter will be our greatest threat, the amount of oil and material resources (not just minerals but even fresh water needed also for mechanized agriculture and manufacturing) we need will be equivalent to at least one more earth.