I didn't say technologies, I said energy sources.

> batteries do not have to become as energy dense as diesel

We need a storage mechanism that allows the energy gained from renewable sources to power things without interruption.

Two examples illustrate the problem today - for renewables to power a cargo ship the battery load-out required to move that loaded container ship would materially reduce its cargo capacity because it's wasting so much space and mass on literally tons of batteries. Compare the capacity, speed, and installed power of MV Yara Birkeland (electric container ship) to the OOCL Hong Kong (diesel powered cargo ship) for an idea. Another example is Tokyo suffering a predictable 3-day cyclone every year, where 27 million people need 22 gigawatts of electricity. Imagine the battery array needed for that (with its inherent cost, maintenance, limited lifespan and acres of space in a space-constrained land). So these are two easy examples of why storage density needs to increase by orders of magnitude to meet the bar you set of 100% replacement.

It won't be Li-Ion, it has to be something else, but that "something else" doesn't exist yet and the track record of an annualized 5% efficiency improvement for storage tech (which is generous but imagine even doubling it to 10%) per year won't catch up in our lifetimes. The math speaks for itself.

> roadblock is not technology, it's proper carbon pricing

If it were just pricing, it presumes that I have equivalent systems to implement and I just need to pay a premium for one vs the other. But that's not the case as illustrated in the examples above (and there are many, many more - airplanes, continuous smelting) where the existing energy storage tech doesn't work. So technology is an enormous roadblock.

As to carbon pricing - carbon pricing regimes require world-wide cooperation. IF you can get that, it effectively means limiting fossil fuel usage, right? Otherwise why are we doing it?

So limiting fossil fuel usage in a situation where there is no suitable replacement as described above, ultimately means you need to tell some guy in India that he can't have an air conditioner and some family in Africa that their agriculture development programs need to take a hit for lack of synthesized ammonia. This is a very unequal proposition. Alternatively, you can preserve that growth rate in the developing world and tell people in the developed world that they need to rewind their lifestyles in all ways (housing, vehicle mass, etc) to the early 1960's, which is when the US last had a consumption rate at the level needed to impact global warming. This is probably the preferable solution, but how tenable do you think either of these propositions really are?

There are undeniable humanitarian costs - not just monetary costs - to reducing fossil fuel use today when there are no (at scale) suitable replacements.