deff

If I were to guess, the metabolism generates waste during activity that gets processed and exhaled as CO2 during sleep.

Impossible to use mechanical doping now with the current inspections. Has it been used before these inspections were implemented? Very likely. An hungarian engineer developed a motor with spools in the rims and the stator in the forks. For sure at some point this offered a better risk/reward than PEDs.

Regarding drugs, yes it´s most likely still happening, but nowhere near the levels it used to be.

Riders are tested a lot and have to provide year-round whereabouts for random testing. They also have a frequently updated blood passport to detect sudden changes in values caused by PEDs. It can never be fully waterproof, but at least serious efforts are made.

That is indeed why you don´t see them collapsing and also why the finals are much longer nowadays. Riders train their guts to be able to eat up to 120g of carbs per hour, for the whole duration of the race.

Regarding stability, this physical inertia is also present in rotating wind turbines. But I guess exploiting this at a meaningful scale would recquire a level of interconnectivity which boils down to the same issue of cost.

I am however optimistic about grid-scale storage. There is a long term trend of rapidly dropping battery prices, and with recent developments in sodium ion batteries there is no fundamental reason this won´t continue. Another enabler could be advancements in lifespan. This could allow storage being installed inside or near wind and PV, cutting down on space and installation costs. Even then however, grid improvements would be needed.

Some problems still need to be solved indeed, but in my (mostly uneducated) opinion, they seem easier than achieving economically viable fusion. But they do still require large investments in R&D and manufacturing capability.