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The momentum of the solar energy transition
(www.nature.com)
Due to technological trajectories set in motion by past policy, a global irreversible solar tipping point may have passed where solar energy gradually comes to dominate global electricity markets, without any further climate policies
Cost mostly. It's really expensive, enough so that the first ~80% of the shift off fossil fuels is going to happen using solar + wind + storage.
To make sense for the last 20%, it's going to need to come down in price enough to beat the emerging longer-duration storage technologies. Not at all clear to me that it can do that.