Nuclear, Wind, and Solar are effectively free
energy, but costly
capex. This leads to a very different economic model than your math is concerned about.
On a daily basis, the USA roughly doubles its electricity consumption to peak hours, and halves it during off-hours. Furthermore, electricity usage during the summer (for air conditioning) can be 2x more than winter (heating costs). So our day-to-day peak/off-peak cycles are roughly on a 1-to-4 ratio. We are already seeing this effect in practice. In states with severe amounts of solar deployment, the price of energy drops to
negative, which is even "better than free". That's just the free market and the realities of our energy market talking.
Bottlenecks are preventing cheap wind and solar energy from reaching high-demand areas.
www.bloomberg.com
So the economic reality is... grossly different... than what you seem to understand.
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So some areas of our country, at certain times, are facing a huge amount of negative electricity prices. My answer: build a H2 plant there to take advantage of free (or even negative-cost) electricity. It doesn't matter if its 50% efficient or 100% efficient, you just benefit from the excess solar power / renewables
that already exist in this country. And as more-and-more renewable energy is deployed, we will see more-and-more of these economic activities pop up.
This economic mismatch happens because grid stability is exceedingly complex in practice. We will not be able to "fix" negative electricity prices, because we need perfect weather prediction to do that. (If the weather is 5F cooler than expected, AC won't spin up as much and bam, excess electricity will be generated). This combined with unpredictable (on a day-to-day basis) solar or wind means that the price of electricity will swing on an hour-to-hour basis as we deploy more renewables. Having plants that can spin up and take advantage of these effects (like H2) is a serious possibility. (Kind of like a reverse-peaker plant: a plant that will consume electricity on demand to stabilize negative, free, or low electricity prices)