We are talking in two different subthreads at the same time.

Stick to the argument here. It is very simple.

Power->gas->power requires capital costs and operating costs. Even if PV is 3x as cost-efficient as nuclear, PV power divided by three and then paying for p->g->p is not cost neutral.

P->g->p has to pay for its costs over the narrow times where it is actually filling in. The rest of the time it is a dead weight.

Ah, but the capital cost of p->g->p is very low, per kW of capacity, compared to a nuclear plant. Like, an order of magnitude cheaper. Combustion turbines are so damned cheap compared to nuclear plants.

(The p->g part can be spread out over longer time periods, with the gas stored underground.)

Capital cost is around $3000/kilowatt of output for p->g.

This is hardly negligible-- indeed it's nearly half the capital cost of nuclear, and doesn't include the costs of storage, the cheap combustion turbine, or the infrastructure to produce the extra input power. Duty cycle for this infrastructure is going to suck, too, because presumably we're not going to be overproducing all the time.

Also, burning the fuel may not be so cheap. Best way to improve the capital cost of p->g relative to actual work done is to do combined heat and power... but this adds its own complexities and costs.

It may prove to be an important piece of the mix, but again: diversity is good.

I want you to be explicit in that $3000/kW figure. Is that per kW of peak OUTPUT, or per KW of effective INPUT? The input cost is spread over a longer time, so the capital cost there per kW is less important. Using nuclear for this would put all the capital cost on the output side, where it is more expensive, operating at a low capacity factor.

Consider a system intended to cover occasional shortages, happing 10% of the time. The p->g->p system would have to generate hydrogen at ~1/10th the rate it is consumed. So, if the turbines are 40% efficient, 1 kW of output capacity would require .25 kW of hydrogen generation capacity (measured in the energy content of the hydrogen; multiply by another smallish factor for efficiency of the electrolyzers).

In contrast, 1 kW of coverage from nuclear would require 1 kW of expensive nuclear capacity. You might be able to claw back some of that cost by selling power at other times, but you'll be getting only a small fraction of the total cost of making it at those times. So, the fixed costs of that nuclear capacity are going to have to be earned during that 10%, and the rate that would have to be charged would be ruinous.

I don't see how nuclear could possibly be competitive for this, if one analyzes the situation properly.

> Consider a system intended to cover occasional shortages, happing 10% of the time.

Which means, in turn, that renewable has to be engineered to be sufficient for 90th percentile circumstances.

And that GTP has to have turbines sufficient for 99.99th percentile - 90th percentile circumstances. This may be a rather long tail-- in the 99.99th percentile circumstance, renewables may be making very little and demand high.

And that PTG has to have electrolyzers that have enough capacity on, say, 0-60th percentile circumstances (because you don't want to tap some things, like reservoir hydroelectric, to run PTG) to make enough gas for those outcomes.

If you have 20% of your power coming from a reliable, constant source, every step in the above chain can be much more than 20% smaller, because you absorb a lot more of the long tail and because load shedding, etc, is more effective against the remaining unreliable power.

As an aside, there's a bit of an analogy to investing. Having a bit of a low-return, reliable instrument in your portfolio is helpful. Yes, it "costs a lot" compared to investing in the market-- that 2% interest bond costs 5x as much as investing in the market to 10% average returns-- but it is a stable source of value and reduces the volatility of the cost of spending money a whole lot.