The efficiency of this process is like 35%. (power to gas to power with methane).
If you're making a bunch of methane anyways, it might be OK to fill in a little with this, but this does not sound like a great overall strategy.
Why not just throw in a little nuclear for base load, and then everything looks a lot better/easier?
Nuclear is basically dead right now because of cost. The biggest factor in nuclear cost is financing and interest rates, which are very risk-sensitive. When existing nuclear plants are shutting down right now, because they're losing major customers to cheaper wind power, what happens to the risk on 50 year investment scales? Risk goes up, interest goes up, and plant cost skyrockets. So the very fact that nuclear costs more than renewables makes nuclear even more expensive than before.
Because power to gas to power delivers a fraction of the input power, and has a bunch of cost itself-- it isn't free.
The cost of PV solar has dropped over 80% in the past decade, and we don't know what the bottom is yet.
So reaching parity seems difficult.
On the other side, gas turbines are incredibly cheap. A simple cycle gas turbine plant costs as little as $400/kW, vs. $10,000/kW for a nuclear plant.
It's this huge cost advantage of combustion turbines that is making natural gas such a killer competitor these days (along with fracking).
> If solar costs less than a third what nuclear does (which is where we're headed, we're already down to half), why do you need nuclear base load? Why not just do this gas conversion?
I objected, because energy to gas costs money, and gas to energy uses money. You have to count the other costs before you can assume cost parity.
Simple enough?
It blows the socks off nuclear at other times.
But nuclear needs to get its high prices 24/7 to make economic sense. Otherwise, the cost of that 20% capacity factor nuclear is going to balloon even higher.
Simple enough?
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.
(The p->g part can be spread out over longer time periods, with the gas stored underground.)
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.
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.
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.
It's almost like you're saying that having 30% of the power completely reliable and non-variable doesn't make the problem considerably easier.
Nuclear makes an annoyingly constant amount that has little to do with demand. Wind makes an annoyingly variable amount that has nothing to do with demand.
That's right. And we know that they work and they can scale with our needs. We know we can make them cleaner and more efficient.
Maybe wind and solar just isn't the technology of the future for anything by niche applications.
Talk about an understatement. Imagine the trillions of tons of CO2 that would not have been emitted into the atmosphere had the developed world invested in nuclear to the same level as France. It would maybe bought us another 50 years.
Really puts into perspective the destructive force of anti-nuclear environmentalism.
>We have less than ten years of current emissions left if we want to stay below 1.5°
Hate to break it to you, solar/wind/battery isn't going to do it. It can't do it today, and there's nothing forthcoming to change that. Germany who went all in, is projecting 2060s as the time they wean themselves off of fossil fuels. France on the other hand is essential fossil-fuel free from power generation today, as is my home province on most days (thanks to Nuclear and Hydro) [1].
So fix that broken process. This is a nonsense result.
But at some point, the variability of renewables is going to start costing two arms and a leg, too. So a bit of dependable, low-carbon power in the mix sounds really good.
Then you size wind and solar for the remaining 70-90% of load, say 70th percentile.
During the remaining 30% of the time, you use agreements that allow you to shed load and you draw upon intermittent hydroelectric resources.
The solar/wind overcapacity factor and the remaining bit of battery or power->gas->power you need can be much, much smaller because the reliable nuclear base load really stretches the hydro and load shedding.
And you can use the "extra nuclear power" when wind/solar are overproducing to pump hydro, charge batteries, or make gas for power->gas->power.
Put another way: the reliable nuclear energy just subtracts a constant amount from grid demand, and the remaining wind/solar production variability is reduced proportionally.
Nuclear is expensive, and you can't shuffle that expense around under three walnut shells hoping it will somehow disappear.
You're playing with apples and oranges. You want us to look the other way while all the exotic things done to fill in for renewable supply/demand mismatches are not amortized over a tiny number of hours of operation, but want to point to the same problem with nuclear.
A diversity of power sources, each with their own problems (cost [nuclear/storage], invariability [nuclear], volatility [wind/pv], total resources available [hydro/geothermal] is what will get us through this. Especially since we're really maxing out what we can do with wind and solar and it's not going to ramp high enough in time to save us.
France's past system is irrelevant, since it was built at a time when renewables were completely noncompetitive. The world has changed now, and changed radically. Going forward, France will be going renewable too.
Sure, it's expensive, but all the things we'll have to do to have an all-renewable grid are pretty expensive themselves and unproven.
Yes, we should end up with a much smaller mix of nuclear than France had, to help optimize cost. But it is an option available now that we know will work, and I believe that the optimum point is not 0% nuclear. (In western democracies, though, nuclear has become practically impossible. This hasn't stopped a large amount of reactor construction in China, so obviously planners there disagree with your assessment).
Further, nuclear and wind are comparable in CO2 emissions, and PV is a few times worse. So if we really care about minimizing CO2 there will be some nuclear in the mix.
Betting everything on power->gas->power when we have basically no evidence that this will be economical at scale is crazy. Betting on pumped hydro or battery storage is also dubious. We should be pursuing all avenues available to us.
Also, making a pure opportunity cost argument is a little weird as well. The investments are not purely fungible. That's why we should both give extensive resources to ramp PV and resources to ramp nuclear and resources to ramp p->g->p, because they're not the same resources.
It is not an option we know will work. The inability of France to replicate their previous putative success means we can't take any of that for granted.
We have evidence that nuclear will NOT be economical at scale. The evidence is there in a cavalcade of disastrous experiences, even in places like France were experience supposedly, by your reasoning, would have told us to expect otherwise.
How much wind and solar you need depends on how good you are with lowering demand, for example by insulating homes, shifting transportation to trains and building heat pumps.