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Comment by adrianN | Hacker News Reader

You build a shitton of wind and solar and a good grid that is as large as possible so that it's always windy somewhere in your grid. Peak production capacity should be a good bit higher than peak consumption. During the buildout phase you replace coal with gas peaker plants (you'll need them later). Then you add enough batteries and hydro storage to get you through a night or a bad day. If you can, use demand shaping technologies, e.g. charge electric cars and run aluminium smelters when it's particularly sunny or windy. Then you add power-to-gas facilities that produce Methane from electricity and use the existing infrastructure for strategic NG reserves to store it. For long periods of low production (e.g. winter) you turn the gas back into electricity.

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.

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> Then you add power-to-gas facilities that produce Methane from electricity and use the existing infrastructure for strategic NG reserves to store it. For long periods of low production (e.g. winter) you turn the gas back into electricity.

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?

I'm in favor of doing that, but I don't think it's necessary or helps a whole lot. Nuclear power plants need to run close to max capacity all the time to make financial sense at all. So you can't use them to bridge over low production for wind and solar. They also take ages to build. Nuclear might make sense for district heating in winter, but people generally don't like having nuclear plants close to where they live.

>Nuclear power plants need to run close to max capacity all the time to make financial sense at all.

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.

Nuclear would have been a good solution if we started thirty years ago. By today we don't have enough time to go 100% nuclear before we emitted to much CO2. We have less than ten years of current emissions left if we want to stay below 1.5°. Building nuclear power plants takes longer than that.

"Building nuclear power plants takes longer than that."

So fix that broken process. This is a nonsense result.

Production of all carbon free energy, sources: solar + wind + nuclear, is not enough to get to 100%in a decade, unfortunately

We can't get to 100% with solar/wind in a decade, either. Do what we can with solar/wind, and also start building nuclear base load.

>Nuclear would have been a good solution if we started thirty years ago.

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].

[1]http://live.gridwatch.ca/home-page.html

And we know they will cost two arms and a leg, compared to renewables.

Yah, I don't advocate a majority-nuclear grid.

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.

But that doesn't work. Adding a little bit of nuclear to a mostly renewable grid is useless. Most of the output of the nuclear plants is thrown away when the renewables are generating, so the marginal cost of covering the remaining slack periods is hideously bad. Other sources would be cheaper (in particular, burning CO2-free hydrogen in turbines, or using natural gas w. atmospheric CO2 capture.)

You add a bit of nuclear-- 10 to 30%.

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.

Your proposal doesn't work, though. It requires that nuclear be subsidized by buying its power 24/7, even when much cheaper sources are available. This opportunity cost, if properly accounted for, makes the cost for the gaps that nuclear fills in for very very expensive. Trying to use the excess nuclear for hydrogen production, battery charging, etc. doesn't save you, for basically the same reason.

Nuclear is expensive, and you can't shuffle that expense around under three walnut shells hoping it will somehow disappear.

Obviously the proposal does work, in that France basically has it implemented. and has 1/10th the emissions per unit of electricity of countries that have moved heavily towards renewables only, and some of the lowest electrical prices in Europe. ;)

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.

No, I continue to think you are mistaken, for the reasons I've given. I think if we optimize out the energy system of the future, taking into account cost of construction and operation, it's going to optimize to 0% nuclear.

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.

France is evidence that we can readily get to low carbon electric grids using nuclear power and relatively little technology.

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.

France is evidence that putative economic buildouts of nuclear are not repeatable, if they were ever actually economical in the first place.

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.

Well, France exists and is not bankrupt. France has managed to do it, and leads Europe in carbon output per unit of electricity, and will not be matched for quite some time.

Yah, you use nuclear for base load, and then conserve hydroelectric resources for times when you need to bridge over missing wind/solar.

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.

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?

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.

> If solar costs less than a third what nuclear does (which is where we're headed, we're already down to half),

Because power to gas to power delivers a fraction of the input power, and has a bunch of cost itself-- it isn't free.

I'm not saying it's free. Sheesh. I'm saying that there's some point on the price curve where it becomes cheaper than nuclear, even for base load. Now, that point may never happen. Or maybe it's already happened, and will be scaled out over the next couple of decades.

The cost of PV solar has dropped over 80% in the past decade, and we don't know what the bottom is yet.

I am saying that even if pv gets cheap enough that the input power through 1/3rd efficiency is the same as nuclear... power to gas costs a lot IN ADDITION to the input power. And then burning that gas in a power plant costs something, too.

So reaching parity seems difficult.

The cost of electrolyzers has also fallen dramatically.

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).

Sure, but the point I am making is: having the input power alone cost the same as something else is not the same as reaching cost parity with it. Because one must consider all expenses, not just the expense of the input power.

Solar has not reached cost parity with nuclear. It has blown through cost parity. Solar and wind are 3-4x cheaper than nuclear, on a levelized basis (depending on location). This gives them both plenty of space to implement storage, curtailment, transmission, and/or demand management and still beat nuclear.

Person A says if solar is 1/3rd the cost of nuclear, and energy-to-gas-to-energy is 1/3rd efficient, it should be cost-neutral with nuclear.

> 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 is cost neutral with nuclear during those occasional times when you're burning the gas to make power.

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?

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.

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