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Are you suggesting that variable renewables plus batteries will approach prices that are... too cheap to meter?

Looking at current cost VRE trends, when variable sources contribute up to 4% of world energy, and surrounded by massive amounts of cheap but high-carbon natural gas, and assuming that the trends will just continue exponentially downward without serious complication, is optimistic.

Cost of integration of variable sources plus batteries is expected in many studies and somewhat intuitively to skyrocket as market penetration increases. When you have enough VRE to cover 100% including the big evening peak with batteries during a clear summer day, the extra generation you build to fill the other gaps gets curtailed. But you have to fill daily and then seasonal gaps, worldwide, including heat in winter and worldwide transportation (not just electricity). Buying that battery that is only even needed at all every third day is 3x the price, yet we prefer if the power doesn't brownout with this frequency. This is difficult. Already we're seeing NIBMYism in large solar installations in california and with transmissions lines. That gets worse with scale.

Nuclear today is a hedge against the possibility that deeply carbonizing with variable renewables + storage at world scale will be harder than we all think and hope it will be.

That said, nuclear certainly needs to drop capital and O&M cost dramatically if it wants to play the game. And security is indeed a big factor in this. Its competition in the small-footprint dispatchable world is natural gas with full CCS, which is also looking pretty cheap.

Yes. Not indefinitely of course but we've seen nothing yet and there's enough in the research pipeline to suggest clear trends over the next two decades in terms of cost improvements, efficiency improvements, cheaper materials, etc. That 4% you mention was less than 1% not so long ago and will be closer to 40% not too long from now. Such is the nature of exponentials.

IMHO 5X cost reduction is basically a done deal even just applying simple economies of scale. You can argue whether this happens in five or ten years maybe but arguing it isn't happening seems futile. Beyond that, 10x is extremely likely to happen as well. There's a lot of research happening that would need to be a complete failure/waste of time for that to not happen. At worst it will happen slower that I might like. Maybe this happens over the next decade. Or two. Or three even. From there, 20x might be quite possible as well.

Beyond that we're indeed talking rapidly diminishing returns. 10X would mean 0.2 cent/kwh. 20x would cut that to about 0.1 cent. This indeed gets you in to territory where metering it becomes more expensive than is worth the trouble. The average household uses about 15000 kwh per year, or about 150$ worth of energy at these prices; much less outside the US. Much of that is going to be produced on people's roofs or in their back yards. At that point it turns into a fixed cost.

Historically the same sources producing the studies you are referencing have been off by magnitudes predicting current adoption and prices for both solar and wind. So, I'd consider that the pessimist glass half empty point of view. Not to dismiss it entirely but arguing cost increases seems a bit far fetched in light of current trends in the market.

Aren't roof solar panels very inefficient? They can't track the sun and you can't have good density from them either. Furthermore, they don't work for office buildings and apartment buildings.

>Not to dismiss it entirely but arguing cost increases seems a bit far fetched in light of current trends in the market.

I think what the parent was saying is that because solar and wind don't reliably produce energy, we will need redundancy. As the market share of solar and wind grows we will need to increase the amount of storage and power generation far beyond what we normally need to operate.

Let's say you have a city that uses 1 GWh of electricity per day. If you were to generate all the electricity with natural gas then you need to have 1 GWh plus some extra for redundancy to fulfill the needs of the city. If you generate 5% with solar and the rest with natural gas then nothing really changes. If the weather is bad then the natural gas plant will step in.

As the share of your solar power generation grows toil need more and more redundant storage and solar power generation. If you rely 100% on solar power generation and the weather can be bad for a week in a row over the city, then you'll need storage that will last for more than that entire week. Not only that, you'll also need extra power generation capability to be able to fill and maintain that storage.

Just to put this into perspective: the US uses about 10 TWh of electricity per day.

> Aren't roof solar panels very inefficient? They can't track the sun

We are well past the point where tracking the sun was desirable. The apparatus that allows solar panels to track the sun is now much more expensive, especially when you consider the maintenance costs, than just using more static panels.

Actually, most new utility scale PV in the US southwest is now using single axis tracking systems. The advantage here is that the power curve is flattened over the day, which both makes better use of the inverters and pushes more production into higher value time periods.

With dirt-cheap renewables it will be more efficient to generate methanol from solar or wind electricity and to use it for long-term storage and redundancy than to burn natural gas or coal. And compared with coal or natural gas with methanol one can use fuel cells to convert it to electricity so one can have relatively small plants for backups in case of really long strips of bad weather.

> Aren't roof solar panels very inefficient?

They are good enough. Low efficiency just means we have to buy more of them. Obviously we'd need solar plants (and maybe wind parks and other clean sources) to also power those with limited access to roof surface.

Of course, bad weather doesn't mean solar stops working; it just reduces the output. The effect is typically very local as well. So, all that means is that you need a bit extra capacity to cover for that or import energy from somewhere else where the weather isn't miserable.

When (not if) the price for solar and wind drops 10x, you'll be able to buy 10x more than what you need and still beat coal/gas/nuclear on price. 10x is an insane safety margin that would mean you produce more than you need even on the most cold, dark, and miserable day imaginable. And of course solar is not the only source of clean cheap energy. Wind would be another popular option.

Bad weather in northern Europe means that everything is covered in snow for a long time. I think that's slightly more than just reduced output. The snow also tends to cover am area that's hundreds of kilometers in every direction too.

I've lived in Sweden and Finland. It's actually the lack of sunlight that is causing issues with solar. The snow is much less of a concern. E.g. Helsinki only gets a few hours of daylight and the sun does not get much above the horizon in the winter months. The reverse is true as well; you get insane amounts of sunlight in the summer months. Luckily there's wind, hydro, wood pellets, and a few other alternatives.

Further south in Germany, Netherlands, etc. Solar is usable throughout the year and quite common. Obviously output in the summer is going to be much better than during the winter.

> That 4% you mention was less than 1% not so long ago and will be closer to 40% not too long from now. Such is the nature of exponentials.

But such is not the nature of the logistic function, which is usually a more accurate model of how technologies penetrate. (yes, in the beginning it looks like an exponential)

There is a final cost decline "baked in" to the curve, though. That's because the lifespan of solar now for calculations is maybe 20 years. Anything more would not make sense as costs are declining so fast. When the tech matures, the final part is extending the lifespan to 40-60 years.

This is very very optimistic. While the prices of panels are going down the rest of the cost isn't (land, permitting, installation labour, etc). And panels are only a small proportion of the cost now.

There is also only so much more efficient the panels can get per sq m. Right now we are approaching 20% efficiency, so the idea that they are going to get 10* cheaper with complete ease seems to be pushing it.

Regardless solar and wind have a lot of externalities that aren't really priced into these 2c/kWh PPA prices. If you need to build a fleet of natural gas plants that are only operational 10% of the time and therefore cost 50c/kWh to take up the slack from low solar days it needs to be priced in somehow.

All the costs have been falling, at various rates.

It's amusing to see "permitting costs" being presented as a barrier, when at the same time "get rid of regulations" is spouted as the panacea for reducing nuclear's costs.

You can't run an electrical grid on wind and solar alone and expect it to be stable enough.

- The prospect of every household having a battery backup big enough to smooth over spikes and dips is ludicrously wasteful. We are already struggling just mining enough to make batteries for cars and phones.

- the sheer scale of the wind and solar farms will leave major environmental impact to wildlife. Look at how massive area solar farms need, and know the area has to be cleared and desolate of life.

Nope, simply untrue. Cars use lithium ion batteries mainly for their energy density. For grid storage, other batteries and ways of storing energy are feasible and probably a lot cheaper as well. Wikipedia has a nice overview: https://en.wikipedia.org/wiki/Grid_energy_storage#Grid-orien...

The wild life impact of solar is relatively minor compared to burning coal, intensive farming, and all the other things we do. We'd need to only cover a relatively small amount of land with solar to produce what we need. And ironically some of the most suitable land for this would be deserts that have relatively little wild life to begin with. Of course the impact of wiping out coal, gas, and petrol usage would be enormously positive.

Windmills do indeed kill some birds. Yet, these things seem to have barely any impact on e.g. the seagull populations in places like Denmark that have a ridiculous amount of wind mills.

(Molten salt reactor is a fluid fuel reactor. Fluid: liquid, gas and plasma.)

Molten salt reactor is a stepping stone for fusion reactors. We need to master liquid and gaseous reactors before going plasma. Our civilization should aim for larger goals. We need some form of nuclear power to terraform other planets and spread earth's precious life and conciousness everywhere.

We do not need nuclear for any of that.

Well, given how solar has an inverse square relation between watts/area and distance from the sun, by the time you get to mars, solar is getting pretty piddly, the asteroid belts and jovian moons its downright comical.

Actually, solar still has huge advantages at the distance of Mars.

In space (actual space, not a planetary surface), it's difficult for nuclear to dissipate its prodigious amounts of waste heat. Solar, in contrast, can be made much lighter than on Earth, as there isn't wind and rain to deal with. And of course in general the Sun is available 100% of the time in space, further improving the economics.

But in any case, the argument wasn't that solar was necessarily better, it was that nuclear wasn't necessary. Solar can provide energy basically anywhere, with power beaming, even out into interstellar space.

Planets rotate so backup power is needed during nights. Spacecraft has to avoid obstracles and has to move, so backup is needed. During interstallar journey there is time delay in communication, so it may take hours to adjust the power beam when spacecraft moves a little bit. Fusion is like solar energy just near to us and MSR will be eventually replaced by fusion reactors.

MSR and many other fluid-fuel reactors run hot and it makes radiators small: https://www.flickr.com/photos/oakridgelab/31537153147/

Stefan–Boltzmann law: Radiation heat transfer is proportional to 4th power of temperature.

> Planets rotate so backup power is needed during nights.

This does not rule out use of solar energy.

> During interstallar journey there is time delay in communication, so it may take hours to adjust the power beam when spacecraft moves a little bit

The vehicle tracks the beam, not vice versa.

> Fusion is like solar energy just near to us and MSR will be eventually replaced by fusion reactors.

Fusion is ridiculous when examined closely. It's like fission, only far worse from an engineering and cost perspective.

> Stefan–Boltzmann law: Radiation heat transfer is proportional to 4th power of temperature.

Which means waste heat from a reactor in space has to be radiated at higher temperature than for a reactor here on Earth, which means nuclear is worse off there than here. In contrast, solar works better in space, as I argued upthread.

It's not an elephant in the room, it's just so obvious that it's not something that needs explained.

You could say the same thing about any airplane, even small planes or drones could be filled with explosives and hit strategic targets like a chemical factory.

You can place the nuclear generators in police stations, military bases, other locations that are already protected, there is no need to have a small nuclear generator in each electronic device like in Fallout.