[maheart]

I recently watched the documentary "Planet of the Humans". For context, the writer of the documentary is an environmentalist.

One of the stated points was that solar and wind cannot be relied upon 24/7 -- to account for the lack of reliability, you need to have a backup power generator (e.g. coal power plant) running. The thing about coal plants (does it apply to natural gas plants too?) is that if you "idle" them, then have to ramp them up to feed demand, then later ramp them down -- it's a very inefficient way of running them. Now based on my understanding, it might be more efficient to just run the coal plant (or natural gas planet?) 24x7, in which case you've just added waste with the use of solar/wind. How much truth is there to this?

[dbspin]

None - the documentary is full of half truths, out of date information, pseudoscience and outright lies. It's been absolutely torn apart both by the research community and the environmental movement.

Some examples:

https://www.theguardian.com/environment/2020/apr/28/climate-...

https://www.commondreams.org/views/2020/05/05/real-problem-m...

https://medium.com/@btincq/10-reasons-planet-of-the-humans-g...

[acidburnNSA]

To be fair it did challenge an extraordinarily popular mainstream narrative that renewable energy is marching in to save the day from climate change without hardly any meaningful negative externalities. Of course the mainstream is going to tear it apart. They knew this in advance.

That said, knowing which statements are outright wrong is indeed valuable.

Still worth watching IMHO.

[anesmike]

Renewables are just a technology totally dependent on fossil fuels from birth to burial. The book by Charles Hall , Energy Return on Investment, opened my eyes to the true nature of renewables . Once fossil fuels are gone, renewables will soon follow.

[pfdietz]

The EROEI of renewables is good and getting better. There is nothing in their manufacture that would be impossible without fossil fuels.

[anesmike]

Think hard about that; huge trucks for mining, huge trucks for transport, huge amount of energy to separate component minerals, the actual energy for manufacture of these renewables, up to this point I don't see renewables at any stage of this process. Diesel fueled trucks to deliver said renewable technologies to their place of use. Oh, their is one worker who drives a tesla ...... Oh at end of their life requires fossil fuels for dismantlement , fossil fuels to transport device to some recycling plant, fossil fuels for the energy to process this dead technology, oh there is one guy there that drives a tesla. I use to believe that renewables would help; but alas when you really look at this technology with a total suspension of bias you reach the same conclusion.

[epistasis]

Those huge truck use electric motors, because electric motors have better torque. The diesel is just there to provide an energy source. There are already several haul trucks that use batteries instead of diesel. And some of them generate more electricity than they use, because they haul large loads downhill and regenerative breaking means that for the truck, its duty cycle is energy positive!

It's important to ask: why do you think thinks like large trucks can not be electrified? What assumptions do you hold that say they could never be powered by carbon free electricity?

[pfdietz]

Nothing you listed there requires fossil fuels.

If you think those activities require fossil fuels, you are basically saying industrial society is impossible after fossil fuels run out.

[Gibbon1]

That problem with that guy is he hasn't done any math to back any of that up.

When you run the numbers for say tractors, trains and mining trucks it pencils out just fine.

[anesmike]

Simply put, there is not a battery big enough for these trucks, the trucks are too massive ,the battery would be massive,it unfortunately will not work, just the laws of the universe.

[anesmike]

Thats right.

[sephamorr]

This is a relatively good point. In the California electricity market, the increase in renewables results in a very large power-ramp rate in the late afternoon (nothing unique to California). In general, more-efficient power plants either cannot, or lose efficiency, when changing operating power levels. A ~60% efficient combined-cycle gas plant cannot ramp power very much, which results in the grid building and running more ~40% efficient gas turbines, which can ramp their power output in order to meet the early-evening power ramp. Interestingly, at this point, adding more Solar to the California grid results in very little emissions reduction, since the additional solar displaces efficient baseload generation with inefficient ramp-able load. The solution, of course, is storage.

[yoavm]

a natural gas plant doesn't really suffer from this "idle" problem you're describing with coal power plants. it's also much cleaner.

[kanox]

Why is that? I was under the impression that gas versus coal just changes the fuel that is burnt.

[ars]

Have you ever had a camp fire/bonfire? It takes a LONG time to get the wood hot enough to burn well.

In contrast your gas stove goes on and off in a moment.

Coal vs gas is the same way.

[Pfhreak]

Natural gas produces about half the CO2 emissions per unit energy as coal. (And presumably less other harmful stuff like radioactive fly ash.)

https://www.eia.gov/tools/faqs/faq.php?id=73&t=11

[icebraining]

A gas plant can be ramped up and down quite fast, so they can be used as a so-called "peaker" plant, only producing when there's a shortage of solar/wind power. Coal takes a while to get hot and to cool down, so it's only worth using it if you need a constant stream of energy.

[qaq]

0? You can have utility scale storage and Nuclear as backup

[acidburnNSA]

Today's nuclear reactors run constantly because the fuel is so cheap compared to the rest of the operations. They want to be selling kWh as much as possible because kWh is money. To convince nuclear operators to do backup, there would have to be some kind of market for their on-demand carbon-free characteristics. This would require market changes.

Of course, it's very possible for nuclear reactors to load follow from a physical point of view. Naval reactors load follow into battle mode quite impressively, and power stations could do the same, again if there were a market for it.

Even traditional reactors can couple to some kind of thermal energy storage system to allow them to stay mostly at 100% while the whole system load follows very nicely.

There are many exciting possibilities in on-demand, low-footprint, low-carbon energy with nuclear technology.

[keithnz]

Nuclear back up? Nuclear is good for base loads, not for peak loads.

[pfdietz]

Nuclear would be ridiculously uneconomical as a backup. You either run nuclear as baseload or you don't bother.

[ktal]

Damn shame we haven't been investing in nuclear over the past few decades. Now when we need it most, it's too late.

[epistasis]

Nuclear is one of the few technologies that has a negative learning curve. As we improve designs, it seems to get more expensive rather than less.

There was a brief window in the 1970s where US nuclear construction projects were finishing on time. But the utility industry had planned for waaaaay too much new capacity. So when all the construction projects with poor execution, that struggled to complete and therefore came in way over budget, finally came online in the early 80s, they were financial disasters in a scale that nearly bankrupted several utilities.

Since then, utilities lost their appetite. And there's basically no way for us to replace the 400 or so reactors in the world that eMate nearing end of life.

However, I'm not sure we will need nuclear. With how cheap wind and solar are getting, far faster than anybody anticipated, we have finally found the technologies that may some day provide energy "too cheap to meter." However, like nuclear they are not dispatchable (except for some designs in France), so if we want to power a grid we either need to overbuild capacity by quite a bit, or use energy storage. There's a cost trade off for the two that depends on how cheap storage gets, and how cheap extra capacity is, and how cheap transmission is from an area with different weather that day. (For example, one can imagine building 2x of panel capacity over the amount of inverter capacity on a solar install, so that even on cloudy days you can chug along at near full energy output... it all depends on the cost trade offs.)

And as fast an solar is getting cheap, far beyond expectations, so is lithium ion storage. And there are many chemistries with high specific energies (and thus unsuitable for vehicles), that we are just now dipping our toes into.

Nuclear would be a nice tool to have, if it was competitive with other technologies, but it's going to be decades before it can prove itself and establish a positive track record for deployment. Utilities have been burned too many times by financial dumpster fires.