driest

there is a very simple physical reason hydrogen for personal transport is not feasible: electrolyzer to fuel cell efficiency is much lower than charging a battery.

we simply don't have enough green energy to afford wasting it on use Cases were batteries are feasible, and this won't change for some time. the article acknowledges that btw, and that is coming from a company that has a vested interest in the contrary due to selling the Mirai.

that's all nice and true, but not at all relevant to the point of long term storage.

is that relevant? the premise of the article was "long term storage", and my comment aimed at putting that into perspective.

if that were the case, how do you explain this sentence? "The heat is then extracted and stored in “bricks” made of steel shot and quartzite for later use,"?.

or did the source simply explain their process incorrectly?

sorry to disappoint, but this article glosses over a pretty significant constraint that prevents this from being long-term storage at all: storing the thermal energy from the compression process.

storing thermal energy over long periods of time is a pretty lossy process, and that 75% efficiency number will be out the window if one tried to use this system for seasonal storage. this system fills the same space as battery storage, which it is also marketed for (over night storage for solar power).

here is a more detailed post on the matter: https://www.rechargenews.com/energy-transition/new-co2-batte...

citing from this: "In Energy Dome’s system, carbon dioxide is compressed at a pressure of 60 bar which heats the gas to 300°C liquid. The heat is then extracted and stored in “bricks” made of steel shot and quartzite for later use, cooling down the CO2 to an ambient temperature. The gas is then condensed into liquid form and stored in carbon-steel tanks.

‘Our lithium-ion battery will have double the energy density of standard Li-ion for same price’

When electricity is required, the liquid CO2 is run through an evaporator to turn it back to a pressurised gas, which is then warmed up back to 290-300°C causing the stored heat."

Aside from not delivering on the topic promised in the title, this article contains several inaccuracies and false claims that are unlikely to be accidental given the author is an industry professional. this looks like a cheap opinion piece promoting a cover story for the fossil fuel industry (CCS).

electricity in Germany does not cost 30 c/kWh, but roughly 7 c/kWh. the rest is taxes and fees for consumers, and the fact that the linked source makes this transparent indicates that it is deliberately mis-cited for drama.

the article severely understates the efficiency of power to gas processes and claims a maximum efficiency of 35%. however, even the 10 year old megawatt scale demonstrator in Falkenhagen Germany reaches roughly 50% efficiency [1]. modern research projects have achieved 76% efficiency in a shipping container sized prototype, and research is ongoing [2].

[1] https://www.deutschlandfunk.de/erneuerbare-energien-power-to.... [2] http://www.helmeth.eu/images/joomlaplates/documents/Publisha...

China's economics on solar might also be a lot different, but given that it doesn't publish these numbers all we have to reason about are the US and maybe Europe.

Btw, ask France about cost of nuclear, I've heard their new reactors are absolutely in time and budget ;)

yes, solar and wind energy generation is intermittent, that's no surprise to anyone. but it is much much cheaper than nuclear energy.

Not OP, but you're wrong about cost. Nuclear is more than twice as expensive as photovoltaics [1], so it's not cheap at all. And that doesn't include dealing with risks like proliferation and extremely hazardous waste for hundreds of years.

the half trillion comment came from the original article, that stated an estimated cost of 440 billion.

[1] https://www.eia.gov/outlooks/aeo/pdf/electricity_generation....

Most of them work in the security industry and do:

* malware analysis (how does this malware work, how can it be detected, can we somehow decrypt data affected by this ransomware, are there any leads to who wrote this malware, etc)

* vulnerability research (finding and exploiting vulnerabilities in closed source software)

* assessment of closed source software (how secure is it, how does it work, does it have undocumented apis and how can those be used, etc.)

there is likely also a small market for analysis of competitor software, but I haven't seen this openly advertised yet.

Usually the reason for this behaviour is that at least one of the parties is not interested in resolving any contentious points, but merely in "winning" the debate by focusing on arguments where they can exploit a weakness in the reasoning of their counterpart.

Usually it's best to not waste time on these people and simply ignore them, up until now I wasn't sure this was really the case, though.

I'm not debunking nuclear, I'm simply stating that just because you have a hammer climate change doesn't magically become a nail. Nuclear is great, but for the reasons I mentioned it is not suitable to combat climate change right now. I'm not advocating against nuclear, I'm simply saying that it's expensive, has problems other energy sources don't have, and relying on the building of new, safe, and cheap, designs will take way too long.

> Renewable alone (Without Coal or Gas) implies nationally to have close to 100% of the production capacity in storage alone (Battery, power2Gas or hydro storage) to compensate solar / wind intermittency. Which no country on Earth is able to do right now

again, straw man's argument. No country is close to 100% nuclear power either. France is pretty far, and they are sitting at less than 70%. and the reactors they are trying to build to increase this number are plagued by budget and timescale overruns of massive proportions. See the new safer EPR designs they have been trying to build since 2005, which are still not finished and have already consumed more than 300% of the initial projected cost [1]. it is delusional to believe we can somehow quickly scale nuclear power to the capacity needed to combat climate change.

cursing and claiming that things are a joke that have already been successfully demonstrated is not going to help make your point...

[1] https://www.popularmechanics.com/science/energy/a33499619/fr...

> No you don't from your arguments.

One can be a fan of something without trying to blindly apply it to areas where it doesn't make sense.

> nuclear reactors designs from the 70s are statistically safer than coal. And kill a lot less than coal.

That's a strawman's argument, I'm not arguing for coal, I'm arguing for storage of renewables.

> France had one of the cheapest electricity in Europe for 3 decades [...] Nuclear is cheap [...]

That is simply false. The levelized cost of nuclear is about twice as high as that of solar or wind, see page 8 of the referenced EIA report [1].

> There is today not a single installation world wide existing of power to gas to the scale it would be needed

Again, strawman's argument. The discussion is about what should be built, not what has been built. There are already megawatt scale plants running for years without problems [2], and there are shipping container scale demonstrators for higher efficient versions [3]. So it's pretty obvious that the technology around power to gas is well understood, and ready for mass production and deployment.

> And that would anhiliate any hypothetical cost of the renewable energy anyway

Again, this is false. As explained above, nuclear energy is twice as expensive as renewables, and power to gas has an end to end loss of roughly 50%. So in reality, renewables + power to gas has roughly the same cost as nuclear, without the proliferation, safety, security, and waste problems. And as an added bonus every MWh you use while renewables are producing costs half of nuclear ;).

[1] https://www.eia.gov/outlooks/aeo/pdf/electricity_generation....

[2] http://hybalance.eu/wp-content/uploads/2019/10/Large-scale-P...

[3] http://www.helmeth.eu/images/joomlaplates/documents/Publisha...

You do realize that batteries are not the only method of energy storage? In fact, there are lots of better ways to store excess energy from renewables over longer periods of time, but power to gas was mentioned as an example that works everywhere, and can use abundant existing storage and distribution systems.

Lets add a reference to get some actual numbers to play with: The US Energy Information Administration has published a report reasoning about the levelized cost of electricity (LCOS) for new power plants of different energy sources [1]. According to page 8 of this report, the LCOS of one megawatt hour of nuclear energy is around 69 USD, while solar is around 33 USD and onshore wind is 37 USD.

If you factor in a 50% loss in converting the renewable energy to gas and back to electricity you end up in the same ball park as nuclear, but without the proliferation, safety, and waste problems.

[1] https://www.eia.gov/outlooks/aeo/pdf/electricity_generation....

I am a fan of nuclear energy for various reasons, and it's obvious that the safety and waste problems can be solved with new technology like small modular reactors with inherently safe designs.

However, even I realize that nuclear energy is not viable to significantly combat climate change due to the following reasons:

* The technology is not there yet. There are a lot of promising companies that are trying to solve the safety problem, and there is a lot of research on how to better deal with the waste, but due to the inherent dangers it will take decades to prove these designs are safe, work as intended and can be produced at a significant scale at the promised cost. Sadly, we don't have decades, we need to start replacing coal right now.

* nuclear energy is way to expensive. Wind and solar are much cheaper. current numbers are roughly 50% cheaper for renewables, and while lots of companies promise cheaper nuclear design, these claims are unproven and the renewables are also still significantly improving in cost. The nuclear cost models I've seen also ignore most of the storage and security cost for handling the waste for millenia. There are cheaper alternatives with existing and proven technology. Power to gas for example has an efficiency of roughly 50%. which funny enough corresponds to its cost advantage over nuclear. simply building a lot more wind and solar capacity and using power to gas to fill existing gas storage systems with excess energy from renewables has roughly the same cost as nuclear, without the safety and proliferation headache, and the added advantage of long term storage.

* proliferation. even if we could solve the problem of safeguarding thousands of SMR in developed countries, you can't just export them to every country on earth. however, that's a requirement for replacing coal, as those countries need to reduce emissions, too.

So yeah, I'd love molten salt SMR to be a thing, and they probably will be in some applications in developed countries in 10-20 years, but the value of this to combat climate change is minimal and people who think otherwise are ignoring the previously mentioned facts.

Great class, thanks for sharing the materials. Would you consider also making the code for the exercises available? I'm working through the slides but the exercises are hard to follow without the provided source code.