Carbon Commentary

I read this analysis of the SMR farm announcement in Canada a few months ago and I found it quite insightful: https://www.carboncommentary.com/blog/2025/5/11/the-first-test-for-new…

That book was a helpful contribution to the debate when it was published in 2008, but by 2017 people were already pointing out[0] its obsolete assumptions about renewables, and there is now an open source collaborative effort to produce a more accurate and up-to-date version.[1] I don't want to speak ill of the late great David MacKay, but it does seem that reality has exposed his pro-nuclear bias, which was already apparent[2] just from the choice of language he used when describing the different technologies. [0] https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09… [1] https://climate.lifeitself.us/without-hot-air/#why-this-project [2] https://www.reddit.com/r/environment/comments/d1rwe/david_mackay_witho…

Note that while it is an excellent book, some of its contents are outdated now as it was published in 2009. In particular: solar, wind and battery technology have improved much faster than predicted. This blog post discusses some possible updates that could be made to the book: https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09…

I also recommend this book heartily - it's amazing. There have been mutterings about crowdsourcing an update, and I think I saw a github repo once but I can no longer find it. Here's an example: https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09…

What that article doesn't address is the concurrent shift to electrify domestic heating. A worked analysis of the impacts can be found here: https://www.carboncommentary.com/blog/2022/2/11/how-much-electricity-w…

That's between 1.5 and 2 million tonnes of hydrogen .. in a world that currently produces about 74 million tonnes of hydrogen annually already. There are multiple sources for those interested, https://www.carboncommentary.com/blog/2021/6/11/some-rules-of-thumb-of… is a brief dot point page, the Hydrogen UK and European Hydrogen Backbone reports are longer more detailed technical report papers.

From the atmosphere, sure. But, if they can succeed in building a viable conversion system, then hot exhaust from factories or other sources can be used instead of air. It could be a closed source system too, for example, in industrial applications that need a lot of heat. An almost closed cycle system may be viable. I have no information about the speed of the reaction, but I guess systems can be scaled. Also, a good amount of heat is produced in the sabatier reaction process itself, which can be used for other systems. Conversion of atmospheric CO2 to usable fuel can become a cheap battery for solar plants. Edit: Such a system already exists, even if as an idea. https://www.carboncommentary.com/blog/2017/7/24/exytron-the-worlds-fir…

This book is from 2008, and, while reportedly very good for its time, now out of date. https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09… In particular, nobody back then anticipated how quickly solar PV prices would drop. https://rameznaam.com/2020/05/14/solars-future-is-insanely-cheap-2020/

State of the art is about 93% efficiency for electrolysis of water "in the lab". It was about 80% efficient at industrial scale back in 2017 (see https://www.carboncommentary.com/blog/2017/7/5/hydrogen-made-by-the-el… so we can expect that to be a few percentage points higher today. Apart from the aforementioned hydrogen agreement with Canada, construction is underway for a wind-powered multi-GW electrolyzer plant in the Netherlands, which is pretty much next door to the German trains from TFA.

Efficiency of a production electrolysis plant today is about 80%, which really doesn't seem that bad. https://www.carboncommentary.com/blog/2017/7/5/hydrogen-made-by-the-el…

Very good book but tech went lot further than David expected in many places (ie. solar power efficiency vs price). This page tried to keep it updated: https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09…

" We can expect 48% of the energy from renewable electricity to be lost in conversion to liquid fuels, using the average value for drop-in diesel technologies from our previous economic modeling work. To compound the problem, according to various studies 70% of the energy in those fuels will be lost when they are combusted in internal combustion engines, for a total efficiency of 16% for the e-fuels pathway. Therefore, the vast majority of the energy from the sun or wind is lost. In contrast, the majority of energy used by electric vehicles actually goes to powering the wheels, losing only 10% in charging and 20% by the motor and for a total efficiency of 72%." https://theicct.org/e-fuels-wont-save-the-internal-combustion-engine/ There is lots of (paywalled) proper economic analysis of current methods of Electrofuel generation from atmospheric carbon, the summary is that the current processes cost multiple times more than similar fossil fuels, with the main cost factor being the cost of electrolyzed hydrogen per kg, and captured atmospheric carbon cost per kg, and all of that comes down to the cost of the energy consumed during the process. https://www.carboncommentary.com/blog/2021/11/18/how-much-will-electro… Edit: other than any research, the main indicator (for me) is that nobody hasn't yet offered renewables based liquid hydrogen or atmospheric carbon Electrofuel at nearly viable prices for today's world. If the technology was energy efficient, these fuels…

> with bike/bus/walking space is an incredibly high impact carbon reduction strategy. It is not. On a CO2 per mile bases cars emit less than non-vegan humans, because it takes a lot of energy to grow food. If you put 2 people in the car it's not even close. https://www.carboncommentary.com/blog/2014/07/22/walking-can-be-more-c… http://web.mit.edu/2.813/www/readings/DrivingVsWalking.pdf > but after it takes place everyone agrees things are much much better with less cars and no one wants to go back. Speak for yourself. Every place that has done that is basically a place I will never go to. Since I'm not there anymore I can't complain, right? It's especially stupid when a downtown of a large city does that - God help anyone who needs city services and lives in the suburbs. (Are you expected to walk for 3 hours? Spend a ton of money on a taxi? There is no bus.) What ends up happening is the city and the surrounding area mentally split into two, and they fight politically.

I posted this about David MacKay's book "Sustainable Energy - without the hot air", which advocates nuclear energy, to a discussion about solar panels, and llukas pointed out that solar power development has exceeded MacKay's expectations, and linked to a page with updates, and dane-pgp also posted some interesting criticisms and links. If Solar Panels Are So Clean, Why Do They Produce So Much Toxic Waste? (forbes.com) https://news.ycombinator.com/item?id=18751049 https://www.forbes.com/sites/michaelshellenberger/2018/05/23/if-solar-… https://news.ycombinator.com/item?id=18751049 DonHopkins on Dec 24, 2018 [-] The late David MacKay's book "Sustainable Energy - without the hot air" is available free online: http://www.withouthotair.com/ Here's the chapter about solar energy: http://www.withouthotair.com/c6/page_38.shtml Here's a 1000 word synopsis he wrote for his talk to the House of Lords: http://www.inference.org.uk/sustainable/book/SUMMARY David MacKay also invented the Dasher text input system: http://www.inference.org.uk/dasher/ llukas on Dec 24, 2018 [-] Very good book but tech went lot further than David expected in many places (ie. solar power efficiency vs price). This page tried to keep it updated: https://www.carboncommentary.com/blog/2017/3/30/l6qcqgoedse1wmjjz87t09… dane-pgp on Dec 24, 2018 [-] David MacKay has done some great work, but I feel I need to present some…

A summary of the virtuous cycle created by cheap renewables and hydrogen electrolyzation: https://www.carboncommentary.com/blog/2020/6/17/renewables-plus-hydrog… Lots of comments on this thread that reveal folks are up to date with the state of hydrogen infrastructure c. 2017. It's changing really fast as billions of dollars are poured into R&D and pilot projects. For example, storage and transport: https://uk.reuters.com/article/uk-japan-hydrogen-chiyoda-corp/japans-c… Siemens has pledged to make turbines that run on 100% hydrogen by 2030: https://new.siemens.com/global/en/company/stories/energy/hydrogen-capa… Hydrogen trains: https://www.snam.it/en/Media/Press-releases/Agreement_Alstom_and_Snam_… Hydrogen in steelmaking: https://www.spglobal.com/platts/en/market-insights/latest-news/metals/… I could post 15 more. Our collective priors were well-grounded just a couple years ago, but it is time for a big update.