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Currently synthesising ammonia requires hydrogen and that comes from fossil fuels (the main process of extracting that hydrogen is steam reforming of natural ga

Currently synthesising ammonia requires hydrogen and that comes from fossil fuels (the main process of extracting that hydrogen is steam reforming of natural gas and, I think, the main carbon emitter from the current ammonia process). Green ammonia would be made with green hydrogen which is made from water with electrolysis with renewable energy. These ideas make it more obvious that any viable solutions to climate change will require a massive increase in energy production. Solar and wind require massive scale and nuclear seems to currently be very hard to set up and unjustifiable if unit costs of electricity go down.

bryanlarsen 5y ago
> Solar and wind require massive scale In what way? None of land area requirements, panel production, battery production nor turbine production seem particularly difficult in the modern economy in relation to the scale of the problem.
- dan-robertson 5y ago
  You need a lot of “stuff” (land, raw materials, labour, etc) for your energy. I’m not sure how true this really is in comparison to e.g. fossil fuel or nuclear power, but I get the sense that a lot of space and resources are required for a very large power output whereas the energy density in land is much lower for solar and wind (though construction is likely cheaper). David MacKay had a great graph showing the power per land density of various energy sources and in the U.K. assuming that we could switch things like heating and transportation to electricity without loss of efficiency, we would need to roughly coat the country in solar or wind to match current energy consumption. Though the numbers may have changed since, they probably haven’t changed by the 2 orders of magnitude or so that would likely be required for the prospect of just solar/wind to be palatable.
  - bryanlarsen 5y ago
    To completely power the US with solar power would take several hundred square miles. In a country with three and a half million of them. We dedicate a lot more land just in parking lots.
  - leoedin 5y ago
    David MacKay's book is great, but it was written in 2009. Just re-reading the part about solar panels from the perspective of 2021 is quite eye-opening. He makes assumptions like 10% efficient panels (panels today are probably 18-22% efficient) and says that the required solar power would be "100 times all the photovoltaics in the whole world". The amount of energy he's talking about - around 1200 TWh - is now only 1.4 times all the photovoltaics in the world. In fact, last year the UK alone generated 11.77 TWh - which is about what the entire world generated in 2009 when the book was written. His book also doesn't really take into account efficiency savings. For example, his "Cars" section calculates 40kWh/day/person - or 0.8 kWh/km (1.25 km/kWh). An average electric car today might get 3 miles/kWh (4.8km/kWh) - as there's no highly inefficient internal combustion engine involved. Likewise his heating section doesn't take into account energy saving measures and it doesn't account for heating from heat pumps. It's also exceedingly unlikely that we'd use solar power in the UK to create fuels for aircraft or ships. So while David does make a good point (I think the book, overall, is excellent and I recommend it frequently), it also overstates significantly the energy required from renewables in the UK.
    - dan-robertson 5y ago
      Thanks for all the information. I think my assumption was that the book would be wrong for efficiency reasons but that it would not be multiple orders of magnitude wrong and that that kind of difference would be required. I suppose in addition to efficiency improvements I may have been overestimating the required solar panel density and underestimating how palatable they are to people.

bryanlarsen 5y ago

> Solar and wind require massive scale In what way? None of land area requirements, panel production, battery production nor turbine production seem particularly difficult in the modern economy in relation to the scale of the problem.

dan-robertson 5y ago
You need a lot of “stuff” (land, raw materials, labour, etc) for your energy. I’m not sure how true this really is in comparison to e.g. fossil fuel or nuclear power, but I get the sense that a lot of space and resources are required for a very large power output whereas the energy density in land is much lower for solar and wind (though construction is likely cheaper). David MacKay had a great graph showing the power per land density of various energy sources and in the U.K. assuming that we could switch things like heating and transportation to electricity without loss of efficiency, we would need to roughly coat the country in solar or wind to match current energy consumption. Though the numbers may have changed since, they probably haven’t changed by the 2 orders of magnitude or so that would likely be required for the prospect of just solar/wind to be palatable.
- bryanlarsen 5y ago
  To completely power the US with solar power would take several hundred square miles. In a country with three and a half million of them. We dedicate a lot more land just in parking lots.
- leoedin 5y ago
  David MacKay's book is great, but it was written in 2009. Just re-reading the part about solar panels from the perspective of 2021 is quite eye-opening. He makes assumptions like 10% efficient panels (panels today are probably 18-22% efficient) and says that the required solar power would be "100 times all the photovoltaics in the whole world". The amount of energy he's talking about - around 1200 TWh - is now only 1.4 times all the photovoltaics in the world. In fact, last year the UK alone generated 11.77 TWh - which is about what the entire world generated in 2009 when the book was written. His book also doesn't really take into account efficiency savings. For example, his "Cars" section calculates 40kWh/day/person - or 0.8 kWh/km (1.25 km/kWh). An average electric car today might get 3 miles/kWh (4.8km/kWh) - as there's no highly inefficient internal combustion engine involved. Likewise his heating section doesn't take into account energy saving measures and it doesn't account for heating from heat pumps. It's also exceedingly unlikely that we'd use solar power in the UK to create fuels for aircraft or ships. So while David does make a good point (I think the book, overall, is excellent and I recommend it frequently), it also overstates significantly the energy required from renewables in the UK.
  - dan-robertson 5y ago
    Thanks for all the information. I think my assumption was that the book would be wrong for efficiency reasons but that it would not be multiple orders of magnitude wrong and that that kind of difference would be required. I suppose in addition to efficiency improvements I may have been overestimating the required solar panel density and underestimating how palatable they are to people.