3 ms·

>gas turbines are only 'renewables-only' if you make the gas from renewable energy There are ways to make hydrocarbons from atmospheric carbon (using any energ

by donny2018 3y ago

>gas turbines are only 'renewables-only' if you make the gas from renewable energy There are ways to make hydrocarbons from atmospheric carbon (using any energy, including renewable) but that is nightmarishly inefficient. Anti-nuclear people's plan though is to use good ol' fossil gas for the times when the weather is unsuitable for renewables. >the efficiency of photovoltaics and wind is only relevant here if Agreed, you can disregard its efficiency if the source energy is free. Fission energy is so high yield that it's also basically free, just like the Sun or wind, with the difference of being able to increase/decrease production on demand. It's the infrastructure to extract that energy that costs money, and those costs could be improved with proper R&D, investments, subsidies and economies of scale, just like with renewables. I do believe nuclear is the part of the Solution together with renewables. At least we will need nuclear before solar extraction and storage are so advanced that they can power the grid all the time by themselves. Yes, that future is certainly is not very far away, but we can't afford much time to start decarbonizing.

kragen 3y ago
fischer-tropsch is about 60% efficient https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process#Process_efficiency https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces... but that's being fed from energy that's already in the form of carbon water electrolysis https://en.wikipedia.org/wiki/Electrolysis_of_water#Efficiency https://en.wikipedia.org/wiki/Electrolysis_of_water#Efficien... is about 80% efficient, except that there's an experimental capillary-fed process that is supposedly 98% efficient i wouldn't call that 'nightmarishly inefficient', particularly if you can do it at hours when electricity prices would otherwise be zero or negative because of abundant solar or wind power but i don't know how efficient carbon dioxide reduction is https://en.wikipedia.org/wiki/Carbon_capture_and_utilization https://en.wikipedia.org/wiki/Carbon_capture_and_utilization nuclear power plants are not normally highly dispatchable, though obviously the naval ones are
- donny2018 3y ago
  >water electrolysis ... 80% efficient It's only to get hydrogen, also there is cost to make it liquid, to store it (it's neither trivial nor cheap) and to extract energy from it in fuel cells. >i don't know how efficient carbon dioxide reduction is If we want to capture carbon from atmosphere and turn it back into hydrocarbon fuel like gas or diesel, thus achieving net zero emissions, that process is still "nightmarishly inefficient". There is a startup that I'm watching (Prometheus Fuels) that promises to do that cheaply, but there haven't been any positive news from them recently
  - kragen 3y ago
    i'm surprised to see you still haven't posted any numbers or cited any sources
    - donny2018 3y ago
      " 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/ https://theicct.org/e-fuels-wont-save-the-internal-combustio... 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-electrofuels-cost https://www.carboncommentary.com/blog/2021/11/18/how-much-wi... 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 would be flooding the market already even at 2x the price, but the cost of producing these is currently 5x or higher. That's why the first target for such fuels is commercial aviation and sea transportation where the cost of fuel can be absorbed less painfully.
      - kragen 3y ago
        52% efficiency sounds fantastic; the other 70% loss is equally present when you're burning fossil fuels in the same engines. of course it is very relevant to the electric vehicle comparison, but not to replacing fossil fuels in peaker plants or airplanes, which is the topic at hand and it's fantastic news that the main cost factor is the cost of the energy input, rather than, for example, defouling or catalyst replacement. because once the electric grid is mostly renewable and intermittent, so that energy is free in the daytime, synthetic fuels will be immensely cheaper than they are now. perhaps by even more than 5x :) initially the carbon dioxide won't come from atmospheric capture; carbon capture at the source is immensely cheaper. perhaps as the number of fossil-fuel and biomass point sources dwindles, atmospheric carbon capture will become competitive, but i suspect that it may 16% cycle efficiency might rule out liquid synfuels for grid-scale energy storage, but hydrogen should be closer to 50% (60% combined-cycle turbine times 80% electrolysis), or perhaps higher with fuel cells, and though that's much lower than batteries, it's still a viable alternative to nuclear if batteries don't work out due to shortages or whatever

kragen 3y ago

fischer-tropsch is about 60% efficient https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process#Process_efficiency https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces... but that's being fed from energy that's already in the form of carbon water electrolysis https://en.wikipedia.org/wiki/Electrolysis_of_water#Efficiency https://en.wikipedia.org/wiki/Electrolysis_of_water#Efficien... is about 80% efficient, except that there's an experimental capillary-fed process that is supposedly 98% efficient i wouldn't call that 'nightmarishly inefficient', particularly if you can do it at hours when electricity prices would otherwise be zero or negative because of abundant solar or wind power but i don't know how efficient carbon dioxide reduction is https://en.wikipedia.org/wiki/Carbon_capture_and_utilization https://en.wikipedia.org/wiki/Carbon_capture_and_utilization nuclear power plants are not normally highly dispatchable, though obviously the naval ones are

donny2018 3y ago
>water electrolysis ... 80% efficient It's only to get hydrogen, also there is cost to make it liquid, to store it (it's neither trivial nor cheap) and to extract energy from it in fuel cells. >i don't know how efficient carbon dioxide reduction is If we want to capture carbon from atmosphere and turn it back into hydrocarbon fuel like gas or diesel, thus achieving net zero emissions, that process is still "nightmarishly inefficient". There is a startup that I'm watching (Prometheus Fuels) that promises to do that cheaply, but there haven't been any positive news from them recently
- kragen 3y ago
  i'm surprised to see you still haven't posted any numbers or cited any sources
  - donny2018 3y ago
    " 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/ https://theicct.org/e-fuels-wont-save-the-internal-combustio... 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-electrofuels-cost https://www.carboncommentary.com/blog/2021/11/18/how-much-wi... 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 would be flooding the market already even at 2x the price, but the cost of producing these is currently 5x or higher. That's why the first target for such fuels is commercial aviation and sea transportation where the cost of fuel can be absorbed less painfully.
    - kragen 3y ago
      52% efficiency sounds fantastic; the other 70% loss is equally present when you're burning fossil fuels in the same engines. of course it is very relevant to the electric vehicle comparison, but not to replacing fossil fuels in peaker plants or airplanes, which is the topic at hand and it's fantastic news that the main cost factor is the cost of the energy input, rather than, for example, defouling or catalyst replacement. because once the electric grid is mostly renewable and intermittent, so that energy is free in the daytime, synthetic fuels will be immensely cheaper than they are now. perhaps by even more than 5x :) initially the carbon dioxide won't come from atmospheric capture; carbon capture at the source is immensely cheaper. perhaps as the number of fossil-fuel and biomass point sources dwindles, atmospheric carbon capture will become competitive, but i suspect that it may 16% cycle efficiency might rule out liquid synfuels for grid-scale energy storage, but hydrogen should be closer to 50% (60% combined-cycle turbine times 80% electrolysis), or perhaps higher with fuel cells, and though that's much lower than batteries, it's still a viable alternative to nuclear if batteries don't work out due to shortages or whatever