3 ms·

If this is the math you did: > A crude calculation (earthradius_equatorial^2 * pi * (1000 W/m^2) * 1 year in units(1) --- gosh, Unix is great!) suggests that t

If this is the math you did: > A crude calculation (earthradius_equatorial^2 * pi * (1000 W/m^2) * 1 year in units(1) --- gosh, Unix is great!) suggests that the total solar energy falling on the earth is about 40000 * 10^20 joules per year. ... that's not a good approximation. There's someone who actually has done less crude math for maximum possible solar energy, at least for the UK: https://www.withouthotair.com/c6/page_38.shtml https://www.withouthotair.com/c6/page_38.shtml (though the HTML version is somewhat annoying because it's still paginated as if it were a book). Spoiler alert: it's roughly enough energy to cover total transportation energy demand, nowhere near total energy demand in the UK.

atoav 3y ago
I mean UK isn't quite known for its sunny weather, right? I would guess in Norway during the dark part of the year it is even going to be worse. The farther north you go the more relevant technologies like wind energy and geothermal will become.
- kragen 3y ago
  and maybe nuclear or synfuel. also, the farther south; there used to be a nuclear reactor in mcmurdo norway in particular gets almost all their electricity from hydroelectric plants https://www.statista.com/statistics/1025497/distribution-of-electricity-production-in-norway-by-source/ https://www.statista.com/statistics/1025497/distribution-of-... but of course its transportation sector is still mostly fossil-powered
kragen 3y ago
you would look much less foolish if you read more than just the introduction to my notes; i did a great deal more math than that while i appreciate mackay's calculations a great deal, his estimates for very polar countries such as the uk are not generally applicable, and even for the uk are probably conditioned on overly pessimistic assumptions; he would undoubtedly agree if he were alive today in particular, he assumed (reasonably) that 10%-efficient solar panels would be much cheaper than 20%-efficient ones, which would remain impractically expensive. but in fact most solar farms are being built with 21%-efficient panels because they're nearly as cheap as the 16%-efficient kind, and the 10%-efficient kind has been competed out of the market. so mackay's excellent calculations are all too low by more than a factor of 2, because one of his reasonable assumptions turned out to be wrong but i do think it's plausible that without wind the uk would have to continue importing energy from abroad, as it has done since the 19th century, unless it goes nuclear. because mackay was aware his estimates for very polar countries such as the uk were not generally applicable, importing solar energy from abroad was in fact what he recommended in the chapter you linked but evidently didn't bother to read
- jcranmer 3y ago
  > you would look much less foolish if you read more than just the introduction to my notes; i did a great deal more math than that Perhaps, but I see nothing in your post that actually corrects for effective solar irradiation on Earth, or for the fact that half the Earth's surface is by definition not receiving any sunlight at any given time, or for the fact that most of the Earth is water and not land (although I suppose you dropping the 4 from the multiplier for the surface area is meant to account for that). In other words, at no point did I see anything that took into account the error I pointed out.
  - kragen 3y ago
    you didn't point out any errors; maybe you noticed one and forgot to mention it. please let me know if so if you're interested in taking the capacity factor into account, which accounts for things like night, clouds, and oblique illumination, a number of my other notes in https://dercuano.github.io/topics/solar.html https://dercuano.github.io/topics/solar.html (linked from the bottom of my above-linked note) do that; for example in https://dercuano.github.io/notes/japan-energy-autarky.html https://dercuano.github.io/notes/japan-energy-autarky.html i calculated that energy autarky for japan, if purely solar, would require 5% of its land area and about 1.7 trillion euros of solar modules, taking into account all of those factors as well as panel efficiency. since then, the price has dropped by more than a factor of 2, but the land area required remains about the same, or slightly increased (floating that 5% of their land area on solar barges off the coast, instead of occupying precious land area, is also clearly feasible; it just isn't economically competitive, much like nuclear power) of course, the real-life solution also involves wind and grid-scale storage perhaps it goes without saying that very few places are as densely populated or as heavily industrialized as japan, so much smaller fractions of their land area would suffice
    - kragen 3y ago
      > you didn't point out any errors; maybe you noticed one and forgot to mention it. please let me know if so i'm still waiting, it's been two days

atoav 3y ago

I mean UK isn't quite known for its sunny weather, right? I would guess in Norway during the dark part of the year it is even going to be worse. The farther north you go the more relevant technologies like wind energy and geothermal will become.

kragen 3y ago
and maybe nuclear or synfuel. also, the farther south; there used to be a nuclear reactor in mcmurdo norway in particular gets almost all their electricity from hydroelectric plants https://www.statista.com/statistics/1025497/distribution-of-electricity-production-in-norway-by-source/ https://www.statista.com/statistics/1025497/distribution-of-... but of course its transportation sector is still mostly fossil-powered

kragen 3y ago

you would look much less foolish if you read more than just the introduction to my notes; i did a great deal more math than that while i appreciate mackay's calculations a great deal, his estimates for very polar countries such as the uk are not generally applicable, and even for the uk are probably conditioned on overly pessimistic assumptions; he would undoubtedly agree if he were alive today in particular, he assumed (reasonably) that 10%-efficient solar panels would be much cheaper than 20%-efficient ones, which would remain impractically expensive. but in fact most solar farms are being built with 21%-efficient panels because they're nearly as cheap as the 16%-efficient kind, and the 10%-efficient kind has been competed out of the market. so mackay's excellent calculations are all too low by more than a factor of 2, because one of his reasonable assumptions turned out to be wrong but i do think it's plausible that without wind the uk would have to continue importing energy from abroad, as it has done since the 19th century, unless it goes nuclear. because mackay was aware his estimates for very polar countries such as the uk were not generally applicable, importing solar energy from abroad was in fact what he recommended in the chapter you linked but evidently didn't bother to read

jcranmer 3y ago
> you would look much less foolish if you read more than just the introduction to my notes; i did a great deal more math than that Perhaps, but I see nothing in your post that actually corrects for effective solar irradiation on Earth, or for the fact that half the Earth's surface is by definition not receiving any sunlight at any given time, or for the fact that most of the Earth is water and not land (although I suppose you dropping the 4 from the multiplier for the surface area is meant to account for that). In other words, at no point did I see anything that took into account the error I pointed out.
- kragen 3y ago
  you didn't point out any errors; maybe you noticed one and forgot to mention it. please let me know if so if you're interested in taking the capacity factor into account, which accounts for things like night, clouds, and oblique illumination, a number of my other notes in https://dercuano.github.io/topics/solar.html https://dercuano.github.io/topics/solar.html (linked from the bottom of my above-linked note) do that; for example in https://dercuano.github.io/notes/japan-energy-autarky.html https://dercuano.github.io/notes/japan-energy-autarky.html i calculated that energy autarky for japan, if purely solar, would require 5% of its land area and about 1.7 trillion euros of solar modules, taking into account all of those factors as well as panel efficiency. since then, the price has dropped by more than a factor of 2, but the land area required remains about the same, or slightly increased (floating that 5% of their land area on solar barges off the coast, instead of occupying precious land area, is also clearly feasible; it just isn't economically competitive, much like nuclear power) of course, the real-life solution also involves wind and grid-scale storage perhaps it goes without saying that very few places are as densely populated or as heavily industrialized as japan, so much smaller fractions of their land area would suffice
  - kragen 3y ago
    > you didn't point out any errors; maybe you noticed one and forgot to mention it. please let me know if so i'm still waiting, it's been two days