5 ms·

Interesting, I assume there is some fundamental calculation that takes the radius of the greenhouse and chimney height in order to estimate the energy output.

sandworm101 3y ago
Yup, and id bet that it doesnt make more than a similarly-sized field of solar panels.
ricardo81 3y ago
There's a photonic limit [0] I think the general idea here is that there's a lot of thermal energy that does not get used in a cost-effective way. IIRC the majority of 'efficiency' wrt energy hitting a panel comes out as heat, and here it's a question of if that heat can cost effectively be stored/used. https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...
- pfdietz 3y ago
  The Shockley-Quiesser limit only applies to single junction PV cells. PV will likely eventually go with stacked cells of different bandgaps.
  - ricardo81 3y ago
    My understanding of this proposition is looking at harvesting the thermal energy, which is beyond PV. The chimney is all about the thermal output.
    - pfdietz 3y ago
      So why did you post a link to something that's explicitly about PV?
      - ricardo81 3y ago
        Because it's part of the answer to the poster's question which is considered sound science. Also that on a large scale the thermal energy of a solar array isn't generally accounted for.
- jodrellblank 3y ago
  > "there's a lot of thermal energy that does not get used in a cost-effective way" Reminds me of a discussion in the comments on Terence Eden's blog[1], where a commenter argues that photovoltaic panels on home roofs are not the best idea, and solar-thermal panels are better; an edited summary: "solar thermal, 4 square meters of roof space will generate 1500kWh per year; to achieve the same with PhotoVoltaics [PV] you would need 16 square meters. Solar thermal would roughly address water heating for showers for a family of 4 for using 4msq of panels. If that doesnt represent a useful amount of energy from a small amount of roof space I don't know what does! And with a lower environmental cost, lower CO2 emission, than PV for that energy." i.e. it's sad that government subsidies are making PV cheaper than solar-thermal, even though it makes worse use of roof space, with worse CO2 profile. [1] https://shkspr.mobi/blog/2013/12/free-money-from-the-sky/ https://shkspr.mobi/blog/2013/12/free-money-from-the-sky/ - comments by 'ben'
  - edent 3y ago
    But hot water isn't as useful as electricity. In summer, when solar is plentiful, radiators aren't run, and showers tend to be cool. In winter, when there's higher demand, there's less solar. Electricity is fungible. It can become heat, or light, or compute, or just about anything. Hot water isn't that versatile.
nine_k 3y ago
The right way to use it is not a greenhouse but a pool of seawater, maybe an existing small bay. The hot air then dissolves a lot of water vapor, brings it upwards while cooling down and rotating turbines, and releases as fresh water. Now you have a desalination plant that produces energy, not consumes it.

sandworm101 3y ago

Yup, and id bet that it doesnt make more than a similarly-sized field of solar panels.

ricardo81 3y ago

There's a photonic limit [0] I think the general idea here is that there's a lot of thermal energy that does not get used in a cost-effective way. IIRC the majority of 'efficiency' wrt energy hitting a panel comes out as heat, and here it's a question of if that heat can cost effectively be stored/used. https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...

pfdietz 3y ago
The Shockley-Quiesser limit only applies to single junction PV cells. PV will likely eventually go with stacked cells of different bandgaps.
- ricardo81 3y ago
  My understanding of this proposition is looking at harvesting the thermal energy, which is beyond PV. The chimney is all about the thermal output.
  - pfdietz 3y ago
    So why did you post a link to something that's explicitly about PV?
    - ricardo81 3y ago
      Because it's part of the answer to the poster's question which is considered sound science. Also that on a large scale the thermal energy of a solar array isn't generally accounted for.
jodrellblank 3y ago
> "there's a lot of thermal energy that does not get used in a cost-effective way" Reminds me of a discussion in the comments on Terence Eden's blog[1], where a commenter argues that photovoltaic panels on home roofs are not the best idea, and solar-thermal panels are better; an edited summary: "solar thermal, 4 square meters of roof space will generate 1500kWh per year; to achieve the same with PhotoVoltaics [PV] you would need 16 square meters. Solar thermal would roughly address water heating for showers for a family of 4 for using 4msq of panels. If that doesnt represent a useful amount of energy from a small amount of roof space I don't know what does! And with a lower environmental cost, lower CO2 emission, than PV for that energy." i.e. it's sad that government subsidies are making PV cheaper than solar-thermal, even though it makes worse use of roof space, with worse CO2 profile. [1] https://shkspr.mobi/blog/2013/12/free-money-from-the-sky/ https://shkspr.mobi/blog/2013/12/free-money-from-the-sky/ - comments by 'ben'
- edent 3y ago
  But hot water isn't as useful as electricity. In summer, when solar is plentiful, radiators aren't run, and showers tend to be cool. In winter, when there's higher demand, there's less solar. Electricity is fungible. It can become heat, or light, or compute, or just about anything. Hot water isn't that versatile.

nine_k 3y ago

The right way to use it is not a greenhouse but a pool of seawater, maybe an existing small bay. The hot air then dissolves a lot of water vapor, brings it upwards while cooling down and rotating turbines, and releases as fresh water. Now you have a desalination plant that produces energy, not consumes it.