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Not just crops and power. I know a guy whose startup is using transparent solar panels in Germany on eco-friendly buildings with grass on roofs, to get power an

Not just crops and power. I know a guy whose startup is using transparent solar panels in Germany on eco-friendly buildings with grass on roofs, to get power and eco-cooling, as well as Oxygen production - at least that is how he explained it. The concept is called green-roofs. Unfortunately I don't remember his startup's name. A link with details about the concept, minus the use of transparent solar panels: https://buildingradar.com/construction-blog/green-roofs/ https://buildingradar.com/construction-blog/green-roofs/

agumonkey 6y ago
Are there places to read about this field ? journals, websites, discord anything ?
nitrogen 6y ago
Do they grow enough grass to produce enough oxygen for the building?
BurningFrog 6y ago
The oxygen claim doesn't inspire confidence. Plants don't produce any useful amount of oxygen, and real scientists know that.
- atoav 6y ago
  A thing that they are good at however, is lowering temperatures in cities (compared to e.g. stone surfaces which store the warmth of the sun) – this alone might be a good reason to look into green roofs, given that we just passed the point of no return for Greenland's ice sheet recently. It takes the same amount of energy to melt 1kg of 0°C ice into 0°C water as it takes to heat 1kg of 0°C water to 80°C.
  - gus_massa 6y ago
    You probably need to have a irrigation keep the plants alive. Probably spraying the concrete surface has the same effect.
    - flukus 6y ago
      You would have to spray the surface every day, plants need watering much less, close to never if they're native to the region.
      - gus_massa 6y ago
        >>> A thing that they are good at however, is lowering temperatures in cities Plants are not magical, so if they get the same solar light influx then: (choose at least one) a) They are actually not good keeping the temperature down? b) The have more reflectivity, i.e. they are more white? (but I think they are darker) c) The complex structure provides some air flow that keep the plant and soil cooler? (like the isolation of fur in animals, but in the other direction) d) The specific heat of plants is greater than concrete? (plants have more water, and water has a big heat capacity) e) The big heat capacity is due not to the water in the plant, but to the water in the soil? f) The difference of temperature is caused by transpiration of the plant? (water has a huge heat of vaporization, plants try not to loos too much water in transpiration anyway) g) Most of the evaporation is water that was in the soil? For f) and g) two you need irrigation. Perhaps not daily because plants and soil are better storing water than concrete, but it is the same amount of water. For d) and e), you need less irrigation, but perhaps it is better to have some kind of water tank of pipes, to avoid water lose. For c) you can try with artificial grass. Does it work? Is it easier to maintain? For b) it is probably better to use and aluminium foil cover (they are popular here it rooftop to avoid rain leaks)
  - BurningFrog 6y ago
    I wonder how that compares to white painted or even reflective roofs? The paint solutions don't require a gardener at least.
    - rini17 6y ago
      Usual white painted surfaces get hot too. And if you use some superhigh-reflectivity surface, you have to keep it clean.
- hutzlibu 6y ago
  So what on this earth is producing useful amounts of oxygen then?
  - tsimionescu 6y ago
    Algae in the ocean, mostly. But also, any growing plants - you could compute for every kg of dry plant matter, how much oxygen is released, as the dry plant matter is almost entirely carbon produced from breaking up CO2. So unless you're collecting tens or hundreds of kilograms of dead plants from your roof every year, it isn't producing much oxygen.
    - Polylactic_acid 6y ago
      This is why we won't solve climate change by simply planting trees. Planting trees is good but once the land is covered in trees like it was you can't go further. You have to start actively putting carbon underground so it doesn't end up in the air again.
      - lxmorj 6y ago
        Well, you can build shit with the wood that's going to last a long time and plant a new tree. Though I'm not sure the lumber processing & construction isn't producing more carbon than the tree sequesters...
    - hutzlibu 6y ago
      And algae are plants last time I checked. Because op said "Plants don't produce any useful amount of oxygen" And I am aware, that room plants do not really add meaningful O2 to the room, their value is in humidifying.
      - BurningFrog 6y ago
        Googling "are algae plants?", gives this as the first answer: > Algae are in the plant kingdom, but technically they are not plants. ... Algae range in size from microscopic to meters long and from single-celled to complex organisms that rival large plants. These organisms may look like true plants, but unlike plants, algae do not have roots or true stems and leaves. Either way, I wasn't thinking of algae or aware that they might be net oxygen producers for the atmosphere.
- lifeisstillgood 6y ago
  Umm ... You may be confusing net production with actual production (ie plants produce pretty much all the O2 but they then reabsorb it) I suspect it is also worth differentiating between production as has been going on for millions of years and industrial production - there is really no way to collect or harvest the oxygen made by plants - but that is kinda implied by the GP statement (that they wanted to cool the roof make electricity and Oxygen production (the implication being something useful to a business based on that roof) So I can see your point. https://en.m.wikipedia.org/wiki/Oxygen_cycle https://en.m.wikipedia.org/wiki/Oxygen_cycle
- felipemnoa 6y ago
  >>Plants don't produce any useful amount of oxygen, and real scientists know that. Could you please add some context to this statement. It is hard to believe that the oxygen produced by plants is so negligible as to be useless. Why?
  - chongli 6y ago
    Because plants use up oxygen when they decay, or when they’re digested by herbivores, and release CO2 in the process. Plants are carbon neutral for this reason. Oxygen comes from algae in the ocean. The reason the ocean carbon cycle isn’t carbon neutral is because the carbon is fixed into calcium carbonate by zooplankton that feed on the algae. When these tiny animals die their calcium carbonate based exoskeletons sink and accumulate on the ocean floor, sequestering the carbon there. Carbon sequestration used to take place on land as well (that’s where all fossil fuels originate) but now we have fungi and animals like beetles that can break down lignin and cellulose instead of allowing it to accumulate.
- titzer 6y ago
  lmgfy https://www.thoughtco.com/how-much-oxygen-does-one-tree-produce-606785 https://www.thoughtco.com/how-much-oxygen-does-one-tree-prod... A fully mature tree produces anywhere from 2 to 10 persons-worth of oxygen. I too am skeptical about the amount of oxygen that can be usefully produced by rooftop plants. Yet I still think it is a good idea.
recuter 6y ago
"Dirt grass and a goat get you a LEED point - does the dirt grass and a goat make it work better? No! But you do feel better about yourself! Dirt is not insulation it's just freaking dirt" - https://en.wikipedia.org/wiki/Joseph_Lstiburek https://en.wikipedia.org/wiki/Joseph_Lstiburek (https://youtu.be/iHBYvqr2_io?t=2224 https://youtu.be/iHBYvqr2_io?t=2224) Gotta love greenwashing. A real forward thinker would also start a second startup simultaneously to undo the damage green roofs will cause down the line to a building. :) Edit: In case somebody misses the point the video from which the quote is sourced is well worth watching if you are curios about building science. tl;dw - What is efficient and good for the environment is counterintuitive. Green roofs often cause more harm than good because reasons.
- hutzlibu 6y ago
  I don't really like having to watch some youtube video, to get the counterpoint, all presented in a non friendly way. So do you have some facts, you want to share, why green roofs, a method for example used in scandinavia for a long time, is bad, if done right? Because you quote ... is not a smart one. Because dirt is definitley insulation. And soild is more than dirt btw.
  - recuter 6y ago
    I didn't mean anything in an unfriendly way. The quote is not dumb but it needs a lot of context I suppose that might be missing.. definitely the key point is "if done right". I can't really condense the video for you, the guy in it does throw in a bunch of jokes from the perspective of a frustrated Canadian building science guy that might put you off but his information is great. My best attempt at a condensed parable: I once found myself driving around with a very environmentally minded person and she refused to turn the AC on in her car but cranked open the window instead.
    - SECProto 6y ago
      > the guy in it does throw in a bunch of jokes from the perspective of a frustrated Canadian building science guy that might put you off but his information is great. As someone else who works with civil (but not structural) engineering in Canada, I agree to a certain extent with his points, but found his tone incredibly condescending and offputting. For example: > Does the dirt, grass, and a goat make it work better? No. But you just feel better about yourself. I mean dirt is not insulation, it's just freaking dirt. If it was insulation we'd put it in our walls, and that'd be stupid. [...] 'well we can store water up there' - Why? You're an idiot. The whole idea of a roof is to get the water off of the damn roof. - Soil is insulating, just with a very crappy K value. You wouldn't use it somewhere that was space sensitive (eg a wall). You wouldn't use it instead of other insulation. But it is absolutely an insulator (that's why we only have to put frost walls 4-8feet deep to prevent frost heave). If your only goal is to insulate the roof better, install an extra inch of rigid foam rather than a foot of soil, it'll work the same. - Storing water where it first strikes is good for reducing site runoff (with safeties installed to cope with bigger rainfall events). > I once found myself driving around with a very environmentally minded person and she refused to turn the AC on in her car but cranked open the window instead. How fast were you driving? There's a breakeven point, depends on the car - I know with mine, it's about 80 km/hr (slower than that, open the window. faster than that, AC is more fuel efficient)
ragebol 6y ago
I'm also considering making a green roof. Apparently, since the plants (sedum/stonecrops and mosses) help cool the roof, the solar panels on top of it are a bit cooler too increasing their efficiency. It also helps retain some water so it does not go to the sewer directly after it rains of the roof and keeps the sewer from getting overloaded. Another claimed benefit it is that a green roof helps reduce fine particulates in the air. And biodiversity etc etc. Its kinda expensive to do right though, so maybe some time.
- prawn 6y ago
  Depending on the style of house, it also makes better use of space if you're otherwise trying to balance space for gardening or for your children to play, etc. I would love to be able to grow my vegetables on the roof and free up the ground level of a basketball ring or more lawn for the kids.
  - ragebol 6y ago
    It's a bungalow so all ground level living (not just handy when you're old but apparently also when SO just delivered a baby) so the roof is also mostly flat. I've considered adding a vegetable garden on the roof too, or maybe just herbs. And thought about a terrace on the roof too, that would be cool but the ground-level garden is nice already as it is.

agumonkey 6y ago

Are there places to read about this field ? journals, websites, discord anything ?

nitrogen 6y ago

Do they grow enough grass to produce enough oxygen for the building?

BurningFrog 6y ago

The oxygen claim doesn't inspire confidence. Plants don't produce any useful amount of oxygen, and real scientists know that.

atoav 6y ago
A thing that they are good at however, is lowering temperatures in cities (compared to e.g. stone surfaces which store the warmth of the sun) – this alone might be a good reason to look into green roofs, given that we just passed the point of no return for Greenland's ice sheet recently. It takes the same amount of energy to melt 1kg of 0°C ice into 0°C water as it takes to heat 1kg of 0°C water to 80°C.
- gus_massa 6y ago
  You probably need to have a irrigation keep the plants alive. Probably spraying the concrete surface has the same effect.
  - flukus 6y ago
    You would have to spray the surface every day, plants need watering much less, close to never if they're native to the region.
    - gus_massa 6y ago
      >>> A thing that they are good at however, is lowering temperatures in cities Plants are not magical, so if they get the same solar light influx then: (choose at least one) a) They are actually not good keeping the temperature down? b) The have more reflectivity, i.e. they are more white? (but I think they are darker) c) The complex structure provides some air flow that keep the plant and soil cooler? (like the isolation of fur in animals, but in the other direction) d) The specific heat of plants is greater than concrete? (plants have more water, and water has a big heat capacity) e) The big heat capacity is due not to the water in the plant, but to the water in the soil? f) The difference of temperature is caused by transpiration of the plant? (water has a huge heat of vaporization, plants try not to loos too much water in transpiration anyway) g) Most of the evaporation is water that was in the soil? For f) and g) two you need irrigation. Perhaps not daily because plants and soil are better storing water than concrete, but it is the same amount of water. For d) and e), you need less irrigation, but perhaps it is better to have some kind of water tank of pipes, to avoid water lose. For c) you can try with artificial grass. Does it work? Is it easier to maintain? For b) it is probably better to use and aluminium foil cover (they are popular here it rooftop to avoid rain leaks)
- BurningFrog 6y ago
  I wonder how that compares to white painted or even reflective roofs? The paint solutions don't require a gardener at least.
  - rini17 6y ago
    Usual white painted surfaces get hot too. And if you use some superhigh-reflectivity surface, you have to keep it clean.
hutzlibu 6y ago
So what on this earth is producing useful amounts of oxygen then?
- tsimionescu 6y ago
  Algae in the ocean, mostly. But also, any growing plants - you could compute for every kg of dry plant matter, how much oxygen is released, as the dry plant matter is almost entirely carbon produced from breaking up CO2. So unless you're collecting tens or hundreds of kilograms of dead plants from your roof every year, it isn't producing much oxygen.
  - Polylactic_acid 6y ago
    This is why we won't solve climate change by simply planting trees. Planting trees is good but once the land is covered in trees like it was you can't go further. You have to start actively putting carbon underground so it doesn't end up in the air again.
    - lxmorj 6y ago
      Well, you can build shit with the wood that's going to last a long time and plant a new tree. Though I'm not sure the lumber processing & construction isn't producing more carbon than the tree sequesters...
  - hutzlibu 6y ago
    And algae are plants last time I checked. Because op said "Plants don't produce any useful amount of oxygen" And I am aware, that room plants do not really add meaningful O2 to the room, their value is in humidifying.
    - BurningFrog 6y ago
      Googling "are algae plants?", gives this as the first answer: > Algae are in the plant kingdom, but technically they are not plants. ... Algae range in size from microscopic to meters long and from single-celled to complex organisms that rival large plants. These organisms may look like true plants, but unlike plants, algae do not have roots or true stems and leaves. Either way, I wasn't thinking of algae or aware that they might be net oxygen producers for the atmosphere.
lifeisstillgood 6y ago
Umm ... You may be confusing net production with actual production (ie plants produce pretty much all the O2 but they then reabsorb it) I suspect it is also worth differentiating between production as has been going on for millions of years and industrial production - there is really no way to collect or harvest the oxygen made by plants - but that is kinda implied by the GP statement (that they wanted to cool the roof make electricity and Oxygen production (the implication being something useful to a business based on that roof) So I can see your point. https://en.m.wikipedia.org/wiki/Oxygen_cycle https://en.m.wikipedia.org/wiki/Oxygen_cycle
felipemnoa 6y ago
>>Plants don't produce any useful amount of oxygen, and real scientists know that. Could you please add some context to this statement. It is hard to believe that the oxygen produced by plants is so negligible as to be useless. Why?
- chongli 6y ago
  Because plants use up oxygen when they decay, or when they’re digested by herbivores, and release CO2 in the process. Plants are carbon neutral for this reason. Oxygen comes from algae in the ocean. The reason the ocean carbon cycle isn’t carbon neutral is because the carbon is fixed into calcium carbonate by zooplankton that feed on the algae. When these tiny animals die their calcium carbonate based exoskeletons sink and accumulate on the ocean floor, sequestering the carbon there. Carbon sequestration used to take place on land as well (that’s where all fossil fuels originate) but now we have fungi and animals like beetles that can break down lignin and cellulose instead of allowing it to accumulate.
titzer 6y ago
lmgfy https://www.thoughtco.com/how-much-oxygen-does-one-tree-produce-606785 https://www.thoughtco.com/how-much-oxygen-does-one-tree-prod... A fully mature tree produces anywhere from 2 to 10 persons-worth of oxygen. I too am skeptical about the amount of oxygen that can be usefully produced by rooftop plants. Yet I still think it is a good idea.

recuter 6y ago

"Dirt grass and a goat get you a LEED point - does the dirt grass and a goat make it work better? No! But you do feel better about yourself! Dirt is not insulation it's just freaking dirt" - https://en.wikipedia.org/wiki/Joseph_Lstiburek https://en.wikipedia.org/wiki/Joseph_Lstiburek (https://youtu.be/iHBYvqr2_io?t=2224 https://youtu.be/iHBYvqr2_io?t=2224) Gotta love greenwashing. A real forward thinker would also start a second startup simultaneously to undo the damage green roofs will cause down the line to a building. :) Edit: In case somebody misses the point the video from which the quote is sourced is well worth watching if you are curios about building science. tl;dw - What is efficient and good for the environment is counterintuitive. Green roofs often cause more harm than good because reasons.

hutzlibu 6y ago
I don't really like having to watch some youtube video, to get the counterpoint, all presented in a non friendly way. So do you have some facts, you want to share, why green roofs, a method for example used in scandinavia for a long time, is bad, if done right? Because you quote ... is not a smart one. Because dirt is definitley insulation. And soild is more than dirt btw.
- recuter 6y ago
  I didn't mean anything in an unfriendly way. The quote is not dumb but it needs a lot of context I suppose that might be missing.. definitely the key point is "if done right". I can't really condense the video for you, the guy in it does throw in a bunch of jokes from the perspective of a frustrated Canadian building science guy that might put you off but his information is great. My best attempt at a condensed parable: I once found myself driving around with a very environmentally minded person and she refused to turn the AC on in her car but cranked open the window instead.
  - SECProto 6y ago
    > the guy in it does throw in a bunch of jokes from the perspective of a frustrated Canadian building science guy that might put you off but his information is great. As someone else who works with civil (but not structural) engineering in Canada, I agree to a certain extent with his points, but found his tone incredibly condescending and offputting. For example: > Does the dirt, grass, and a goat make it work better? No. But you just feel better about yourself. I mean dirt is not insulation, it's just freaking dirt. If it was insulation we'd put it in our walls, and that'd be stupid. [...] 'well we can store water up there' - Why? You're an idiot. The whole idea of a roof is to get the water off of the damn roof. - Soil is insulating, just with a very crappy K value. You wouldn't use it somewhere that was space sensitive (eg a wall). You wouldn't use it instead of other insulation. But it is absolutely an insulator (that's why we only have to put frost walls 4-8feet deep to prevent frost heave). If your only goal is to insulate the roof better, install an extra inch of rigid foam rather than a foot of soil, it'll work the same. - Storing water where it first strikes is good for reducing site runoff (with safeties installed to cope with bigger rainfall events). > I once found myself driving around with a very environmentally minded person and she refused to turn the AC on in her car but cranked open the window instead. How fast were you driving? There's a breakeven point, depends on the car - I know with mine, it's about 80 km/hr (slower than that, open the window. faster than that, AC is more fuel efficient)

ragebol 6y ago

I'm also considering making a green roof. Apparently, since the plants (sedum/stonecrops and mosses) help cool the roof, the solar panels on top of it are a bit cooler too increasing their efficiency. It also helps retain some water so it does not go to the sewer directly after it rains of the roof and keeps the sewer from getting overloaded. Another claimed benefit it is that a green roof helps reduce fine particulates in the air. And biodiversity etc etc. Its kinda expensive to do right though, so maybe some time.

prawn 6y ago
Depending on the style of house, it also makes better use of space if you're otherwise trying to balance space for gardening or for your children to play, etc. I would love to be able to grow my vegetables on the roof and free up the ground level of a basketball ring or more lawn for the kids.
- ragebol 6y ago
  It's a bungalow so all ground level living (not just handy when you're old but apparently also when SO just delivered a baby) so the roof is also mostly flat. I've considered adding a vegetable garden on the roof too, or maybe just herbs. And thought about a terrace on the roof too, that would be cool but the ground-level garden is nice already as it is.