The oxygen claim doesn't inspire confidence.
Plants don't produce any useful amount of oxygen, and real scientists know that.
Plants don't produce any useful amount of oxygen, and real scientists know that.
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.
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)
The paint solutions don't require a gardener at least.
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?
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.
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.
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.
> 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.
Individual oxygen atoms alternate between being in CO₂ molecules and O₂ molecules, as plants grab the carbon to build their bodies and return it after death.
But since the total mass of plant life doesn't change much, it all evens out.
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.
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.