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Countering climate change with cool pavements

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Re: Countering climate change with cool pavements

#51

Post by cesarb »

wruza wrote: post #49
clairity wrote: post #3

> “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.” this is one of the reasons why i'm an advocate for street trees, and urban foliage in general (cuts down both incident and reflective radiation), and why i'm maddened when i see urban trees cut down or cut back…

I would add that city people underestimate or simply do not know about the ability of vegetation to cool off its environment. My city has areas (few abandoned plots) with a wild high grass and bushes on them. When it’s hot and you walk nearby, like 2-3m close, it is as if you went from the street to under AC. I don’t know how they do it, but my guess is that photosynthesis is a hell of an endothermic process. And you…

> [..] it is as if you went from the street to under AC. I don’t know how they do it, but my guess is that photosynthesis [...]

My guess would be evapotranspiration, not photosynthesis.

Re: Countering climate change with cool pavements

#52

Post by compressedgas »

wruza wrote: post #49
clairity wrote: post #3

> “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.” this is one of the reasons why i'm an advocate for street trees, and urban foliage in general (cuts down both incident and reflective radiation), and why i'm maddened when i see urban trees cut down or cut back…

I would add that city people underestimate or simply do not know about the ability of vegetation to cool off its environment. My city has areas (few abandoned plots) with a wild high grass and bushes on them. When it’s hot and you walk nearby, like 2-3m close, it is as if you went from the street to under AC. I don’t know how they do it, but my guess is that photosynthesis is a hell of an endothermic process. And you…

It's called transpiration. It is how the plants keep their temperature below the point at which photosynthesis no longer is possible.

Re: Countering climate change with cool pavements

#53

Post by strogonoff »

moonchrome wrote: post #31
clairity wrote: post #3

> “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.” this is one of the reasons why i'm an advocate for street trees, and urban foliage in general (cuts down both incident and reflective radiation), and why i'm maddened when i see urban trees cut down or cut back…

How do you get trees to avoid destroying concrete/pavement with roots ? We have a lot of old trees around and the pavement around them is bulged, cracked and deformed.

> How do you get trees to avoid destroying concrete/pavement with roots?

If that type of tree is known to have extensive roots, perhaps you could use smaller tiles on the pavement nearby and let the roots find their way.

The eventual result might look unsettling to some, though[0] (I know it does to me).

I guess it does make part of the pavement inaccessible for wheelchair users… But then I believe that must be a massive old tree there.

[0] https://imgur.com/a/k8OUF84

Re: Countering climate change with cool pavements

#54

Post by elric »

barsonme wrote: post #45
berikv wrote: post #8

Why wouldn’t you just plant some trees. You don’t need any fancy pavement if it is below a tree.. European cities are filled with trees to cool the streets below them. Obviously, you’d need smaller streets that fit pedestrians and bicycles instead of massive urban highways for trees to be effective.

US cities have trees, too. One downside, though, is the roots can grow and break up the sidewalk. There are some sidewalks in Seattle that are completely inaccessible to wheelchairs or even folks with walkers.

If roots were the biggest obstacle for wheelchair use, I'm sure many a wheelchair user would rejoice. I doubt that's anywhere near the case. Cars parking on the pavement, silly delivery robots, shops with oversized signs, all kinds of rubbish, inaccessibly high kerbs, are likely bigger issues.

Re: Countering climate change with cool pavements

#55

Post by wruza »

compressedgas wrote: post #52
wruza wrote: post #49

Earlier quoted context omitted.

I would add that city people underestimate or simply do not know about the ability of vegetation to cool off its environment. My city has areas (few abandoned plots) with a wild high grass and bushes on them. When it’s hot and you walk nearby, like 2-3m close, it is as if you went from the street to under AC. I don’t know how they do it, but my guess is that photosynthesis is a hell of an endothermic process. And you…

It's called transpiration. It is how the plants keep their temperature below the point at which photosynthesis no longer is possible.

TIL. But that means plants move heat somewhere, and not pack it into chemical bonds. This maybe defeats the idea, because these areas are cold because they are rare. If ubiquitous, in a still hot day they would just raise humidity and probably make things worse?

Re: Countering climate change with cool pavements

#56

Post by clairity »

harmmonica wrote: post #44
bcrosby95 wrote: post #41

Earlier quoted context omitted.

You also have to be careful of mainlines and turning that into swiss cheese with the root system. Ultimately it takes a fair amount of research to pick the right location and tree.

like parent commenter said LA actually has a list of acceptable “street trees” that they’ve approved so they don’t kill the sidewalks. some of the most glorious trees you’ll see here are ficus, but those are not on the list because they do blow away sidewalks, streets, utilities. unbelievable shade trees though that require very little water.

i just learned that a huge, grand old tree in my neighborhood is a species of ficus, and indeed, the sidewalk next to it is a buckled, gnarled mess. but i’d rather deal with that problem than harm the tree (it seems like it would be pretty straightforward to build a concrete ramp over the roots, like a mini-bridge).

Re: Countering climate change with cool pavements

#57

Post by elric »

berikv wrote: post #8

Why wouldn’t you just plant some trees. You don’t need any fancy pavement if it is below a tree.. European cities are filled with trees to cool the streets below them. Obviously, you’d need smaller streets that fit pedestrians and bicycles instead of massive urban highways for trees to be effective.

> European cities are filled with trees

Bit of an overly broad generalization. Some European cities, sure. But many are desolate and devoid of trees. Many old cities have very narrow streets, which aren't great for trees. A few shrubs, maybe. Wider strees in Belgian cities are generally devoid of trees, because parking spaces are apparently more important -- and we wouldn't want to impede the view of shops and billboards! Whenever urban trees are cut down, there's a bit of protest, but nevertheless it just keeps happening :-(

Re: Countering climate change with cool pavements

#58

Post by na85 »

Nbox9 wrote: post #38
na85 wrote: post #29

Earlier quoted context omitted.

Why so certain?

I’m in the 98% not feasible category for a few reasons. I’m open to new information or arguments, but I can’t see a way over a few very large hurdles. 1. Pavement is a very poor conductor, energy doesn’t move easily through it. 2. The Delta between ambient air temp and pavement temp low. Generating power would most likely include moving energy between the higher temp pavement to the lower temp air and capturing some…

>Pavement is a very poor conductor, energy doesn’t move easily through it.

Oh dear I'm certainly not proposing running electricity through the pavement itself. I'm suggesting you harvest the heat from the asphalt with e.g. a thermocouple and use that to produce a voltage.

>The Delta between ambient air temp and pavement temp low.

Perhaps, but not between the pavement and the soil a foot or so underneath.

Re: Countering climate change with cool pavements

#59

Post by ToJans »

clairity wrote: post #3

> “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.” this is one of the reasons why i'm an advocate for street trees, and urban foliage in general (cuts down both incident and reflective radiation), and why i'm maddened when i see urban trees cut down or cut back…

FYI I've brainstormed on an innovation use case once that would allow citizens to use an app to suggest things like planting trees everywhere using AR etc. When discussing with academics, I was flabbergasted to find out that in street canyons, trees can have a negative effect because they reduce air flow. So, apparently it's not as simple as "just plant some trees"...
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