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Countering climate change with cool pavements

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Re: Countering climate change with cool pavements

#61

Post by Ma8ee »

godelski wrote: post #9
frosted-flakes wrote: post #7

Earlier quoted context omitted.

Why would they cost a fortune to maintain? Apart from leaf collection and end-of-life removal, what costs are associated with street trees?

They require water, which requires irrigation (may not already be in place and of course has logistical problems), trees also root systems can lift and crack sidewalks/pipes/other things, you now have biological contaminants, there's bugs and fungus and things that can spread, and so much more. I'm not saying we shouldn't do this. I really like seeing plant life in cities and I think it really makes a psychological d…

How much irrigation that is needed very much depends on where you are and what kind of tree. After the first few years it take to settle, trees have deep roots and rarely need watering.

And I have never heard of trees contribution negatively to "biological contaminants", whatever that means. Rather, trees contribute to a cleaner and healthier environment.

Re: Countering climate change with cool pavements

#62

Post by peterbraden »

wruza wrote: post #55
compressedgas wrote: post #52

Earlier quoted context omitted.

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?

Not at all. The areas where they are ubiquitous, which we normally call forests, are still cool.

Re: Countering climate change with cool pavements

#64

Post by csomar »

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…

> the tree trimmers i see doing this have no idea what they're doing

Or maybe they do know what they are doing. Trees need trimming.

> not to contemplate consequences or consider other options.

Like?

Re: Countering climate change with cool pavements

#65

Post by agurk »

na85 wrote: post #58
Nbox9 wrote: post #38

Earlier quoted context omitted.

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.

Conductor can be used to describe more energy types than electricity. In this case they were referring to heat energy.

This would be important as if you moved the energy from the hot pavement to a cold source you're cooling the small part where you're taking heat from. As pavement is a poor heat conductor all the energy in the surrounding mass of pavement would flow only very slowly to the patch you were using. This would severly limit your ability to move heat and therefore generate electricity.

This is also why using the ground as the cold sink isn't a great idea. Once you have moved the heat energy to the ground it sits there only slowly moving away. This is why the ground is noticeably cooler just a foot beneath the hot pavement. Once your cold source is warm, the ability to move heat is again limited.

Air is also a bad conductor of heat, but as it's a gas it can move. So once you heat up some cool air it will become less dense and move away. This is convection.

Re: Countering climate change with cool pavements

#66

Post by axelroze »

ToJans wrote: post #59
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"...

They can also be a hazard as they can crash much easier during a storm, earthquake or hurricane. Especially if they are dry and not alive any more.

IMO solving overheated cities is not just more trees but less population density. Less buildings, less concrete, less asphalt. Less generation of heat and pollution in the first place. Less is more essentially.

Re: Countering climate change with cool pavements

#67

Post by Tempest1981 »

csomar wrote: post #64
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…

> the tree trimmers i see doing this have no idea what they're doing Or maybe they do know what they are doing. Trees need trimming. > not to contemplate consequences or consider other options. Like?

There is a guideline, to not prune more than 15-20% of a tree per season. And less if the tree is struggling.

Often urban trees are struggling, but I've seen workers still prune them heavily.

Re: Countering climate change with cool pavements

#68

Post by Tempest1981 »

robocat wrote: post #47
harmmonica wrote: post #13

Earlier quoted context omitted.

from one LA resident to another, amen to that. we were just walking down our street this morning and discussing, for the umpteenth time, whether our neighbors would actually be willing to take care of trees if we went out and bought them and planted them. the problem, as other commenters have pointed out, is that they do require upkeep, but since they're living/breathing things the more hardy ones can really be abuse…

> people who have never been here can point out the expensive neighborhoods because they are the greener ones This is normal in many cities. Trees can mean high status because (a) you need excess land to have trees. (b) old wealthy suburbs often have old trees (a massive old oak tree implies something). (c) single dwelling houses that are near the city often have very old trees due to the age of the location, and can…

> Trees can mean high status

Yep, check out a satellite view of Atherton, CA vs Redwood City next door. A huge contrast.

Re: Countering climate change with cool pavements

#69

Post by Tempest1981 »

clairity wrote: post #56
harmmonica wrote: post #44

Earlier quoted context omitted.

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).

See if you can get a rubber sidewalk:

https://www.npr.org/templates/story/story.php?storyId=561579... (2006)

Re: Countering climate change with cool pavements

#70

Post by mellavora »

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.

So maybe the tree is more valuable than the pavement? It is a living being, it has lived there for many years. Maybe we can show it some respect? Learn to live with it, as it lives with you? Appreciate the many benefits it brings, direct and indirect?

We aren't separate from nature, killing it is killing ourself.

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