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Albedo Shade + Rain Harvester + Wind Breaker + Soil cooler

Bounce back sunlight, use shade and water
  [vote for,

This is a simple four-in one idea (for a shortcut, see drawing).

1. Recent research suggests that merely painting roofs and sidewalks in the world's largest cities white can help cool the planet considerably. Changing the albedo of the planet is not such a ridiculous idea after all.

2. My albedo technology takes us to the Sahel, where desertification, erosion, deforestation and water scarcity are huge, interrelated problems.

3. The material used consists of highly reflective, cheap metal plates which are bent at the bottom so as to form a half-pipe.

4. The plates are positioned in a 45° inclination facing the Sun (or whichever inclination is best to bounce back sunlight at the project place). When you look at them horizontally, they are also placed in a very slight inclination. This is needed to channel water through gravity. The screens are attached to simple poles, while the halfpipe rests on the ground.

5. Now consider the advantages:

-sunlight is bounced back in a major way: this brings in 'albedo credits' (similar to 'carbon credits'). This cash should be sufficient to finance a big part of the project (see below).

-the reflectors also provide shade and cool the soil behind them.

-furthermore, the screens act as a wind-breaker, which is very important so as to limit erosion and nutrient-loss of the soil.

-last but not least, it does rain occasionally in the Sahel, some 200 to 500mm per year, depending on the location. Not enough for a thriving agricultural industry, but enough to grow something.

The large surface area of the screens, with their halfpipe, are perfect to catch rainwater and channel it to a large centralised cistern where it is stored.

-a simple set of photovoltaic panels and a drip irrigation system (a tube), are installed behind the screens.

-when all these things are in place, it becomes possible to start using the soil and grow hardy fruit trees, wood trees and shrubs.

-you keep the screens in place as long as you need to water the trees. Say, after 5 years, you can remove them, because the trees will have established themselves well.

-obviously, this biomass that is now capable of growing will sequester copious amounts of CO2, thus fighting climate change once more.

-after the trees have matured and grown deep roots, you can take away the screens and move them to a next place.

-the strong trees now take over the role of the reflectors: they provide shade, act as a wind-breaker, thus reducing erosion, they trap moisture in the soil, their falling leaves and branches add biomass and nutrients to the soil, bringing it alive, and they have a reflective quality of themselves (high albedo). This micro-climate now makes it possible to grow food crops between the rows of trees.

Let's look at the economics of this highly integrated little idea.

According to the research mentioned earlier, a 1,000-square-foot (92m²) white roof could offset 10 metric tons of carbon dioxide. Note, a metal reflector can bounce back even more sunlight (don't know how much, tough, so we'll stick with the white roof quote).

For the ease of calculation, we say that one reflective panel is 92m² in surface area. (Say 30m long and 3 meters wide).

The current carbon price in Europe is 23.2 euros per ton.

So you get for 1 panel, a one time sum of 232 euros.

I calculate that the steel costs and installation costs amount to 5 euros per square meter. This requires a total investment of 460 euros. Minus 232 = 228 euros needed to break even.

Per 30 meters of shadow, you can plant, say 3 big trees and 3 small shrubs. Combined, this biomass will sequester something like 200 kg of carbon dioxide per year, over a lifetime of, say 30 years. This sequestration effort is worth: 200kg * 30 = 6 tonnes. At an average carbon price of 40 euros per ton (CO2 is expected to become costlier in the future), this represents 240 euros.

Okay, so we have already broken even (the 12 spare euros go to solar panels, the drip irrigation tube and the seedlings).

Now the added advantages are: the halt of desertification and deforestation in the Sahel; the opportunity to grow food, which is very important in this region, because people there have some of the world's highest fertility rates (abundant food and food security is needed for them to develop and transit to lower fertility rates); and of course climate mitigation at a cost of *zero* euros/dollars.

The potential profit from food production will go to offsetting the emissions caused by making the steel and shipping it to the Sahel.

Should be okay!! Perhaps!

(Reminder: the metal would bounce back more sunlight than a white roof, so it should fetch higher albedo credits, making the economics look better still !!!)

I made a drawing of the idea.

django, Sep 16 2008

Albedo shade, wind breaker, soil cooler, water harvester http://i3.photobuck...el/albedomirror.jpg
Simple idea!! [django, Sep 16 2008]

Aluminum can shingle Aluminum_20can_20shingle
When you wrote "reflective, cheap metal halfpipe" I thought of this old idea. [bungston, Sep 16 2008]

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       err... so the sunlight after bouncing off the reflector back into space, is then absorbed by the photovoltaic panels, after which it's used to grow trees ? Come help me with my taxes, if you would.
Also, the "wealth breeds a lower fertility rate" rule-of-thumb so far works with a statistical sampling of 1, ie: Christian-based society. Whether it works for the other 3 billion people on the planet has yet to be determined.
FlyingToaster, Sep 16 2008

       Err... no.   

       You use no photovoltaic panels (except for the tiny one over there, far away, which pumps up water for use in the drip irrigator).   

       I estimate that a 1 square meter photovoltaic panel is needed per 10,000 square meters of metal reflectors, or so.   

       Obviously, plants use sunlight. But there's a difference between the unbearable intensity of the plain sun in the desert, and a place where large tracts are shaded, with the shade moving throughout the day. The crops grow on the border between the shade and the patch of sunlight that reaches down between two rows of reflectors. But mostly, they grow in a mild shade (they do receive some indirect light from the reflector facing them).   

       Shading crops is done throughout agriculture, especially in places that are too sunny.
django, Sep 16 2008

       Sorry, I'm going to have to put this idea in another category. Apparently someone is moving it around (me?), it won't stay under "terraforming", which is the best way to describe it (since there's no real category for ideas related to fighting climate change in this way, or for greening-the-desert-ideas).
django, Sep 16 2008

       so the plants get full-day "ambient"(sky light) and a few minutes (or whatever it takes) at local noon and you're using a non-specified strain that won't literally shrivel up and die when you take the shade away. I like the way you're putting in erosion-inhibitors.
Given you created 'albedo credits' then built a device to maximize same, I still want help with my taxes.
FlyingToaster, Sep 16 2008

       //and you're using a non-specified strain that won't literally shrivel up and die when you take the shade away//   

       See, as the plants grow, they grow taller and eventually become bigger than the shade (at which point we remove it). This is a very gradual process, making it possible for the trees to adapt to the tiny incremental amounts of sunlight they receive as they grow.   

       I hope! :-)
django, Sep 16 2008

       I think this would work to some extent. The plants would be gradually sun-hardened as they grew above the shade, and providing temporary shade while plants are established in a harsh deforested habitat works (I've helped a friend do exactly that, although not quite in a desert). Concentrating the water in a low rainfall area, using swales etc, has also been done.   

       Objections: I also am nervous about the "make everyone rich so they stop breeding and damaging the planet" theory. If you pour a lot of kerosine on a fire really really quickly it might just put it out, but the result is not predictable.   

       Non-porous structures don't make good windbreaks. They absorb little energy and can create turbulence, which might be worse (an exception is fully enclosed areas which contain low-speed air). I've often thought that the wind-slowing effect of wind turbines might be exploited so they function as wind breaks and energy harvesters.   

       I'm also sceptical of the global warming offset thing; doing something good does not make a bad thing not bad, especially if metal, energy, and other resources are used in the process. (Yes, your honour, I murdered 5 people, but I also raped 25, 7 of whome became pregnant, so on the whole I've made more people than I've destroyed and should be rewarded.)
spidermother, Sep 16 2008

       Yep, agree on the fundamental dubiousness of offsetting emissions. But if offset schemes result in major social and humanitarian advantages, then I'd be willing to consider them.   

       The correlation between wealth and low fertility rates is rather strong, but it's obviously not determined by a single factor like the existence of an efficient agricultural industry capable of feeding everyone. This reason is not sufficient, but it is a necessary one.   

       Good point about the non-porous windbreaks. We should examine whether its beneficial to perforate the metal sheets, or to just leave them as they are.
django, Sep 16 2008

       //...derive about 80 litres of fresh water...//
per hour ?
FlyingToaster, Sep 17 2008


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