1 March 2006 at 9:07 pm #30481
I had a great idea for an emergency solution to our problems the other night..but someone had thought of it already of course. Still intrigued by the idea though..we need some distraction. Perhaps someone could shoot this one down for me?
From New Scientist back pages:
“Would it be possible to reduce the impact of the greenhouse effect by painting roofs of buildings white to reflect sunlight in the same way the polar icecaps do? Does a paint exist that would mimic the reflective properties of snow?
Painting roofs white would reflect more sunlight and it might also compensate for global warming. The Global Rural Urban Mapping Project (GRUMP), undertaken by the Earth Institute at Columbia University in New York, shows that roughly 3 per cent of the Earth's land surface is covered with buildings.
â€œThe Earth reflects 29 per cent of sunlight, painting all roofs white could raise that figureâ€The Earth has an albedo of 0.29, meaning that it reflects 29 per cent of the sunlight that falls upon it. With an albedo of 0.1, towns absorb more sunlight than the global average. Painting all roofs white could nudge the Earth's albedo from 0.29 towards 0.30. According to a very simple “zero-dimensional” model of the Earth, this would lead to a drop in global temperature of up to 1 Â°C, almost exactly cancelling out the global warming that has taken place since the start of the industrial revolution. A zero-dimensional model, however, excludes the atmosphere and, crucially, the role of clouds. It would be interesting to see if more sophisticated models predict a similar magnitude of cooling.”
Mike Follows Willenhall, West Midlands, UK
“A better use of roofs would be to use them as mini power stations by installing photovoltaic tiles. This would displace a significant proportion of the fossil carbon that we emit without relying on perturbing the Earth's delicate and complex climate system. Sure prevention is much better than uncertain cure.”
Mike Hulme, Norwich, UK
From issue 2527 of New Scientist magazine, 26 November 2005, page 932 March 2006 at 8:47 am #32848Nick GrantMember
3% of land covered in buildings? Surely not? Even 'building' to include parking, pavements etc.
mmmm….2 March 2006 at 10:26 am #32849
Far from being mad, California has already proposed doing this in order to reduce the state's electricity use for cooling. (About 40% of the USA's electricity is used for cooling buildings.)
There's a huge impact also if roads and car parks are made of white or light grey concrete or paving slabs rather than black tarmacadam. This reduces the temperature of the air near buildings.
However, like Nick I don't think 3% of the earth is covered by buildings. Barely 1% of the UK is paved over and we're densely-populated by world standards.
David.28 July 2006 at 3:15 pm #32850AnonymousGuest
There is a book recently published called Roof Cooling or something similar, which is about…roff cooling. This is full of interesting stuff, however, I have a paper from the 2004(?) World Green Roof Congress, which discusses the equivalent albedo of a typical extensive green roof when factoring in the energy used for evapotranspiration. The paper suggests an equivalent albedo for the green roof as 0.95, which the equivalent of the best clean white roof surfaces. Of course this high green roof performance does rely upon availablity of water for the evapotranspiration to take place. I also have figures from a 3 year study in Berlin (slightly less rainfall than London) that shows 300+kw/m^2 per annum of energy going into the process of evapotranspiration.
I have been mulling over the energy balance of PVs as whilst a percentage of solar energy received is converted to electricity, in terms of energy balance, does this beat a white or green roof?14 November 2006 at 8:25 pm #32851
OK. This discussion is getting too sensible. How many square miles of silver foil need to be put in orbit to buy us say another 200 years before average global temperature rise goes above 2 degrees? Would there be an optimum balance between the global shading resulting (replacing global dimming) and sunlight for food production, or more importantly access to a nice sun tan?
I suppose we could use all that newly redundant multi foil insulation that doesn't work so well in lofts, perhaps spreading it out over (someone else's) landscapes (or letting it loose in deserts to blow freely around in the wind…)
Now if someone can answer that – I'll buy them a drink.18 November 2006 at 5:42 pm #32852
There was a recent paper in Nature about the huge carbon sequestration potential of biomass charcoal; apparently charcoal lasts in soils for centuries and also improves their fertility. If true, biomass should be gasified and only the gas used for energy; the residue should be ploughed into the soil.
D16 December 2006 at 8:08 pm #32853
David – any chance of seeing that article re biomass charcoal without subscribing to Nature…?
I like this (below)…I wondered if the mad idea of silver foil was as impractical as i feared – maybe not silver foil but…
“Space Sunshade Might Be Feasible In Global Warming Emergency
The possibility that global warming will trigger abrupt climate change is something people might not want to think about.
The graphic shows the 2 foot-diameter flyers at L1. They are transparent, but blur out transmitted light into a donut, as shown for the background stars. The transmitted sunlight is also spread out, so it misses the Earth. This way of removing the light avoids radiation pressure, which would otherwise degrade the L1 orbit. (Illustration: Courtesy of UA Steward Observatory)
But University of Arizona astronomer Roger Angel thinks about it.
Angel, a University of Arizona Regents' Professor and one of the world's foremost minds in modern optics, directs the Steward Observatory Mirror Laboratory and the Center for Astronomical Adaptive Optics. He has won top honors for his many extraordinary conceptual ideas that have become practical engineering solutions for astronomy.
For the past year, Angel has been looking at ways to cool the Earth in an emergency. He's been studying the practicality of deploying a space sunshade in a global warming crisis, a crisis where it becomes clear that Earth is unmistakably headed for disastrous climate change within a decade or two.
Angel presented the idea at the National Academy of Sciences in April and won a NASA Institute for Advanced Concepts grant for further research in July. His collaborators on the grant are David Miller of the Massachusetts Institute of Technology, Nick Woolf of UA's Steward Observatory, and NASA Ames Research Center Director S. Pete Worden.
Angel is now publishing a first detailed, scholarly paper, “Feasibility of cooling the Earth with a cloud of small spacecraft near L1,” in the Proceedings of the National Academy of Sciences. The plan would be to launch a constellation of trillions of small free-flying spacecraft a million miles above Earth into an orbit aligned with the sun, called the L-1 orbit.
The spacecraft would form a long, cylindrical cloud with a diameter about half that of Earth, and about 10 times longer. About 10 percent of the sunlight passing through the 60,000-mile length of the cloud, pointing lengthwise between the Earth and the sun, would be diverted away from our planet. The effect would be to uniformly reduce sunlight by about 2 percent over the entire planet, enough to balance the heating of a doubling of atmospheric carbon dioxide in Earth's atmosphere.
Researchers have proposed various alternatives for cooling the planet, including aerosol scatterers in the Earth's atmosphere. The idea for a space shade at L1 to deflect sunlight from Earth was first proposed by James Early of the Lawrence Livermore National Laboratory in 1989.
“The earlier ideas were for bigger, heavier structures that would have needed manufacture and launch from the moon, which is pretty futuristic,” Angel said. “I wanted to make the sunshade from small 'flyers,' small, light and extremely thin spacecraft that could be completely assembled and launched from Earth, in stacks of a million at a time. When they reached L1, they would be dealt off the stack into a cloud. There's nothing to assemble in space.”
The lightweight flyers designed by Angel would be made of a transparent film pierced with small holes. Each flyer would be two feet in diameter, 1/5000 of an inch thick and weigh about a gram, the same as a large butterfly. It would use “MEMS” technology mirrors as tiny sails that tilt to hold the flyers position in the orbiting constellation. The flyer's transparency and steering mechanism prevent it from being blown away by radiation pressure. Radiation pressure is the pressure from the sun's light itself.
The total mass of all the fliers making up the space sunshade structure would be 20 million tons. At $10,000 a pound, conventional chemical rocket launch is prohibitively expensive. Angel proposes using a cheaper way developed by Sandia National Laboratories for electromagnetic space launchers, which could bring cost down to as little as $20 a pound.
The sunshade could be deployed by a total 20 electromagnetic launchers launching a stack of flyers every 5 minutes for 10 years. The electromagnetic launchers would ideally run on hydroelectric power, but even in the worst-case environmental scenario with coal-generated electricity, each ton of carbon used to make electricity would mitigate the effect of 1000 tons of atmospheric carbon.
Once propelled beyond Earth's atmosphere and gravity with an electromagnetic launcher, the flyer stacks would be steered to L-1 orbit by solar-powered ion propulsion, a new method proven in space by the European Space Agency's SMART-1 moon orbiter and NASA's Deep Space 1 probe.
“The concept builds on existing technologies,” Angel said. “It seems feasible that it could be developed and deployed in about 25 years at a cost of a few trillion dollars. With care, the solar shade should last about 50 years. So the average cost is about $100 billion a year, or about two-tenths of one percent of the global domestic product.”
He added, “The sunshade is no substitute developing renewable energy, the only permanent solution. A similar massive level of technological innovation and financial investment could ensure that.
“But if the planet gets into an abrupt climate crisis that can only be fixed by cooling, it would be good to be ready with some shading solutions that have been worked out.”
“Dr. Angel, the University of Arizona astronomer, told members of the science academy of his idea for an orbital sunshade, calling the proposal less important than the goal of encouraging bold thought.
“This could engage a whole generation,” he said in an interview. “All I'm saying is, let's start thinking about these kinds of things in case we need them one day.” Such visionary plans are still far from winning universal acclaim. James E. Hansen of the NASA Goddard Institute for Space Studies in New York, who attended the talk and strongly advocates curbing emissions, belittled the orbital sunshade as “incredibly difficult and impractical.”
Dr. Crutzen, the Nobel laureate from the Max Planck Institute, has also drawn fire for his paper about injecting sulfur into the stratosphere. “There was a passionate outcry by several prominent scientists claiming that it is irresponsible,” recalled Mark G. Lawrence, an American scientist who is also at the institute.”17 December 2006 at 4:12 pm #32854
I think the link I posted in Nature takes you to a discussion of biomass charcoal.
Coupled with that German press release I posted about turning woody biomass efficiently into liquid fuels, burning solid fuels locally may be the wrong thing not just due to emissions; maybe we need much larger-scale conversion into clean fuels and/or charcoal.
Another technique of course is to adjust the pH of the oceans slightly so that marine organisms take up more calcium carbonate, which eventually becomes chalk and limestone. The world's limestone contains far more C than living organisms or the world's coal deposits.
David.11 April 2007 at 8:49 pm #32855
I like to keep up to date with mad ideas for saving the world – if we don't reduce our emissions then we will need 'global emergency medicine' to buy us more time to do so: http://www.msnbc.msn.com/id/17612990/
Any more on these?
I await the NASA report.17 April 2007 at 7:25 pm #32856Mark SiddallParticipant
I've been racking my brain to come up with world saving concepts. The best I have come up with so far is the one I heard that Buckminster Fuller proposed: a global electrical grid. The benefits of such a grid being that 1) peaks demand could be better managed 2)given that some part of the earth is always facing the sun I think he also proposed that all/most electrical power could be generated from PVs.
Mark17 April 2007 at 7:56 pm #32857
Yes, that fits the bill….but in an emergency (when will it be evident that we have a global runaway climate emergency?) could it be built in time?!20 April 2007 at 8:29 pm #32858Mark SiddallParticipant
That's perhaps why its a mad idea……20 April 2007 at 10:18 pm #32859
There was an article on biomass charcoal in Renew (regular journal from EERU, OU). Not mad at all really, but the idea can't be patented so maybe it won't appeal to many large companies.
I think a worldwide electrical grid *could* be mad, given the transmission losses, although there are power engineers who believe in it. If it worked you wouldn't have PV, you'd use solar thermal power stations as they're cheaper in the sunbelt with all the direct sunshine and their waste heat can be used to desalinate water or probably to cool buildings.
David.26 June 2007 at 9:39 pm #32860
more on use of charcoal as carbon sequestration and soil improvement..
http://forums.hypography.com/terra-preta/10546-making-charcoal-2.html27 June 2007 at 11:47 am #32861Nick GrantMember
Rather than burying the charcoal the benefit could be much greater if fed to cows and vegetarians….
Can we have a stab at world peace now?
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