Changing Roofs and/or walls from black to white to reduce/increase household absorption.
This seems like a simple enough idea and has been looked into and researched before. The link attached shows that there are tiles out there that change colour with temperature so a roof will be white when it is warm (reducing household absorption) and black when it is cold (increasing household absorption). This is a relatively simply means of cutting down on heating and aircon energy output. Instead of maybe using these tiles which may be too expensive or fragile a simple ‘billboard’ type device could be used where the roof/walls could be
switched manually by lever.
There are many poorly insulated house out there. So i'm guessing this could work on them. It could also help reduce the cost of insulating a house. Seems like a win win. Paint is contrary to this idea....The idea is to change colour at will. Repainting your house every other day wouldn't be an option. Keep the debate going though. Every idea helps.
The solar collection on the skin of the building may be somewhat de-coupled from the insulated interior by constructing an air space just outside of the insulated portion of the envelope. Then heated air may be used at will.
marblar.com/challenge/earth...
1) Simply painting a roof white can reduce emissions:
www.whiteroofs.org.nz/html/...
2) The adaptive change is interesting to have homeostatic temperature control, like in the daisy world: en.wikipedia.org/wiki/Daisy...
From 1) you can see that if you can keep everything white most of the time and black during winter days (but not nights in order to preserve heat), you can greatly reduce energy consumption.
You could go further and propose also treated wood or chameleon furniture (with more colors to make it nice and trendy). A higher tech alternative is using intelligent control with some kind of e-ink which only consumes energy (and only a little) when changing color.
www.paintwithpearl.com/colo...
However they do mention that
"How long will it be before someone solves the UV issue? Imagine...A roofing material that changes from black to white in hot weather is the greeenest, most sustainable and energy efficient material in the world Figuring this one out would make the inventor a billionaire. Simply figure out a UV protectant that can make this pigment last for 30 years in direct sun."
So it seems that this material is plausible but needs some sort of UV protection to protect the active pigment. Anyone know of any readily available UV protectors?
Might be some relevant overlap there. Not sure how complex it would be to create roofing tiles, coat with the pigment, coat with the UV protective layer (and possible another, hard-wearing sealant) and what the economics would be though.
store.acrytech.com/CeramaX-...
www.surecoatsystems.com/whi...
Just take New York. Now "cool roofs", as they call them, are compulsory:
www.globalcoolcities.org/wp...
en.wikipedia.org/wiki/Refle...
, but you still need waterproofing. New York is rainy:
hypertextbook.com/facts/200...
There are ways around that problem.
www.polyglass.com/public/CA...
How about, now this might be a bit crazy ( and forget for the moment about energy consumption doing it or the logistics of it).....but using an electric field to change a magnetized material from black to white. We have all seen iron filings and how the react to a magnet. What if one side of the iron filings were white and the other side black. So during the day you apply an electric field to align all the iron filings one direction, white, then at night you do the opposite and the filings turn black. This idea of course might negate all possible energy savings but maybe with a few marblar suggestions it could be theoretically made more efficient. A thought experiment is under way :)
My other idea (i think you may have mixed me up with a Richard) about the manual roll to change colours is definately more suited to the developing world. It would be cheaper, would need no energy input (bar elbow grease) and would apply to all and any existing roofs and walls. Any dwellings that could not use the colour changing paint idea could definately use the roll idea.
If anyone's truly interested, they can contact me directly.
One nice thing about that idea is that not much energy would be needed to shift the scroll/screen around to block/permit sun. Or it might be multiple static screens with the fritting merely tuned to reject high-angle sunlight....
That sounds like a totally different idea. Hey, judges, how will you assess whether and by whom an idea has morphed into an entirely different idea?!?
The screen(s) notion is eminently marketable as a product.
There are historical architectural materials and textures/shapes that have been used that demonstrate this is proven technology using textures that shade surfaces to change the radiation and absorption based on seasonal solar angles - this has been done in Melbourne and is simple known architectural practice. A pull down shade sits at the opposite end of the innovation scale unless conceived of within the design and fabric of a new structure.
A paint & texture that can be applied to existing roofs, walls, etc given house orientation opens out immediate opportunity to introduce into the mainstream service market a simple technology that can be applied at low cost. Couple that with a well developed network of painters and housing material suppliers and it makes pull down screen look pedestrian at best. In the end, the technology that wins out in a competitive marketplace is the one that creates the least 'friction' to the consumers wallet when bringing benefits.
A problem with thermochromic materials: in winter, when 'free' heat is desirable, the material will swiftly heat up to its thermal switching temperature and then turn white, thereafter rejecting useful solar energy. Unless you plan to cool the surface with a continual flow of air/water, it will get just about as hot in winter as in summer and you won't have a good mechanism for selective control.
I think there may be valid applications for both ideas.
I don't get your approach. EFTE bubbles do little for existing buildings and at what cost - I have worked many times with Architectural Offices (Fosters included) in London, the metro (self breathing mechanisms) , Self-ridges new building (future systems) and so on - a smart paint is still achievable and this is perhaps the forum to explore that >> 'chameleon house' << idea. A pull down screen and ETFE bubbles seem extravagant, unrealistic costly architectural arrogance's for making impact with existing dwellings - when one might jump to simple smart surface material coatings bound to new science ( a photochromic UV switch) for all buildings.
Why not set up an entry about the merits of EFTE building advantages for saving carbon in domestic dwellings? Or if you are truly brave - post your solution rather than alluding to people posting you a private note for your information 'gem. If this forum is about sharing information and crowd-sourcing to build solutions openly via collaboration you might be missing out on the spirit of marblar.
[1] - en.wikipedia.org/wiki/Starlite
[2] - video of coated egg
www.youtube.com/watch?v=Rxq...
[3] - The miracle 'everything-proof' paint that could change the world
www.dailymail.co.uk/science...
With the roller blind type idea i first thought of this as a third world option. not expensive at all, for small domestic houses, manually controlled and easily fixed if broken. The paint idea i think would be more a developed world idea for larger dwellings and buildings, more technologically advanced, more expensive but much less maintenance.
The notion of a thin film of material standing off from the original building surface is a response to the dual design problems of: a) heat and mass transfer from a solar collector surface and b) vapor trapping / vapor drive in a 'reservoir'-type exterior surface, such as brick (which is quite common in GB, I understand). Many paints are so vapor-closed they trap moisture in the substrate material, leading to its rapid degradation. This is exacerbated when the paint is heated by the sun, because the heating forces the moisture to drive inward into the assembly, where mold growth and other nasty stuff relentlessly breaks down the building. Creating an air space outside of the structural envelope clears up a lot of these problems, because it allows moisture a means of escape. Given such a conduit, sun-heated air actively removes moisture from the assembly AND can deliver heated air where it can be useful, while also carrying away the potentially unwanted film of heated air immediately at the surface of the building. Paint alone does none of these things.
A good resource on moisture, building envelopes, insulation: www.buildingscience.com/ind...
Your end goal needs refining/articulating. Is it your desire for the entire building to turn white whenever full sun hits the building? Why? What about cold, clear winter days, when the solar energy would be a boon?
I'm not trying to kill the idea; I'm trying to make it stronger. An ordinary light-roofed, dark-walled residence in a northern latitude might outperform one indiscriminately slathered in photochromic paint. WHAT surfaces are we talking about? WHEN exactly does the paint switch colors? HOW do we control so it is intelligently responsive to environmental forces, instead of becoming a dumbly and non-usefully responsive art piece?
Or are we only talking about glazed surfaces??? That reminds me of another idea, which I may selfishly post elsewhere....
[1] - phys.org/news159732927.html
[1] - www.matsui-color.com/photop...
[2] - www.matsui-color.com/sheets...
The writer Arthur C. Clarke wrote about this idea.
I think in his book Profiles of the Future (1962), he also complained about how terrible batteries were in that book and voted that it should be one of the top priorities for engineering.
As I recall he described it as tiny black and white flowers (?) that when hot the white flowers "bloomed" and covered the neighboring black flowers and when cold the opposite.
I guess he could have gotten the idea from GAIA, black flowers melting the poles and cleaning the surface of the earth.
I am from Utah and 75% of wintering have 2 feet of snow on my roof as to many other city north of my home town. How would it make any difference here when we are buried? This also effects northern states as well.
Chameleon Shield
There are many different ways this method could be
implemented and many different materials that could be used to make it more or
less costly, effective or available. Materials like the Philips designed e-ink
could very easily be used in this idea and it would work perfectly and
efficiently but as it would be that much more expensive it would take it out of
the reach of the less well off countries. For reasons such as this I have
chosen to use the cheapest materials and the most available technology for this
proposal so it will have maximum availability. It could however be easily
changed to suit the end user.
The device itself will be similar to a shutter rolling up
& down /back & across as needed. To make it the most accessible I’m
proposing the colour change happens through a manual process. Something like a hand
crank. Again solar-power or something similar could be integrated into it to
ease usability but this would increase cost and maintenance so I’m not
including this.
There are a few different setups that could be used. The chameleon
shield could be white on one side and black on the other. It would simply be a
matter of cranking the chameleon shield around to black or white depending on
what you needed. Another method would be to have the underlying structure
(house, wall, roof) painted either black or white. Depending on the prevalent
climate of the area the house could be permanently white, say in a warm
climate, and the chameleon shield would then just need to be black. The
opposite, of course, could also occur (white chameleon shield, black underlying
structure). This method would reduce the wear and tear, possible maintenance
and the intrusion of the device. This latter method could only be used though
if the underlying structure could be painted either black or white.
Every house, building, school or server room would find this
advantageous. The energy needed to cool a room even by 1 degree is substantial
so any sort of saving on cooling (or heating a room) is an instant saving and it
scales up as the building and the room inside gets bigger.
It would be possible to customise your chameleon shield. I
guess as long as the hoarding you’re covering your structure with is mainly
white then you could get away with customising it. Having a picture,
advertising, company name….and so on. You could even copy a picture of the
underlying structure onto the chameleon shield.
It would hopefully be a once off installment. It could be
easily retrofitted to any structure of any size or shape. On newer buildings it
could easily be incorporated into the architectural plans as it wouldn’t be
obtrusive to the eye. Building architects and designers could even have a lot
of fun with it and its personalisability. On a normal dwelling the device that
houses the chameleon shield could be hidden within the eaves of the house: see
diagram below or if on the roof hidden away incorporated into the ridge of the
roof or along the walls on a flat roof. This would reduce intrusion.
Cost to build: I would imagine very minimal. The technology
to do this type of thing is well established. Roller shutter windows and doors
are everywhere. There would be no new technology needed to incorporate this
idea to be able to cover walls and roofs instead of windows and doors. No motor
is required as I am going for the cheapest and most available option. The
material involved is probably the biggest expense. A lot of people do window
shutters/security doors. These can be quoted at about $20 per square meter but
there are large security door shutters http://www.alibaba.com/product-gs/863284070/large_steel_roller_shutter.html,
Which go for $100 that would fit easily enough to fill the side/roof of a home.
This is of course just an example as the material used for this chameleon
shield need only be one colour and doesn’t need to be expensively secure so
much cheaper material could be used….even cardboard, plastic or rope. So if a
strong metal door can go for $100 a much cheaper cardboard or rope shutter would
be significantly cheaper. For the purposes of my idea I’m going to propose
using plastic as it is durable, cheap, readily available and easy to maintain. The
installation of the device would be simple. All one need do is secure the
device to the wall. Then a rope would attach down to a crank where the occupant
could easily reach it (probably have it indoors for maximum ease). Then with a
simple twist the chameleon shield would fill across the roof or wall.
Making it cheaper like this makes it more available to those
on a budget or those hoping to cover a large area. Making it out of cheaper
material also makes repairing it much cheaper and easier and possibly even DIY-able.
If the material was also wet the evaporative process would impart extra cooling
to the structure.
It’s impossible to say how much money can be saved (due to
local pricing)per degree of heating or cooling achieved but if you only even
heat or cool the house, room, building by 1 degree then over a year you could
save 3-5 % on your heating/cooling bill.
The above link tells how ‘Increasing the temperature set point by 1oC will
reduce the amount of power your air conditioner uses by up to 10 per cent,
saving 200 kg of carbon pollution. The set point defines the temperature level
required to make an air-conditioned space comfortable. When the temperature
rises above or drops below the set point, the system's control measures start
working to return to that level. The lower the set point in summer, the harder
the system has to work. In winter, the reverse is true – the higher the set point,
the harder the system works’.
Market:
To market this I think it should first be pushed onto larger buildings such as schools, hospitals or other public buildings. A lot of
governments give out grants for environmental impact building solutions so I
think this idea should be enveloped in with this. This would introduce the
simple technology to the market and eventually it would also reduce the costs
to apply it to smaller homes.
Summing up.
My chameleon shield will be a rollerblind type device that can be used on roofs or
walls of structures. It could be housed in the eaves of buildings to reduce the
aesthetic impact. If the structure could be painted either black or white to
start then the chameleon shield need only be used half of the time. I propose
plastic (or rope) is used as a material as it is durable, flexible, easily
maintained, easily repaired, affordable and abundant. It could be wetted to aid
evaporative cooling if needed. It should
be just a once off installation. It doesn’t include any electronics as it is
hand cranked. It is retrofittable and easily incorporated into future designs.
It is easily scalable as it could be used to cover any height or width of roof.
It could be customizable. Instead of having a pure black or white covering the
material could be customized to add pictures, text, advertising, company
slogans etc…I think as long as the overall colour scheme is either dark or
white then the chameleon shield will work.
Overall.
The technology and the techniques are there to do this, it is easily made, reliable
and cheap. Even a one degree difference can achieve significant saving’s
monetarily and carbon pollution. It’s adaptable, customisable, scalable and
retrofittable. It has a global reach and the materials used for it can be
easily changed to suit the market it’s being sold in. If enough roofs were
using it it would contribute to the amount of energy sent back into space,
increasing the albedo affect, in effect, and helping reduce global warming. It
is a win win win situation.
