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MIT Controls The Sun With Color

Color Changing Roof Tiles Absorb Heat In Winter, Reflects In Summer

sunWhat colors? Well, your basic power colors of course, black and white. Or to make your art teacher cringe – black and white makes green.

Black surfaces absorb the sun’s heat very efficiently, producing hot surfaces. In the wintertime, that can be a good thing: A dark roof heats up in the sun and helps reduce your heating bill. But in summertime, it’s definitely a bad thing: Your house gets even hotter, and your air conditioning has to work harder. In most places, the summertime penalty is greater than the wintertime gain, it turns out, so that’s why many people, including U.S. Secretary of Energy Steven Chu, strongly advocate switching to white roofs.

It’s no small matter. In fact, Chu says that turning all the world’s roofs white would eliminate as much greenhouse gas emissions in 20 years as the whole world produces in a year. But some critics point out that in northern cities, the gain in summer could be outweighed by the loss in winter. The ideal situation, then, would be to get the advantage of white roofs when it’s hot and black roofs when it’s cold.

Now, there may be a way to have both. A team of recent MIT graduates has developed roof tiles that change color based on the temperature. The tiles become white when it’s hot, allowing them to reflect away most of the sun’s heat. When it’s cold they turn black and absorb heat just when it’s needed.

The team’s lab measurements show that in their white state, the tiles reflect about 80% of the sunlight falling on them, while when black they reflect only about 30%. That means in their white state, they could save as much as 20% of present cooling costs, according to recent studies. Savings from the black state in winter have yet to be quantified.

The team, which the students call Thermeleon, which rhymes with chameleon, because of its color-changing property.

Nick Orf PhD ’09, a member of the Thermeleon team, explains that he and his teammates originally tried to develop a color-shifting roof tile using a system of mixed fluids, one dark and one light, whose density would change with temperature: the dark substance would float to the top when it was cold, and white would float when it was hot. But the system proved too complicated, and instead they hit on a simpler, less expensive method.

Now, they use a common commercial polymer (in one version, one that is commonly used in hair gels) in a water solution. That solution is encapsulated — between layers of glass and plastic in their original prototype, and between flexible plastic layers in their latest version — with a dark layer at the back.

091015-heat-tiles-02

A blast from a heat gun has turned most of the black tile in this image white

When the temperature is below a certain level (which they can choose by varying the exact formulation), the polymer stays dissolved, and the black backing shows through, absorbing the sun’s heat. But when the temperature climbs, the polymer condenses to form tiny droplets, whose small sizes scatter light and thus produce a white surface, reflecting the sun’s heat.

They are now working on an even simpler version in which the polymer solution would be micro-encapsulated and the tiny capsules carried in a clear paint material that could be brushed or sprayed onto any existing surface. The tiny capsules would still have the color-changing property, but the surface could easily be applied over an existing black roof, much more inexpensively than installing new roofing material.

Although they have not yet made specific plans for forming a business to commercialize their concept, Orf says the team members are determined to pursue the project and develop it into a marketable product.

Because the materials are common and inexpensive, team members think the tiles could be manufactured at a price comparable to that of conventional roofing materials — although that won’t be known for sure until they determine the exact materials and construction of their final version.

The biggest remaining question is over durability, and answering it will require spending some time to do accelerated testing by running the material through repeated hot-cold cycles.

…… as the green future unfolds.

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No Responses to “MIT Controls The Sun With Color”

  1. Barbara Says:

    Another wonderful article. I have awarded you The Best Blog Award. Please come by and pick it up!

  2. Linda Says:

    Hi Barbara … Thanks so much! I am on my way over! 😀

  3. Choosing a Good Yoga Mat | All about Yoga Says:

    […] MIT Controls The Sun With Color | […]

  4. Karen Says:

    I love it when the sky turns black. It reminds me that we have no control. Only God has complete control!

  5. Linda Says:

    Hi Karen … absolutely true! But sometimes it is a little scary.

  6. dhemz Says:

    came here from adgitize!
    .-= dhemz´s last blog ..White and Purple Phalaenopsis Orchids =-.

  7. Linda Says:

    Hi dhemz … come back again!

  8. Diane Scott Says:

    This is such an excellent idea! I’m not sure I understand why anyone would think it’s scary (your reply)??
    .-= Diane Scott´s last blog ..High Pay Minimal Schooling 10 Jobs To Check Out =-.

  9. Linda Says:

    Hi Diane …. These brilliant minds at MIT. So bright yet can be manipulated.

  10. binge eating treatments Says:

    Wow! This is definitely a green innovation and an absolute power saver as well. Got to admire the guys at MIT for this ingenious product. I do wonder if these is already available in the market.

    Gerry
    .-= binge eating treatments´s last blog ..Save A Loved One With The Right Intervention Services =-.

  11. Linda Says:

    Hi Gerry … Nope not on the market yet. They get to beat them to death in an accelerated durability test first to see if/how long they can hold up to the harsh environment of roof tops.

  12. Faber & Kell’s Heating and Air Conditioning of Buildings, Ninth Edition | Heating And Air Conditioning Says:

    […] MIT Controls The Sun With Color (forcedgreen.com) […]

  13. Earth Friendly Goodies Says:

    Very ingenious thinking, however I don’t see a benefit in the winter for those areas “gifted” with gobs of fluffy white snow that would cover their magic paint. Now if they could come up with a paint that included little elves that popped up and blasted the snow with tiny hair driers to melt it – which would then reveal the black coating on the roof tiles…
    .-= Earth Friendly Goodies´s last blog ..Bye Bye Siggy BPA Free ThinkSport Bottle Giveaway =-.

  14. Linda Says:

    Hi Earth Friendly … Well here in Texas, we are gifted – every 25 years – with snow. However, it would be more beneficial HERE than say Kodiak, Alaska. As for the little popping elves…. EFG, I think it is a little early to be hitting the eggnog, my friend! 😀

  15. Maureen Says:

    This is a great idea. Your articles are great Linda-
    .-= Maureen´s last blog ..Generic Marketing System Confusion =-.

  16. Linda Says:

    Hi Maureen .. We aim to please and inform all of what is out there. Glad to hear that you enjoy them.

  17. Finding the right Contractor to Fix the Hail Damage you Detected on your Roof | Home Decorating Says:

    […] MIT Controls The Sun With Color (forcedgreen.com) […]

  18. ConnieFoggles Says:

    I can use those tiles here in Florida. It would save us a lot of electricity and money too.
    .-= ConnieFoggles´s last blog ..Mom Surgery Tomorrow =-.

  19. Linda Says:

    Hi Connie … You bet it would! Where you live, certainly lots of sunshine!

  20. Using The Weather To Go Green | Innovation Toronto Says:

    […] MIT Controls The Sun With Color (forcedgreen.com) […]

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