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

What 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.

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.

The Sears Tower

It has been known that commercial buildings take a lot of energy to keep them going.

The Sears Tower (Chicago) is going to be renamed to the Willis Tower later this summer and is now going to undergo a $350 million “green” retrofit for the 110-story office tower.

The plan calls for a reduction in its electricity consumption by 80 percent and water usage by 40 percent.

To achieve the savings, owner American Landmark Properties and its partners plan to:

- Replace the 1973 tower’s 16,000 tinted single-pane windows and create a “thermal break” between Chicago’s frigid winters and hot summers and the interior.
- Install gas boilers equipped with fuel cells, which generate electricity, heat and cooling.
- Revamp the tower’s 104 elevators and 15 escalators to cut their electricity usage by 40 percent.
- Conserve 24 million gallons of water with new restroom fixtures and “condensation capture.”
- “Harvest daylight” by installing systems that automatically dim lighting based on available natural light.
- Install solar panels to heat water.
- Erect wind turbines on building setbacks, if possible.
- Plant green roofs that will be among the highest in the world to reduce storm runoff and the urban heat island effect.
- Replace granite plazas and walls surrounding the tower with terraced park space, trees, glass storefronts and an interactive digital display.

They feel that will all of these changes that they could qualify for the LEED (Leadership in Energy and Environmental Design) certification.

And not to be outdone …

The Empire State Building

The Empire State Building’s retrofit aims to prevent the release of 105,000 metric tons of CO2 annually—the same amount Washington, D.C puts out in nearly 10 days.

* Window insulation: This would include the refurbishment of glass  windows, using existing glass and sashes to create triple-glazed insulated panels with new components that dramatically reduce both summer heat load and winter heat loss.
* Radiator insulation: Added insulation behind radiators would be used to reduce heat loss and more efficiently heat the building perimeter.
* Tenant lighting improvements: Introduction of improved lighting designs, controls, and plug load occupancy sensors in common areas and tenant spaces to reduce electricity costs and cooling loads.
* Air handler replacements: Replacement of air handling units—devices used to condition and circulate air as part of a heating, ventilating, and air-conditioning system, or HVAC—with variable frequency drive fans to allow increased energy efficiency in operation while improving comfort for individual tenants.
* Chiller/air-conditioning plant retrofit: Reuse of existing chiller shells—chillers are used in AC units to cool and dehumidify air—while removing and replacing “guts” to improve chiller efficiency and controllability, including the introduction of variable frequency drives.
* Whole-building control system upgrade: Upgrade of existing building control system to optimize HVAC operation, as well as to provide more detailed submetering information.
* Ventilation control upgrade: Introduction of demand control ventilation in occupied spaces to improve air quality and reduce energy required to condition outside air.
* Tenant energy management systems: Introduction of individualized, web-based power usage systems for each tenant to allow more efficient management of power usage

These retrofits are to cost about $20 million with the end result of reducing the utilities by 30 – 50 percent.

Do you feel the movement? When our tallest buildings are “going green”, then there is something afoot!

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Cool-N-Save can instantly save you up to 30% on your Air Conditioning costs!

Unless you are getting rain, which I am NOT, the temperatures have been hitting the high 90′s or low 100′s. I know that the air conditioning is really working hard to keep your place cool. So, I would like to introduce
the following to you to help reduce that cost!

Cool-n-Save is an amazing new, patented product, that is actually based on the same scientific Principles that large corporations have used to save themselves money for years.

Installed in less than five minutes with no tools required, the Cool-n-Save system affixes to the top of most home air conditioning units. The system is activated only when the AC unit turns on; hot air from the condenser unit’s fan raises the flap on the patented Cool-n-Save control valve allowing water to flow to the misters that surround the AC unit. When the ultra-fine mist is released into the air, it evaporates almost instantly creating what is known as a “Flash Evaporation,” which literally sucks heat out of the air as water absorbs the energy it needs to evaporate. The result of the immediate evaporation constitutes a substantial drop in ambient temperature without wetness—up to 30 degrees Fahrenheit

The problem with the AC system is that in extreme heat, many conventional air conditioners are unable to effectively transfer their stored heat into the surrounding air. They are forced to work harder and longer to cool the air in your home, shortening their life and producing unreasonably high electric bills.

To combat this problem, large commercial AC users such as commercial factories, warehouses and office buildings have been installing professional misting systems around their AC condensers for years. These misting system are much like the misters you may have encountered in restaurant patios and amusement parks.

Folks for $99.00, it is worth the investment as this really could reduce your summer bills! Give it a try!

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