Paint it White: One Way to Chill the Electric Bill

SolveClimate
Renee Cho
Sunday, June 28, 2009

Could something as simple as white roofs actually make a dent in our carbon emissions and help curb global warming?

Physicist Steven Chu, our Nobel Prize-winning Secretary of Energy, thinks so. At the St. James’s Palace Nobel Laureate Symposium in London last month, he pushed for a global initiative to lighten the color of roofs, roads and pavements to cut carbon emissions by the equivalent of taking all cars off the road for 11 years.

As residents of hot countries have known for centuries, buildings painted white stay cooler because they reflect the sun’s heat. Light colored materials reflect more solar radiation, including visible, ultraviolet and infrared light (which accounts for most of the heat), than dark materials which absorb heat. Albedo, the gauge of solar reflectivity, is calculated from 0.0 to 1.0, with 1.0 being the highest measure of reflectivity.

Maximizing the number of high albedo surfaces around the world could significantly help cool the planet, said Chu, former director of the Lawrence Berkeley National Laboratory (LBNL).

Chu’s ideas have been shaped by the work of Dr. Arthur Rosenfeld (formerly at LBNL, now on the California Energy Commission), and fellow LBNL scientists Hashem Akbari and Surabi Menon. In 1985, they began studying how light colored roofs and pavement could mitigate the urban heat island effect – when urban areas are 2˚F to 8˚F warmer than surrounding areas due to the heat absorbed by pavement and buildings.

In 2004, they realized that their research might also help curb climate change.

“When we did the calculations, initially we couldn’t believe the results,” Akbari said.

They figured that changing 100 square feet of dark roof area to white would have an effect equivalent to offsetting the emission of one ton of CO2. On a global scale, increasing the albedos of urban roofs and paved surfaces would be equivalent to offsetting about 44 billion tons of CO2 emissions.

White roofs and cool roofs, those made from other high albedo materials, result in less carbon emissions because they reflect the sun, and reduce the need for air conditioning and thus the energy from CO2 emitting power plants.

Cool roofs also curtail the heat island effect and its accompanying smog, make buildings more comfortable, ease stress on the energy grid, help buildings comply with energy efficiency codes, and extend the life of roofs because lower temperatures make for less wear and tear.

White roofs, however, are difficult to keep clean and may lose up to 1/3 of their reflectivity within a few years, so resistance to dirt accumulation is important for roof coatings. And some critics have questioned whether white roofs increase winter heating costs in cooler climates. But Michelle van Tijen from the Cool Roof Rating Council, explained,

“In areas with hot summer and cold winters, the energy savings during hot weather are still greater than the incremental loss of heat in the winter.” This is because roofs do not absorb much heat from the sun in winter when days are shorter and cloudier, and the sun is less intense.

Proof Is in the Payoff

Several examples of shifting to dark to white roofs have shown the value.

In 1995, The Florida Solar Energy Center applied a white acrylic coating onto the 12,000-foot roof of Our Savior’s Elementary School in Cocoa Beach, Fla. After a year, the school’s energy consumption was down 13,000 kWh and its power usage had dropped 10 percent for an overall savings of $850.

The Heat Island Group, led by Akbari, tested light colored roofs on three commercial buildings in Davis, Gilroy and San Jose, Calif. The roofs’ albedos increased from 0.20 to 0.60, roof surface temperatures on summer afternoons fell from 175 degrees Fahrenheit to 120, and average electricity use for air-conditioning dropped by 18 percent in the Davis building, 13 percent in the Gilroy building, and 2 percent in the San Jose store.

The Philadephia Cool Homes Project, which installed white roofs on approximately 340 low-income seniors’ homes from 2001-2003, eliminated solar heat gain through the roofs, reduced ceiling temperatures by 4 to 5 degrees, and saved 560 kWh of air-conditioning electricity use per year.

White roofs also make good economic sense for cities. The 2006 report Mitigating New York City’s Heat Island with Urban Forestry Living Roofs and Light Surfaces compared the effectiveness and cost-benefits of urban forestry, green roofs, light surfaces, and some combined strategies, in mitigating the heat island effect. For every 1 degree of temperature reduction, light roofs and surfaces cost less than green roofs or tree plantings.

What Makes a Roof Cool?

A roof’s “coolness” is determined by its solar reflectance (albedo) and thermal emittance, the ability of the material to release absorbed heat.

The EPA and Department of Energy have established minimum solar reflectivity criteria for their Energy Star roofing materials. Low slope roofs, usually commercial buildings, must have an initial solar reflectance of greater than or equal to 0.65 to qualify. Steep slope roofs, usually homes, must have an initial solar reflectance of greater than or equal to 0.25.

Currently, emittance criteria are not required for Energy Star qualification. Some materials, like metal, are highly reflective, but if their emittance is low they won’t release absorbed heat effectively, so the best cool roofing materials have both high albedo and high emittance.

“Some roofing product types are more likely to be designed as cool (spray-on foam, single-ply, some metal products), while others are typically black (modified bitumen or built-up roofing),” said Molly Trobley-McCann of the Cool Roof Rating Council. “But anything can be coated white.”

Though plain white paint can increase a roof’s albedo, white roof coatings help prevent leaks and protect the roof better than simple paint. According to the Consumer Energy Center, the cost of cool roof and traditional roof products are generally comparable, but the advantage of cool roof coatings is that they can be applied every 10 to 15 years, reducing the need for expensive roof overhauls.

Because residential owners have been reluctant to put white roofs on their homes, mainly for aesthetic reasons, LBNL’s Environmental Energies Technology Division is collaborating with Oak Ridge National Laboratory and pigment and roofing manufacturers to develop high albedo roofing products in a variety of colors and materials.

Cool Roof Rules and Standards

Since 2005, California has led the movement to adopt white roofs by requiring all flat roofs to be white. On August 1, its new Title 24 building standards will require both residential and nonresidential buildings to have cool roofs.

A number of other states and cities have also adopted cool roof standards and rebate programs, including Arizona, Arkansas, Florida, Georgia, Hawaii, Illinois, Louisiana, New Mexico, North Carolina, South Carolina and Texas. Still others promote voluntary programs and initiatives. Voluntary programs such as the Green Building Initiative’s Green Globes and the U.S. Green Building Council’s LEED rating systems give credit for cool roofs.

In January, the DOE ruled that all states must certify that their building codes meet the requirements in ANSI / ASHRAE / IESNA’s 90.1-2004 Energy Standard for Buildings Except Low Rise Residential Buildings.

These standards, crafted by the American National Standards Institute, American Society of Heating, Refrigeration and Air Conditioning Engineers, and Illuminating Engineering Society of North America, provide minimum energy efficiency standards (including cool roof requirements) for new buildings, new parts of buildings, and new systems and equipment in existing buildings.

ASHRAE is currently developing standards for 2010 that will save 30 percent more energy, with a goal to have net-zero buildings by 2015.

Flexible Solar Power Shingles Transform Roofs From Wasted Space To Energy Source

ScienceDaily

Monday, June 8, 2009

A transparent thin film barrier used to protect flat panel TVs from moisture could become the basis for flexible solar panels that would be installed on roofs like shingles.

The flexible rooftop solar panels – called building-integrated photovoltaics, or BIPVs – could replace today’s boxy solar panels that are made with rigid glass or silicon and mounted on thick metal frames. The flexible solar shingles would be less expensive to install than current panels and made to last 25 years.

“There’s a lot of wasted space on rooftops that could actually be used to generate power,” said Mark Gross, a senior scientist at the Department of Energy’s Pacific Northwest National Laboratory. “Flexible solar panels could easily become integrated into the architecture of commercial buildings and homes. Solar panels have had limited success because they’ve been difficult and expensive to install.”

Researchers at PNNL will create these flexible panels by adapting a film encapsulation process currently used to coat flat panel displays that use organic light-emitting diodes, or OLEDs. The work is made possible by a Cooperative Research and Development Agreement recently penned between Vitex Systems and Battelle, which operates PNNL for the federal government.

PNNL researchers developed the thin film technology in the 1990s. At the time, the lab’s team investigated 15 possible applications, including solar power. Vitex licensed the technology from Battelle in 2000 and focused its initial efforts on developing the ultra-barrier films for flat-panel displays. Now PNNL and Vitex are taking a hard second look at solar power.

The encapsulation process and the ultra-barrier film – called Barix™ Encapsulation and Barix™ Barrier Film, respectively – are already proven and effective moisture barriers. But researchers need to find a way to apply the technology to solar panels that are made with copper indium gallium selenide, called CIGS, or cadmium telluride, called CdTe.

Under the agreement, researchers will create low-cost flexible barrier films and evaluate substrate materials for solar panels, which are also called photovoltaics, or PVs. Both the film and substrate must be able to survive harsh ultraviolet rays and natural elements like rain and hail for 25 years.

The agreement also calls for researchers to develop a manufacturing process for the flexible panels that can be readily adapted to large-scale production. If successful, this process will reduce solar panel manufacturing costs to less than $1 per watt of power, which would be competitive with the 10 cents per kilowatt-hour that a utility would charge.

“Vitex is proud to continue its long, successful relationship with PNNL,” said Martin Rosenblum, Vitex’s vice president of operations and engineering. “Vitex is excited to further its Barix™ technology’s proven barrier performance for photovoltaics toward mass manufacturing. Together, we look forward to creating a product that will help alleviate America’s dependence on foreign oil and increase America’s access to an abundant renewable energy source – the sun.”

Battelle, which is the majority shareholder of Vitex, is optimistic that this research agreement will contribute to a new way of generating solar power. Battelle recently increased its investment in Vitex for new state-of-the-art thin film encapsulation equipment and expanded its intellectual property portfolio.

“We’re confident that Vitex will be uniquely positioned to help meet the demand for flexible solar panels, OLED displays and lighting that should rise along with the economy,” said Martin Inglis, Battelle’s chief financial officer.

PNNL’s research efforts will be paid for with up to $350,000 from the DOE’s Energy Efficiency and Renewable Energy Technology Commercialization Fund. Last year, DOE announced that up to $1.5 million from the fund would be available to PNNL for projects that help commercialize technologies that reduce energy use or tap renewable energy sources. Because the fund requires commercial partners to match funding, Vitex will provide up to $350,900 of in-kind labor, equipment and materials for this project.

Build An Eco-Friendly House!

This great article is about a genuine family home in Wales. It was built by it’s residents, with help from passers by and visiting friends. 4 months after starting they moved in! Estimate construction time of 1000-1500 man hours and around $6000 are all it cost to this point! Not really so much in house buying terms (roughly $120/sq m excluding labor). Read more