Күн сәулесін шағылыстыру арқылы жер температурасын төмендету әдістері

Reflective surfaces, or ground based albedo modification (GBAM), is a solar radiation management method of enhancing Earth's albedo (the ability to reflect the visible, infrared, and ultraviolet wavelengths of the Sun, reducing heat transfer to the surface). The IPCC described this method as "whitening roofs, changes in land use management (e. g., no till farming), change of albedo at a larger scale (covering glaciers or deserts with reflective sheeting and changes in ocean albedo)." The most well known type of reflective surface is a type of roof called the "cool roof". While cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for both commercial and residential buildings.

As a method to address global warming, the IPCC 2018 report indicated that the potential for global temperature reduction was "small," yet was in high agreement over the recognition of temperature changes of 1 3 °C on a regional scale. Reflective surfaces can be used to change the albedo of agricultural and urban areas, noting that a 0.04 0.1 albedo change in urban and agricultural areas could potentially reduce global temperatures for overshooting 1.0 °C.

White thermoplastic membrane roofs (PVC and TPO) are inherently reflective, achieving some of the highest reflectance and emittance measurements of which roofing materials are capable. A roof made of white thermoplastic, for example, can reflect 80 percent or more of the sun's rays and emit at least 70% of the solar radiation that the roof absorbs. An asphalt roof only reflects between 6 and 26% of solar radiation. In addition to the white Thermoplastic PVC and TPO membranes used in many commercial cool roof applications, there is also research in the field of cool asphalt shingles. Asphalt shingles make up the majority of the North American residential roofing market, and consumer preferences for darker colors make creating solar reflective shingles a particular challenge, causing asphalt shingles to have solar reflectances of only 4% 26%. When these roofs are designed to reflect increased amount of solar radiation, the urban heat island effect can be reduced through the reduced need for cooling costs in the summer. Though a more reflective roof can lead to higher heating costs in the colder months, studies have shown that the increased winter heating costs are still lower than the summer cooling cost savings. To satisfy the consumer demands for darker colors which still reflect significant amounts of sunlight, different materials, coating processes, and pigments are used. Since only 43% of light occurs in the visible light spectrum, reflectance can be improved without affecting color by increasing the reflectance of UV and IR light. High surface roughness can also contribute to the low solar reflectances of asphalt shingles, as these shingles are made of many small approximately spherical granules which have a high surface roughness. To decrease this, other granule materials are being investigated, such as flat rock flakes, which could reduce the reflectance inefficiencies due to surface roughness. Another alternative is to coat the granules using a dual coat process: the outer coating would have the desired color pigment, though it may not be very reflective, while the inner coating is a highly reflective titanium dioxide coating. Natural white gravel covering can be seen as an alternative option to obtain cool roofing and cool pavements. The highest SRI rating, and the coolest roofs, are stainless steel roofs, which are just several degrees above ambient under medium wind conditions. Their SRI's range from 100 to 115. Some are also hydrophobic so they stay very clean and maintain their original SRI even in polluted environments. [A]

An existing (or new) roof can be made reflective by applying a solar reflective coating to its surface. The reflectivity and emissivity ratings for over 500 reflective coatings can be found in the Cool Roofs Rating Council.

Researchers at the Lawrence Berkeley National Laboratory have determined that a pigment used by the ancient Egyptians known as "Egyptian blue" absorbs visible light, and emits light in the near infrared range. It may be useful in construction materials to keep roofs and walls cool. They have also developed fluorescent ruby red coatings which have reflective properties similar to white roofs.

Green roofs provide a thermal mass layer which helps reduce the flow of heat into a building. The solar reflectance of green roofs varies depending on the plant types (generally 0.3–0.5). Green roofs may not reflect as much as a cool roof but do have other benefits such as evapotranspiration which cools the plants and the immediate area around the plants, aiding in lowering rooftop temperatures but increasing humidity, naturally. Moreover, some Green roofs need maintenance such as regular watering.

The Roof Savings Calculator (RSC) is a tool developed by the U. S. Department of Energy's Oak Ridge National Laboratory which estimates cooling and heating savings for low slope roof applications with white and black surfaces. This tool was the collaboration of both Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory in order to provide industry consensus roof savings for both residential and commercial buildings. It reports the net annual energy savings (cooling energy savings minus heating penalties) and thus is only applicable to the buildings with a heating and/or cooling system.

Solar reflective cars or cool cars reflect more sunlight than dark cars, reducing the amount of heat that is transmitted into the car's interior. Therefore, it helps decrease the need for air conditioning, fuel consumption, and emissions of greenhouse gases and urban air pollutants.

Cool color parking lots are parking lots made with a reflective layer of paint. Cool pavements which are designed to reflect solar radiation may use modified mixes, reflective coatings, permeable pavements, and vegetated pavements.

Mirrors are being explored as a reflective surface to reflect solar radiation and cool temperatures. MEER is a nonprofit using recycled materials to manufacture mirrors and polymer reflective films for potential widespread use on rooftops and in open spaces such as farmland. Trials have been undertaken in California and further application opportunities are developing in New Hampshire, India, and Africa.

In some climates where there are more heating days than cooling days, white reflective roofs may not be effective in terms of energy efficiency or savings because the savings on cooling energy use can be outweighed by heating penalties during winter. According to the U. S. Energy Information Administration, 2003 Commercial Buildings Energy Consumption Survey, heating accounts for 36% of commercial buildings' annual energy consumption, while air conditioning only accounts for 8% in United States. Energy calculators generally show a yearly net savings for dark colored roof systems in cool climates. A perfect roof would absorb no heat in the summer and lose no heat in the winter. To do this it would need a very high SRI to eliminate all radiative heat gains in summer and losses in winter. High SRI roofs act as a radiant barrier, providing a thermos bottle effect. High emissivity cool roofs carry a climate penalty due to winter radiative heat losses, which reflective bare metal roofs, such as stainless steel, do not.

In a 2001 federal study, the Lawrence Berkeley National Laboratory (LBNL) measured and calculated the reduction in peak energy demand associated with a cool roof's surface reflectance. LBNL found that, compared to the original black rubber roofing membrane on the Texas retail building studied, a retrofitted vinyl membrane delivered an average decrease of in surface temperature, an 11% decrease in aggregate air conditioning energy consumption, and a corresponding 14% drop in peak hour demand. The average daily summertime temperature of the black roof surface was , but once retrofitted with a white reflective surface, it measured Without considering any tax benefits or other utility charges, annual energy expenditures were reduced by $7,200 or $0.07/square foot. (This figure is for energy charges as well as peak demand charges). Instruments measured weather conditions on the roof, temperatures inside the building and throughout the roof layers, and air conditioning and total building power consumption. Measurements were taken with the original black rubber roofing membrane and then after replacement with a white vinyl roof with the same insulation and HVAC systems in place. Though a full year of actual data was collected, due to aberrations in the data, one month of data was excluded along with several other days which didn't meet the parameters of the study. Only 36 continuous pre retrofit days were used and only 28 non continuous operating days were used for the post retrofit period.

In July 2010, the United States Department of Energy announced a series of initiatives to more broadly implement cool roof technologies on DOE facilities and buildings across the country. As part of the new efforts, DOE will install a cool roof, whenever cost effective over the lifetime of the roof, during construction of a new roof or the replacement of an old one at a DOE facility. In October 2013, the United States Department of Energy ranked Cool Roofs as a 53 out of 100 (0 to 100 weighted average) for a cost effective energy strategy. "Climate issues can affect cool roof performance. Cool roofs are more beneficial in warmer climates and may cause energy consumption for heating applications to rise in colder climates. Cool roofs have a lower impact the more insulation is used. The Secretary of Energy directed all U. S. Department of Energy (DOE) offices to install cool roofs, when life cycle cost effectiveness is demonstrated, when constructing new roofs, or when replacing old roofs at DOE facilities. Other Federal agencies were also encouraged to do the same." Warranties for reflective roof products must be equal in all material respects to warranties offered for comparable non reflective roof products, either by a given company or relative to industry standards. Unlike other Energy Star rated products, such as appliances, this rating system does not look at the entire roof assembly, but only the exterior surface. Consumers (i. e. building owners) may believe that the Energy Star label means their roof is energy efficient; however, the testing is not as stringent as their appliance standard and does not include the additional components of a roof (i. e. roof structure, fire rated barriers, insulation, adhesives, fasteners, etc.). A disclaimer is posted on their website "Although there are inherent benefits in the use of reflective roofing, before selecting a roofing product based on expected energy savings consumers should explore the expected calculated results that can be found on the Department of Energy's "Roof Savings Calculator" website at www. roofcalc. com. Please remember the Energy Savings that can be achieved with reflective roofing is highly dependent on facility design, insulation used, climatic conditions, building location, and building envelope efficiency." (CRRC) has created a rating system for measuring and reporting the solar reflectance and thermal emittance of roofing products. This system has been put into an online directory of more than 850 roofing products and is available for energy service providers, building code bodies, architects and specifiers, property owners and community planners. CRRC conducts random testing each year to ensure the credibility of its rating directory. CRRC's rating program allows manufacturers and sellers to appropriately label their roofing products according to specific CRRC measured properties. The program does not, however, specify minimum requirements for solar reflectance or thermal emittance.

The Green Globe system is used in Canada and the United States. In the U. S., Green Globes is owned and operated by the Green Building Initiative (GBI). In Canada, the version for existing buildings is owned and operated by BOMA Canada under the brand name 'Go Green' (Visez vert). Green Globe uses performance benchmark criteria to evaluate a building's likely energy consumption, comparing the building design against data generated by the EPA's Target Finder, which reflects real building performance. Buildings may earn a rating of between one and four globes. This is an online system; a building's information is verified by a Green Globes approved and trained licensed engineer or architect. To qualify for a rating, roofing materials must have a solar reflectance of at least 0.65 and thermal emittance of at least 0.90. As many as 10 points may be awarded for 1–100 percent roof coverage with either vegetation or highly reflective materials or both. The basis in physics of a high emittance is quite questionable, since it merely describes a material which easily radiates infrared wavelength heat to the environment, contributing to the greenhouse effect. Highly reflective, low emittance materials are much better at reducing energy consumption.

The U. S. Green Building Council's Leadership in Energy and Environmental Design (LEED) rating system is a voluntary, continuously evolving national standard for developing high performance sustainable buildings. LEED provides standards for choosing products in designing buildings, but does not certify products. Unlike a building code, such as the International Building Code, only members of the USGBC and specific "in house" committees may add, subtract or edit the standard, based on an internal review process. Model Building Codes are voted on by members and "in house" committees, but allow for comments and testimony from the general public during each and every code development cycle at Public Review hearings, generally held multiple times a year. Under the LEED 2009 version, to receive Sustainable Sites Credit 7.2 Heat Island Effect Roof, at least 75% of the surface of a roof must use materials having a solar reflective index (SRI) of at least 78. This criterion can also be met by installing a vegetated roof for at least 50% of the roof area, or installing a high albedo and vegetated roof in combination that meets this formula: (Area of Roof meeting Minimum SRI Roof/0.75) + (Area of vegetated roof/0.5) ≥ Total Roof Area. Examples of LEED certified buildings with white reflective roofs are below. Building name Owner Location LEED level Wildomar Service Center Southern California Edison Wildomar, California Platinum Donald Bren School of Environmental Science & Management University of California, Santa Barbara Santa Barbara, California Platinum Frito Lay Jim Rich Service Center Frito Lay, Inc. Rochester, New York Gold Edifice Multifunction Travaux Public et Services Gouvernementaux Canada Montreal, Quebec Gold Seattle Central Library City of Seattle Seattle, Wash. Silver National Geographic Society Headquarters Complex National Geographic Society Washington, D. C. Silver Utah Olympic Oval Salt Lake City Olympic Winter Games 2002 Organizing Committee Salt Lake City, Utah Certified Premier Automotive Group North American Headquarters Ford Motor Company Irvine, California Certified

This project is co financed by the European Union in the framework of the Intelligent Energy Europe Programme. The aim of the proposed action is to create and implement an Action Plan for the cool roofs in EU. The specific objectives are: to support policy development by transferring experience and improving understanding of the actual and potential contributions by cool roofs to heating and cooling consumption in the EU; to remove and simplify the procedures for cool roofs integration in construction and building's stock; to change the behaviour of decision makers and stakeholders so to improve acceptability of the cool roofs; to disseminate and promote the development of innovative legislation, codes, permits and standards, including application procedures, construction and planning permits concerning cool roofs. The work will be developed in four axes, technical, market, policy and end users. In tropical Australia, zinc galvanized (silvery) sheeting (usually corrugated) do not reflect heat as well as the truly "cool" color of white, especially as metallic surfaces fail to emit infrared back to the sky. European fashion trends are now using darker colored aluminium roofing, to pursue consumer fashions.

NYC °CoolRoofs is a New York City initiative to coat rooftops white with volunteers. The program began in 2009 as part of PlaNYC, and has coated over 5 million square feet of NYC rooftops white. On Wednesday, September 25, 2013 Mayor Michael R Bloomberg declared it "NYC °CoolRoofs Day" in New York City with the coating of its 500th building and reducing the carbon footprint by over 2000 tons. Volunteers use paintbrushes and rollers to apply an acrylic, elastomeric coating to the roof membrane. A 2011 Columbia University study of roofs coated through the program found that white roofs showed an average temperature reduction of 43 degrees Fahrenheit when compared to black roofs.

White Roof Project is a US nationwide initiative that educates and empowers individuals to coat rooftops white. The program's outreach has helped complete white roof projects in more than 20 US states and five countries, engaged thousands in volunteer projects, and sponsored the coating of hundreds of nonprofit and low income rooftops.

An urban heat island occurs where the combination of heat absorbing infrastructure such as dark asphalt parking lots and road pavement and expanses of black rooftops, coupled with sparse vegetation, raises air temperature by higher than the temperature in the surrounding countryside. Green building programs advocate the use of cool roofing to mitigate the urban heat island effect and the resulting poorer air quality (in the form of smog) the effect causes. By reflecting sunlight, light colored roofs minimize the temperature rise and reduce cooling energy use and smog formation. A study by LBNL showed that, if strategies to mitigate this effect, including cool roofs, were widely adopted, the Greater Toronto metropolitan area could save more than $11 million annually on energy costs.