Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 


Pavements Designed to Fight Climate Change Could Increase Energy Consumption in Surrounding Buildings

A push to replace old, heat-trapping paving materials with new, cooler materials could actually lead to higher electricity bills for surrounding buildings, engineers at the University of California, San Diego, have found. Researchers published their findings Oct. 29 in the new Journal of Urban Climate.
The new paving materials are designed to lower the overall temperature of the areas where they are used—something that the study, which was focused on local solar radiation and energy consumption, was not designed to measure.

The study sounds a note of caution at a time when both federal and state legislatures have been pushing for increased use of the new highly reflective pavement materials. Assembly Bill 296, which became law in California this year, is designed to advance cool pavement practices in the state and requires the compilation of a Cool Pavement Handbook. The federal Heat Island and Smog Reduction Act of 2011, currently under consideration in Congress, would specifically require paving materials with higher solar reflectivity.

“Our findings suggested that some benefits associated with reflective pavements are tied to the environment where they’re used,” said Jan Kleissl, a professor of environmental engineering at the Jacobs School of Engineering at UC San Diego. “More studies are needed to determine where these new materials would be most beneficial.”

The new materials could have a positive effect in areas where buildings can automatically respond to additional sunlight because they are equipped with smart lighting solutions, such as dimmers run by photo-sensitive cells.

However, buildings without these features do not fare as well. The increases in consumption of cooling energy due to the new pavements ranged anywhere from 4.5 to 9.5 percent for typical newer, and better insulated, buildings; and from 5 to 11 percent for older structures. That’s because the new paving materials stay cool by reflecting significantly more of the sun’s rays than traditional pavements. Many rays are reflected back into space, helping to cool surrounding areas—and the planet. However, a portion of these rays gets reflected onto the windows of nearby buildings. In the researchers’ study, windows facing the reflective pavements got 40 percent more daily sunshine in summer as windows facing more traditional paving surfaces (in winter the difference was only 12 percent). That in turn increases temperatures inside the building, especially if the windows do not have solar-control coating. So the buildings’ occupants turn up the air conditioning. Meanwhile, office buildings that have smart lighting or energy-conscious occupants may actually benefit from the additional sunlight by being able to reduce energy use due to artificial lighting.

The worst-case scenario is when these new cooler pavements are used in office park settings with many mid-rise buildings with large window areas. The best-case scenario would be to use the new paving materials near buildings without windows; on roads or large parking lots that are not surrounded by buildings; or in warehouse districts where structures don’t have air conditioning, Kleissl said.

Kleissl and Jacobs School Ph.D. student Neda Yaghoobian looked at annual energy use related to air conditioning in both older and newer four-story buildings in Phoenix, Ariz. Yaghoobian used a complex weather and building model she developed, called the Temperature of Urban Facets Indoor-Outdoor Building Energy Simulator (TUF-IOBES). The model fills an important gap by allowing the detailed simulation of the interaction between indoor and outdoor climate. The program links indoor and outdoor energy balance dynamically by taking into account real weather conditions, indoor heat sources, building and urban material properties, composition of the building envelope (such as windows and insulation), and waste heat from air conditioning.

Yaghoobian found that, as expected, temperature for the traditional, darker pavement was up to 27 degrees Fahrenheit higher than the temperature of the newer, reflective pavement. But the walls of buildings standing near the reflective pavement were up to 4 degrees Fahrenheit warmer. Specific results varied widely depending on the buildings’ make up.

Natural vs. artificial light

A watt of daylight can replace up to two watts of fluorescent lighting, depending on the lighting needs of a building. In the best-case scenario, each watt of extra daylight could reduce lighting power demand by two watts. This would also decrease the building’s heat gain by one watt (net), saving another third of a watt in cooling power. Further study is needed to quantify these potential savings.

Technical background on energy simulating software

Most existing building energy models do not allow modifying outdoor ground surfaces that radiatively interact with the building. On the other hand, urban surface energy balance models in the meteorological community usually treat the buildings as hollow cubes and exclude dynamic modeling of the indoor building energy balance. A new tool was necessary and created in TUF-IOBES.

TUF-IOBES goes beyond previously available models; it is the first three-dimensional fully-coupled and computationally efficient indoor-outdoor building energy simulator. Given the complexity of solar irradiance fields in the urban canopy the surface temperature fields and energy use can be simulated more faithfully. TUF-IOBES provides unprecedented insight on urban canopy and building energy heat transfer processes. It can improve our understanding of how urban geometry and material modifications and the interaction between buildings and their surroundings and dynamic combination of all of these effects in three dimensions modify the urban energy use.

Ioana Patringenaru | EurekAlert!
Further information:

More articles from Power and Electrical Engineering:

nachricht Neutrons pave the way to accelerated production of lithium-ion cells
20.03.2018 | Technische Universität München

nachricht Monocrystalline silicon thin film for cost-cutting solar cells with 10-times faster growth rate fabricated
16.03.2018 | Tokyo Institute of Technology

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Forscher entdecken neues Anti-Krebs-Protein

Ein internationales Forscherteam hat ein neues Anti-Krebs-Protein entdeckt. Das Protein namens LHPP verhindert, dass sich Krebszellen in der Leber ungebremst vermehren. Zudem eignet es sich als Biomarker für die Diagnose und Prognose von Leberzellkrebs. Dies berichten Forscher unter der Leitung von Prof. Michael N. Hall vom Biozentrum der Universität Basel in «Nature».

Die Häufigkeit von Leberkrebs, auch bekannt als Leberzellkarzinom, nimmt stetig zu. In der Schweiz hat sich die Zahl der Erkrankungen in den letzten zwanzig...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: LifeTime – ein visionärer Vorschlag für ein EU-Flagschiff

Zuverlässig vorherzusagen, wann eine Krankheit ausbricht oder wie sie verläuft, erscheint wie ein Traum. Ein europäisches Konsortium will ihn Wirklichkeit werden lassen und dabei vor allem neue Technologien der Einzelzellbiologie nutzen. Führende Forscherinnen und Forscher haben daher einen Antrag für ein FET-Flagschiff mit dem Namen LifeTime eingereicht.

Nachdem das Humangenomprojekt 2001 abgeschlossen war, haben Wissenschaft und Medien das Genom als „Buch des Lebens“ bezeichnet. Darin könne man nachlesen, wie...

Im Focus: Forscher des Fraunhofer FHR begleiten Wiedereintritt der chinesischen Raumstation Tiangong-1

Die chinesische Raumstation Tiangong-1 wird in wenigen Wochen in die Erdatmosphäre eintreten und zu einem großen Teil verglühen. Dabei können auch Trümmerteile den Erdboden erreichen. Tiangong-1 kreist unkontrolliert und mit ca. 29 000 km/h um die Erde. Die Wiedereintrittsprognose kann derzeit nur im Bereich von mehreren Tagen angegeben werden. Die Wissenschaftler des Fraunhofer FHR in Wachtberg bei Bonn beobachten Tiangong-1 bereits seit Wochen mit ihrem TIRA (Tracking and Imaging Radar) System, einem der leistungsfähigsten Radare zur Weltraumbeobachtung weltweit, um das nationale Weltraumlagezentrum und die ESA mit ihrer Expertise bei den Wiedereintrittsprognosen zu unterstützen.

Nach Verlust des Funkkontakts mit Tiangong-1 im Jahr 2016 ist es aufgrund der niedrigen Bahnhöhe unausweichlich, dass die chinesische Raumstation in die...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Alle Focus-News des Innovations-reports >>>



Industrie & Wirtschaft

Hybrid-elektrisch angetriebene Verkehrsflugzeuge – Zukunft oder Fiktion?

20.03.2018 | Veranstaltungen

Konferenz zur virtuellen Realität kommt nach Reutlingen

19.03.2018 | Veranstaltungen

Veranstaltungen zur Digitalisierung in der Weiterbildung

19.03.2018 | Veranstaltungen

Wissenschaft & Forschung
Weitere VideoLinks im Überblick >>>
Aktuelle Beiträge

Neue Akteure der Atherosklerose identifiziert

22.03.2018 | Medizin Gesundheit

Forscher entwickeln Lösung für sparsamen digitalen Pigmentdruck auf Textil

22.03.2018 | Materialwissenschaften

Modulares Safety-Konzept erhöht Flexibilität beim Anlagenumbau

22.03.2018 | HANNOVER MESSE

Weitere B2B-VideoLinks
im innovations-report
in Kooperation mit academics