Research program – IV:
Design, Development and
Testing of Innovative Materials for Urban Cooling

To promote advanced technologies to mitigate urban heat island and to simulate impact of infrastructure materials, an integrated study of the design, development and testing of innovative materials for urban cooling was undertaken with support from The Global Kaiteki Center.  In this project, efforts include development and use of computer simulations of urban buildings and urban centers as well as a novel approach to asphalt pavement formulation to promote a more durable material that also improve thermal properties.

Computer simulations have been developed to understand the benefits of innovations in materials for building roof, wall, and road construction. These benefits take the form of reduced energy consumption and improved thermal comfort in both indoor and outdoor environments. Our analyses focus on 5 moderate to hot climate cities: Atlanta GA, Barcelona SPAIN, Jakarta INDONESIA, Phoenix AZ, and Tokyo JAPAN. By using whole building-energy models, pavement transient conduction models, and regional-scale atmospheric models, we have identified optimum design and deployment characteristics for passive daytime radiative cooling roofing materials, cross-laminated timber buildings, and aerogel-enhanced paving materials. 

For advanced paving materials, our research has shown that addition of aerogel composite (aMBx) to asphalt binders or mixtures increases the resistance to heat flow, improves temperature susceptibility, and mitigates the urban heat island making the paved materials more durable and better suited to warm climate regions facing urban heat.  Laboratory optimization of the material design and manufacturing has resulted in promising preliminary data which is currently being verified in field testing in collaboration with local industry.

The two interconnected projects also included mathematical temperature simulations of various paving scenarios including aMBx paving materials each focused on answering a common question: how can urban centers be cooled through the design and deployment of novel materials in built environments?  Through close collaboration and communication, the results of laboratory and field demonstrations for paving materials provide novel data for climate simulations while promising parameters identified through energy simulations drive laboratory simulations on paving materials.

Currently, climate simulations are being optimized for the five target urban centers to quantify the energy savings and climate benefits possible through optimal material selection.  Asphalt material development work is being extended to consider surface treatments typically used in road maintenance.  Both projects show tremendous promise and will seek continued support through multiple avenues.

Research project IV.1: Modeling and Simulation of Building Materials and Urban Climate

The modeling work for the Urban Cooling Project has three key elements:

The paving and building modeling efforts are focusing on five representative hot climate cities based on ASHRAE Climate Zones; Atlanta, GA (Climate Zone[1] – 3A), Barcelona, SPAIN (Climate Zone – 4A), Jakarta, INDONESIA (Climate Zone – 1A), Phoenix, AZ (Climate Zone – 2B) and Tokyo, JAPAN (Climate Zone – 3A). As the performance of the tested building technologies depends on the type of building to which they are applied, our building modeling uses multiple vintages of five different building archetypes: Office, Midrise apartment, Outpatient Hospital, Hotel, and Single-Family Homes. The building energy simulation software which is used to simulate the building archetypes is EnergyPlus, an open-source platform developed by the U.S. Department of Energy.  The paving model has been developed in-house based on a standard transient 1-D heat conduction model, validated against observational studies. The atmospheric modeling work at the city-regional scale uses the urbanized version of the Weather Research and Forecasting (WRF) model.

The value of this research is that it answers the overarching question “by how much can we cool cities through widespread adoption of such technologies?”. Furthermore, this work allows development of technology selection and optimization guidelines that will aid industry and local governments in rapid development and deployment of these technologies.  

Research project IV.2: Innovative Design of Paving Materials using Aerogel Composite (aMBx)

The research team is also investigating the use of Aerogel composite in asphalt materials modification. Our novel Aerogel composite (aMBx) is a high-performance insulation material with extremely low density and high thermal resistance properties. Adding aMBx to the asphalt binder or mixture would increase resistance to flow, more significantly improves temperature susceptibility, and potentially mitigates the nighttime urban heat island.  Early research results found promising outcomes from laboratory experiments to optimize and quantify the operational, maintenance and thermal cooling benefit of this material. These laboratory results were incorporated into the field-testing design which showed lower day-time temperatures for thin asphalt layers and lower night-time temperatures for thick asphalt layers. These findings support the initial hypothesis that our novel aerogel composite (aMBx) potentially mitigate the effect of urban heat island; however, the research team is looking forward to analyze data during field deployment during hot summer periods in Arizona.

Preliminary Life Cycle Cost Assessment (LCCA) of the aMBx modified pavement results showed favorable outcomes for the aMBx modified pavement based on laboratory testing. For the LCCA, we considered product cost information, typical road maintenance costs, and conducted laboratory tests to estimate the durability of the modified pavement based on laboratory tests of stiffness and fatigue.  However, this LCCA needs further evaluation to consider the raw materials cost, which still need to be reduced through industrial scale production.

Collaborations

Research personnel

Publications

  1. Papers in peer-reviewed journals
  2. Anand, J., D.J. Sailor, A. Baniassadi, 2020. “The relative role of solar reflectance and thermal emittance for passive daytime radiative cooling technologies applied to rooftops,” Sustainable Cities and Society, https://doi.org/10.1016/j.scs.2020.102612

Patents pending:

[1] Climate Zones refer to geographic regions defined by the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) for the purpose of classifying cities based on common heating and air conditioning demands.