CBE Energy Seminar Speaker: Jorge González-Cruz

Description

This presentation focuses on coastal city research – a nexus of climate, energy, and air quality. The well-known Urban Heat Island (UHI) effect is the result of surface energy balance changes and anthropogenic heat emissions, largely from buildings, which forms a two-way feedback. In warm seasons, excess heat from the UHI is a major driver of tropospheric ozone production once combined with nitrogen emissions, from transportation or industry, and with volatile organic compounds, from vegetation. Building exhalations are also a major source of environmental emissions, via their ventilation systems. These systems emit Volatile Organic Compounds (VOC) and Volatile Compound products (VPC), which are suspected to be major contributors for ozone production. As such, there is direct positive feedback in warm seasons between extreme heat, energy demands, and sources for ozone production. In cold seasons, this nexus also prevails; cold climates motivate energy demands, which leads to pollutants from the gas or coal driven building heating systems, enhancing the UHI which results in negative feedbacks. We present a unified observation and modeling approach to investigate this nexus in the two end-use cases of New York City and Houston. Observations and modelling from two major summer field campaigns are used to explore ozone episode cases driven by heat waves. The modeling used an urbanized weather model, which incorporates a building energy model, and is coupled to a chemical model, referred to as uWRF-Chem. The modeling framework was validated against the wide range of observations, including satellite and surface stations, and demonstrated that incorporating urban effects is indeed necessary for accurate prediction of meteorological-chemical events. Observations showed a complex spatial and temporal interaction between the surface meteorology, UHI, sea-breeze front, and the ozone peak ridge. Results showed maximum ozone production took place in the city. Resulting high concentrations were then advected to the urban outskirts, where the sea-breeze collapsed and led to ozone peaks. Total energy for the city reached seasonal peaks during these events as well. Building energy use was found to be a key contributor to both UHI intensification and maximum ozone production directly and indirectly. Finally, we explore implications of this nexus changing in future winters, as cities develop plans towards full electrification.

Prof. González earned his Doctorate (1994) and Bachelor (1988) degrees in Mechanical Engineering from the Georgia Institute of Technology and from the University of Puerto Rico-Mayagüez, respectively. He joined The City College of New York faculty in 2008 after tenures at Santa Clara University, California, as Professor and David Packard Scholar, and as Chairman and Professor of Mechanical Engineering at the University of Puerto Rico-Mayagüez. He teaches and conducts research in urban energy sustainability, urban weather and climate, urban remote sensing, and regional climate modeling and analysis.