Urban heating and cooling to play substantial role in future energy demand under climate change

Existing studies predominantly focus on chemical feedback loops, that are large-scale processes involving complex interactions between energy use, greenhouse gas emissions and the atmosphere. Nevertheless, a research group led by the University of Illinois Urbana-Champaign focuses on the often-overlooked physical interactions between urban infrastructure and the atmosphere that may contribute to local microclimates and, ultimately, global climate.

A brand new study led by civil and environmental engineering professor Lei Zhao emphasizes that smaller-scale city-level waste heat from residential and industrial property heating and cooling efforts can result in big impacts on local climates and energy use. The study findings are published within the journal Nature Climate Change.

“The warmth generated from heating and cooling systems is a considerable a part of the whole heat generated inside urban areas,” Zhao said. “These systems generate a variety of heat that’s released into the atmosphere inside cities, making them hotter and further increasing the demand for indoor cooling systems, which feeds much more heat into local climates.”

This process is a component of what researchers call a positive physical feedback loop between constructing cooling-system use and the warming of local urban environments. The authors also note that rising temperatures under climate change could potentially decrease energy demand in the course of the colder months, a negative feedback loop that must be considered in any temperature and energy demand projections.

In response to the study, less heating use would result in less heat being released into the urban environment, inducing less urban warming than under the current climate.

“This process forms a negative physical feedback loop that will dampen the heating demand decrease,” Zhao said. “Nevertheless it doesn’t by any means cancel out the positive feedback loop effect. As a substitute, our model suggests that it could polarize the seasonal electricity demand, which poses its own set of problems for which careful planning is required.”

To incorporate these missed physical contributions into the larger overall picture of climate change, the team used a hybrid modeling framework that mixes dynamic Earth system modeling and machine learning to look at the worldwide urban heating and cooling energy demand under urban climate change variability and uncertainties — including the spatial and temporal challenges posed by the indisputable fact that cities vary in income, infrastructure, population density, technology and temperature tolerance.

“I believe the take-home message for this study is that energy projections that integrate the results of positive and negative physical feedback loops are needed and can lay the groundwork for more comprehensive climate impact assessment, science-based policymaking and coordination on climate-sensitive energy planning.”

Zhao’s team is already learning how variables and uncertainties like humidity, constructing materials and future climate-mitigating efforts will further factor into their models to enhance energy-demand projections.

Zhao is also affiliated with the Institute for Sustainability, Energy, and Environment, the National Center for Supercomputing Applications and the Gies College of Business at Illinois.

The National Science Foundation and iSEE on the University of Illinois Urbana-Champaign supported this study.