Source: PNAS www.pnas.org/cgi/doi/10.1073/pnas.1606035114
Global scenarios of urban density and its impacts on building energy use through 2050
Burak Güneralpa,b,1, Yuyu Zhouc, Diana Ürge-Vorsatzd, Mukesh Guptad, Sha Yue, Pralit L. Patele, Michail Fragkiasf,
Xiaoma Lic,g,h, and Karen C. Setog
aDepartment of Geography, Texas A&MUniversity, College Station, TX 77843; bCenter for Geospatial Science, Applications and Technology (GEOSAT), Texas
A&M University, College Station, TX 77843; cDepartment of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011; dCentre for
Climate Change and Sustainable Energy Policy, Central European University, 1051 Budapest, Hungary; eJoint Global Change Research Institute, Pacific
Northwest National Laboratory, College Park, MD 20740; fDepartment of Economics, Boise State University, Boise, ID 83725; gYale School of Forestry and
Environmental Studies, Yale University, New Haven, CT 06511; and hState Key Laboratory of Urban and Regional Ecology, Research Center for Eco-
Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People’s Republic of China
Edited by Jay S. Golden, Duke University, Durham, NC, and accepted by Editorial Board Member B. L. Turner, November 29, 2016 (received for review July
Urban density significantly impacts urban energy use and the quality of life of urban residents. Here, we provide a global-scale analysis of future urban densities and associated energy use in the built environment under different urbanization scenarios. The relative importance of urban density and energy-efficient technologies varies geographically. In developing regions, urban density tends to be the more critical factor in building energy use. Large-scale retrofitting of building stock later rather than sooner results in more energy savings by the middle of the century. Reducing building energy use, improving the local environment, and mitigating climate change can be achieved through systemic efforts that take potential co-benefits and trade-offs of both higher urban density and building energy efficiency into account.
Although the scale of impending urbanization is well-acknowledged, we have a limited understanding of how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use for heating and cooling. Globally, the energy use for heating and cooling by the middle of the century will be between 45 and 59 exajoules per year (corresponding to an increase of 7–40% since 2010). Most of this variability is due to the uncertainty in future urban densities of rapidly growing cities in Asia and particularly China. Dense urban development leads to less urban energy use overall. Waiting to retrofit the existing built environment until markets are ready in about 5 years to widely deploy the most advanced renovation technologies leads to more savings in building energy use. Potential for savings in energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared with the business-as-usual scenario in South Asia and Sub-Saharan Africa but significantly contributes to energy savings in North America and Europe. Systemic efforts that focus on both urban form, of which urban density is an indicator, and energy-efficient technologies, but that also account for potential co-benefits and trade-offs with human well-being can contribute to both local and global sustainability. Particularly in growing cities in the developing world, such efforts can improve the well-being of billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas.