Low carbon effects of urban underground space

Highlights

• Urban underground space (UUS) as a contributor to low carbon cities is analyzed.

• Quantification measures for positive low carbon effects of UUS are set up.

• Negative effects of UUS on low carbon cities are summarized and responded.

• UUS planning implications for low carbon cities are concluded.

Abstract

Urbanization is progressing rapidly, while problems raised by climate change are occurring across the globe. Cities are at the center of both of the two tendencies therefore, low carbon or zero carbon cities are being promoted. Urban underground space (UUS) is a key component in the process of urbanization and plays a significant role in creating low carbon cities, as highlighted in this paper. Meanwhile, UUS also involves unavoidable drawbacks regarding energy consumption in terms of lighting, ventilation and dehumidification. In this paper, the advantages of UUS in creating low carbon cities are analyzed, and a framework for calculating the positive low carbon effects derived from UUS use is established. Additionally, some alleviating measures in response to the potential low carbon disadvantages of UUS are proposed. Based on the analysis, some planning and design implications for the development of urban underground space in order to fulfill its role as a contributor to urban sustainability are discussed.

Introduction

In recent years, extreme weather conditions worldwide, such as droughts, heat waves, extreme precipitation, flooding, wildfires, etc., seem to be occurring with higher frequency, some of which are increasing due to climate change to certain extent. The prevailing interpretation for such phenomena is the cumulative emissions of greenhouse gases, of which carbon dioxide is considered the most principal. Carbon dioxide contributes as much as 70% of all energy-related greenhouse gas emissions (Satterthwaite, 2008). Cities are at the center of the fundamental shift toward increased greenhouse gas emissions; however, the ever-increasing global urban population requires more energy consumption and thus generating additional potential greenhouse gas emissions. It can be concluded that cities can be regarded as both a problem and a solution for climate change (Popartan & Morata, 2017). In this context, low carbon city as a solution is widely accepted across the globe.

In parallel with rapid urbanization, urban underground space (UUS) is becoming more actively utilized, particularly in dense aggregations such as central business districts (CBDs) or downtowns, due to the increasing demand for urban space while ensuring ecological modernization. UUS will undoubtedly play a role, either positively or negatively, in the process of creating low carbon cities. For instance, in Chinese cities where low carbon strategies have been broadly adopted (Khanna, Fridley, & Hong, 2014; Yang & Li, 2013), UUS use is a key factor for urban development (Bobylev, 2016; Qiao & Peng, 2016; Zhao, Peng, Wang, Zhang, & Jiang, 2016) and urban sustainability (Bobylev, 2009; Sterling et al., 2012). However, even though the fact that urban underground space could be a contributor to low carbon cities has been widely acknowledged by academics (Delmastro, Lavagno, & Schranz, 2014; Yokotsuka, Matozaki, Kasuya, & Ohmura, 2014), many issues, e.g., how to measure its contribution and how will it guide UUS planning and design, have not been made explicit so far. Moreover, there is still a gap in the existing research with regard to the unavoidable drawbacks of urban underground space in energy consumption, e.g., lighting and ventilation. To bridge these gaps, in this paper, tentative research is carried out based on a case study of the Shanghai Hongqiao CBD. Here, the extent to which urban underground space would influence low carbon city development through both qualitative and quantitative measures of the low carbon effects of UUS is investigated. Additionally, the corresponding strategies of urban underground space planning and design to maximize the UUS advantages and to minimize the potential UUS disadvantages for sustainable low carbon cities are considered. It is anticipated that the findings of this research will assist future UUS development in achieving low carbon and sustainable cities.