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Global urban development is increasingly becoming an aspect of focus as nations fight sustainability challenges. A review of the current literature on urban sustainability suggests that research on development of cities, in both developed and developing countries, is growing fast, with an emphasis on sustainable development. However, very little of this research contains an integrated framework to systematically identify and examine the various dimensions of urban sustainability and to measure and evaluate them appropriately. Cities are more than the sum of their sectors, and are complex and interdependent systems on whose dynamics the quality of life of millions of human beings and a good part of the economy depend. Environmental, economic, social and governance problems can create formidable barriers to urban sustainability. Governance remains a critically important dimension of urban sustainability, especially when discussing urbanization in developing countries, given rapid population movements and imbalances in socio-economic development. Understanding how cities function is fundamental to resolving these imbalances. The aim of this paper is to provide a review and analysis of the concept of urban sustainability and to propose the development of a holistic framework through integration of environmental, economic, social, and governance dimensions of sustainability. Such a review would make it possible to understand the complex dynamics of the four dimensions and to assess the progress and challenges in moving towards urban sustainability, taking the case of Nairobi, Kenya, as an example. The paper argues that, for urban sustainability in developing countries, more emphasis should be placed on the governance dimension, because this is where the biggest challenge exists, with increasing needs for immediate management of rapid urbanization.

Abstract The rapidly growing construction industry has accelerated water and energy scarcity in China, threatening its sustainable development. This study integrates multi-regional input-output (MRIO) and data envelopment analysis (DEA) to investigate the water-energy nexus in the construction industry at the provincial level through the entire industrial supply chain. Results show that the construction industry accounts for 8.97% and 27.20% of virtual water and embodied energy in China, respectively. The western area experiences the most energy- and water-intensive construction processes given its backward economy and outdated technological development. The northern area faces great challenges with regard to energy intensity improvements, whereas the central regions suffer from large pressure relating to inefficient water use. The manufacture of non-metallic mineral products, smelting, and the pressing of metals are the largest suppliers of virtual water and embodied energy. The efficiency assessment results demonstrate that Jiangsu and Zhejiang are two DEA-effective regions. China has achieved a relatively high level of scale efficiency but suffers from backward technology.

Abstract Renewable electricity generations have been growing rapidly in recent years worldwide as a result of efforts to address the global energy issue. However, it has also imposed increasing challenges on the balance of power grids due to their intermittent nature. Building sector, as the largest consumer, is expected increasingly to play an important role in providing ancillary services (AS) to relieve stress and reduce the needs of investment for power balance of the smart grids. Grid-responsive building therefore becomes a worthwhile and essential feature of buildings today and in the future. This paper provides an overview of the classification, benefits, applications as well as methods/technologies for HVAC systems in non-residential buildings to provide ancillary services, as fast responses (i.e., in the magnitude of seconds or minutes) to the needs of smart grids. In addition, the challenges of applications and potential solutions are investigated and summarized. The potential capacities of HVAC systems in the entire non-residential building sector in Hong Kong for providing frequency regulation (FR) and spinning reserve are also quantified.

Abstract Low-carbon economy has played an important role in green energy economics in last two decades. The number of studies conducted on low-carbon economy has increased steadily since 1990 and now in a fast-growing stage of its academic articles’ production life cycle. An increasing number of scholars have paid their attentions to low-carbon economy research. Hence, the low-carbon economy has been an important and popular topic in the past 30 years as evidenced by numerous papers in journals listed in several subject categories in the Web of Science (WoS) online database. This research reviewed more than 14,000 bibliographic records from the Science Citation Index and Social Science Citation Index of WoS. In this work, paper citations, subject categories, cited journals, top countries, productive institutes, authors, cited references and publications’ citations or research collaborations are analysed from published literature. We have found that the top three productive journals in low-carbon economy research are Energy Policy, Renewable and Sustainable Energy Reviews and Journal of Cleaner Production. The U.S. has an apparent advantage in the quantity and quality of low-carbon economy research. In addition, the U.S. is in the centre of international collaboration networks, including two top productive institutes, which summarized as University of California Berkeley and Carnegie Mellon University accordingly. An overall trend of the developing analysis of low-carbon economy research can provide a clear knowledge map and deep understanding of academic research on low-carbon economy.

Sustainability is a global issue and its enhancement through modern forms of procurements, such as public-private partnership (PPP), has become topical considering the huge impact of PPP activities on society, the economy, and the environment. However, one way of promoting sustainability thorough PPPs is the adoption of social responsibility (SR) initiatives/factors. This paper aims to empirically investigate the SR factors in PPPs through a comparative study between China and Ghana. An empirical questionnaire survey was conducted in both China and Ghana. Further, the mean score ranking, Kendall’s coefficient of concordance, and Mann-Whitney U test were used for data analysis. Results show that SR factors related to the economic efficiency of PPP projects and climate change adaptation are critical in China, whereas in Ghana, SR factors directly related to job creation and environmental protection are critical. The outputs of this study inform investors of the critical SR initiatives to consider when engaging in PPPs in Asia and Africa. In addition, they provide a solid knowledge base for the continuous international debate on how sustainability could be enhanced through PPP policy.

Energy crisis and carbon emission have become two seriously concerned issues universally. As a feasible solution, Energy Internet (EI) has aroused global concern once proposed. EI is a new power generation developing a vision of evolution of smart grids into the Internet. The communication infrastructure is an essential component to the implementation of EI. A scalable and permanent communication infrastructure is crucial in both construction and operation of EI. In this paper, we present an introduction and the motivation to the evolution from smart grid to EI. We also introduce a representative EI architecture, i.e., the future renewable electric energy delivery and management system. Four critical EI features are emphasized. Then, we summarize the essential requirements that EI systems have to meet. With several key supporting technologies, EI shall realize the optimal utilization of highly scalable and distributed green energy resources, so that the situation of severe energy source crisis and carbon emission can be efficiently relieved. Since an EI system might have extensively distributed consumers and devices, the guarantee of its reliability and security is extremely significant. The further specific exploration for challenges, including reliability and security, will be stated in this paper.

Abstract Flexible and wearable energy storage devices are expected to provide power support for the burgeoning smart and portable electronics. In particular, textile substrate and wearable technology derived supercapacitors (TWSCs) bear the inherent merits of high flexibility, stretchability, washability and compatibility over the non-textile devices, therefore, attract the excitement for achieving high performance and truly wearable energy storage products. In this review, the fundamental mechanisms of supercapacitor and typical technologies of wearable textiles are presented, with emphasis on the main advantages and progress of TWSCs. In view of the current challenges of TWSCS, we propose the strategies for the performance improvement, with expectation to open new avenues to promote the future development of the flexible and wearable supercapacitors.

The explosive development of Information and Communication Technology (ICT) has significantly enlarged both the energy demands and the CO 2 emissions, and consequently contributes to make the energy crisis and global warming problems worse. However, as the main force of the ICT field, the mobile networks, are currently focusing on the capacity, variety and stability of the communication services, without paying too much severe concerns on the energy efficiency. The escalating energy costs and environmental concerns have already created an urgent need for more energy-efficient "green" wireless communications. In this paper, we survey and discuss various remarkable techniques toward green mobile networks to date, mainly targeting mobile cellular networks. We also summarize the current research projects related to green mobile networks, along with the taxonomy of energy-efficiency metrics. We finally discuss and elaborate future research opportunities and design challenges for green mobile networks.