Future Cities and Environment

The question of density is closely connected to urbanization and how our cities may evolve in the future. Density and compactness are two closely related but different criteria, both relevant for sustainable urban development and the transformation of cities; however, their relationship is not always well understood. While a high degree of compactness is desirable, too much density can be detrimental to liveability, health and urban well-being. The purpose of this article is to report first on an extreme case of hyper-density: the Kowloon Walled City (demolished in 1993), where 50,000 residents led a grim life in one of the most densely populated precincts in the world with intolerable sanitary conditions. While the Walled City was a truly mixed-use and extremely compact precinct, it was neither a ‘liveable neighbourhood’ nor sustainable. The article then explores some more recent cases of optimized quality density in developments in Singapore, Sydney and Vancouver. This article sets out to answer the question: Since density is key to sustainable urbanism, what are the drivers and different planning approaches in relation to establishing an optimal density? And what is the ideal density model for tomorrow’s sustainable cities? Some of the critical thinking around the high-density cases is replicable and could translate to other cities to inform new approaches to quality density. Medium to high-density living is acceptable to residents as long as these developments also provide at the same time an increase in quality green spaces close by. The article explores which density types could help us to create highly liveable, economically vibrant, mixed-use and resilient neighbourhoods of the future. It concludes that every development requires a careful optimization process adapted to the conditions of each site.

Năng lượng là yếu tố không thể thiếu cho mọi hoạt động của con người. Giao thông, sản xuất công nghiệp, thương mại, truyền thông, v.v. phụ thuộc vào khả năng cung cấp năng lượng. Truyền thống, người tiêu dùng đáp ứng nhu cầu năng lượng của họ bằng cách mua điện và nhiên liệu từ các công ty phân phối. Đối với việc sản xuất năng lượng điện mà người tiêu dùng tiêu thụ, một phần lớn được sản xuất tại các nhà máy nhiệt điện truyền thống. Tại các nhà máy điện hiện đại, tổng thiệt hại trong năng lượng có thể lên tới 52,5% mà không có bất kỳ hình thức hồi phục nào. Năng lượng nhiệt được thu được từ nhiên liệu mà người tiêu dùng đã mua trong các hệ thống đốt với hiệu suất trung bình tối đa, tốt nhất, khoảng 90% (10% bị mất). Đối mặt với vấn đề này, yêu cầu nâng cao hiệu suất của quá trình sản xuất điện và tạo ra nhiệt để giảm chi phí tài chính và môi trường đặt ra. Do đó, như một sự thay thế cho các nhà máy điện truyền thống lớn, việc sản xuất điện phân tán xuất hiện, đặc biệt là đồng phát điện (cogeneration), nhằm khai thác các hạn chế vốn có của việc chuyển đổi nhiệt thành công việc. CHP (Nhiệt điện kết hợp) là một quy trình kết hợp sản xuất và khai thác năng lượng nhiệt và điện, trong một hệ thống tích hợp, từ cùng một nguồn sơ cấp. Mặc dù không phải là công nghệ mới nhưng các ứng dụng của nó chủ yếu được sử dụng trong ngành công nghiệp. Các hệ thống như vậy cũng góp phần giảm lượng phát thải CO2 ra môi trường. Mục tiêu của nghiên cứu này là phân tích tiềm năng kỹ thuật và kinh tế của một tình huống thực tế tại một khách sạn nhỏ nằm ở thành phố Portugal. Thay vì chỉ sử dụng CHP, nhiệt sinh ra cũng được sử dụng cho quá trình làm mát - CHCP (Nhiệt, làm lạnh và điện kết hợp). Để làm điều đó, ngoài phân tích năng lượng được thực hiện, còn thực hiện một phân tích kinh tế chi tiết nhằm đánh giá tính khả thi và rủi ro liên quan đến các tham số chính cần xem xét, cụ thể là NPV (Giá trị hiện tại ròng), IRR (Tỷ suất hoàn vốn nội bộ), Thời gian hoàn vốn và PES (Tiết kiệm năng lượng sơ cấp) cũng như lượng phát thải bị trì hoãn (AE) của CO2. Các kết luận chính thu được là CHCP góp phần vào PES là 57 tep/năm, AE là 68 teq CO2/năm. Thời gian hoàn vốn là 3,6 năm.

Urban and building energy simulation models are usually driven by typical meteorological year (TMY) weather data often in a TMY2 or EPW format. However, the locations where these historical datasets were collected (usually airports) generally do not represent the local, site specific micro-climates that cities develop. In this paper, a humid sub-tropical climate context has been considered. An idealised “urban unit model” of 250 m radius is being presented as a method of adapting commonly available weather data files to the local micro-climate. This idealised “urban unit model” is based on the main thermal and morphological characteristics of nine sites with residential/institutional (university) use in Hangzhou, China. The area of the urban unit was determined by the region of influence on the air temperature signal at the centre of the unit. Air temperature and relative humidity were monitored and the characteristics of the surroundings assessed (eg green-space, blue-space, built form). The “urban unit model” was then implemented into micro-climatic simulations using a Computational Fluid Dynamics – Surface Energy Balance analysis tool (ENVI-met, Version 4). The “urban unit model” approach used here in the simulations delivered results with performance evaluation indices comparable to previously published work (for air temperature; RMSE <1, index of agreement d > 0.9). The micro-climatic simulation results were then used to adapt the air temperature and relative humidity of the TMY file for Hangzhou to represent the local, site specific morphology under three different weather forcing cases, (ie cloudy/rainy weather (Group 1), clear sky, average weather conditions (Group 2) and clear sky, hot weather (Group 3)). Following model validation, two scenarios (domestic and non-domestic building use) were developed to assess building heating and cooling loads against the business as usual case of using typical meteorological year data files. The final “urban weather projections” obtained from the simulations with the “urban unit model” were used to compare the degree days amongst the reference TMY file, the TMY file with a bulk UHI offset and the TMY file adapted for the site-specific micro-climate (TMY-UWP). The comparison shows that Heating Degree Days (HDD) of the TMY file (1598 days) decreased by 6 % in the “TMY + UHI” case and 13 % in the “TMY-UWP” case showing that the local specific micro-climate is attributed with an additional 7 % (ie from 6 to 13 %) reduction in relation to the bulk UHI effect in the city. The Cooling Degree Days (CDD) from the “TMY + UHI” file are 17 % more than the reference TMY (207 days) and the use of the “TMY-UWP” file results to an additional 14 % increase in comparison with the “TMY + UHI” file (ie from 17 to 31 %). This difference between the TMY-UWP and the TMY + UHI files is a reflection of the thermal characteristics of the specific urban morphology of the studied sites compared to the wider city. A dynamic thermal simulation tool (TRNSYS) was used to calculate the heating and cooling load demand change in a domestic and a non-domestic building scenario. The heating and cooling loads calculated with the adapted TMY-UWP file show that in both scenarios there is an increase by approximately 20 % of the cooling load and a 20 % decrease of the heating load. If typical COP values for a reversible air-conditioning system are 2.0 for heating and 3.5 for cooling then the total electricity consumption estimated with the use of the “urbanised” TMY-UWP file will be decreased by 11 % in comparison with the “business as usual” (ie reference TMY) case. Overall, it was found that the proposed method is appropriate for urban and building energy performance simulations in humid sub-tropical climate cities such as Hangzhou, addressing some of the shortfalls of current simulation weather data sets such as the TMY.

This paper endeavours to understand the climate change phenomenon and identify measures taken to contain it. It discusses global warming causes and consequences and assesses effectiveness of the United Nations (UN) polices following failure of the Kyoto Protocol to reduce greenhouse gas emissions. In pursuing this course of action, this paper utilizes data collected from East Africa region. Key issues discussed in the paper include findings of the Intergovernmental Panel on Climate Change and the role of urbanization in global warming as cities emit most of greenhouse gases. Special reference is made to developing cities which are growing extremely fast and will consume more energy in future. They are becoming economic engines and adopting industrialization as an economic model while developed cities are experiencing de-industrialization. Developing cities have neither the ability to adopt green technology nor the capacity to establish large capacity public transport systems to reduce carbon dioxide (CO2) emissions. It is evident that UN efforts to combat climate change are not effective because past experience shows that CO2 generation cuts weren’t near enough. The recent Paris Agreement may restore a faith in UN process if implemented but doesn’t reduce temperatures as needed unless all drivers of climate variability are considered, particularly the abortive role of developing cities. The UN Programme appears to be focusing on attaining urban resilience rather than targeting grassroots causes. Urbane-bias global policies drive the rural population to leave their land and flood cities while over-usage of natural resources by the rich is left unchecked. A new UN strategy making the countryside a more appealing place to live in and work whilst normalising urban growth is needed as well as mobilizing local leaders who enjoy more autonomy to enact regulations. It should also alleviate poverty, deter excessive practices and put science and technology under community control.

This study explored the effect on photocatalytic degradation in aqueous solution with high- concentration ammonia where immobilized TiO2 on glass beads was employed as the photocatalyst. TiO2 film was prepared via deep coating TiO2 in a sol–gel system of tetrabutyl titanate precursor and calcinating it at the temperature between 400 to 650 °C. Several crucial factors affecting on the rate of removal of ammonia were investigated. These factors included annealing temperature, catalyst composition, coated times of TiO2 film, aqueous initial pH, UV exposure time, repetitions times, etc. The results validate the effectiveness as TiO2 glass beads was employed for photocatalytic degradation treatment in high concentration ammonia solutions.

Monthly-averaged daily global irradiation data are now easily available from NASA website for any global location. Using established models it is then possible to decompose the daily to averaged-hourly global irradiation. The missing link so far has been hourly averaged diffuse irradiation. In this article data was pooled from 14 world-wide locations to obtain a regression model to complete the above missing link. It was presently shown that the averaged–data regressions are distinctly different from previously available hour-by-hour regressions.

More than half of the world’s population currently lives in cities. An essential constituent of future sustainable cities is energy efficient and ecologically sound buildings which ensure high levels of comfort and convenience without reducing the standards of living. At present, a significant part of primary fossil fuels is spent for heating/cooling of buildings, thus, greatly contributing to total GHG emissions. In this paper, typical heat losses in dwellings are considered taking the United Kingdom and the Russian Federation as examples. The role of adsorption-based technologies for more rational use of heat in buildings is discussed. Fundamentals of inter-seasonal adsorptive heat storage (AHS) are briefly considered. A tentative upper limit of the AHS storage density is estimated. Current practice of inter-seasonal AHS and novel smart adsorbents promising for this emerging technology are overviewed. Since a portion of the heat losses in ventilation system significantly increases in modern buildings, a new approach to regenerating heat and moisture in this system is discussed. Finally, optimization trends of the AHS in buildings are briefly considered.