Future Cities and Environment

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.

As one of the most energy-, emission- and pollution-intensive industries, iron and steel production is responsible for significant emissions of greenhouse gas (GHG) and air pollutants. Although many energy-efficiency measures have been proposed by the Chinese government to mitigate GHG emissions and to improve air quality, lacking full understanding of the costs and benefits has created barriers against implementing these measures widely. This paper sets out to advance the understanding by addressing the knowledge gap in costs, benefits, and cost-effectiveness of energy-efficiency measures in iron and steel production. Specifically, we build a new evaluation framework to quantify energy benefits and environmental benefits (i.e., CO2 emission reduction, air-pollutants emission reduction and water savings) associated with 36 energy-efficiency measures. Results show that inclusion of benefits from CO2 and air-pollutants emission reduction affects the cost-effectiveness of energy-efficiency measures significantly, while impacts from water-savings benefits are moderate but notable when compared to the effects by considering energy benefits alone. The new information resulted from this study should be used to augment future programs and efforts in reducing energy use and environmental impacts associated with steel production.

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.

Building energy evaluation tools available today are only able to effectively analyse individual buildings and usually either they require a high amount of input data or they are too imprecise in energy predictions at a city (district) scale because of too many assumptions made. In this paper, two tools based on 3D models are compared to see whether there is an approach that would probably be able to fit both – the amount of data available and the number of assumptions made. A case study in the German town of Essen was chosen in the framework of the research project WeBest, where six building types representing the most important building periods were analysed. The urban simulation tool SimStadt, an in-house development of HFT Stuttgart, based on 3D urban geometry, is used to calculate the heat demand for both single building scale and city district scale. The individual building typology results are compared with the commercial dynamic building simulation software TRNSYS. The influence of the availability and quality of data input regarding the geometrical building parameters on the accuracy of simulation models are analysed. Different Levels of Details (LoDs) of the 3D building models are tested to prove the scalability of SimStadt from single buildings to city districts without loss of quality and accuracy in larger areas with a short computational time.

The planned energy-efficient retrofitting of a residential building in Bologna, North-Center Italy is presented. The building is a detached house with an unheated basement, three floors with 2 apartments each, and an unheated attic. The total heated floor area is 281.9 m2. The external wall is made of solid brick masonry and most windows are single glazed; no thermal insulation is present. Space heating is supplied by a gas boiler and radiators in the rooms. DHW is supplied by single-apartment electric boilers in 5 apartments and by a gas boiler in one apartment. Lighting is obtained by incandescent lamps. The proposed retrofitting includes: external thermal insulation of the vertical walls by calcium silicate hydrates and loft insulation by mineral wool; replacement of windows; installation of a multifunction air-to-water heat pump for heating, cooling and DHW; replacement of the radiators by new heat exchangers; LED lighting; installation of PV panels. The building has been simulated by TRNSYS 17, and the heat pump has been simulated by own MATLAB codes. The retrofitting will reduce the total annual use of primary energy (excluding appliances) from 332.5 to 44.8 kWh/m2, and will yield an important improvement of thermal comfort.

Solar panel conversion efficiency, typically in the twenty percent range, is reduced by dust, grime, pollen, and other particulates that accumulate on the solar panel. Cleaning dirty panels to maintain peak efficiency, which is especially hard to do for large solar-panel arrays. To develop a transparent, anti-soiling Nano-TiO2 coating to minimize the need for occasional cleaning is the purpose of this study. In our study, a 2D rainwater runoff model along tilted solar panel surface based on the Nusselt solution was established to have better understanding and predicting the behavior of runoff rain water, especially in contact with solar-panel surfaces with Nano-TiO2 coating. Our simulation results demonstrate that solar-panel surfaces with Nano-TiO2 coating create a superhydrophilic surface which cannot hold water, showing features of more pronounced in increasing runoff water film velocity comparing to the uncoated surfaces during raining event resulting in better effect of self-cleaning. Validation of our model was performed on titled solar panels for real time outdoor exposure testing in Switzerland. It is found that the dust particles are not easy to adhere to the coated surfaces of the slides comparing with uncoated surfaces, showing great potential for its use in harsh environmental conditions. This study suggests that superhydrophilic self-cleaning solar panel coating maximize energy collection and increases the solar panel’s energy efficiency.

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.

India is known to emit large amounts of black carbon (BC) particles, and the existing estimates of the BC emission from the transport sector in the country widely range from 72 ~ 456 Gg/year (for the 2000’s). First, we reduce the uncertainty range by constraining the existing estimates by credible isotope analysis results. The revised estimate is from 74 ~ 254 Gg/year. Second, we derive our own BC estimate of the transport section in order to gain a new insight into the mitigation strategy and value. Our estimate shows that the transport section BC emission would be reduced by about 69 % by adopting the US standards. The highest emission reduction comes from the vehicles in the 5–10 year old age group. The minimum emission reduction would be achieved from the vehicles in the 15–20 year old age category since their population is comparatively small in comparison to other age categories. The 69 % of 74 ~ 254 Gg/year is 51 ~ 175 Gg/year, which is the estimated BC emission reduction by switching to the US on-road emission standard. Assuming that global BC radiative forcing is 0.88 Wm−2 for 17.8 Tg/year of BC emission, we find that the reduced BC emission translates into −0.0025 ~ −0.0087 W m−2 in global forcing. In addition, we find that 51 ~ 175 Gg of BC emission reduction amounts to 0.046 – 0.159 B carbon credits which are valued at 0.56 – 1.92 B US dollars (using today’s carbon credit price). In a nutshell, India could potentially earn billions of dollars per year by switching from the current on-road emission levels to the US levels.

The building sector accounts for around 40-50 % of the energy consumed in developing countries and contribute over 30 % of CO2 emissions. In Cameroon, the electricity access is less than 5 % in rural areas against 50 % in urban areas. All sectors combined the Cameroonian final energy consumption amounts to approximately 5235 kilo-tonnes of oil equivalent (Ktoe) and 73 % of this energy are assigned for residential use. This energy can be considerably reduced with the development of low energy buildings using Building Integrated Photovoltaic (BIPV), since it has been proven an effective solution to achieve significant energy savings and conservation. However, photovoltaic (PV) panels produce a substantial amount of heat, while generating power. Consequently, BIPV’s concept, where the photovoltaic (PV) panel is integrated on the building envelops has significant influence on the amount of heat transfer through the building fabrics, and could affect the indoor air temperatures and the comfort of the occupants, since, it changes the thermal resistance of the building envelops. In this paper, the effect of the BIPV on the indoor air temperatures and humidity (IATH) of a multiple storey buildings under the tropical climatic conditions of Yaoundé, Cameroon has been modelled and analysed. Two cases of BIPV made of 290 m2 area of PV have been considered, i) roof integrated and ii) façade integrated. In addition, building orientation, roof pitch and the building materials are also been explored and optimised to provide the best combination. It has been observed that for both cases, BIPV increases the building’s indoor air temperature by about 4 °C, when compare to a building of the same size without PV integrated.