Article

Saving Energy and Improving Air Quality in Urban Heat Islands

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Abstract

Temperatures in urban areas have increased because solar energy is more strongly absorbed by additional roofs and pavements. Downtown Los Angles is now 2.5 Kelvin warmer than in the 1930s, which requires 1–1.5 GWe more electricity to cool buildings on summer days, costing an extra $100 million∕year. Cool roof and pavement materials with increased reflectivity of 0.25 can lower surface temperatures by 10 K. If Los Angles urban temperatures could be reduced by 3 K, ozone concentrations could be reduced considerably.

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... Simulations for Los Angeles indicated that thanks to the combined albedo and greening changes, the urban annual saving reached up to $71Million. Analysis of the hourly energy demand showed that cool pavement would save a peak power estimated 100 MW in L.A [87].Through the large-scale application of heat island mitigation strategies, about 20% of national cooling energy demand was estimated to be saved in America. This amounted to a saving of 40 TWh/year, worth over $4 Billion/year in cooling energy saving alone [87]. ...
... Analysis of the hourly energy demand showed that cool pavement would save a peak power estimated 100 MW in L.A [87].Through the large-scale application of heat island mitigation strategies, about 20% of national cooling energy demand was estimated to be saved in America. This amounted to a saving of 40 TWh/year, worth over $4 Billion/year in cooling energy saving alone [87]. Pomerantz et al. estimated the maximum energy saving by increasing the surface albedo of city, as presented in Table 2 [88]. ...
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With the rapid expansion of urbanization around the world, the urban heat island effect embraced an enormous negative impact on megacities, including energy, environment and health conditions. Unfortunately, construc-tive geometry and human activities of megacities severely intensified the urban heat island phenomenon. Giving the contributions of pavement on the deterioration of urban heat island in megacities, this literature review synthesized the state-of-the-art potential strategies of pavement cooling technologies and applications to mitigate the urban heat island effect. Firstly, the optical-thermal balance on surface and the interior thermal behavior of pavement were comprehensively analyzed. Afterwards, this paper redefined the cool pavement technologies as the passive mitigation strategies, involved the application of reflective pavement, evaporation pavement, heat- induced pavement and phase change materials. Especially, urban canyon impact and urban design were emphasized, which tended to be neglected on the implementations of cool pavement. In addition, the solar collector technologies on the pavement were proposed to sustainably reuse solar energy, acting as active stra-tegies and renewable sources. Typically, representatives of solar collectors, including heat collection and ther-moelectric pavement, were described and investigated. Existing research results presented the promising potential of pavement cooling technologies to mitigate the urban heat island impact and renewable energy sustainability. Moreover, prospects were also summarized to show the opportunities and avenues for future study.
... Mitigasi pada LCZ Tipe E, untuk kawasan Bandar Udara Ahmad Yani dapat dilakukan greening parking lots dan vegetation around building, sedangkan untuk jalan beraspal dapat dilakukan high-albedo pavement. Peningkatan nilai albedo akan menghasilkan banyak radiasi yang dipantulkan, sebaliknya jika radiasi banyak yang diserap maka akan menghasilkan pemanasan udara dan peningkatan suhu (Akbari, 2008). ...
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Urbanization in Indonesia has continued to increase starting in 2011. The increasing population impacted the conversion of agricultural land to non-agricultural land. Reduction in the proportion of green open space results in changes in the spatial pattern of the area which affects the increase in urban temperatures, thus triggering the occurrence of UHI. This study aims to determine the spatial distribution of LST and LCZ in Semarang City by using quantitative descriptive analysis. Semarang City has LST variation values between 24.72ºC to 32.56ºC. Semarang City has 13 types of LCZ, consisting of 6 LCZs based on building types and 7 LCZs based on land cover. LCZ type B is the largest LCZ which reaches 58.52 km² or 15.12% of the total area. The highest LST is LCZ type E, reaching 32.10 °C which displays rock landscapes or asphalt cover. The lowest value is LCZ type G, reaching 25.09°C, which is an open water body such as reservoirs and ponds. Climate-based urban planning can be carried out in the LCZ area which has a high temperature by observing and mitigating it through the constituent components of each LCZ.
... C. Korelasi Antara Perubahan Penutupan Lahan Dengan Kenaikan Suhu Permukaan Serta Kaitannya Dengan Urban Heat Island di Kota Pontianak Akbari (2008) menyatakan bahwa radiasi surya yang sampai di permukaan akan mengalami pemantulan dan penyerapan radiasi. Semua jenis tutupan lahan memiliki nilai albedo. ...
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ABSTRAK Salah satu penyebab perubahan penutupan lahan adalah semakin bertambahnya jumlah penduduk. Sementara luas Kota Pontianak tidak bertambah, perkembangan pusat perdagangan, industri, permukiman dan pertambahan jumlah kendaraan bermotor akan mengubah pola penutupan lahan dan berbagai sarana dan prasarana fisik sebagai penunjang aktivitas penduduk kota. Perubahan fisik yang dilakukan di sisi lain menimbulkan dampak negatif diantaranya adalah meningkatnya suhu permukaan. Deteksi perubahan penutupan lahan mencakup penggunaan citra penginderaan jauh di wilayah tertentu dan dari data tersebut perubahan penutupan lahan serta peningkatan suhu permukaan untuk setiap waktu dapat dipetakan dan dibandingkan.Tujuan dari penelitian ini adalah untuk mengetahui korelasi antara perubahan penutupan lahan dengan perubahan sebaran suhu permukaan, dan menganalisis kaitannya dengan urban heat island. Penelitian ini menerapkan teknologi penginderaan jauh dan Sistem Informasi Geografis. Data yang tersedia dapat berupa piktoral maupun digital kemudian diolah untuk mendapatkan informasi yang diperlukan. Informasi yang diperoleh dapat digabungkan dengan data-data yang mendukung ke dalam satu Sistem Informasi Geografis. Berdasarkan hasil interpretasi dan analisis citra landsat 5 TM pada tahun 2000 dan citra landsat 7 ETM tahun 2010 didapatkan bahwa terjadi perubahan penutupan lahan dari lahan yang bervegetasi menjadi lahan yang tidak bervegetasi, Perubahan penutupan lahan tersebut berpengaruh terhadap peningkatan suhu permukaan dan penurunan kelembaban. Distribusi suhu permukaan di Kota Pontianak pada tahun 2000 berdasarkan estimasi band 6 pada citra landsat 5 TM mempunyai nilai suhu antara <20,00 0C – 31,99 0C. Nilai suhu dengan luasan distribusi terbesar adalah suhu dengan rentang 24,00 0C – 24,99 0C yang terdistribusi di seluruh wilayah Kota Pontianak. Sedangkan distribusi suhu permukaan di Kota Pontianak pada tahun 2010 berdasarkan band 6 pada citra landsat 7 ETM mempunyai nilai suhu antara 20,00 0C - ≥ 34,00 0C. Nilai suhu dengan luasan distribusi terbesar adalah suhu ≥34,00 0C yang terdistribusi di seluruh wilayah Kota Pontianak. Nilai suhu ini cukup tinggi sehingga memunculkan fenomena Urban Heat Island. Kata Kunci : penginderaan jauh, suhu permukaan, urban heat island.
... Mohan et al. (2012) explain that UHI occurs in urban areas with infrastructures and commercial centres. According to Akbari (2008), an urban centre's high air temperature is due to the strong absorption of radiation by roofs and pavements. High air temperature occurs, also, during the summer months in large international cities such as London, Los Angeles, China, and in large Indonesian cities such as DKI Jakarta, Surabaya, Semarang, and Bandung. ...
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Urban Heat Island (UHI) is a phenomenon exhibited by many worldwide cities. Cities, which exhibit UHI, possess higher air temperature as compared with air temperature in the surrounding areas. However, existing UHI profiles are those occurring in subtropical areas which are, of course, very much different from those in tropical cities. Therefore, the objectives of this study are to describe the UHI’s profile and the role of tree vegetation in controlling and reducing air temperature in a tropical region’s urban areas and, particularly, in DKI Jakarta. In this study, we carried out a spatial analysis of land cover and the distribution of air temperature. In this regard, we based our analysis of the potency of tree vegetation in reducing air temperature in UHI’s profile on the distribution of air temperature in various types of land cover which extended from north to south and from east to west. The ranges of air temperature in land cover in the form of built-up areas were 29.2-39.5 ⁰C, non-tree vegetation 28.6-35.6 ⁰C, and tree vegetation 27.0-35.7 ⁰C. Accordingly, tree vegetation has the highest potential to reduce air temperature and to overcome the phenomenon of UHI.
... Hal ini harus diantisipasi karena dapat menyebabkan peningkatan suhu udara dan penurunan kenyamanan. Akbari (2008) menyatakan bahwa radiasi surya yang sampai per mukaan akan mengalami pemantulan dan penyerapan radiasi. Semua jenis tutupan lahan memiliki nilai albedo. ...
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... Based on the Rushayati et al. [6] research which uses dynamic system models, it is known that the percentage of high temperatures are in the area I which is the northern part of Bandung Regency region dominated by built area. Similarly, Akbari [7] research in the United States, shows that during the day in summer, the air temperature in the city could reach 2.5 Kelvin (K) as in urban land cover is dominated by built area and the streets, compared with the surrounding area. ...
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The large scale implementation of high-albedo building materials and urban surfaces and the reforestation of low vegetation urban areas are being encouraged as energy-saving measures. These strategies will result in modification of the physical properties of millions of buildings (e.g., roof reflectance) and their microclimates (e.g., shading, wind, and evapotranspiration effects of trees). This paper is about the atmospheric impacts of regional scale changes in building properties, paved-surface characteristics, and their microclimates. It discusses the possible meteorological and ozone air quality impacts of increases in surface albedo and urban trees in California's South Coast Air Basin (SoCAB). The photochemical model simulations of a late August period indicate that implementing high-albedo materials in the SoCAB would have a net effect of reducing ozone concentrations. Domain-wide population-weighted exceedance exposure to ozone above the California Ambient Air Quality Standard would be decreased by up to 12% during peak afternoon hours. With respect to the National Standard, exceedance exposure would be reduced by up to 17%. The simulations also indicate that the net effect of increased urban vegetation is a decrease in ozone concentrations if the additional vegetation (trees) are low emitters of biogenic hydrocarbons. With respect to the California standard, domain-wide population-weighted exceedance exposure to ozone above this threshold would be decreased by up to 14% during peak afternoon hours. With respect to the National Standard, the reduction would be up to 22%. In terms of total daytime exposure, these strategies can decrease exceedance exposure by up to 12% with respect to the California Standard and up to 20% with respect to the National Standard. Comparing the simulated air quality impacts of increased albedo and vegetation cover with the impacts of other strategies reveals that they are of the same order of magnitude. For instance, the simulations for this episode, using updated 1987 emission inventories for the SoCAB, indicate that the air quality benefits of albedo and vegetation increase strategies are comparable to those of converting at least 50% of the mobile sources operating in 1987 in the SoCAB to zero emitting vehicles (these findings are for ozone reductions only; removing or converting motor vehicles has several other advantages as well). At this time, this comparison is preliminary as there are uncertainties in the modeling system and emission inventories. In particular, mobile source emissions may be underestimated by as much as two-fold. These findings will be updated when other episodes are modeled and more representative emission inventories become available.
Article
Large-scale tree planting programs have been proposed, and are being implemented, as a means of reducing energy demand, mitigating urban heat islands, and improving air quality. However, many species of trees emit highly photochemically reactive hydrocarbons and the rates of such emissions can vary by four orders of magnitude, depending upon the tree species. Thus, planting of high-emitting trees species on a massive scale has the potential to adversely affect air quality rather than leading to improvement. However, the selection of low-emitting trees is difficult because emission rates have been experimentally determined for only a limited number of species. The present study describes a methodology for assigning biogenic emission rates based on taxonomic relationships. Using this methodology, direct emission measurements from 124 tree and shrub species found in the California South Coast Air Basin (SoCAB) are used to assign emission rates to 253 other species found in the SoCAB but for which there are no measured emission rates. The combined listing of 377 species is ranked according to total (isoprene and monoterpenes) biogenic emission rate on an hourly basis. Although the ranking of trees developed here is specific to Southern California, the methodology described can be applied to other geographic areas to assist in the planting of low-emitting urban forests.