• Energy Research

AbstractRooftop photovoltaics (RPVs) are crucial in achieving energy transition and climate goals, especially in cities with high building density and substantial energy consumption. Estimating RPV carbon mitigation potential at the city level of an entire large country is challenging given difficulties in assessing rooftop area. Here, using multi-source heterogeneous geospatial data and machine learning regression, we identify a total of 65,962 km2 rooftop area in 2020 for 354 Chinese cities, which represents 4 billion tons of carbon mitigation under ideal assumptions. Considering urban land expansion and power mix transformation, the potential remains at 3-4 billion tons in 2030, when China plans to reach its carbon peak. However, most cities have exploited less than 1% of their potential. We provide analysis of geographical endowment to better support future practice. Our study provides critical insights for targeted RPV development in China and can serve as a foundation for similar work in other countries.

202307 bcww ; Accepted Manuscript ; RGC ; Published ; Green (AAM)

Abstract This paper studies the use of Remote Sensing (RS) technologies and Geographic Information Systems (GIS) for estimation of city-wide photovoltaic (PV) potential in Hong Kong. It investigates the spatial distribution of cloud coverage through geostationary satellites from the Multi-functional Transport Satellite (MTSAT). The results indicate that a non-prominent spatial variation of cloud cover presides over a majority of Hong Kong territories. Appropriate locations for deploying solar PV panels, such as rooftops, were delineated using RS, GIS, and existing ancillary data. Extraction and filtering of pixels based on a set of criterions were used to identify optimal PV rooftops. This study shows that the summarization of PV potentials in Hong Kong is 2.66 TWh on building rooftops. The methodologies and findings from this study permits detailed spatial estimation of city-wide solar energy potential, and assists the policy-decision process on the use of renewable energy in Hong Kong.

Abstract Ridesharing has potential to mitigate traffic emissions. To better support policymaking, this paper endeavors to estimate and analyze emission reductions by large-scale ridesharing combining the Shareability-Network approach, the COPERT III emission model, and a speed-density traffic-flow model. Using Shanghai as a case, we show that ridesharing per se can reduce fuel-consumption (FC) by 22.88% and 15.09% in optimal and realistic scenarios, respectively, with corresponding emissions reductions. Ridesharing’s spontaneous first-order speed effect further reduces FC by 0.34–0.96%. Additionally, spatial analyses show that ridesharing reduces more emissions on severely polluted roads, leading to two spatial patterns; temporal analyses demonstrate patterns shifted from disorganized to organized. Both the phenomena can be explained by the aggregation of trips and the grading and topology of the roads. Moreover, ridesharing may also increase emissions on some branch roads, creating a new environmental injustice, which, however, is estimated to be less significant than expected.

Climate variability has been documented as being key to influencing human wellbeing across cities as it is linked to mortality and illness due to changes in the perceived weather cycle. Many studies have investigated the impact of summer temperature on human health and have proposed mitigation strategies for summer heat waves. However, sub-tropical cities are still experiencing winter temperature variations. Increasing winter perceived temperature through the decades may soon affect city wellbeing, due to a larger temperature change between normal winter days and extreme cold events, which may cause higher health risk due to lack of adaptation and self-preparedness. Therefore, winter perceived temperature should also be considered and integrated in urban sustainable planning. This study has integrated the increasing winter perceived temperature as a factor for developing spatiotemporal protocols for mitigating the adverse impact of climate change. Land surface temperature (LST) derived from satellite images and building data extracted from aerial photographs were used to simulate the adjusted wind chill equivalent temperature (AWCET) particularly for sub-tropical scenarios between 1990 and 2010 of the Kowloon Peninsula, Hong Kong. Compared with perceived temperature based on the representative station located at the headquarters of the Hong Kong Observatory, the temperature of half the study area in the Kowloon Peninsula has raised by 1.5 °C. The areas with less green space and less public open space in 2010 show higher relative temperatures. Socioeconomically deprived areas (e.g., areas with lower median monthly income) may suffer more from this scenario, but not all types of socioeconomic disparities are associated with poor sustainable planning. Based on our results and the “no-one left behind” guideline from the United Nations, climate change mitigation should be conducted by targeting socioeconomic neighborhoods more than just aging communities.

Les objectifs de développement durable (ODD) de l'Agenda 2030 des Nations Unies appellent toutes les nations à agir pour promouvoir la prospérité économique tout en protégeant la planète. La projection du changement futur d'affectation des terres dans le cadre des scénarios des ODD est une nouvelle tentative d'atteindre scientifiquement les ODD. Ici, nous avons proposé quatre hypothèses de scénario basées sur les ODD, y compris l'économie durable (ECO), les céréales durables (GRA), l'environnement durable (env) et les scénarios de référence (REF). Nous avons prévu le changement d'affectation des terres le long de la Route de la soie (résolution : 300 m) et comparé les impacts de l'expansion urbaine et de la conversion des forêts sur les réservoirs de carbone terrestres. Il y avait des différences significatives dans les futurs changements d'affectation des terres et les stocks de carbone, dans le cadre des quatre scénarios des ODD, d'ici 2030. Dans le scénario ENV, la tendance à la diminution des terres forestières a été atténuée et les stocks de carbone forestier en Chine ont augmenté d'environ 0,60 % par rapport à 2020. Dans le scénario GRA, le taux de diminution de la superficie des terres cultivées a ralenti. La superficie cultivée en Asie du Sud et du Sud-Est ne montre qu'une tendance à la hausse dans le scénario GRA, alors qu'elle montre une tendance à la baisse dans d'autres scénarios ODD. Le scénario ECO a montré les pertes de carbone les plus élevées associées à une expansion urbaine accrue. L'étude améliore notre compréhension de la façon dont les ODD peuvent contribuer à atténuer la dégradation environnementale future grâce à des simulations précises qui peuvent être appliquées à l'échelle mondiale. Los Objetivos de Desarrollo Sostenible (ODS) de la Agenda 2030 de las Naciones Unidas exigen la acción de todas las naciones para promover la prosperidad económica al tiempo que protegen el planeta. La proyección del futuro cambio en el uso de la tierra en los escenarios de los ODS es un nuevo intento de alcanzar científicamente los ODS. En este documento, propusimos cuatro supuestos de escenarios basados en los ODS, que incluyen la economía sostenible (eco), el grano sostenible (gra), el medio ambiente sostenible (ENV) y los escenarios de referencia (REF). Previmos el cambio en el uso de la tierra a lo largo de la Ruta de la Seda (resolución: 300 m) y comparamos los impactos de la expansión urbana y la conversión forestal en los reservorios terrestres de carbono. Hubo diferencias significativas en el cambio futuro del uso de la tierra y las reservas de carbono, en los cuatro escenarios de los ODS, para 2030. En el escenario ENV, se mitigó la tendencia a la disminución de las tierras forestales y las reservas forestales de carbono en China aumentaron aproximadamente un 0,60% en comparación con 2020. En el escenario gra, la tasa decreciente de superficie cultivada se ha desacelerado. La superficie cultivada en el sur y sudeste de Asia solo muestra una tendencia creciente en el escenario gra, mientras que muestra una tendencia decreciente en otros escenarios de los ODS. El escenario eco mostró las mayores pérdidas de carbono asociadas con una mayor expansión urbana. El estudio mejora nuestra comprensión de cómo los ODS pueden contribuir a mitigar la degradación ambiental futura a través de simulaciones precisas que se pueden aplicar a escala global. Sustainable development goals (SDGs) in the United Nations 2030 Agenda call for action by all nations to promote economic prosperity while protecting the planet. Projection of future land-use change under SDG scenarios is a new attempt to scientifically achieve the SDGs. Herein, we proposed four scenario assumptions based on the SDGs, including the sustainable economy (ECO), sustainable grain (GRA), sustainable environment (ENV), and reference (REF) scenarios. We forecasted land-use change along the Silk Road (resolution: 300 m) and compared the impacts of urban expansion and forest conversion on terrestrial carbon pools. There were significant differences in future land use change and carbon stocks, under the four SDG scenarios, by 2030. In the ENV scenario, the trend of decreasing forest land was mitigated, and forest carbon stocks in China increased by approximately 0.60% compared to 2020. In the GRA scenario, the decreasing rate of cultivated land area has slowed down. Cultivated land area in South and Southeast Asia only shows an increasing trend in the GRA scenario, while it shows a decreasing trend in other SDG scenarios. The ECO scenario showed highest carbon losses associated with increased urban expansion. The study enhances our understanding of how SDGs can contribute to mitigate future environmental degradation via accurate simulations that can be applied on a global scale. تدعو أهداف التنمية المستدامة في خطة الأمم المتحدة لعام 2030 إلى العمل من قبل جميع الدول لتعزيز الرخاء الاقتصادي مع حماية الكوكب. يعد توقع التغيير المستقبلي في استخدام الأراضي في إطار سيناريوهات أهداف التنمية المستدامة محاولة جديدة لتحقيق أهداف التنمية المستدامة علميًا. هنا، اقترحنا أربعة افتراضات سيناريوهات بناءً على أهداف التنمية المستدامة، بما في ذلك الاقتصاد المستدام (ECO)، والحبوب المستدامة (GRA)، والبيئة المستدامة (ENV)، والسيناريوهات المرجعية (REF). توقعنا تغير استخدام الأراضي على طول طريق الحرير (القرار: 300 م) وقارنا آثار التوسع الحضري وتحويل الغابات على مجمعات الكربون الأرضية. كانت هناك اختلافات كبيرة في التغير المستقبلي في استخدام الأراضي ومخزونات الكربون، في إطار سيناريوهات أهداف التنمية المستدامة الأربعة، بحلول عام 2030. في سيناريو البيئة، تم التخفيف من اتجاه تناقص أراضي الغابات، وزادت مخزونات الكربون في الغابات في الصين بنحو 0.60 ٪ مقارنة بعام 2020. في سيناريو GRA، تباطأ المعدل المتناقص لمساحة الأراضي المزروعة. تُظهر مساحة الأراضي المزروعة في جنوب وجنوب شرق آسيا فقط اتجاهًا متزايدًا في سيناريو تقييم المخاطر العالمية، بينما تُظهر اتجاهًا تناقصيًا في سيناريوهات أهداف التنمية المستدامة الأخرى. أظهر سيناريو منظمة التعاون الاقتصادي أعلى خسائر الكربون المرتبطة بزيادة التوسع الحضري. تعزز الدراسة فهمنا لكيفية مساهمة أهداف التنمية المستدامة في التخفيف من التدهور البيئي في المستقبل من خلال عمليات محاكاة دقيقة يمكن تطبيقها على نطاق عالمي.

As a clean and renewable resource, solar energy is increasingly being used to relieve the pressures on environmental protection and the exhaustion of conventional energy. Although photovoltaic modules have been installed in many cities, the lack of quantitative mapping of the annual solar energy potential of urban surfaces hinders the effective utilization of solar energy. Herein, we provide a solar irradiation estimation solution for three-dimensional (3D) cities to quantify annual irradiations on urban envelopes and to investigate the effect of urban morphology on the resulting solar capacity. By modelling urban surfaces as 3D point clouds, annual irradiations of the point clouds were estimated. An empirical investigation across ten cities suggests that urban areas at lower latitudes tend to have larger values of annual irradiation; moreover, an area having greater building heights consistently has the largest third quartile of irradiation compared with lower buildings in the same city. Conversely, areas with many low buildings have a larger proportion of useable areas; in this arrangement, façades can optimally utilize solar energy, meaning that large irradiations are concentrated on certain façades. The Pearson correlation coefficients between solar capacity and urban morphology indices suggest that urban morphology has an important effect on solar capacity.