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Gas production from an offshore hydrate-bearing sediment (HBS) by depressurization will reduce the strength of cementation and increase the effective stress of hydrate reservoirs, which can result ...

Since the utilization of renewable energy is crucial to achieve carbon neutrality, the global installation of photovoltaic (PV) devices has been growing exponentially in the past decade. As outdoor devices, PV will interact with the ambient environment, leading to impacts on power generation efficiency, system structure safety, and the surrounding microclimate. To investigate the various interactions between PV and its ambient environment, simulation with Computational Fluid Dynamics (CFD) is a frequently employed approach. Given the rapid increase of studies using CFD to investigate PV-environment interactions, this study provides a comprehensive review of the research reported in journal publications on this topic within the last decade, aiming to answer two questions: (1) Which interactions can be simulated using CFD? (2) How to simulate those interactions using CFD? A total of 69 studies were surveyed and they were categorized into six research subjects based on various interactions. According to the results, most studies applied CFD for simulations regarding PV thermal characteristics, PV cooling, and dust deposition & mitigation, whereas less were for investigating airflow & ventilation, wind loading, and microclimate. Practices of CFD setups were summarized for different steps of a simulation procedure. It was found that component scale, PV module geometry, three-dimensional modelling, Reynolds-averaged Navier-Stokes type, and SST k-ω turbulence model are generally favoured in simulations. Future research may focus on developing simplified models, boundary conditions, and parameterization methods for simulations in urban-scale and involving more complex physical phenomena.

Abstract Driven by wind and buoyancy effects in the urban environment, ventilation performance and pollutant transmission are highly related to human health. In order to investigate characteristics of the single-sided natural ventilation and interunit dispersion problem, this study conducted scaled outdoor experiments in summer and winter periods in two-dimensional street canyons. Tracer gas method was adopted to predict the ventilation rate and simulate the pollutant dispersion. It was found the ventilation performance of windward and leeward rooms showed different trends with wind velocities. Archimedes number Ar was used to examine the interactions of the buoyancy and the wind forces. It revealed that the non-dimensional ventilation rates of all rooms were generally smaller than the results of buoyancy effect only. It indicates that interactions between the buoyancy and wind effects were destructive, which reduced the ventilation rates. The interunit dispersion characteristics with the wind effect were highly dependent on source locations. The results of the tracer gas concentrations of the reentered rooms were not showing simple increasing or decreasing trends. This study provides authentic and instant airflow and pollutant dispersion information in an urban environment. The dataset of this experiment can offer validations for further numerical simulations.

202306 bcww ; Not applicable ; RGC ; Published ; 24 months

Abstract Wind pressures on buildings with different aspect ratios were investigated via higher-order dynamic mode decomposition (HODMD) in this study. Taken’s embedding theorem was used to augment the spatial dimensionality of the original snapshot matrix by introducing time delay coordinates. HODMD was applied to reveal the spatial-temporal evolution characteristics of fluctuating wind pressures on building surfaces. It was found that HODMD can successfully extract the modes and corresponding frequencies from the random pressure field. As the aspect ratio increases, the main mode is more dominant than other modes. Moreover, comparisons between HODMD and proper orthogonal decomposition (POD) suggests that the first-order mode shapes extracted by HODMD and POD are generally similar, and both can reflect the main characteristics of the fluctuating pressure field. However, the higher-order mode shapes extracted by HODMD and POD are different due to higher-order nonlinearities. The modes of HODMD oscillate at a fixed frequency while those of POD resemble random signals, indicating the physical meaning of HODMD is more evident. Furthermore, HODMD is proven to be superior to POD in reconstructing pressure fields with less root mean square errors, because HODMD reconstructs the pressure field directly while POD primarily aims to rebuild the energy field.

Valorisation of food waste offers an economical and environmental opportunity, which can reduce the problems of its conventional disposal. Food waste is commonly disposed of in landfills or incinerated, causing many environmental, social, and economic issues. Large amounts of food waste are produced in the food supply chain of agriculture: production, post-harvest, distribution (transport), processing, and consumption. Food waste can be valorised into a range of products, including biofertilisers, bioplastics, biofuels, chemicals, and nutraceuticals. Conversion of food waste into these products can reduce the demand of fossil-derived products, which have historically contributed to large amounts of pollution. The variety of food chain suppliers offers a wide range of feedstocks that can be physically, chemically, or biologically altered to form an array of biofertilisers and soil amendments. Composting and anaerobic digestion are the main large-scale conversion methods used today to valorise food waste products to biofertilisers and soil amendments. However, emerging conversion methods such as dehydration, biochar production, and chemical hydrolysis have promising characteristics, which can be utilised in agriculture as well as for soil remediation. Valorising food waste into biofertilisers and soil amendments has great potential to combat land degradation in agricultural areas. Biofertilisers are rich in nutrients that can reduce the dependability of using conventional mineral fertilisers. Food waste products, unlike mineral fertilisers, can also be used as soil amendments to improve productivity. These characteristics of food wastes assist in the remediation of contaminated soils. This paper reviews the volume of food waste within the food chain and types of food waste feedstocks that can be valorised into various products, including the conversion methods. Unintended consequences of the utilisation of food waste as biofertilisers and soil-amendment products resulting from their relatively low concentrations of trace element nutrients and presence of potentially toxic elements are also evaluated.

Abstract A new model of photovoltaic (PV) panel is proposed. The model precisely replicates sub-cell level degradation, such as cracks and interconnect failures, and reproduces their effect at the panel level I–V characteristic. Moreover, a regression method is proposed, which infers the model’s parameters from combination of electroluminescent (EL) image and degraded I–V characteristic. The combination of quantitative (EL image) and qualitative (I–V characteristic) enables to characterize the degradation of the cells embedded in the PV panel, without physical access to the cells. The proposed model and the regression problem is experimentally verified on a set of 3 single cell measurements and a set of 4 crystalline PV panels with various levels of degradation.

202303 bcww ; Not applicable ; Others ; Research Institute for Sustainable Urban Development (RISUD); Hong Kong Polytechnic University ; Published ; 24 months

Abstract The relationship between urban form and building energy use has received increasing attention in recent literature. However, findings from existing studies are diverse and sometimes contradictory, and this issue has not been extensively discussed in previous reviews. This paper provides a systematic review of studies on the relationship between urban form and building energy use based on the proposed classification framework. The classification framework categorizes existing studies by their measure definitions, mechanism assumptions, and methodologies. Aside from these conceptual differences, the differences in site contexts of the selected cases are also reviewed. On the basis of the review results, this paper summarizes the consideration of mechanisms by pathway maps and provides an updated understanding of the three main debates in this field. These debates concern the magnitude of influence, impact of densification, and preference of typology. This review also reveals many challenges in this field, including the limited measures of urban form and building energy use, lack of understanding of pathway contributions, and uncertainty and validity issues of tools and models. In addition, future research directions are provided to inform urban planning and policy making decisions for sustainable urban development.