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The offshore wells are subject to hostile environments of such areas as the North Sea, GOM and the high arctic. The strong loop ocean currents and induced eddies can pose significant problems for deep-water well. Broadly divided ocean currents, surface currents, bottom currents and vertical currents, interact with the deep water well structures as one of environmental forces. One of the engineering challenges in deep water drilling is temperature gradient. In the past the temperature in the wellbore was ignored and an isothermal system was assumed because no practical means existed to determine the well bore temperature profile. But the fact is that the negative thermal gradient exists between surface to seafloor and it becomes positive below the seafloor. The extreme values could be as low as 40°F and as high as 150∼200°F. In addition to low temperature condition, the significant heat exchange also occurs for high temperature and geothermal reservoirs. The universal matrix form of implicit finite differential equations is introduced to predict the temperature profile of the fluid in the well and near-wellbore formation. This paper is to combine various factors together to derive a solver for the transient temperature modeling during the dirculation of riserless drilling, which can be the basis to describe the near-wellbore well stability under geo-thermal stress and predict the annular pressure during HPHT injection or production, which can also be used to including but not limited to the dynamic temperature profile and bottom-hole temperature, improving cementing program design, casing thermal stresses to be determined.

Abstract The present study is aimed to investigate and compare effects of biodiesel-ethanol (BE) and biodiesel-n-butanol (BBu) blends on combustion, performance and emissions of a direct-injection diesel engine. Experiments were conducted on BE5 (5% ethanol and 95% biodiesel, v/v), BE10, BE15, BBu5, BBu10 and BBu15, at five engine loads and at 1800 rpm. In regard to combustion characteristics, effects on maximum heat release rate, maximum in-cylinder pressure, start of combustion, combustion duration and coefficients of variations (COVs) of IMEP and maximum increase rate of in-cylinder pressure were investigated. In regard to engine performance, effects on BSFC and BTE were investigated. The blended fuels have adverse effects on engine performance especially at low load, with the BE blends having more adverse effects than the BBu blends. Moreover, on average of the five engine loads, the BBu and BE blends increase CO emission by 13.7% and 22.8% and HC emission by 5.6% and 29.2%, respectively; but reduce NOx emission by 6.5% and 28.0%, particle mass concentration by 20.7% and 20.6% and particle number concentration by 22% and 21%, respectively. Overall, the BE blends are more effective in reducing particulate and NOx emissions but the BBu blends would lead to less increase in CO and HC emissions.

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.

Abstract Renewable energy utilisation, latent energy storage, optimal system design, and robust system operation are critical elements for carbon-free buildings and communities. Machine learning methods are effective to assist the energy-efficient renewable systems during multi-criteria design and multi-level uncertainty-based operation periods. However, the current literature provides little knowledge on this topic. In this study, a state-of-the-art-review on phase change materials for cooling applications is presented, in terms of smart ventilations, intelligent PCMs charging/discharging, deterministic parametrical analysis, stochastic uncertainty-based performance prediction and optimisation. Furthermore, technical effectiveness of machine learning methods in single and multi-objective optimisations has been presented, through hybrid PCMs integrated renewable systems. Multivariables involved in the review include thermo-physical, geometrical and operating parameters of PCMs. Multi-criteria employed in the review include heat transfer rate, cooling energy storage density, heat storage and release efficiency, and indoor thermal comfort. The literature review presents technical challenges, such as tradeoff solutions between computational accuracy and efficiency, generic methods for effective selection amongst multi-diversified optimal solutions along the Pareto front, the general methodology for multi-level uncertainty quantification, smart controllers with accurate predictions under high-level parameters’ uncertainty and stochastic occupants’ behaviors. The future outlook and recommendations of machine learning methods in PCMs integrated cooling systems have also been presented as avenues for upcoming research.

Abstract Ground source heat pump (GSHP) systems can provide cost effective and sustainable heating and cooling for buildings while using considerably less fossil fuel than conventional heating and cooling systems. This benefit can be further enhanced by adopting hybrid GSHP (HGSHP) systems wherein the GSHP component provides the baseload thermal energy with the balance provided by conventional systems. This study compares the costs of GSHP and HGSHP systems against conventional systems under a variety of climatic conditions, exemplified by those encountered across Australia, but including conditions encountered elsewhere. The results indicate that the comparative performance of GSHP and HGSHP systems depend on many parameters including climatic conditions, ground conditions, drilling prices and prices of electricity and gas in the regions where the systems are installed. Here we show that in general, adopting GSHP or HGSHP systems over conventional systems allow property owners to pay lower lifetime costs under most climatic conditions and gas to electricity energy price ratios. The results also indicate that conventional systems may be preferred in highly heating or cooling dominant climates and at locations with high drilling costs or low energy prices. In contrast, GSHP and HGSHP systems are preferred in locations with a more balanced climate, lower drilling costs and/or higher energy prices. There is no “one size fits all” rule given the many factors that can influence the lifetime costs. The paper shows that climatic conditions, ground conditions, drilling and energy costs must all be carefully considered when assessing the most cost effective sustainable energy technologies for space heating and cooling.

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.

Global urban development is increasingly becoming an aspect of focus as nations fight sustainability challenges. A review of the current literature on urban sustainability suggests that research on development of cities, in both developed and developing countries, is growing fast, with an emphasis on sustainable development. However, very little of this research contains an integrated framework to systematically identify and examine the various dimensions of urban sustainability and to measure and evaluate them appropriately. Cities are more than the sum of their sectors, and are complex and interdependent systems on whose dynamics the quality of life of millions of human beings and a good part of the economy depend. Environmental, economic, social and governance problems can create formidable barriers to urban sustainability. Governance remains a critically important dimension of urban sustainability, especially when discussing urbanization in developing countries, given rapid population movements and imbalances in socio-economic development. Understanding how cities function is fundamental to resolving these imbalances. The aim of this paper is to provide a review and analysis of the concept of urban sustainability and to propose the development of a holistic framework through integration of environmental, economic, social, and governance dimensions of sustainability. Such a review would make it possible to understand the complex dynamics of the four dimensions and to assess the progress and challenges in moving towards urban sustainability, taking the case of Nairobi, Kenya, as an example. The paper argues that, for urban sustainability in developing countries, more emphasis should be placed on the governance dimension, because this is where the biggest challenge exists, with increasing needs for immediate management of rapid urbanization.

AbstractUnder the US Environmental Protection Agency's Renewable Fuel Standard (RFS) program, mandates to increase the consumption of renewable fuels in transportation in the USA are leading to the emergence of a biofuel economy with infrastructure implications. This shift requires immediate consideration, as current engineering infrastructures may not be sufficient to support the realization of the mandates. New biorefineries will need to be established where suitable land is available and the climate is appropriate for growing feedstocks. Investments may need to be made to accommodate increases in local, regional, and national traffic from the transport of feedstocks and finished biofuels. Further, the large water demands of biorefineries and of growing feedstocks impose even greater pressure on water supply utilities. Higher sediment and nutrient runoffs from more intensive cultivation of corn (as feedstock for ethanol) have negative water quality effects that may lead to the need for upgrading drinking‐water treatment facilities. Any infrastructure expansion should be conducted strategically, keeping in mind resource constraints, and environmental and social impacts. To understand the infrastructure needs and bottlenecks of biofuel development, a systems approach encompassing all aspects of the problem is essential. Research is needed to quantify the interdependencies, resiliency, and sustainability of the entire system in meeting biofuel goals. Research is also needed to integrate the social and physical aspects of the problem into a holistic framework for planning and management purposes. This paper reviews the literature to gain insights into some implications of biofuel development for engineering infrastructures in the USA. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd

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.