A decision making tool for assessing grid electrification versus stand-alone power supply options for remote users

Includes bibliography.The objective of this study is to compile a micro-computer based tool to aid in the evaluation of power supply options for remote sites. The options considered are stand-alone photovoltaic, diesel generation, and grid extension power supplies. The basis on which the various options are compared is the unit cost of energy expected from the system. This is determined by combining all capital costs, running costs, and other payments on a present value basis over the project lifetime. The comparison of the unit energy cost expected from each option is only meaningful if the reliability of each supply system is known. The Loss of Energy Probability of each option is therefore established to provide a common ground on which to compare these costs.

Development of vibration design procedures for representative structural types Final technical report, Sep. 1965 - Jul. 1966

Effects of multimode and damping on random fatigue of cantilever beams and bracket

Symbolic Regression Approaches for the Direct Calculation of Pipe Diameter

This study provides novel and accurate symbolic regression-based solutions for the calculation of pipe diameter when flow rate and pressure drop (head loss) are known, together with the length of the pipe, absolute inner roughness of the pipe, and kinematic viscosity of the fluid. PySR and Eureqa, free and open-source symbolic regression tools, are used for discovering simple and accurate approximate formulas. Three approaches are used: (1) brute force of computing power, which provides results based on raw input data; (2) an improved method where input parameters are transformed through the Lambert W-function; (3) a method where the results are based on inputs and the Colebrook equation transformed through new suitable dimensionless groups. The discovered models were simplified by the WolframAlpha simplify tool and/or the equivalent Matlab Symbolic toolbox. Novel models make iterative calculus redundant; they are simple for computer coding while the relative error remains lower compared with the solution through nomograms. The symbolic-regression solutions discovered by brute force computing power discard the kinematic viscosity of the fluid as an input parameter, implying that it has the least influence

Conceptual Design of a Small Hybrid Unmanned Aircraft System

UAS (Unmanned Aircraft System) technologies are today extremely required in various fields of interest, from military to civil (search and rescue, environmental surveillance and monitoring, and entertainment). Besides safety and legislative issues, the main obstacle to civilian applications of UAS systems is the short time of flight (endurance), which depends on the equipped power system (battery pack) and the flight mission (low/high speed or altitude). Long flight duration is fundamental, especially with tasks that require hovering capability (e.g., river flow monitoring, earthquakes, devastated areas, city traffic monitoring, and archeological sites inspection). This work presents the conceptual design of a Hybrid Unmanned Aircraft System (HUAS), merging a commercial off-the-shelf quadrotor and a balloon in order to obtain a good compromise between endurance and weight. The mathematical models for weights estimation and balloon static performance analysis are presented, together with experimental results in different testing scenarios and complex environments, which show 50% improvement of the flight duration

Hole Cleaning And Cuttings Transportation Modelling And Optimization

Efficient hole cleaning in drilling operation is essential to ensure optimum rate of penetration. This complex problem involves simultaneous analysis of multiple parameters, including cuttings characteristics, fluid rheology and the geometry of the annulus space. For instance, accurate calculations of the equivalent circulation density (ECD) requires the effect of the mud density increase due to the cuttings’ concentration to be considered, which itself is a function of the settling velocity and the rate of penetration (ROP). Analytical models, lab experiments and numerical simulations have been used to determine the optimum flow rate for efficient hole cleaning. Most of these models are based on the drag coefficient-Reynolds number relationship, where both parameters are velocity dependent, making the calculation workflow to be implicit, tedious and time consuming. While several attempts have been made to present explicit correlations, precise equations covering a wide range of Reynolds numbers are not available.Terminal settling velocity was used in this research to determine the minimum required transportation velocity of drilling cuttings in the annulus space to ensure an optimal cleaning. The ROP also affects the hole cleaning as it defines the volume of the cuttings produced. We first used analytical models to investigate the effect of the cuttings size, density, and fluid properties as a function of wellbore deviation and circulation rate on hole cleaning efficiency. The results were compared with lab experiments using a slurry loop. The analytical models predict the critical velocities for lifting and rolling the cuttings particles based on the equilibrium cuttings bed height model and forces acting on a cuttings bed. For vertical sections of the wellbore, the critical transportation velocity showed to be proportional to the terminal settling velocity of the drill cuttings. Hence, we developed two new methods to predict the hindered terminal settling velocity due to the presence of wellbore and pipe walls and particle shape. We then used the Artificial Neural Network (ANN) algorithm and generated two models to predict the terminal velocity of drill cuttings and proppants considering the particles shape and the wall effect. The results of both analytical models and ANN were applied to estimate ECD. In addition, the drilling Mechanical Specific Energy (MSE) was calculated to determine the effect of different drilling parameters on hole cleaning and ECD. A new model was proposed for predicting the ECD in vertical and deviated wellbores that considers fluid and formation properties as well as wellbore and drill string geometry and drilling operational parameters. The developed model was used to study the effect of different drilling parameters on ECD and help engineers to optimize their operational parameters. The final step of this study was to investigate the effect of stabilizers geometry on hole cleaning. A total of more than 30 different designs of straight, straight with offset and helical blades geometries were built numerically and the results were compared. The reliability of the numerical simulation was confirmed against experimental and field data from the literature. The effect of size and shape of the stabilizer blades on the motion of the particles was investigated. Numerical simulation results showed that the straight blade geometry causes less disturbance to the cuttings transportation as compared to the straight with offset and helical blades, respectively

Application of inert wastes in the construction, operation and closure of landfills: calculation tool

Waste from construction and demolition activities represents one of the highest volumes of waste in Europe. 500 million tonnes are produced throughout the whole EU every year. In some EU members like Spain, approximately 83 per cent of such waste is disposed in landfills. The remaining part is classified and processed in treatment facilities so that it can later be used as recycled aggregates in the construction sector (sand, gravel, aggregates, etc.) but without much commercial success. The aim of this study is to use recycled aggregates from inert wastes (IW) in the different phases of a landfill (construction, operation and closure) with the aid of a new computer tool called LABWASTE.14. This tool incorporates the mathematical relationship among the activities of the landfill and provides as a result the economic viability of using recycled aggregates compared to aggregates from quarries. Therefore, knowing the needs of aggregates in landfills (dams, drainage layers, covering layers, collection wells, etc.) may determine the amount of IW that could be recovered. These calculations can be obtained from some of the data that is introduced (population, land physiography, etc.). Furthermore, the use of LABWASTE.14 makes it possible to reduce the demand for aggregates from quarries

Sampling in the South African minerals industry.

This paper was first presented at the, Sampling and analysis: Best-practice in African mining Conference, 4–6 June 2013, Misty Hills Country Hotel and Conference Centre, Cradle of Humankind, Muldersdrift, South Africa.Although not fully accepted in South Africa, the Theory of Sampling originally proposed by Pierre Gy is fast becoming the cornerstone of sampling practice throughout the world. The growing acceptance of Gy's Theory of Sampling in South Africa can be attributed to a number of factors, chief amongst them being the development of a tradable mineral asset market, the promulgation of the Mineral and Petroleum Resources Development Act (MPRDA), the growing number of commercial and academic courses that are offered on sampling, and the regulation of the industry through internationally acceptable guidelines and rules for reporting and trading in mineral assets. The size of the South African minerals industry and the dependence of our economy on mineral production have also meant that correct sampling is of key importance to mineral trade. ISO standards have been the principal guides for producers of mineral bulk commodities who produce to customers' specifications, whereas Gy's insights have been most readily accepted by precious and base metals producers whose product is sold into metal markets. Understanding of small-scale variability is essential in the precious and base-metal industries, but detailed studies of the effects of heterogeneity have not been as productive in the bulk commodities. Sampling practices at different stages of mineral development from exploration, face sampling and grade control, ore processing and handling, metallurgical sub-sampling, point of sale sampling, and sampling in the laboratory are considered in the gold, platinum, ferrous metal, and coal industries. A summary of the impact of poor sampling in these industries is presented. Generally it appears that poor sampling practice is most likely to erode mineral asset value at the early stages of mineral development. The benefits of good sampling are considered, especially with regard to the financial implications of bias and error on large and consistent consignments of bulk commodities.MvdH2016http://www.saimm.co.za/publications/journal-paper

Natural ventilation in double-skin façade design for office buildings in hot and humid climate

This research seeks to find a design solution for reducing the energy usage in high-rise office buildings in Singapore. There are numerous methods and techniques that could be employed to achieve the purpose of designing energy efficient buildings. The Thesis explores the viability of double-skin façades (DSF) to provide natural ventilation as an energy efficient solution for office buildings in hot and humid environment by using computational fluid dynamic (CFD) simulations and case study methodologies. CFD simulations were used to examine various types of DSF used in office buildings and the behaviour of airflow and thermal transfer through the DSF; the internal thermal comfort levels of each office spaces were analyzed and compared; and an optimization methodology was developed to explore the best DSF configuration to be used in high-rise office buildings in the tropics. The correlation between the façade configurations, the thermal comfort parameters, and the internal office space energy consumption through the DSF is studied and presented. The research outcome of the Thesis has found that significant energy saving is possible if natural ventilation strategies could be exploited with the use of DSF. A prototype DSF configuration which will be best suited for the tropical environment in terms of its energy efficiency through cross ventilation strategy is proposed in this Thesis. A series of comprehensive and user-friendly nomograms for design optimization in selecting the most appropriate double-skin façade configurations with considerations of various orientations for the use in high-rise office buildings in the tropics were also presented

Assessment and minimization of potential environmental impacts of ground source heat pump (GSHP) systems

Ground source heat pumps (GSHPs) gained increasing interest owing to benefits such as low heating and cooling costs, reduction of greenhouse gas emissions, and no pollutant emissions on site. However, GSHPs may have various possible interactions with underground and groundwater, which, despite the extremely rare occurrence of relevant damages, has raised concerns on their sustainability. Possible criticalities for their installation are (hydro)geological features (artesian aquifers, swelling or soluble layers, landslide-prone areas), human activities (mines, quarries, landfills, contaminated sites), and groundwater quality. Thermal alterations due to the operation of GSHPs may have an impact on groundwater chemistry and on the efficiency of neighboring installations. So far, scientific studies excluded appraisable geochemical alterations within typical ranges of GSHPs (±6 K on the initial groundwater temperature); such alterations, however, may occur for aquifer thermal energy storage over 40 °C. Thermal interferences among neighboring installations may be severe in urban areas with a high plant density, thus highlighting the need for their proper management. These issues are presented here and framed from a groundwater quality protection perspective, providing the basis for a discussion on critical aspects to be tackled in the planning, authorization, installation, and operation phase. GSHPs turn out to be safe and sustainable if care is taken in such phases, and the best available techniques are adopted