A New Statistical based Energetic-economic Methodology for Wind Turbine Systems Evaluation☆

Abstract The present paper deals with the implementation of a new statistical based methodology for energetic and economic evaluation of wind turbine systems without using anemometric measurements for specific installation sites. In particular, the procedure aims at the evaluation of single small wind turbine, as well as small wind turbine fields. The choice of using small wind turbines is due to the impact of the wind velocity measurements from both the cost and the time-needed point of view. Monte Carlo Method was used to study statistically the effects of wind velocity variability on wind turbines energy production and consequently on the economic performance of the system. Starting from the average wind velocity for the site, the type of the site (plain, hill, mountain, etc.), as well as the height of the turbine, the procedure analyses different wind velocity statistical distributions (based on Weibull distribution) to obtain energy production and then investment profitability. In order to test the methodology a case study was analysed using both classical (using one year of wind velocity measurements) and new procedure (using only the average value of the wind velocity for the same installation site). On the basis of the results it is possible to state that the new methodology is able to determine the Net Present Value of the investment showing small differences between new and classical procedure

A site selection model to identify optimal locations for microalgae biofuel production facilities in sicily (Italy)

The lack of sustainability and negative environmental impacts of using fossil fuel resources for energy production and their consequent increase in prices during last decades have led to an increasing interest in the development of renewable biofuels. Among possible biomass fuel sources, microalgae represent one of the most promising solutions. The present work is based on the implementation of a model that facilitates identification of optimal geographic locations for large-scale open ponds for microalgae cultivation for biofuels production. The combination of a biomass production model with specific site location parameters such as irradiance, geographical constraints, land use, topography, temperatures and CO2 for biofuels plants were identified in Sicily (Italy). A simulation of CO2 saved by using the theoretical biofuel produced in place of traditional fuel was implemented. Results indicate that the territory of Sicily offers a good prospective for these technologies and the results identify ideal locations for locating biomass fuel production facilities. Moreover, the research provides a robust method that can be tailored to the specific requirements and data availability of other territories. © Research India Publications

Design of a vertical-axis wind turbine: how the aspect ratio affects the turbine's performance

This work analyses the link between the aspect ratio of a vertical-axis straight-bladed (H-Rotor) wind turbine and its performance (power coefficient). The aspect ratio of this particular wind turbine is defined as the ratio between blade length and rotor radius. Since the aspect ratio variations of a vertical-axis wind turbine cause Reynolds number variations, any changes in the power coefficient can also be studied to derive how aspect ratio variations affect turbine performance. Using a calculation code based on the Multiple Stream Tube Model, symmetrical straight-bladed wind turbine performance was evaluated as aspect ratio varied. This numerical analysis highlighted how turbine performance is strongly influenced by the Reynolds number of the rotor blade. From a geometrical point of view, as aspect ratio falls, the Reynolds number rises which improves wind turbine performance

wind turbine placement optimization by means of the monte carlo simulation method

This paper defines a new procedure for optimising wind farm turbine placement by means of Monte Carlo simulation method. To verify the algorithm's accuracy, an experimental wind farm was tested in a wind tunnel. On the basis of experimental measurements, the error on wind farm power output was less than 4%. The optimization maximises the energy production criterion; wind turbines' ground positions were used as independent variables. Moreover, the mathematical model takes into account annual wind intensities and directions and wind turbine interaction. The optimization of a wind farm on a real site was carried out using measured wind data, dominant wind direction, and intensity data as inputs to run the Monte Carlo simulations. There were 30 turbines in the wind park, each rated at 20 kW. This choice was based on wind farm economics. The site was proportionally divided into 100 square cells, taking into account a minimum windward and crosswind distance between the turbines. The results highlight that the dominant wind intensity factor tends to overestimate the annual energy production by about 8%. Thus, the proposed method leads to a more precise annual energy evaluation and to a more optimal placement of the wind turbines

Flow similitude laws applied to wind turbines through blade element momentum theory numerical codes

This paper deals with the analysis of the per- formance of different wind turbines using the Similitude Theory. Wind turbine performance was determined as a function of geometrical similarity coefficient, which is related to all parameters of the Similitude Theory. There- fore, a mathematical model simplification is possible in the 'in similitude' wind turbines comparison. The mathemati- cal model for wind turbine performance is based on BEM Theory, and its efficacy was verified several times by comparing different wind turbine experimental data. The original mathematical model was modified to take into account Similitude Theory parameters. The model is able to determine which wind turbine is most suited to particular design specification. This work presents power and torque curves, power and torque coefficients as functions of rotational speed and wind velocity. All the results are function of the geometrical similarity coefficient. With this methodology it is possible to maximize the power coeffi- cients of a wind turbine, and it is possible to identify a family of wind turbines, geometrically different, but with the same high performances

Heat Exchange Numerical Modeling of a Submarine Pipeline for Crude Oil Transport

Abstract The present paper deals with a real issue of the Exxon-Mobil refinery in Augusta (Sicily). The crude oil, which is transported by oil tankers, is transferred through a submarine pipeline where it remains for a long time. In order to predict the transient temperature of the pipe, two numerical approaches were developed. The simplest one was a conductive model, based on the Finite Element Method, implemented by using the ANSYS Thermal FEM software for a first approximation solution. After having carried out an accurate grid resolution study and having evaluated the thermal error, a prediction of thermal profiles and heat fluxes was obtained. Thanks to the axisymmetrics of the physical problem, only a limited portion of the 3D pipe was modelled. The second approach was instead based on the use of a more accurate CFD Finite Volume Model, developed in ANSYS Fluent. In this case, in order to have reasonable calculation time and thanks to the aforementioned axisymetrics, the problem was carried out in 2D. Moreover, both grid and time step sensitivity was evaluated. Accurate buoyancy and turbulence models as well as viscosity and density temperature dependence models were used in order to obtain the most accurate physical modelling. The CFD model was developed basing on codes validated in the scientific literature. The comparison between FEM conductive and CFD results demonstrated the superior accuracy of the CFD, thanks to an accurate modelling of the internal convective motions

Public sector accounting harmonization in the European Union through the lens of the garbage can model

The public sector accounting harmonization process that started in the European Union in the aftermath of the financial crisis led the European Commission to launch a project for the development of a set of European Public Sector Accounting Standards (EPSAS). This paper analyses the process and the decision-making around development of the EPSAS through the lens of the garbage can model (Cohen, M. D., March, J. G., & Olsen, J. P. (1972). A garbage can model of organizational choice. Administrative Science Quarterly, 17(1), 1–25). More specifically, by identifying problems, participants, solutions, and choice opportunities, it discusses why the development of the EPSAS is taking so long and why the process does not seem to be progressing as planned. To this end, documents related to the process of EPSAS development are analyzed. The results provide evidence of problematic preferences and fluid participation possibly coupled with flight decisions—three elements of the garbage can model. Postponing decisions can be an option to dampen reluctance. The more the public sector becomes accustomed to the International Public Sector Accounting Standards (IPSAS) by adopting IPSAS-like accrual accounting standards while waiting for the completion of the EPSAS, the less resistance there might be to moving to accrual accounting standards. However, at the same time, an imminent change to a new set of EPSAS standards might become less plausible if changes demand extra reform

Are SDGs being translated into accounting terms? Evidence from European cities

IMPACT: The challenge launched by the United Nations (UN) on the achievement of SDGs requires local governments to rethink how to devote their resources and report on their results regarding SDGs. The article analyses how existing frameworks communicate, through financial indicators, the efforts done towards sustainable development. The Voluntary Local Reviews (VLR) published by European cities and made available on the UN website can stimulate further reflection and actions toward making SDGs an accounting issue

Elevated trace metals and REE contents in the CO2-rich groundwaters of Florina (N. Greece) a natural analogue of carbon storage systems

The Florina basin, being the main commercial source of CO2 in Greece, represents a good natural analogue for the study of the impact of geologic carbon storage. It is part of a NNW-SSE trending graben filled with ~600 m Plio-Pleistocene fluvial and lacustrine deposits. The area is characterized by the upflow of great quantities of geogenic CO2 probably associated to presently extinct Quaternary volcanic activity. The gas originates mainly from crustal sources but has also a minor (~10%) mantle contribution. This strong upflow of nearly pure CO2 can be recognized in industrially exploitable gas reservoirs, high pCO2 shallow groundwaters and surface gas manifestations. But the increased CO2 content has a deleterious impact on groundwater quality. Due to the increased aggressiveness of the low-pH CO2-rich waters with respect to the aquifer rocks, EU drinking water limits are exceed for many parameters (e.g. Electric conductivity, pH, Na+, SO42-, F-, Al, B, Ba, Fe, Mn and Ni). Considering the additional impact of widespread agricultural activities, which is recognizable in sometimes elevated NO3- contents, only few of the sampled waters (4 out of 40) could be used for potable purposes. Aquifer waters are also characterized by high REE contents with ΣREE up to ~12 µg/l. Shale-normalized profiles show positive La and Y anomalies and Ce negative anomalies probably indicating a main derivation from iron oxyhydroxide dissolution. The positive Eu anomaly evidences also carbonate dissolution while the enrichment in HREE is probably due to the abundant presence of HCO3-, which increases HREE solubility through complexation. Future developments of carbon capture and storage programs in the nearby sedimentary basin of Ptolemais and Servia have to carefully take in account the possible deterioration of their groundwater resources due to CO2 leaks from the storage reservoirs

A New Tool to Optimize ICE Performance and Emissions Via 1D Code Coupled with Gas

Abstract The aim of this paper is to propose a new strategy to optimize the performance and to reduce the emission levels of Internal Combustion Engines by varying intake valve lift profile and timing. The object of the study was an ICE – SI, GDI, 1.4 l, four cylinders, 16 V, turbocharged. It was equipped with an electrohydraulic VVA system which allows the intake valves to vary, at the same time, lift and timing in order to realize early IVC and/or late IVO. Thanks to this, the engine can always operate in the optimal fluid dynamics conditions in order to achieve the best performance and emission levels. A model of the engine was implemented in GT-Power™ for several operating conditions (partial load, full load, low and high engine speed), and then coupled with a single-objective genetic algorithm, evolved subsequently into a multi-objective genetic algorithm. Two different analysis were carried out: the first one for reducing CO2 emissions at partial load and low engine speed (single-objective optimization), and the second one for increasing the brake torque at full load (multi-objective optimization). The proposed model shows the possibility to quickly find optimal solutions for the test cases considered, and it let the opportunity to be further developed and improved in order to optimize many other parameters of the ICE