Search results for "Energy engineering"
showing 10 items of 1099 documents
A practical method to test the safety of HV/MV substation Grounding Systems
2015
The adequacy of a Grounding System (GS) to the safety conditions has to be periodically tested by measurements. The test methods and techniques used to verify the electrical characteristics of the GS include the measurements of step and touch voltages. The goal of the test is to verify that touch voltage and step voltage remain below a safe value in all the zones of the installation. The measurements can present some operational difficulties. The purpose of this paper is to present the procedure, step-by-step, of a practical method of measuring touch/step voltages in grounding systems located in urban or industrial areas with reduced accessibility. The suggested method uses auxiliary curren…
The Global Grounding System: Definitions and guidelines
2015
The present paper presents the preliminary results of the ongoing Italian METERGLOB project on the contribution given by the exposed conductive parts to a Global Grounding System. One of the expected results of METERGLOB is to carry out guidelines for the identification of a Global Grounding System. These guidelines must be defined on the basis of the definitions and methods present in the current international standards on grounding and safety. In the paper some definitions and elements to be taken into account for the identification of a Global Grounding System are given.
Optimization of hybrid – ground coupled and air source – heat pump systems in combination with thermal storage
2010
Ground coupled heat pumps are attractive solutions for cooling and heating commercial buildings due to their high efficiency and their reduced environmental impact. Two possible ideas to improve the efficiency of these systems are decoupling energy generation from energy distribution and combining different HVAC systems. Based on these two ideas, we present several HVAC configurations which combine the following equipments: a ground coupled heat pump, an air to water heat pump and a thermal storage device. These HVAC configurations are linked to an office building in a cooling dominated area in order to evaluate in these conditions the total electrical consumption of each configuration to o…
Effects of electrical and mechanical parameters on the transient voltage stability of a fixed speed wind turbine
2011
Abstract In this paper the dynamic behaviour of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed with the Simulink simulation tool (Matlab Inc.) It is composed of the induction generator, the shaft system, an aerodynamic model of the wind turbine rotor and the pitch control system. Using this model, a three-phase fault is applied close to the wind turbine and cleared by disconnecting the faulty line. The rigorous implementation of the simulink model allowed the authors to evaluate the exact dependence of various electrical parameters for the induction generator on voltage stability. Furthermore, the effects of wind turbine mechan…
Modeling and Simulation of a Cylinder Hoisting System for Real-Time Hardware-in-the-Loop Testing
2016
Summary Modeling-and-simulation software that is used in the design and development of drilling equipment provides testing and redesigning of offshore machines early in the product-development process. Typically, models of offshore equipment are complex and suitable only for offline simulations that allow testing of just predefined functions of the system without the possibility of controlling it with the operator's inputs in real time (RT). This is related to the fact that, usually, complex models put high demands on the computational power of the simulator hardware and, thus, limit its RT performance. On the basis of the authors' observations, it is concluded that RT performance can be di…
An analytical approach for the evaluation of the optimal combustion phase in spark ignition engines
2009
It is well known that the spark advance is one of the most important parameters influencing the efficiency of a spark ignition engine. A change in this parameter causes a shift in the combustion phase, whose optimal position, with respect to the piston motion, implies the maximum brake mean effective pressure for given operative conditions. The best spark timing is usually estimated by means of experimental trials on the engine test bed or by means of thermodynamic simulations of the engine cycle. In this work, instead, the authors developed, under some simplifying hypothesis, an original theoretical formulation for the estimation of the optimal combustion phase. The most significant parame…
A Refined Model for Knock Onset Prediction in Spark Ignition Engines Fueled With Mixtures of Gasoline and Propane
2015
In the last decade, gaseous fuels, such as liquefied petroleum gas (LPG) and natural gas (NG), widely spread in many countries, thanks to their prerogative of low cost and reduced environmental impact. Hence, bi-fuel engines, which allow to run either with gasoline or with gas (LPG or NG), became very popular. Moreover, as experimentally demonstrated by the authors in the previous works, these engines may also be fueled by a mixture of gasoline and gas, which, due to the high knock resistance of gas, allow to use stoichiometric mixtures also at full load, thus drastically improving engine efficiency and pollutant emissions with respect to pure gasoline operation without noticeable power los…
Concurrent optimization of size and switch-on priority of a multisource energy system for a commercial building application
2015
Abstract In recent years, the governments of most nations have pledged to (i) limit carbon dioxide emissions, (ii) reduce primary energy consumption by increasing production, distribution and end-use efficiency and (iii) increase the utilization of renewable energy sources. In general, these goals are pursued separately by law, by subsidizing renewable energy technologies, reducing the demand or using high efficiency technologies. In this context, multi-source systems for the fulfillment of energy demands are highly advantageous because they are based on different technologies which use renewable, partially renewable and fossil energy sources. However, the main issues of multi-source system…
Simulation model of a molten carbonate fuel cellemicroturbine hybrid system
2011
A Hybrid System based on High Temperature Fuel Cells coupled to a Microturbine allows a high efficiency, low environmental pollution and it may be exploited as a CHP System producing heat and electricity both Grid Connected and Stand Alone; the overall electrical efficiency could reach a very high value (up to 60%) and total efficiency could be over 70% including the contribution due to heat recovery. In the context of wide research activities of ENEA on High Temperature Fuel Cells and Hybrid Systems e that involve materials, system BoP and fuels e a very great effort has been devoted to design and build, in the ENEA Research Centre of “Casaccia”, an experimental Test-Rig based on a Molten …
Distribution grid analysys through PSAT open source tools
2015
In this paper a study of an electrical distribution grid with presence of renewable energy sources performed using the Power System Analysis Tool is presented. The paper describes the load flow analysis of a real existing grid owned by the Italian DSO “ENEL Distribuzione SpA” and located in an urban area.