Antonio Peretto

A Microcontroller-Based Power Management System for Standalone Microgrids With Hybrid Power Supply

The paper presents a microcontroller-based power management system (PMS) designed for the online operation of an experimental low voltage microgrid equipped with a battery storage system and two power supplies: a kilowatt (kW)-class proton exchange membrane (PEM) fuel cell (FC) and a photo-voltaic (PV) module emulator, both connected to a low voltage ac node. The connections of the energy sources to the common ac bus make use of power inverters with specific functionalities. The ac node feeds electric active and reactive load emulators able to reproduce programmable profiles. The automatic PMS provides the microgrid monitoring and the FC power scheduling in both grid-connected and islanded operating conditions. The paper describes the structure and functionalities of the PMS as well as a specific experimental investigation aimed at assessing the dynamic performance of the microgrid in islanded conditions.

A Parametric Thermodynamic Evaluation of High Performance Gas Turbine Based Power Cycles

This paper discusses the gas turbine performance enhancement approach that has gained a lot of momentum in recent years in which modified Brayton cycles are used with humidification or water/steam injection, termed wet cycles, or with fuel cells, obtaining hybrid cycles. The investigated high performance cycles include intercooled steam-injected gas turbine cycle, recuperated water injection cycle, humidified air turbine cycle, and cascaded humidified advanced turbine cycle, Brayton cycle with high temperature fuel cells (molten carbonate fuel cells or solid oxide fuel cells), and their combinations with the modified Brayton cycles. Most of these systems, with a few exceptions, have not yet become commercially available as more development work is required. The results presented show that the cycle efficiency achievable with the aforementioned high performance systems can be comparable or better than a combined cycle system, a currently commercially available power generation system having maximum cycle efficiency. The main emphasis of this paper is to provide a detailed parametric thermodynamic cycle analysis, using uniform design parameters and assumptions, of the above mentioned cycles and discuss their comparative performance including advantages and limitations. The performance of these cycles is also compared with the already developed and commercially available gas turbines without water/steam injection features, called dry cycles. In addition, a brief review of the available literature of the identified high performance complex gas turbine cycles is also included in this paper.

Gas Turbine Power Augmentation Technologies: A Systematic Comparative Evaluation Approach

Increasing electric rates in peak demand period, especially during summer months, are forcing power producers to look for gas turbine power augmentation technologies (PATs). One of the major undesirable features of all the gas turbines is that their power output and fuel efficiency decreases with increase in the ambient temperature resulting in significant loss in revenues particularly during peak hours. This paper presents a systematic comparative evaluation approach for various gas turbine power augmentation technologies (PATs) available in the market. The application of the discussed approach has been demonstrated by considering two commonly used gas turbine designs, namely, heavy-duty industrial and aeroderivative. The following PATs have been evaluated: inlet evaporative, inlet chilling, high pressure fogging, overspray, humid air injection and steam injection. The main emphasis of this paper is to provide a detailed comparative thermodynamic analysis of the considered PATs including the main variables, such as ambient temperature and relative humidity, which influence their performance in terms of power boost, heat rate reduction and auxiliary power consumption.Copyright

Numerical Simulation of Biomass Derived Syngas Combustion in a Swirl Flame Combustor

In this work a numerical investigation is carried out on a model combustor characterized by swirl flow conditions, fed with a biomass derived syngas fuel (which incorporates CH4 , CO and H2 ) and operated in laboratory at atmospheric pressure. The combustor internal aerodynamics and heat release in case of syngas combustion have been simulated in the framework of CFD-RANS techniques, by means of different available models and by adopting different levels of kinetic mechanism complexity. In particular, the applicability of reduced mechanisms involving CO and H2 species and also of detailed kinetic mechanisms are assessed. The results obtained by means of the CFD simulations on the model combustor and a comparison with available experimental data on flow field and thermal field are presented in the paper. In the test-case of syngas-air swirled flames, the turbulent non premixed combustion “flamelet” model with detailed non-equilibrium chemistry, originally developed for methane-air combustion, provides encouraging results in terms of temperature distribution. Nevertheless, a simpler chemical path including the main fuel species integrated in a general purpose, widely used in industry, turbulent combustion model still provides acceptable results.Copyright

Gas Turbine Compressor Performance Characteristics During Wet Compression: Influence of Polydisperse Spray

The available literature shows that there exists a lack of understanding about the impact of wet compression, involving two-phase flow, on the physics of flow in the compressor stages of a gas turbine engine. In recent years, analytical models have been proposed which provide effects of wet compression on the overall compressor performance and in few studies on the stage-by-stage performance. In spite of the fact that the wet compression technology for power augmentation has been commercially implemented on numerous gas turbines from all the major gas turbine manufacturers, many issues such as, effects of polydisperse spray, droplets dynamics, influence on the performance characteristics of individual stages, stage and overall surge margin, etc., remain not completely understood. This investigation clearly shows importance of considering effects of polydisperse spray on the overall and stage-by-stage compressor performance characteristics. The presented results show that for a given droplets distribution and ambient condition, later stages of a compressor are prone to reduced surge margin under wet compression process due to redistribution of stage loading. Moreover, the study shows that smaller distributions allow the achievement of higher performance, but the compressor surge is reached with a lower amount of injected water.Copyright

Available and Future Gas Turbine Power Augmentation Technologies: Techno-Economic Analysis in Selected Climatic Conditions

There exists a widespread interest in the application of gas turbine power augmentation technologies in both electric power generation and mechanical drive markets, attributable to deregulation in the power generation sector, significant loss in power generation capacity combined with increased electric rates during peak demand period, and need for a proper selection of the gas turbine in a given application. In this study, detailed thermo-economic analyses of various power augmentation technologies, implemented on a selected gas turbine, have been performed to identify the best techno-economic solution depending on the selected climatic conditions. The presented results show that various power augmentation technologies examined have different payback periods. Such a techno-economic analysis is necessary for proper selection of a power augmentation technology.

Development and Validation of a Model for Axial Compressor Fouling Simulation

Gas turbine axial compressor performance are heavily influenced by blade fouling; as a result, the gas turbines efficiency and producible power output decrease. In this study a model, able to evaluate the performance degradation of an axial compressor due to fouling, is developed and validated. The model is validated against experimental results available in literature and included into a computer code developed by the Authors (IN.FO.G.T.E) which is able to estimate the performance of every commercial gas turbine by using a stage stacking methods for the simulation of compressor behavior. The goal of this study is to show and discuss the change in gas turbine main performance (such as efficiency, power output, compressor inlet mass flow rate, pressure ratio) due to compressor fouling and also highlight and discuss the change in compressor stages performance curves.Copyright

Performance Evaluation of the Integration Between a Thermo-Photo-Voltaic Generator and an Organic Rankine Cycle

The present study deals with the integration between a Thermo-Photo-Voltaic generator (TPV) and an Organic Rankine Cycle (ORC) named here TORCIS (Thermo-photo-voltaic Organic Rankine Cycle Integrated System). The investigated TORCIS system is suitable for CHP applications, such as residential and tertiary sector users. The aim of the research project on this innovative system is the complete definition of the components design and the pre-prototyping characterization of the system, covering all the unresolved issues. This paper shows the results of a preliminary thermodynamic analysis of the system. More in details, TPV is a system to convert into electric energy the radiation emitted from an artificial heat source (i.e., combustion of fuel) by the use of photovoltaic cells; in this system, the produced electric power is strictly connected to the thermal one, as their ratio is almost constant and cannot be changed without severe loss in performance; the coupling between TPV and ORC allows to overcome this limitation and to realize a cogenerative system which can be regulated with a large degree of freedom changing the electric-to-thermal power ratio. The paper presents and discusses the TORCIS achievable performance, highlighting its potential in the field of distributed generation and cogenerative systems.© 2012 ASME