# ENERGY SYSTEMS

## Learning outcomes of the course unit

The course provides the basic knowledge on the theory of Energy Conversion Plants, with reference both to their components and to whole plants for power generation. In particular the study will focus on most common actual Power Plants used for energy generation: steam plants, gas turbines, reciprocating internal combustion engines. Knowledge and understanding:

At the end of the course the student will know the main characteristics of systems for energy generation and the most common power plants used today. He/she will also acquire the knowledge concerning the evaluation of thermodynamic processes, their representation on thermodynamic diagrams, the calculation of the thermodynamic parameters and the amount of heat and work exchanged, both with reference to the ideal and real cases. He/she will then need to know problems, limitations, advantages and disadvantages power plants/engines and their main components.

Applying knowledge and understanding:

The student will be able to calculate performance parameters of engines and power plants with particular reference to efficiency and specific fuel consumption. He/she will also be able to define the performance of the ideal and real thermodynamic processes that occur in Energy Conversion Systems in order to assess in a qualitative and quantitative way thermodynamic states in different locations of the plant as well as the methods to improve conversion efficiency. Making judgments:

The student will have tools and knowledge needed to critically evaluate and compare different solutions for the realization of specific energy conversion processes and power generation in Engines and Power Plants starting from main performance parameters usually used to this purpose and taking into account any possible alternatives.

Communication skills:

The student must have the necessary tools to effectively present evaluations and comparisons of different solutions for the realization of specific energy conversion processes and power generation in Engines and Power Plants through both graphs and numerical calculations and representation of thermodynamic cycles giving a clear idea of the key performance parameters usually used to this purpose.

Learning skills:

The student will be able, starting from the basic knowledge acquired in the course, to get by himself information and technical data on different Energy Conversion Systems that can be studied and/or proposed on the market, thus continuously updating their skills on the solutions proposed and/or applied in the field of conversion processes and energy generation.

## Prerequisites

A basic knowledge of fundamentals of Mathematics, Physics Thermodynamics and Fluid Mechanics is required.

## Course contents summary

Energy consumption in Italy and in the world: traditional and renewable energy sources. Energy systems and fluid machinery: characteristics and classification. Internal and external combustion Power Plants. Elements of thermodynamics: 1st and 2nd principle, gases and vapors, thermodynamic diagrams and their use. The Mollier diagram. Applications of the fundamental equations: continuity, energy and momentum. Basics on the utilization of hydraulic power plants: basin and flowing water schemes, Pelton, Francis, Kaplan turbines. Energy from fossil fuels: combustion processes and fuel properties. Mass balance, composition of products, air/fuel ratio. Thermodynamic cycles: representation on thermodynamic diagrams, thermodynamic processes, calculation of work and heat exchanges. Ideal, limit and real cycles. The efficiency diagram , specific fuel consumption. Cost of energy, utilization coefficient.

The compressible fluid machinery. De St.Venant equation, compressibility effects and dynamic pressure, Hugoniot equation, Mach number, ideal and real nozzles and diffusers. Mass flow rate in nozzles. Compression and expansion transformations on thermodynamic diagrams, work and efficiency in compressions and expansions.

Steam plants: basic circuit, cycles in saturated steam and superheated steam. Steam generators: types and layouts. Efficiency of the steam generator. Superheaters and economizers. Air preheaters. The condenser and cooling towers. Regeneration and reheat. Thermodynamic cycles on (h,s) and (T,s) diagrams. Performance evaluation for steam plants with simple cycle, with reheat and regeneration. Optimization of steam cycles with reference to specific work and efficiency.

Gas turbines, reference thermodynamic cycles, efficiency and specific work. Air-fuel ratio, combustion chambers. Thermodynamic cycles on (h, s) and (T,s) diagrams. Performance evaluation for simple and regenerated gas cycles. Optimization of gas cycles with reference to specific work and efficiency. The turbine inlet temperature (TIT): effects on efficiency and problems arising from materials strenght. Basics on blade cooling.

Reciprocating internal combustion engines (ICE). Operating principles and basic components. Ideal thermodynamic cycles. Calculation of power output in internal combustion engines. Brake Mean Effective Pressure (bmep). Volumetric efficiency. Combustion processes in spark-ignition and Diesel engines. Air intake and fuel injection in ICE: intake and exhaust systems, valves and actuation systems, ideal and real valve timing and related polar diagram. Fundamental on supercharging and turbocharging.

## Course contents

Energy consumption in Italy and in the world: traditional and renewable energy sources. Energy systems and fluid machinery: characteristics and classification. Internal and external combustion Power Plants. Elements of thermodynamics: 1st and 2nd principle, gases and vapors, thermodynamic diagrams and their use. The Mollier diagram. Applications of the fundamental equations: continuity, energy and momentum. Basics of the utilization of hydraulic power plants: basin and flowing water schemes, Pelton, Francis, Kaplan turbines. Energy from fossil fuels: combustion processes and fuel properties. Mass balance, composition of products, air/fuel ratio. Thermodynamic cycles: representation on thermodynamic diagrams, thermodynamic processes, calculation of work and heat exchanges. Ideal, limit and real cycles. The efficiency diagram , specific fuel consumption. Cost of energy, utilization coefficient.

The compressible fluid machinery. De St.Venant equation, compressibility effects and dynamic pressure, Hugoniot equation, Mach number, ideal and real nozzles and diffusers. Mass flow rate in nozzles. Compression and expansion transformations on thermodynamic diagrams, work and efficiency in compressions and expansions. Steam plants: basic circuit, cycles in saturated steam and superheated steam. Steam generators: types and layouts. Efficiency of the steam generator. Superheaters and economizers. Air preheaters. The condenser and cooling towers. Regeneration and reheat. Thermodynamic cycles on (h,s) and (T,s) diagrams. Performance evaluation for steam plants with simple cycle, with reheat and regeneration. Optimization of steam cycles with reference to specific work and efficiency.

Gas turbines, reference thermodynamic cycles, efficiency and specific work. Air-fuel ratio, combustion chambers. Thermodynamic cycles on (h, s) and (T,s) diagrams. Performance evaluation for simple and regenerated gas cycles. Optimization of gas cycles with reference to specific work and efficiency. The turbine inlet temperature (TIT): effects on efficiency and problems arising from materials strenght. Basics on blade cooling.

Reciprocating internal combustion engines (ICE). Operating principles and basic components. Ideal thermodynamic cycles. Calculation of power output in internal combustion engines. Brake Mean Effective Pressure (bmep). Volumetric efficiency. Combustion processes in spark-ignition and Diesel engines. Air intake and fuel injection in ICE: intake and exhaust systems, valves and actuation systems, ideal and real valve timing and related polar diagram. Fundamental on supercharging and turbocharging.

## Recommended readings

C.Caputo, "Gli impianti convertitori di energia", Masson, 1997.

C.Caputo, "Le Macchine Volumetriche", Masson, 1999.

C.Carcasci, B.Facchini, "Esercitazioni di Sistemi Energetici", ed.Esculapio, 2016.

G.Negri di Montenegro, M.Bianchi, A.Peretto, "Sistemi Energetici e Macchine a Fluido", ed.Pitagora, 2009.

Suggestions for further readings:

O.Acton, C.Caputo, Macchine a fluido, vol.1, 'Introduzione allo studio delle Macchine', UTET, 1979.

O.Acton, C.Caputo, Macchine a fluido, vol.2, 'Impianti Motori', UTET, 1992. O.Acton, Macchine a Fluido, vol.3, "Turbomacchine", UTET, 1990. G.Ferrari, "Motori a Combustione Interna", Il Capitello, 2016.

## Teaching methods

Learning activities will be developed in for of frontal lectures (or online if the health situation relating to COVID requires it) focused on the study of thermodynamic processes and thermodynamic cycles in Energy Conversion Systems and for the calculation of their operational characteristics and performance. The course will be supported by numerical examples and exercises to allow the student to acquire the necessary familiarity with the units of measurement, with the quantitative calculation of ideal and real thermodynamic transformations, as well as with the performance evaluations of the Engines and Power Plants that use primary energy sources.

## Assessment methods and criteria

Verification of learning is achieved through the final exam only, which ascertains the acquisition of knowledge and skills (ie the acquisition of learning results) through a written test and oral interview.

The written test lasts 1.5 hours and the use of notes or books of any kind is not allowed, but the (enthalpy,entropy) diagram for H2O diagram (Mollier diagram) is required. The written test consists of a calculation problem closely similar to those solved during lectures, and in particular it involves the numerical calculation of a thermodynamic cycle applied to a power plant and the quantitative evaluation of related performance and operating parameters. The written test requires that results provided to the specific questions are correct within reasonably limits: a correct answer to the first questions is necessary to be admitted to the oral test with a partial score of 18/30. The other questions allow you to increase the partial vote up to 30/30.

Students who pass the first test will be admitted to an oral test, consisting in: (1) a review of the written test in which the examiners inform the student about the correction criteria, receive any clarifications from the student and decide whether to change the judgment; (2) two theoretical questions on the topics covered in the course and on the application of the theory to original problems: in particular the critical ability, the language skills and the ability to correlate topics will be evaluated. Each of the two questions is assessed on a scale from 0 to 30. To pass the exam the partial grade for each single question should be at least equal to 18/30. The final grade is obtained by calculating the arithmetic average of the marks in the written test and the two questions in the oral test (both out of thirty). The final grade is communicated immediately at the end of the exam session.

Please note that online registration for the exam is MANDATORY to take the exam.

The aforementioned tests will be in attendance if the health situation permits. Otherwise the tests will be administered with the same procedure in online mode through the Elly platform for the first test (written test) and through Teams for the second test (oral test).

## Other informations

Attendance to the course lectures and to the presentation of numerical examples is highly recommended.