# ENERGY SYSTEMS

## Learning outcomes of the course unit

The course provides the basic knowledge and the skills (i.e., the ability to apply knowledge) required to understand the operating characteristics and to evaluate the performance of Energy Conversion Plants, with particular reference to most common actual Power Plants (steam plants, gas turbines, reciprocating internal combustion engines). In order to develop the basic skills - however essential - required in assessing the performance of any Power Plant for energy generation and conversion, student is asked to demonstrate by the end of the module the achievement of the following objectives.

Knowledge and understanding:

At the end of the course the student will know the main characteristics of systems for energy generation and the most widely used Power Plants. 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 ideal and real cases. He/she will know problems, limitations, advantages and disadvantages of considered Power Plants/Engines and of 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 will 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 her/his 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. Basics of thermodynamics. Applications of the conservation equations. Basics on the utilization of hydraulic power plants. Energy from fossil fuels. Thermodynamic cycles. Ideal, limit and real cycles. The efficiency diagram, specific fuel consumption. Cost of energy, utilization coefficient.

Compressible fluid machinery. Recall on ideal nozzles and diffusers. Mass flow rate in nozzles. Compression and expansion transformations on thermodynamic diagrams.

Steam plants: basic circuit, cycles in saturated steam and superheated steam. Steam generators: superheaters and economizers, air preheaters. The condenser and cooling towers. Regeneration and reheating. Thermodynamic cycles. Performance evaluation for steam plants and optimization.

Gas turbines, reference thermodynamic cycles, efficiency and specific work. Air-fuel ratio, combustion chambers. Thermodynamic cycles. Performance evaluation for simple and regenerated gas cycles and optimization. The turbine inlet temperature (TIT). Basics on blades cooling.

Reciprocating internal combustion engines (ICE). Operating principles and basic components. Ideal thermodynamic cycles. Power output, Brake Mean Effective Pressure (bmep), Volumetric efficiency. Basics on combustion processes and air intake and fuel injection. Basics on supercharging and turbocharging.

Fundamental parameters for the performance characterization of fluid machinery: basics of dimensional analysis, non-dimensional parameters, characteristic curves.

## 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.

Fundamental parameters for the performance characterization of fluid machinery: basics of dimensional analysis, non-dimensional parameters, characteristic curves.

## Recommended readings

Topics discussed during the course are reported following the same approach and the same nomenclature in the following books:

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

C.Caputo, "Le Macchine Volumetriche", ed.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.

Suggested readings for extended studies are:

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

O.Acton, C.Caputo, Macchine a fluido, vol.2, 'Impianti Motori', ed.UTET, 1992.

O.Acton, Macchine a Fluido, vol.3, "Turbomacchine", ed.UTET, 1990.

G.Ferrari, "Motori a Combustione Interna", ed.Il Capitello, 2016.

## Teaching methods

Learning activities will be developed in the form of frontal lessons. The course subjects are discussed from both a theoretical point of view, in order to allow the understanding of the presented topics (linking them where appropriate with the knowledge already acquired by the student), and a practical approach, by presenting quantitative examples of Power Plants and calculation procedures that lead to the numerical evaluation of the operational characteristics, the performance parameters and the thermodynamic transformations of the Plant.

In more details, theoretical lectures will be focused on the study of thermodynamic processes and thermodynamic cycles in Energy Conversion Systems and for the calculation of their operational characteristics and performance. Practical applications will be presented as numerical examples to allow the student to acquire the necessary familiarity with measurement units, with 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.

The described activities will be mainly developed on the blackboard, in order to allow the student to follow actively the procedures and methodologies involved.

The teacher is available during the reception hours and also by appointment (e-mail) for explanations.

## Assessment methods and criteria

The assessment of learning is carried out through the final exam only, which ensures the acquisition of knowledge and skills (i.e. acquisition of learning outcomes) through a written test and oral interview.

The written test has a duration of 1.5 hours and the use of notes or books of any kind is not allowed. However, the (h,s) diagram for H2O (Mollier diagram) is mandatory. It is based on calculation problem similar to those presented in the course, and it requires the numerical calculation of a thermodynamic cycle applied to a power plant and the quantitative evaluation of the related performance and operating parameters. Results given to specified questions of the written test should be correct within reasonable deviations related to the approximations followed. In particular, answering to the first question is required to be admitted to the oral test with a partial score of 18/30. The other questions allow to increase the partial score up to 30/30.

If the written test is passed, the student is admitted to the oral exam, which consists in:

- a review of the written test, where the examiners inform the student about the correction criteria, receive any clarifications from the student and decide whether to modify the judgment;

- two theoretical questions on the topics of the course and on the application of the theory to original problems: the critical capacity, the ability to explain and to correlate involved issues will be evaluated.

Each question is evaluated on a scale from 0 to 30. To pass the exam a partial score of at least 18/30 is required for both questions.

The final score is obtained by calculating the arithmetic mean of the scores of the written test score and of the two oral test questions. The final score is communicated at the end of the exam.

Please note that online registration is MANDATORY to be admitted to the exam.

## Other informations

Attendance to the course lectures is highly recommended.