Preface

The concept of exergy is very important in engineering and science analyses. The useful amount of work extracted from any system could be obtained using the principles of exergy considering the equilibrium of the system with the surrounding environment in a reversible state. This book is divided into two sections, each of which includes four chapters: "New Technologies in Exergy" and "Applications of Exergy".

In Chapter 1, drying is emphasized as an energy-intensive process in food preservation because it eliminates extra moisture and increases the longevity of food products. The chapter examines the use of both renewable and non-renewable energy sources to generate the energy needed for drying. It highlights the merits of using solar energy as the best source of energy for drying processes, including the drying of agricultural produce. The main components of a typical solar dryer are the fan, the solar air heater (SAH), and the dryer chamber. The chapter also carries out an exergy economic analysis to ensure that the primary contributing factors to system exergy loss are recognized and understood.

Compressing images and reconstructing them without degrading their original quality is a major challenge in our modern world. Thus, Chapter 2 proposes a coding system that considers the implementation of both quality and compression rate considering high synthetic entropy coding schema. This coding schema can store the compressed image at the smallest size possible without affecting its original quality. The chapter considers a technique based on Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT). The evaluation of the test case was carried out using different standard color images and various performance metrics of the variables to reflect the effectiveness of the proposed scheme.

The approach of nonreciprocal photonic management can turn the absorption-emission balance to the advantage of absorption and improve the conversion efficiency more than the usual Shockley–Queisser balanced limit. Chapter 3 examines the use of nonreciprocal photovoltaic (PV) cells to convert the entire exergy (Helmholtz free energy) of quasimonochromatic radiation into electric power. It presents the evaluation of the limiting performance of a typical nonreciprocal, dissipation-less monochromatic converter and discusses the limiting efficiency of the nonreciprocal converter based on the adverse effect of the greenhouse. The chapter also presents a thorough modeling of the greenhouse effect in the gallium arsenide (GaAs) PV converter along with the performance of a PV in converting laser radiation. The presented results show that the greenhouse filter ensured a sharp absorption edge and reduced conversion losses related to the distributed PV bandgap and laser-cell matching losses.

In a bid to replace fossil fuels with renewable energy resources, biofuels have emerged as potential replacements for diesel fuels. These biofuels can be used in an engine cylinder without any modifications by blending them with conventional diesel fuels. Evaporation of fuel droplets in engine cylinders is a process involving the atomization of fuel to release gases. This evaporation process is directly connected to the efficiency of the engine. Chapter 4 presents the evaporation characteristics of conventional diesel fuel and biofuels under different working conditions. It also models the evaporation phenomenon using

computational fluid dynamics (CFD) and the effects of cylinder conditions. The results show that biofuel droplets have a better evaporation rate at high operating conditions in an engine cylinder.

Chapter 5 presents the dynamic behavior of a non-commercial shrink tank heat transfer process, considering two different arrangements of electrical resistances for water heating. Thorough numerical simulations are carried out based on the implicit method of alternating directions (ADI). The evaluation of the system's performance based on heating times with their respective temperature distributions shows that the arrangement with four resistances is the most efficient for the process of heating the water in the shrink tank.

Chapter 6 estimates entropy generation in terrestrial systems and the atmosphere by imitating the entropy analysis of steam power generation (STPG). The maximum entropy generation is related to the outgoing longwave radiation flux. The presented results show that the most significant terms of entropy generation (heat dissipation) in different processes are related to the hidden and sensible heat fluxes. It is observed that the vegetation cover (boiler system) destroyed a part of solar energy absorption in the form of entropy generated by the formation of water vapor and transpiration (steam turbine).

Chapter 7 presents the state of the art of marine current turbine (MCT) system faults. The MCT topology consists of a marine turbine, a generator (permanent magnet synchronous generator (PMSG) or doubly fed induction generator (DFIG)) and a PWM power converter. This chapter explores the several faults related to the turbine, generator, blades, and converters in an MCT. These faults generate oscillations in the speed and the torque, which may lead to mechanical vibrations and the rapid destruction of the insulating material generator.

Chapter 8 examines the importance of exergy-based parameters like exergy efficiency, environmental compatibility, sustainability index, and depletion number, as well as the Improvement Potential (IP) of hydrocarbon fuel utilization. The IP of hydrocarbon fuel utilization is the product of the square of the depletion number and the fuel input exergy. Various metrics are used to evaluate the fuel exergy performance in the presented study. Due to the fact that exergy destruction is linked to material depletion, the fuel exergy flow is therefore proportional to its material flow. This chapter shows that if the IP, is high, it means that the exergy losses are too high and there is a big room for exergy efficiency improvement.

> **Kenneth Eloghene Okedu** Smart Energy Unit, Victoria University, Melbourne, Australia

Section 1

New Technologies in Exergy

Melbourne Institute of Technology, School of Information Technology and Engineering, Melbourne, Australia Section 1
