Organic Rankine Cycle (ORC) Power Systems

Technologies and Applications

Ennio Macchi, Marco Astolfi

• Publisher: Woodhead Publishing
• Year: 2016
• Topic: Technology & Engineering
• eBook ISBN:
  9780081005118
• Subtopic: Renewable Power Resources
• Index: Technology & Engineering

Organic Rankine Cycle (ORC) Power Systems: Technologies and Applications provides a systematic and detailed description of organic Rankine cycle technologies and the way they are increasingly of interest for cost-effective sustainable energy generation. Popular applications include cogeneration from biomass and electricity generation from geothermal reservoirs and concentrating solar power installations, as well as waste heat recovery from gas turbines, internal combustion engines and medium- and low-temperature industrial processes. With hundreds of ORC power systems already in operation and the market growing at a fast pace, this is an active and engaging area of scientific research and technical development.  The book is structured in three main parts: (i) Introduction to ORC Power Systems, Design and Optimization, (ii) ORC Plant Components, and (iii) Fields of Application. - Provides a thorough introduction to ORC power systems - Contains detailed chapters on ORC plant components - Includes a section focusing on ORC design and optimization - Reviews key applications of ORC technologies, including cogeneration from biomass, electricity generation from geothermal reservoirs and concentrating solar power installations, waste heat recovery from gas turbines, internal combustion engines and medium- and low-temperature industrial processes - Various chapters are authored by well-known specialists from Academia and ORC manufacturers

Part One

Introduction to Organic Rankine Cycle power systems

Outline

1. Theoretical basis of the Organic Rankine Cycle

2. History of Organic Rankine Cycle systems

3. Technical options for Organic Rankine Cycle systems

4. Organic fluids for Organic Rankine Cycle systems: classification and calculation of thermodynamic and transport properties

5. Thermal stability of organic fluids for Organic Rankine Cycle systems

6. Dynamic modeling and control of Organic Rankine Cycle plants

7. Thermodynamic and technoeconomic optimization of Organic Rankine Cycle systems

1

Theoretical basis of the Organic Rankine Cycle

E. Macchi Politecnico di Milano, Milan, Italy

Abstract

This chapter aims to define a set of general correlations for the estimation of axial-flow turbine efficiency in the Organic Rankine Cycle (ORC) field. A dedicated numerical tool is used for the optimization of several hundreds of turbines and the results are presented in terms of specific parameters (SP, V_r, and Ns) according to similarity rules. The analysis is carried out for single, two, and three stages turbines. For each case a correlation of efficiency at optimal rotational speed is calibrated in function of the equivalent single stage SP and the total isentropic V_r. Three sensitivity analyses are proposed in order to highlight the effects of each single parameter on stage efficiency. Finally, the effect of fluid choice on turbine performance and dimension is discussed with a numerical example.

Keywords

Carnot; Heat sources; Organic Rankine Cycle; Power cycle; Recuperator; Working fluid

1.1. Introduction

It is well known that gas and steam cycles play a dominant role in large-scale stationary power generation. Open-cycle gas turbines (often combined with steam cycles) are widely used, especially where low-cost natural gas is available, while steam cycles are the preferred solution when the energy source characteristics, typically coal or nuclear, require a closed-cycle power plant.

However, there is a large variety of energy sources (see Fig. 1.1) for which neither gas nor steam cycles offer a technically and/or economically viable solution to generate electric power. When the temperature and/or the thermal power available from the energy source is limited, it becomes attractive to adopt a different class of prime movers, universally known with the acronym ORC (Organic Rankine Cycle).

This volume focuses on ORC, aiming to provide the reader with a comprehensive overview of all aspects of this fascinating new field in the power generation industry. It is organized into three main parts.

Figure 1.1 A representation of ORC applications fields in the heat source temperature-power output plane.

Part 1 of the volume is devoted to the fundamental bases of the technology:

• This introduction explains why the ORC technology is the unrivaled technical solution for producing electricity (or coproducing electricity and heat) from a wide-ranging variety of energy sources and illustrates the guidelines for selecting the proper fluid and the proper cycle for each application.

• In Chapter 2, the founder of Ormat, which is the undisputed world leading company in ORC, illustrates the exciting and successful history of ORCs, from the pioneering applications to the latest developments.

• Chapter 3 illustrates the possible technical options for ORC applications, in terms of thermodynamic cycles (from simple one pressure level to multipressure solutions), plant layouts, and main component characteristics.

• Chapter 4 provides a theoretical basis and a thorough review of the most up-to-date methods and available tools for calculating the thermodynamic and transport properties of working fluids for ORC.

• Chapter 5 addresses the topic of thermal stability of working fluids, a fundamental aspect in ORC applications, since thermal stability ​sets the limit to the maximum temperature of the thermodynamic cycle, strictly related to its conversion efficiency.

• Chapter 6 illustrates the basic principles of the dynamic modeling of ORC systems and how these models can be the basis for a reliable control of ORC, particularly in applications characterized by fast variations of operating conditions.

• Chapter 7 illustrates the most up-to-date methods to optimize an ORC system, both in terms of thermodynamic performance and economic aspects. A few examples demonstrate the intrinsic worth of these advanced design approac...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Energy
• Part One. Introduction to Organic Rankine Cycle power systems
• Part Two. Organic Rankine Cycle plant components and system optimization
• Part Three. Fields of application
• Index