Cogeneration Design Guide
Including two case studies to help illustrate the entire design process, this guide offers a thorough discussion of the theoretical as well as the practical aspects of a cogeneration system design.
TABLE OF CONTENTS Cogeneration Design Guide
Chapter Two: Prime Movers
Overview
Cogeneration is the thermodynamically sequential production of two useful forms of energy from a single energy source; the prime mover, which converts thermal or chemical energy into power, is the heart of any cogeneration system. Commercially available energy conversion devices include internal combustion reciprocating engines and combustion turbines as well as steam-driven turbines and reciprocating engines. This chapter reviews the characteristics of prime movers most commonly utilized in cogeneration applications: combustion turbines, steam turbines, and reciprocating engines. Combined cycles, which are a combination of combustion and steam turbines, and emerging technologies are also reviewed.
Definitions
Several definitions are necessary to understand and compare the performance of prime movers and for the evaluation of alternative cogeneration concepts. The most basic of these definitions is mechanical efficiency, which is the prime mover's mechanical output divided by the fuel energy input. Mechanical efficiency is also referred to as thermal efficiency, generally expressed as the prime mover's heat rate (Btu/hp-h), where the engine's fuel input is expressed in Btu and the output is measured in horsepower-hours (hp-h). In those cases where the output is measured as the electrical production of the engine/generator, the term is expressed as Btu per kilowatt-hour (Btu/kWh). Another measure of efficiency applied to steam turbine applications is the system steam rate, which is defined as the amount of steam, usually measured in pounds, required to produce a kilowatt hour (pounds/kWh). In some cases, vendors may express efficiency as a percentage, with the prime mover input and...
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