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Combined Cycle Power Plants

Lee Layton, P.E.


Course Outline

The course begins with an in-depth look at the natural gas industry including what natural gas is, and where it is found.  The course reviews the many different ways that natural gas is categorized and an attempt is made to help understand the concept of “ gas reserves”.

Following a review of the natural gas industry, the course covers each major component of a combined cycle power plant and then walks the reader through a typical plant from the delivery of the natural gas to the exhaust of waste heat.  Finally, the course reviews some of the environmental concerns with natural gas-fueled power plants.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

After taking this course you should,

Intended Audience

This course is intended for electrical engineers and others who want to understand the operation of combined cycle power plants.

Benefit to Attendees

Combined cycle power plants will be a major component of utility generator fleets for many years.  Understanding the benefits – and the environmental issues – of combined cycle plants will help the reader understand the generation choices that utilities must make to meet future power needs.

Course Introduction

Fossil fuel-fired power plants use either steam or combustion turbines to provide the mechanical power to electrical generators. Pressurized high temperature steam or gas expands through various stages of a turbine, transferring energy to the rotating turbine blades. The turbine is mechanically coupled to a generator, which produces electricity. 

The Combined Cycle power plant is a combination of a fuel-fired turbine with a Heat Recovery Steam Generator (HRSG) and a steam powered turbine. These plants are very large, typically rated in the hundreds of mega-watts.  They combine the Rankine Cycle (steam turbine) and Brayton Cycle (gas turbine) thermodynamic cycles by using heat recovery boilers to capture the energy in the gas turbine exhaust gases for steam production to supply a steam turbine.

Natural gas is a major fuel source for electric generation through the use of gas turbines and steam turbines. Most grid peaking power plants and some off-grid engine-generators use natural gas. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Natural gas burns more cleanly than other fossil fuels, such as oil and coal, and produces less carbon dioxide per unit energy released. For an equivalent amount of heat, burning natural gas produces about 30% less carbon dioxide than burning petroleum and about 45% less than burning coal. Combined cycle power generation using natural gas is thus the cleanest source of power available using fossil fuels, and this technology is widely used wherever gas can be obtained at a reasonable cost.

Combined-cycle power plants have high thermal efficiency, high reliability and economic power generation for application in base load utility service. 

In this course, we will take a detailed look at the natural gas industry including where the current and expected gas reserves are located.  Then we will go into the details of how a combined cycle power plant works.  Finally, we will discuss some of the environmental impacts of a combined cycle power plant. 

Course Content

This course content is in the following PDF document:

Combined Cycle Power Plants

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Course Summary

Natural gas is a vital fuel for maintaining America's thriving, robust economy and new natural gas resources will continue to allow natural gas to be a choice fuel for electric power generation for many years.  To meet growing demand and to diversify our energy supply, the United States needs to continue to exploit the benefits of shale gas as well as bring in natural gas from overseas in the form of liquefied natural gas (LNG).

Because of high thermal efficiency, low initial cost, high reliability, relatively low gas prices and low air emissions, combined-cycle gas turbines have been the new resource of choice for bulk power generation for well over a decade and will continue to be a significant source of central station power generation for many years.

Proximity to natural gas mainlines and high voltage transmission is the key factor affecting the siting of new combined-cycle plants. Secondary factors include water availability, ambient air quality and elevation.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.