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Lesson 6 How Can You

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Lesson 6 How Can You

    Electricity Innovative Technologies towards Sustainable Development

    ‘Learning-by-Notes’ Package for

    Senior School - Physics

    Lesson 6: Steam

    How Do We Make Electricity from Steam?

    Teaching Sustainability in High Schools:

    Subject Supplement

    Developed by:

    Funded by:

    As part of the:

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

? The Natural Edge Project (‘TNEP’) 2008

    The material contained in this document is released under a Creative Commons Attribution 3.0 License. According to

    the License, this document may be copied, distributed, transmitted and adapted by others, providing the work is

    properly attributed as: ‘Desha, C., Hargroves, S., Smith, M., Stasinopoulos, P. (2008) Sustainability Education for

    High Schools: Year 10-12 Subject Supplements. Module 2: Electricity Innovative Technologies towards Sustainable

    Development. The Natural Edge Project (TNEP), Australia.’ This document is freely available electronically.

    Disclaimer

    While reasonable efforts have been made to ensure that the contents of this publication are factually correct, the

    parties involved in the development of this document do not accept responsibility for the accuracy or completeness of

    the contents. Information, recommendations and opinions expressed herein are not intended to address the specific

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    Acknowledgements

    The development of the ‘Sustainability Education for High Schools: Year 10-12 Subject Supplements has been

    supported by a grant from the Port of Brisbane Corporation as part of the Sustainable Living Challenge. The Port of

    Brisbane Corporation is a Government Owned Corporation responsible for the operation and management of

    Australia’s third busiest container port. Its vision is, ‘To be Australia’s leading port: here for the future’. Sustainability

    for the Port of Brisbane Corporation means making economic progress, protecting the environment and being socially

    responsible. In response to the recent drought, and the wider global debate on climate change, the Port is committed

    to working with the port community to showcase the Port of Brisbane as a sustainable business precinct. Initiatives

    aimed at reducing the Port of Brisbane’s ecological footprint include energy efficiency, a green corporate fleet and

    constructing green buildings.

    The development of this publication has been supported by the contribution of non-staff related on-costs and

    administrative support by the Centre for Environment and Systems Research (CESR) at Griffith University; and the

    Fenner School of Environment and Society at the Australian National University. The material has been researched

    and developed by the team from The Natural Edge Project. Versions of the material have been peer reviewed by

    Cameron Mackenzie, Queensland Department of Education, and Ben Roche, National Manager, Sustainable Living

    Challenge, University of New South Wales.

    Project Leader: Mr Karlson ‘Charlie’ Hargroves, TNEP Director Principle Researcher: Ms Cheryl Desha, TNEP Education Director

    TNEP Researchers: Mr Michael Smith, Mr Peter Stasinopoulos

    Copy-Editor: Mrs Stacey Hargroves, TNEP Editor

    The Natural Edge Project

    The Natural Edge Project (TNEP) is an independent non-profit Sustainability Think-Tank based in Australia. TNEP

    operates as a partnership for education, research and policy development on innovation for sustainable development.

    TNEP's mission is to contribute to, and succinctly communicate, leading research, case studies, tools, policies and

    strategies for achieving sustainable development across government, business and civil society. Driven by a team of

    early career Australians, the Project receives mentoring and support from a range of experts and leading

    organisations in Australia and internationally, through a generational exchange model. TNEP’s initiatives are not-for-

    profit. Our main activities involve research, creating training and education material and producing publications. These

    projects are supported by grants, sponsorship (both in-kind and financial) and donations. Other activities involve

    delivering short courses, workshops, and working with our consulting associates as we seek to test and improve the

    material and to supplement the funds required to run the project. All support and revenue raised is invested directly

    into existing project work and the development of future initiatives.

    Enquires should be directed to: Mr Karlson ‘Charlie’ Hargroves, Co-Founder and Director, The Natural Edge Project charlie@naturaledgeproject.net www.naturaledgeproject.net Prepared by The Natural Edge Project 2008 Page 2 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

    Lesson 6: Steam

    How Do We Make Electricity from Steam?

    According to an estimate by the Centre for International Economics,

    Australia has enough geothermal energy to contribute electricity for 450 years.

    1Sydney Morning Herald, April 2007

    Educational Aim

    The aim of this lesson is to describe the key components of steam turbines and electric

    generators, and the processes used by these technologies to generate electricity from steam.

    Key Words for Searching Online

    Steam turbines, nozzle blade, rotor blade, nozzles, impulse turbine, reaction turbine, electric

    generators, electromagnetic induction, alternator

    Key Learning Points

    1. Making electricity from steam is generally a three step process, involving:

    1) Converting water to high pressure steam

    2) Using the high pressure steam in a steam turbine to rotate the turbine shaft

    3) Using the rotating turbine shaft in an electric generator to generate electricity

    In most cases, the used steam is converted back to water and returned to the source.

    2. Water is converted to high pressure steam using either the heat from burning fuels,

    2geothermal energy or the heat from atomic fission.

    3. Steam turbines convert high pressure steam to mechanical rotation in a process which

    involves steam at high-pressure (high pressure potential energy) and with some velocity

    (some linear kinetic energy) entering the turbine and being sucked through sets of different

    turbine blades, eventually exiting at (normal) atmospheric pressure. During this process:

    1) The steam first encounters a set of stationary blades, called nozzles, that guide the

    steam towards the next set of blades.

    2) The steam then encounters a set of moving blades, called rotor blades, which are

    connected to the turbine shaft. When the rotor blades move, the turbine shaft rotates

    (rotational kinetic energy).

    Thus the steam turbines convert the combined input pressure potential energy and linear

    kinetic energy of steam to output rotational kinetic energy of the turbine shaft. 4. Each pair of nozzles and rotor blades is called a stage. Some turbines use multiple stages in

    succession to convert as much steam energy into shaft energy as is economical.

     1 Garnaut, J. (2007) Scientists get hot rocks off over green nuclear power’, Sydney Morning Herald, 12 April 2007. Available at www.smh.com.au/news/environment/hot-rock-power-the-way-ahead/2007/04/11/1175971183212.html. Accessed 12 May 2008. 2 Geothermal energy involves finding vast blocks of ‘hot rocks’ with fracture systems that could generate electricity through water being injected, circulated through the fractures, and being returned to the surface as steam. Prepared by The Natural Edge Project 2008 Page 3 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

5. The energy conversion as the steam flows through the blades depends on whether the

    turbine is an impulse turbine or a reaction turbine. The difference between these two types of

    turbines lies in their blade configurations:

    1) In an impulse turbine, the force that moves the blades is a result of the steam striking the

    blades. This force is known as an impulse. As the steam passes through the nozzle, all

    of its pressure potential energy is converted to linear kinetic energy. Then as the steam

    passes through the rotor blades, all of its linear kinetic energy is converted to rotational

    kinetic energy.

    2) In a reaction turbine, the force that moves the blades is a result of the blades changing

    the direction of the steam’s flow. This force is known as a reaction force. As the steam

    passes through the nozzle, some of its pressure potential energy is converted to linear

    kinetic energy. Then as the steam passes through the rotor blades, all of its remaining

    pressure potential energy and all of its linear kinetic energy is converted to rotational

    kinetic energy.

    6. An electric generator is a device that converts the rotating turbine shaft’s kinetic energy into

    electricity, or an electric current. The electricity then generates a voltage across an electrical

    load.

    7. An electric generator works under the principle of electromagnetic induction, which means

    that if an electrical conductor, such as a wire, is moved through a magnetic field, then an

    electric current will be generated in the conductor.

    8. The principle of electromagnetic induction is applied in an alternating current (AC) electric

    generator, or alternator.

Prepared by The Natural Edge Project 2008 Page 4 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

Brief Background Information

    Making electricity from steam is generally a three step process, where water is converted to high

    pressure steam, then the high pressure steam is converted to mechanical rotation of a turbine

    shaft, and the rotating turbine shaft then drives an electric generator.

    Step 1: Water to Steam

    In steam electric power plants, water is usually converted to high pressure steam using one of

    the following options:

    - A boiler, which creates heat energy by burning fuels such as coal, oil, natural gas, wood or 3 municipal waste as shown in Figure 6.1.

    - Geothermal energy, which is the heat energy in the ground near the Earth’s core, as shown

    in Figure 6.2. Geothermal energy exploration involves finding blocks of underground

    radioactive ‘hot rocks’ which contain fractures through which water can pass. The

    proposition is that these support electricity generation by water being injected, circulated

    through the fractures, and then returned to surface as steam.

    South Australia has been described as ‘Australia's hot rock haven’. According to an estimate

    by the Centre for International Economics, Australia has enough geothermal energy to

    4contribute electricity for 450 years. A geothermal power plant is already generating 80 kW of

    5electricity at Birdsville, in southwest Queensland. - Atomic fission, which creates heat energy by splitting large atoms in to smaller atoms (see

    6Figure 6.3).

    Fundamentals

    The pressure of a gas in an enclosure

    varies with temperature (if the volume

    remains the same):

    - pressure temperature

    The heat energy is absorbed by the

    gas particles, which then become

    more active and thus have more

    frequent and forceful collisions with

    each other and the enclosure’s walls.

    These collisions cause pressure.

     3 Onsite SYCOM Energy Corporation (1999) Review of Combined Heat and Power Technologies, Office of Industrial Technologies, p 12. Available at http://www.eere.energy.gov/de/pdfs/chp_review.pdf. Accessed 17 April 2007. 4 Garnaut, J. (2007) Scientists get hot rocks off over green nuclear power’, Sydney Morning Herald, 12 April 2007. Available at http://www.smh.com.au/news/environment/hot-rock-power-the-way-ahead/2007/04/11/1175971183212.html Accessed 12 May 2008. 5 Hargroves, K. and Smith, M. (2007) Energy superpower or sustainable energy leader?’, CSIRO Ecos, Oct-Nov 2007. Available at http://www.publish.csiro.au/?act=view_file&file_id=EC139p20.pdf. Accessed 12 May 2008. 6 See Clean and Safe Energy Coalition How a Nuclear Power Plant Works at http://www.cleansafeenergy.org/CASEnergyClassroom/HowaNuclearPowerPlantWorks/tabid/170/Default.aspx. Accessed 4 January 2008.

    Prepared by The Natural Edge Project 2008 Page 5 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

    Figure 6.1. A steam electric power plant powered by a boiler

    7 Source: TXU Energy

    Figure 6.2. A steam electric power plant powered by geothermal energy

    8Source: US Department of Energy

    Figure 6.3. A steam electric power plant powered by nuclear fission

    9Source: Clean and Safe Energy Coalition

     7 See TXU Energy Steam Turbines at http://www.txucorp.com/responsibility/education/generation/steam.aspx. Accessed 5 December 2007. 8 See US Department of Energy Geothermal Power Plants at http://www1.eere.energy.gov/geothermal/powerplants.html. Accessed 12 November 2007.

    Prepared by The Natural Edge Project 2008 Page 6 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

2. Convert High Pressure Steam to Mechanical Rotation

    10Steam Turbines convert high pressure steam to

    Fundamentals mechanical rotation. Their power output can range from

    11Kinetic energy is a form of energy in 0.5 megawatts to over 1300 megawatts. Steam turbines

    moving objects. Kinetic energy can be convert 10-40 percent of the combined input pressure either linear or rotational: potential energy and linear kinetic energy of steam to

    12- linear kinetic energy linear output rotational kinetic energy of the turbine shaft in

    velocity2the following process: - High-pressure steam (high pressure potential energy) - rotational kinetic energy

    and with some velocity (linear kinetic energy) enters 2rotational velocity the turbine and is sucked through sets of different Potential energy is a form of stored turbine blades, exiting at atmospheric pressure. energy in objects that can be

    converted to kinetic energy. Potential - The steam first encounters a set of stationary blades,

    energy results in gases that are which are also converging nozzles, that guide the between regions of different pressure: steam towards the next set of blades.

    - pressure potential energy - The steam then encounters a set of moving blades, pressure difference between called rotor blades, which are connected to the regions

    turbine shaft such that when the rotor blades move,

    the turbine shaft rotates (rotational kinetic energy).

    - Each pair of nozzles and rotor blades is called a stage. Some turbines use multiple stages in

    succession to convert as much steam energy into shaft energy as is economical. The energy

    conversion as the steam flows through the blades depends on whether the turbine is an

    impulse turbine or a reaction turbine. The Fundamentals difference between these two types of turbines lies Gases will move from small volumes in their blade configurations. Each blade at high pressure to large volumes at configuration uses a different type of primary force low pressure (if the temperatures of

    (impulse or reaction) to move the rotor blades, but both regions are the same) in a

    process known as expansion. also uses the other type of force (reaction or

    impulse) secondarily. The two can also be The pressure of the air we breathe is

    called atmospheric pressure, and is combined into an impulse-reaction configuration, relatively low. relying heavily on both impulse and reaction

     9 See Clean and Safe Energy Coalition How a Nuclear Power Plant Works at http://www.cleansafeenergy.org/CASEnergyClassroom/HowaNuclearPowerPlantWorks/tabid/170/Default.aspx. Accessed 4 January 2008. 10 Onsite SYCOM Energy Corporation (1999) Review of Combined Heat and Power Technologies, Office of Industrial Technologies, pp 12-13. Available from http://www.eere.energy.gov/de/pdfs/chp_review.pdf. Accessed 17 April 2007. 11nd Educogen (2001a) The European Education Tool on Cogeneration, 2 ed., The European Association for the Promotion of Cogeneration, Belgium, p 47. Available at http://www.cogen.org/Downloadables/Projects/EDUCOGEN_Tool.pdf. Accessed 17 April 2007; Onsite SYCOM Energy Corporation (1999) Review of Combined Heat and Power Technologies, Office of Industrial Technologies, pp 5, 12. Available at http://www.eere.energy.gov/de/pdfs/chp_review.pdf. Accessed 17 April 2007; United Nations Environment Programme (n.d.) Energy Technology Fact Sheet: Cogeneration, UNEP Division of Technology, Industry and Economics - Energy and OzonAction Unit, France. Available at http://www.cogen.org/Downloadables/Publications/Fact_Sheet_CHP.pdf. Accessed 17 April 2007. 12nd Educogen (2001a) The European Education Tool on Cogeneration, 2 ed., The European Association for the Promotion of Cogeneration, Belgium, p 47. Available at http://www.cogen.org/Downloadables/Projects/EDUCOGEN_Tool.pdf. Accessed 17 April 2007; Onsite SYCOM Energy Corporation (1999) Review of Combined Heat and Power Technologies, Office of Industrial Technologies, p 5. Available at http://www.eere.energy.gov/de/pdfs/chp_review.pdf. Accessed 17 April 2007; United Nations Environment Programme (n.d.) Energy Technology Fact Sheet: Cogeneration, UNEP Division of Technology, Industry and Economics - Energy and OzonAction Unit, France. Available at http://www.cogen.org/Downloadables/Publications/Fact_Sheet_CHP.pdf. Accessed 17 April 2007.

    Prepared by The Natural Edge Project 2008 Page 7 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

    forces to move the rotor blades.

    Fundamentals Impulse Turbines A nozzle is a tube-like device that

    The energy conversion for an impulse turbine is shown either converges or diverges. As a

    fluid flows through a nozzle, its linear in Figure 6.4. In the impulse blade configuration (see

    velocity increases as the nozzle Figure 6.5(a) and Figure 6.5(b)), there is high pressure converges and decreases as the at the nozzle’s inlet, atmospheric pressure between the nozzle diverges. The increase/ nozzle and rotor blade, and atmospheric pressure at decrease in the fluid’s linear velocity, the rotor blades outlet. A nozzle is usually at the outlet and hence its linear kinetic energy, is

    converted from/to its pressure of a guiding tube and rotor blades are connected to the

    potential energy: rotor, which is also connected to the turbine’s shaft.

    - linear velocity 1/pressure Since the nozzle’s inlet pressure is higher than its outlet

    pressure, the steam expands through the nozzle most of the steam’s pressure potential energy is

    converted to linear kinetic energy. After flowing through

    the nozzle, steam then strikes the rotor blades and

    applies a force. This force results in an impulse on the

    Fundamentals rotor blades, transferring most of the steam’s linear

    Applying a force on an object for some kinetic energy

    time results in an impulse. An impulse to the rotor increases the object’s velocity in the blades linear direction of the force. kinetic energy

    and hence the

    turbine shaft’s rotational kinetic energy.

    Since a rotor blade’s inlet and outlet are both at atmospheric pressure, the steam does not

    expand and thus rotor blades are not designed to converge nor diverge (see Figure 6.5(c)). After

    flowing through the rotor blades, the steam is finally exhausted at low pressure and low velocity.

    A commonly recognised application of the impulse configuration is the Pelton wheel (see Figure

    6.5(d)).

    Figure 6.4. Energy conversion in an impulse turbine.

    Prepared by The Natural Edge Project 2008 Page 8 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

    (a) (b)

    (c) (d)

Figure 6.5. (a) Single-nozzle impulse turbine; (b) four-nozzle impulse turbine; (c) impulse nozzle

    blade configuration; (d) Pelton wheel

    1314 (b) Integrated Publishing (n.d.); (c) Adapted from Source: (a) US Department of Energy;1516Beardmore, R (2006) by TNEP; (d) Adapted from The Free Dictionary by TNEP Reaction Turbines

    The energy conversion for a reaction turbine is shown in Figure 6.6. In the reaction blade

    configuration (see Figure 6.7(a) and Figure 6.7(b)), there is high pressure at the nozzle’s inlet,

    moderate pressure between the nozzle and rotor blade, and atmospheric pressure at the rotor

    blade’s outlet. Nozzles are usually connected to the turbine’s casing and rotor blades are connected to the rotor, which is also connected to the turbine’s shaft. Since the nozzle’s inlet pressure is higher than its outlet pressure, the steam expands through the nozzle some of the steam’s pressure potential energy is converted to linear kinetic energy. After flowing through the nozzle, steam then flows through the rotor blades, where it is forced to change direction. This

    force on the steam results in a reaction force on the rotor blades, transferring most of the

    steam’s pressure potential energy and linear kinetic energy to the rotor blades linear kinetic energy and hence the turbine shaft’s rotational kinetic energy.

     13 See US Department of Energy Microhydropower System Turbines, Pumps, and Waterwheels at http://www.eere.energy.gov/consumer/your_home/electricity/index.cfm/mytopic=11120. Accessed 20 December 2007. 14 Integrated Publishing (n.d.) ‘Chapter 10: Actuators’ in Fluid Power, Integrated Publishing, pp 10.11-10.12. Available at http://www.tpub.com/content/engine/14105/css/14105_164.htm. Accessed 20 December 2007. 15 Beardmore, R. (2006) Thermodynamics Steam Turbine. Available at http://www.roymech.co.uk/Related/Thermos/Thermos_Steam_Turbine.html. Accessed 20 December 2007. 16 See The Free Dictionary Turbine at http://www.thefreedictionary.com/Turbines. Accessed 20 December 2007.

    Prepared by The Natural Edge Project 2008 Page 9 of 17

     Electricity Innovative Technologies towards Sustainable Development

    Lesson 6: Electricity from Steam

    Figure 6.6. Energy conversion in a reaction turbine

    (a) (b)

    (c) (d)

    Figure 6.7. (a) Blades of a single-stage reaction turbine; (b) Blades of a two-stage reaction

    turbine; (c) reaction nozzle blade configuration; (d) Catherine wheel

    1718 (c) Adapted from Beardmore, R. (2006); (d) Adapted Source: (a) & (b) Global Security (n.d.);19from The Free Dictionary

     17th Global Security (n.d.) Aircraft Gas Turbine Engines, Subcourse No. AL0993, 5 edition, Lesson 2: Major Engine Sections. Available at http://www.globalsecurity.org/military/library/policy/army/accp/al0993/le2.htm. Accessed 21 December 2007. 18 Adapted from Beardmore, R. (2006) Thermodynamics Steam Turbine, Roymech, UK. Available at http://www.roymech.co.uk/Related/Thermos/Thermos_Steam_Turbine.html. Accessed 20 December 2007. 19 See The Free Dictionary Turbine at http://www.thefreedictionary.com/Turbines. Accessed 20 December 2007. Prepared by The Natural Edge Project 2008 Page 10 of 17

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