Electric Power Concepts. Prof. Sid Suryanarayanan Div. of Engg., Colorado School of Mines

Transcription

1 Electric Power Concepts Prof. Sid Suryanarayanan Div. of Engg., Colorado School of Mines

2 Outline of presentation How is electricity produced? Or How does a power plant work? How is electricity delivered? Or What is the electric grid? How is electricity used? Or How different are electric loads? Each topic will be a 15 presentation Handouts and web links will be provided

3 Introduction Raising student interest in electric power is important Almost 50% of the power industry workforce will be eligible to retire in less than 5 years Electric power engineering relies strongly on concepts of mathematics and science Pre-college students have to be motivated in Math and Sci. to maintain US competitiveness

4 Introduction Studies indicate many students lose interest in Math & Sci. in high school and middle school years To capture the interest of K-12 students, we must present electric power concepts in eye-catching modes Simulations, applets, interactive modules, etc.

5 Electric power systems - a brief history Picture taken directly from [2] 1879: Edison perfects work on electric light 1882: Edison opens Pearl St. Station, NYC DC generators ( dynamos ) 30 kw load of 110 V incandescent lighting 59 customers spread over 1 sq. mile Picture taken directly from [3]

6 Electric power systems - a brief history 1885: Stanley develops transformer and installs AC distribution system in MA More attractive option than DC 1888: Tesla invents 2φ induction and sync motors Patents purchased by Westinghouse 1889: first operational AC transmission line in US 1φ 4 kv 21 km (13 miles) b/w Portland and Oregon City 1893: First 3 φ line in US 12 km (7.5 miles) at 2.3 kv 20th century US NAE names electrification most important engineering achievement of 20th C All pictures taken directly from [2]

7 Electric power systems 21 st C 2005: Energy Policy Act Distributed Generation 2007: Energy Independence and Security Act Smart Grid Initiative 2009: American Recovery and Reinvestment Act $$ for Smart Grid projects Abundant opportunities for education, jobs, & careers for power engineers of future Catch them young, watch them grow!

8 How is electricity produced? Electricity is produced from other sources coal, natural gas, wind, nuclear, hydro Typically, electricity is generated in a power plant Depending on type of fuel used, power plants operate differently We will look at the operation of a thermal power plant

9 How is electricity produced? Thermal power plant uses steam as the main driver to produce electricity Coal, nuclear, geothermal are all thermal power plants Let us see how a coal-fired thermal power plant works

10 How is electricity produced? Coal-fired thermal power plant uses coal as the fuel Sulfur content in coal determines its cleanness (lower Sulfur cleaner coal) Coal is brought to the power plant from the mines via trains and stored in silos When required, coal is crushed into a fine powder in coal mills This helps the coal burn efficiently Information on slide adapted from [4]

11 How is electricity produced? Finely crushed coal is then brought to a boiler where it is fired at 3000 o F The high energy from burning this coal is used to convert water to superheated steam Water circulates in pipes within the boiler and becomes steam The steam, which has high energy, is now brought to a turbine Information on slide adapted from [4]

12 How is electricity produced? As the steam passes through the turbine, it moves the blades on the turbine This happens at high speeds As this happens, steam cools off and needs to be reconverted to water for use again The cooled steam in the pipe is then passed through cold water The steam in the pipes cool further to become water The cold water outside the pipe becomes steam and is let off through smoke stacks Information on slide adapted from [4]

13 How is electricity produced? The blades of the turbine are connected to a shaft that spins an electric generator This is where mechanical energy of the shaft is converted to electricity Generator has a moving part (rotor) and a stationary part (stator) essentially an electromagnet As the rotor moves within the stator, an electric current is produced Thus, electricity is produced and awaits delivery Information on slide adapted from [4]

14 How is electricity produced? Picture taken directly from [5]

15 How is electricity delivered? Electricity produced by generators are at lower voltages Typically, power plants are located far from load centers (cities, etc.) Power needs to travel long distances over transmission lines to reach cities To do so, the voltage of electricity must be raised Imagine voltage as an equivalent of pressure; electricity as water; and transmission lines as pipes Higher pressure is needed to push water through pipes over long distances An electrical device called transformer performs the task of raising the voltage of electricity at the power plant

16 How is electricity delivered? A Volts generator step-up transformer Picture taken directly from [6]

17 How is electricity delivered? Through the power grid (aka network) 3 large interconnections of transmission lines and other components crisscrossing North America The power grid has been called the most complex man made machine

18 How is electricity delivered? The US electric grid Source: Technology Review, Jul 01 [7]

19 How is electricity delivered? WHY INTERCONNECT? WECC Source: DoE Distributed Energy Program [8]

20 How is electricity delivered? Advantages of interconnection Ability to supply loads from a combination of generators across the nation Since electricity travels almost at the speed of light, we can get electrical power produced by a generator in NYC delivered to Golden CO (a distance of ~1800 miles) in 100 th of 1 second! Drawback of interconnection Because the system is fully interconnected, any bad event in one part of the system has the potential to show up across the system (cascade)

21 How is electricity delivered? Applet developed by Univ. of Illinois for introducing power grid to K-12 students Interactive module with real time simulation screens Accompanying lessons and games available for teachers on the web site

22 How is electricity delivered? Educational objectives met by applet [1] : Students learn how energy is transferred from generators to loads via the power grid through transmission lines, substations, and transformers Benefits and drawback of interconnections Power and energy is conserved at all places Fuel type affects power ratings, controllability and environmental impact Lines can carry only up to their rated values; When excess power is forced through lines, they disconnect

23 How is electricity consumed? The power grid transfers electricity from far away generators using a high voltage network of components This electricity is still at high voltage that is not readily usable by homes and buildings Distribution systems High voltage electricity must be converted to lower voltage electricity Again, a transformer will do the job of stepping-down voltage too! Voltage is stepped-down in several stages Loads such as TVs, Nintendo Wii consume electricity that is delivered

24 How is electricity consumed? Transformers Picture taken directly from [9] Picture taken directly from [11] Picture taken directly from [10]

25 How is electricity consumed? Different loads in different places have different characteristics Let us look at some electrical loads and see how they behave Before that, we must understand how we are billed by the utility for the electricity we consume Cost of 1 unit of electric energy ($/kwh) x Σ{Power rating of device (kw) x time of use (h)} Electricity used is measured using a energy meter or kilowatthour meter

26 How is electricity consumed? Applet developed by Univ. of Illinois for introducing power and energy use at home to K-12 students Interactive module with real time simulation screens Accompanying lessons and games available for teachers on the web site

27 How is electricity consumed? Educational objectives met by applet [1] : Students learn that energy is delivered from distribution network to the various home loads Electrical loads vary in power demand Energy is power used over time Energy is metered and priced over time in units of kwh Energy and money can be saved by using more efficient loads (like E-star)

28 The Smart Grid Initiative Picture taken directly from [12]

29 Acknowledgements Prof. Thomas Overbye, UIUC Prof. Zeb Tate, Univ. of Toronto Ms. Jana Sebastik, UIUC

30 References 1) J. E. Tate, T. J. Overbye, J. Sebestik, G. C. Reese, Interactive Lessons for Pre-University Power Education, IEEE. Trans Pwr Sys, vol. 23, no. 3, pp , Aug ) C. L. Sulzberger, Triumph of AC: from pearl street to Niagara, IEEE Power & Energy Magazine, v. 1, no. 3, pp , May ) Smithsonian Institution. Powering a generation: Views of Pearl street station [Online] {Available} (Accessed Jun 09) 4) Xcel Energy. Welcome to Energy Classroom [Online] {Available} (Accessed Jun 09) 5) Tenn Valley Authority. [Online] {Available} (Accessed Jun 09) 6) Mitsubishi Electric Power Products Inc. [Online] {Available} %20345%20kV.JPG (Accessed Jun 09) 7) Technology Review. A smarter power grid. [Online] {Available} (Accessed Jun 2009) 8) US Dept. of Energy. Distributed energy program: US power grids. [Online] {Available} (Accessed Jun 2009) 9) How Stuff Works. How power grids work [Online] {Available} (Accessed Jun 2009) 10) Pauwels Transformers Inc. Three phase pad mount distribution transformer [Online] {Available} (Accessed Jun 2009) 11) Big Rivers Group Jackson Energy Purchase Corp. [Online] {Available} (Accessed Jun 2009) 12) US Dept. of Energy. Office of Electricity Delivery and Energy Reliability [Online] {Available} (Accessed Jun 2009)

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32 Handouts IEEE transactions paper by Zeb Tate and Tom Overbye Lessons on power grid and home energy use from applets Accompanying TCIP slides for information ( Education-NSFReview2009-Zeb.ppt )