Electricity generation, electricity consumption, system integration, production and consumption balance

Transcription

1 Prof. Dr. Andrej Gubina University of Ljubljana, Faculty of Electrical Engineering Electricity generation, electricity consumption, system integration, production and consumption balance Maribor, Slovenia, 13. February 2014

2 Electrical Power (Energy) Systems Energy Electrical Energy Systems Renewable

3 ENERGY

4 Energy, the greatest challenge facing mankind Questions Environmental impact Sources for the future Renewable energy Intellectually challenging Long time horizon

5 Energy Primary Energy Requirement CO 2 Emissions Mtoe Mt CO International Energy Agency Year 0

6 Electricity Final Share of Total World Energy Consumption 8000 Mtoe Electricity Other Coal Biomass etc Gas Oil 0 International Energy Agency Year

7 ELECTRICITY GRIDS

8 Motivation Transform raw energy forms available in nature into electricity (generation) Transmit this electricity to the end user (transmission/distribution) Transform it back into useful energy of various types (load)

9 Generator Power system Transmission Distribution Load Load

10 Generation (10KV) step up Transmission (meshed) High Voltage 110KV 765KV Middle voltage Sub-transmission Distribution (radial) Lower Voltages 38KV & below Load

11 Slovenian power plants AUSTRIA CROATIA ITALY HPP TPP NPP Coal mine

12 Frequency same in all locations, global nature Voltage different at points in system, local nature

13 Electricity BASIC CONCEPTS

14 Electricity: Basic Concepts Generation: Alternating current Alternating voltage Fixed frequency AC compatible with rotating machines Easy to produce and change AC voltage level

15 i v Electrical Power p=vi p=vi Real Power, P Reactive Power, Q

16 Electrical Power Real power P: Magnitude of fluctuating power, Useful power transmitted Units: W, 1 MW=1000 kw Energy is amount of power P over a time period Electricity bill, kwh Reactive power Q Magnitude of fluctuating power, zero average and does no useful work Units: Var, 1 MVar=1000 kvar Establishes and sustains electric and magnetic fields of motors, generators, transformers & lines Important for controlling voltage Takes up capacity on the system (losses)

17 Fundamental power system operation Electrical power we consume must be generated at the same instant Storage? Not cost effective Fundamental requirements of a power system it must supply power wherever the customer demands Supplied power must meet quality requirements constant frequency constant voltage

18 Load An understanding of the load is a prerequisite to the design of the generators and system that supply it Load something which takes power from the system motors, heaters, electronics, lights industrial, domestic usually consumes reactive power

19 Individual loads may be random in nature Pattern emerges at distribution transformer Lumped loads vary in predictable fashion Variations relatively slow

20 Daily Load Curve MW 4300 February 8 th, 2005, Ireland Morning Rise Night Valley 3am 6am 9am 12pm 3pm 6pm 9pm Time

21 Source: Michael Power, EirGrid

22 GENERATION

23 Fuel Types Coal Gas Oil expensive plant combustion byproducts cheaper/simpler plant cleaner fuel relatively simple plant used as backup in gas/coal plants Nuclear Fission Fusion Renewables Wind Wave Tidal Solar Biomass

24 Prime Movers Rotating turbines attached to generators produce most electricity Direct energy conversion techniques fuel cells, photovoltaic unlikely to replace rotating generators in near future Turbines rotated by steam oil, coal, biomass burned > heat water > produce steam steam spins turbine hot gasses fuel burned > hot gasses hot gasses spin turbine water flowing/falling water spins turbine wind

25 Slovenia Energy Fuel Mix % 5% 23% 39% JE TE HE Other mall producers (TSO net) Other small producers (DSO net) 32% Source: AGEN RS

26 Steam Turbines Basic cycle Boiler generates steam high pressure/ temperature Turbine steam expands in high pressure (HP) stage of turbine causing it to spin after HP stage steam reheated in boiler at lower pressure passed to intermediate pressure (IP) and low pressure (LP) stage Condenser cools the steam to liquid Feed pump pumps water back to boiler Feed heaters heat water before it reenters boiler

27 Features ~35% efficient cycle efficiency increases with temperature metallurgical limitations modern turbine operates ~600oC, >200 x normal atmospheric pressure extreme conditions >thermal stresses must be kept within tolerances Steam Turbines

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29 Open Cycle Gas Turbine Three major components air compressor combustion system turbine All on same shaft Operation ambient air drawn through inlet system to inlet of compressor air compressed and passed to combustion system mixed with fuel and ignited hot gasses flow to turbine where they expand and cause turbine to spin exhaust gasses flow to atmosphere

30 Open Cycle Gas Turbine Features ~36% efficient increased combustion temperature > increased efficiency, more stresses very rapid start fast ramp rates suitable for peak load duty

31 Combined Cycle Gas Turbine Features suitable for base load or intermediate duty similar to open cycle except exhaust gasses used to create steam steam generator and turbine need time to reach full loading steam turbine also included >50% efficiency

32 Hydro

33 Pumped Storage Upper reservoir Used for limited power storage Very fast reaction time Limited resource Turlough hill Turbines & pumps Lower reservoir

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36 Emissions/ MWh Carbon Dioxide (CO 2 ) Sulphur Dioxide (SO 2 ) Oxides of Nitrogen (NO x ) Calorific content important Technology important

37 Electricity SUPPLY/DEMAND BALANCE

38 Electrical Generators Mostly synchronous Asynchronous in particular renewable Stator connects to power system (stationary) Rotor connects to prime mover (rotates) 3 phase supply creates stator rotating magnetic field Rotor magnetic field intensity controlled via supply to rotor (where possible) Magnetic fields interact to generate electricity Generators spin in synchronism (some asynchronous)

39 Synchronous Machine Rotor driven by a prime mover Stator winding arranged in three slots on stator surface Magnetic field intensity controlled via dc current in rotor

40 Asychronous Machine Rotating Stator Magnetic Field Cuts rotor conductors inducing EMF causing current to flow Amount of induction related to difference in speed

41 Synchronous Generator Control Prime mover Synchronous generator Real power control, P Reactive power control, Q

42 50 Hz Small System

43 Big System

44 System Inertia Analogy System Frequency Generation Load If generation and load are matched water level (system frequency) will remain constant Mismatches will result in a change in water level (system frequency)

45 Low system inertia High system inertia

46 Frequency control 50.2 Margin/Tolerance 50.1 Hz 50.0 Arc furnace off Pump on am 2.15 am 2.30 am 2.45 am 3.00 am Time

47 :51:21 09:51:30 09:51:39 09:51:48 09:51:57 09:52:06 09:52:15 09:52:24 09:52:33 09:52:42 09:52:51 09:53:00 09:53:09 09:53:18 09:53:27 09:53:36 09:53:45 09:53:54 09:54:03 09:54:12 09:54:21 09:54:30 09:54:39 09:54:48 09:54:57 09:55:06 09:55:15 09:55:24 09:55:33 09:55:42 09:55:51 09:56:00 09:56:09 09:56:18 09:57:12 Time MW Hz SYSTEM GENERATION FREQUENCY Frequency control & reserve

48 Primary, Delivered & Useful Energy The overall coal to light process has an overall energy conversion efficiency of 1.6%! Source: Bob Hanna, DCMNR

49 Efficiency

50 Pumped storage Coal to electricity 35 % Losses on transmission system 5 % Losses on distribution system 3 % Efficiency of pumped storage 75 % Total efficiency = 0.35*(1 0.05)*(1 0.03)*(0.75) = = %

51 Solar Wind Water Fission CO 2 Storage Biomass

52 Electricity IRELAND EXPERIENCE

53 Ireland: All Island Grid 53

54 European Wind Resources Onshore Source: Sustainable development commission, Wind Power in the UK, 2005 Offshore 54

55 System Frequency Control 5500 DAILY LOAD CURVES :00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 MW 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Supply Demand System Frequency Storage is TIME Dec Jul-06

56 Wind Power Forecasting Std. Dev. of Forecast Error Forecast Horizon (hours) Corr Coeff Distance (km) 56

57 The Network Challenge 57

58 Wind Generation 58 Principal form of renewable generation will be wind Relatively large amount of high voltage transmission required low cost may be difficult to deploy Improved forecasting and additional storage appear not to give significant economic benefit

59 Electricity WHAT CAN GO WRONG?

60 What can go wrong If we lose control of frequency and or voltage system can collapse Blackout Typically happens after a trigger event causes a cascading of other events Systems designed to avoid this however as Mr. Rumsfeld said

61 Recent major blackouts Date Location Effect 14 August 2003 USA/Canada 50 Million people 23 September 2003 Sweden and Denmark 28 September 2003 whole Italy except Sardinia 57 million people 4 th Nov 2006 France, Germany, Italy, Spain, Portugal millions in the dark 5 February 2013 Slovenia ¼ million in the dark for many days

62 NE of USA/Canada: before

63 NE of USA/Canada: after

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65 Italian Blackout 28 th September 2003

66 The Oregonian, 24 August 2003, after C. Taylor

67 Slovenia, February 2014

68 Questions? Prof. Dr. Andrej Gubina lj.si lj.si