Energy Systems Research Laboratory, FIU
Clean, Green Coal• “Clean coal” is a vague term that refers to a number of
processes by which coal can be used to make electricity with less “pollution.”
• These technologies include– Electrostatic precipitators, which remove particles
from the flue gases. Precipitators are uniformly used.– Scrubbers are used to remove sulfur dioxide, which
was implicated in creating acid rain. – Low NOx burners are used to remove nitrogen oxides
(Nox).– CO2 removal is more difficult, with sequestration an
option
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Growth in Coal Generation: US and China
Source http://www.netl.doe.gov/coal/refshelf/ncp.pdf
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Background on the Electric Utility Industry
• First real practical uses of electricity began with the telegraph (around the civil war) and then arc lighting in the 1870’s (Broadway, the “Great White Way”).
• Central stations for lighting began with Edison in 1882, using a dc system (safety was key), but transitioned to ac within several years. Chicago World’s fair in 1893 was key demonstration of electricity
• High voltage ac started being used in the 1890’s with the Niagara power plant transferring electricity to Buffalo; also 30kV line in Germany
• Frequency standardized in the 1930’s
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Regulation and Large Utilities• Electric usage spread rapidly, particularly in urban areas. Samuel
Insull (originally Edison’s secretary, but later from Chicago) played a major role in the development of large electric utilities and their holding companies– Insull was also instrumental in start of state regulation in 1890’s
• Public Utilities Holding Company Act (PUHCA) of 1935 essentially broke up inter-state holding companies– This gave rise to electric utilities that only operated in one state– PUHCA was repealed in 2005
• For most of the last century electric utilities operated as vertical monopolies
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Vertical Monopolies
• Within a particular geographic market, the electric utility had an exclusive franchise
Generation
Transmission
Distribution
Customer Service
In return for this exclusivefranchise, the utility had theobligation to serve all existing and future customersat rates determined jointlyby utility and regulators
It was a “cost plus” business
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Vertical Monopolies
• Within its service territory each utility was the only game in town
• Neighboring utilities functioned more as colleagues than competitors
• Utilities gradually interconnected their systems so by 1970 transmission lines crisscrossed North America, with voltages up to 765 kV
• Economies of scale keep resulted in decreasing rates, so most every one was happy
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
History, cont’d -- 1970’s• 1970’s brought inflation, increased fossil-fuel
prices, calls for conservation and growing environmental concerns
• Increasing rates replaced decreasing ones• As a result, U.S. Congress passed Public Utilities
Regulator Policies Act (PURPA) in 1978, which mandated utilities must purchase power from independent generators located in their service territory (modified 2005)
• PURPA introduced some competition, but its implementation varied greatly by state
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
PURPA and Renewable Energy• PURPA, through favorable contracts, caused the growth
of a large amount of renewable energy in the 1980’s (about 12,000 MW of wind, geothermal, small scale hydro, biomass, and solar thermal)– These were known as “qualifying facilities” (QFs)– California added about 6000 MW of QF capacity during the
1980’s, including 1600 MW of wind, 2700 MW of geothermal, and 1200 MW of biomass
– By the 1990’s the ten-year QFs contracts written at rates of $60/MWh in 1980’s, and they were no longer profitable at the $30/MWh 1990 values so many sites were retired or abandoned
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Electricity Prices, 1990-2007
Source: EIA, annual energy review, 2007
Total USA solar/pv energy production was essentially flat from 1990 to 2005 (0.06 quad vs. 0.065)
Total wind generation stayed flat during 1990’s (around 0.03) but is now growing (0.32 in 2007; solar/pv is 0.08 in 2007)
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
History, cont’d – 1990’s & 2000’s• Major opening of industry to competition occurred
as a result of National Energy Policy Act of 1992• This act mandated that utilities provide
“nondiscriminatory” access to the high voltage transmission
• Goal was to set up true competition in generation • Result over the last few years has been a dramatic
restructuring of electric utility industry (for better or worse!)
• Energy Bill 2005 repealed PUHCA; modified PURPA
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
State Variation in Electric Rates
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Historical Electricity Use
Source: EIA, annual energy review, 2008
• Total USA solar/pv energy production was essentially flat from 1990 to 2005 (0.06 quad vs. 0.065)
• Total wind generation stayed flat during 1990’s (around 0.03) but is now growing (0.32 in 2007; solar/pv is 0.08 in 2007)
• In 2008, largest sources of renewable energy in descending order: hydroelectric, wood, biofuels, wind, waste, geothermal, solar/PV
http://www.eia.doe.gov/aer/pdf/aer.pdf
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Historical Electricity Generation
• In 2008, fossil fuels (coal, petroleum, and natural gas) accounted for 71% of all net generation
• Nuclear contributed 20%• Renewable energy resources contributed 9% • In 2008, 67% of the renewable energy came from conventional
hydroelectric powerSource: EIA, annual energy review, 2008
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
The California-Enron Effect
Source : http://www.eia.doe.gov/cneaf/electricity/chg_str/regmap.html
RI
AK
electricityrestructuring
delayedrestructuring
no activity suspendedrestructuring
WA
OR
NV
CA
ID
MT
WY
UT
AZ
CO
NM
TX
OK
KS
NE
SD
ND MN
IA
WI
MOIL IN OH
KYTN
MSLA
AL GA
FL
SCNC
WVA VA
PANY
VT ME
MINHMA
CTNJ
DEMD
AR
HI
DC
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
August 14th, 2003 Blackout
https://reports.energy.gov/
Read the blackout report:
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Source: http://www.dsireusa.org/
Renewable Portfolio Standards (September 2009)
State renewable portfolio standard
State renewable portfolio goal
Solar water heating eligible *† Extra credit for solar or customer-sited renewables
Includes separate tier of non-renewable alternative resources
WA: 15% by 2020*
CA: 20% by 2010
☼ NV: 25% by 2025*
☼ AZ: 15% by 2025
☼ NM: 20% by 2020 (IOUs)10% by 2020 (co-ops)
HI: 40% by 2030
☼ Minimum solar or customer-sited requirement
TX: 5,880 MW by 2015
UT: 20% by 2025*
☼ CO: 20% by 2020 (IOUs)10% by 2020 (co-ops & large munis)*
MT: 15% by 2015
ND: 10% by 2015
SD: 10% by 2015
IA: 105 MW
MN: 25% by 2025(Xcel: 30% by 2020)
☼ MO: 15% by 2021
WI: Varies by utility; 10% by 2015 goal
MI: 10% + 1,100 MW by 2015*
☼ OH: 25% by 2025†
ME: 30% by 2000New RE: 10% by 2017
☼ NH: 23.8% by 2025
☼ MA: 15% by 2020+ 1% annual increase(Class I Renewables)
RI: 16% by 2020
CT: 23% by 2020
☼ NY: 24% by 2015
☼ NJ: 22.5% by 2021
☼ PA: 18% by 2020†
☼ MD: 20% by 2022
☼ DE: 20% by 2019*
☼ DC: 20% by 2020
VA: 15% by 2025*
☼ NC: 12.5% by 2021 (IOUs)10% by 2018 (co-ops & munis)
VT: (1) RE meets any increase in retail sales by 2012;
(2) 20% RE & CHP by 2017
29 states & DChave an RPS
5 states have goals
KS: 20% by 2020
☼ OR: 25% by 2025 (large utilities)*5% - 10% by 2025 (smaller utilities)
☼ IL: 25% by 2025
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Impact of 2009 Stimulus Bill on Renewable Energy
• American Recovery and Reinvestment Act (ARRA)• The 2009 stimulus bill contained several provisions
related to renewable energy– $32 billion to enhance the electric power grid– A three year extension to renewable production tax credits – About $40 billion for energy efficiency in various forms– $2 billion for advanced battery manufacturing
• Also a lot of synchrophasor-related ARRA projects– http://www.naspi.org/meetings/workgroup/workgroup.stm– Synchrophasors and renewable energy integration are related
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Power System Structure
• All power systems have three major components: Load, Generation, and Transmission/Distribution.
• Load: Consumes electric power• Generation: Creates electric power.• Transmission/Distribution: Transmits electric
power from generation to load.• A key constraint is since electricity can’t be
effectively stored, at any moment in time the net generation must equal the net load plus losses
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
2007 USA Electric Energy FlowNote, Electricity is “Refined” Energy
Source: EIA 2007 Annual Energy ReviewProfessor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
2008 USA Electric Energy Flow
Source: EIA 2008 Annual Energy ReviewNote- this graphic does NOT show losses
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
LOADS
• Can range in size from less than one watt to 10’s of MW
• Loads are usually aggregated for system analysis • The aggregate load changes with time, with strong
daily, weekly and seasonal cycles– Load variation is very location dependent
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Loads- Household Consumption
Source: EIA 2008 Annual Energy Review
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Example: Daily Variation for CA
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Example: Weekly Variation
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Example: Annual System Load
0
5000
10000
15000
20000
250001
518
1035
1552
2069
2586
3103
3620
4137
4654
5171
5688
6205
6722
7239
7756
8273
Hour of Year
MW
Loa
d
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Load Duration Curve• A very common way of representing the annual load is
to sort the one hour values, from highest to lowest. This representation is known as a “load duration curve.”
6000
5000
4000
3000
2000
1000
0
DEM
AN
D (M
W)
0 1000 HRS 7000 8760
Load duration curve tells how much generation is needed
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
GENERATION
• Large plants predominate, with sizes up to about 1500 MW.
• Coal is most common source (56%), followed by nuclear (21%), hydro (10%) and gas (10%).
• New construction is mostly natural gas, with economics highly dependent upon the gas price
• Generated at about 20 kV for large plants
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
New Generation by Fuel Type(USA 1990 to 2030, GW)
Source: EIA Annual Energy Outlook 2007
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Basic Gas Turbine Efficiency
Compressor
Fuel100%
Fresh air
Combustion chamber
Turbine
Exhaustgases 67%
Generator
ACPower 33%
1150 oC
550 oC
Brayton Cycle: Working fluid is always a gas
Most common fuel is natural gas
Maximum Efficiency550 2731 42%
1150 273
Typical efficiency is around 30 to 35%
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Gas Turbine
Source: Masters
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Combined Heat and Power
Compressor
Fuel100%
Fresh air
Combustion chamber
Turbine
Exhaust gases
Generator
ACPower 33%
Heat recovery steamgenerator (HRSG)
Water pump
Feedwater
Exhaust 14%
Steam 53%
Process heat
Absorption cooling
Space & water heating
Overall Thermal Efficiency = 33% (Electricity) + 53% (Heat) = 86%
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Combined Cycle Power Plants
Efficiencies of up to 60% can be achieved, with even higher values when the steam is used for heating
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Determining operating costs• In determining whether to build a plant, both the fixed
costs and the operating (variable) costs need to be considered.
• Once a plant is build, then the decision of whether or not to operate the plant depends only upon the variable costs
• Variable costs are often broken down into the fuel costs and the O&M costs (operations and maintenance)
• Fuel costs are usually specified as a fuel cost, in $/Mbtu, times the heat rate, in MBtu/MWh– Heat rate = 3.412 MBtu/MWh/efficiency– Example, a 33% efficient plant has a heat rate of 10.24
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Heat Rate• Fuel costs are usually specified as a fuel cost, in
$/Mbtu, times the heat rate, in MBtu/MWh– Heat rate = 3.412 MBtu/MWh/efficiency– Example, a 33% efficient plant has a heat rate of
10.24 Mbtu/MWh– About 1055 Joules = 1 Btu– 3600 kJ in a kWh
• The heat rate is an average value that can change as the output of a power plant varies.
• Do Example 3.5, material balance
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Historical and Forecasted Heat Rates
http://www.npc.org/Study_Topic_Papers/4-DTG-ElectricEfficiency.pdf
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Fixed Charge Rate (FCR)• The capital costs for a power plant can be annualized by
multiplying the total amount by a value known as the fixed charge rate (FCR)
• The FCR accounts for fixed costs such as interest on loans, returns to investors, fixed operation and maintenance costs, and taxes.
• The FCR varies with interest rates, and is now below 10%.
• For comparison this value is often expressed as$/yr-kW
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Annualized Operating Costs
• The operating costs can also be annualized by including the number of hours a plant is actually operated
• Assuming full output the value is
Variable ($/yr-kW) = [Fuel($/Btu) * Heat rate (Btu/kWh) + O&M($/Kwh)]*(operating hours/hours in year)
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Coal Plant Example• Assume capital costs of $4 billion for a 1600 MW coal
plant with a FCR of 10% and operation time of 8000 hours per year. Assume a heat rate of 10 Mbtu/MWh, fuel costs of 1.5 $/Mbtu, and variable O&M of $4.3/MWh. What is annualized cost per kWh?
Fixed Cost($/kW) = $4 billion/1.6 million kW=2500 $/kWAnnualized capital cost = $250/kW-yrAnnualized operating cost = (1.5*10+4.3)*8000/1000
= $154.4/kW-yrCost = $(250 + 154.4)/kW-yr/(8000h/yr) = $0.051/kWh
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Capacity Factor (CF)
• The term capacity factor (CF) is used to provide a measure of how much energy a plant actually produces compared to the amount assuming it ran at rated capacity for the entire year
CF = Actual yearly energy output/(Rated Power * 8760)
• The CF varies widely between generation technologies,
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Generator Capacity Factors
Source: EIA Electric Power Annual, 2007
The capacity factor for solar is usually less than 25% (sometimes substantially less), while for wind it is usually between 20 to 40%). A lower capacity factor means a higher cost per kWh
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
One-line Diagrams
• Most power systems are balanced three phase systems.
• A balanced three phase system can be modeled as a single (or one) line.
• One-lines show the major power system components, such as generators, loads, transmission lines.
• Components join together at a bus.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
PowerWorld Simulator Three Bus System
Bus 2 Bus 1
Bus 3Home Area
204 MW102 MVR
150 MW
150 MW 37 MVR
116 MVR
102 MW 51 MVR
1.00 PU
-20 MW 4 MVR
20 MW -4 MVR
-34 MW 10 MVR
34 MW-10 MVR
14 MW -4 MVR
-14 MW 4 MVR
1.00 PU
1.00 PU
106 MW 0 MVR
100 MWAGC ONAVR ON
AGC ONAVR ON
Load withgreenarrows indicatingamountof MWflow
Usedto controloutput ofgenerator Direction of arrow is used to indicate
direction of real power (MW) flow
Note thepower balance ateach bus
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Power Balance Constraints
• Power flow refers to how the power is moving through the system.
• At all times in the simulation the total power flowing into any bus MUST be zero!
• This is know as Kirchhoff’s law. And it can not be repealed or modified.
• Power is lost in the transmission system.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Basic Power Flow Control
• Opening a circuit breaker causes the power flow to instantaneously (nearly) change.
• No other way to directly control power flow in a transmission line.
• By changing generation we can indirectly change this flow.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Transmission Line Limits
• Power flow in transmission line is limited by heating considerations.
• Losses (I2 R) can heat up the line, causing it to sag.
• Each line has a limit; Simulator does not allow you to continually exceed this limit. Many utilities use winter/summer limits.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Overloaded Transmission Line
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Interconnected Operation• Power systems are interconnected. Most of
North America east of the Rockies is one system, with most of Texas and Quebec being exceptions
• Interconnections are divided into smaller portions, called balancing authority areas (previously called control areas)
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Balancing Authority (BA) Areas
• Transmission lines that join two areas are known as tie-lines.
• The net power out of an area is the sum of the flow on its tie-lines.
• The flow out of an area is equal to
total gen - total load - total losses = tie-flow
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Area Control Error (ACE)• The area control error is the difference
between the actual flow out of an area, and the scheduled flow.
• Ideally the ACE should always be zero.• Because the load is constantly changing, each
utility must constantly change its generation to “chase” the ACE.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Automatic Generation Control• BAs use automatic generation control (AGC)
to automatically change their generation to keep their ACE close to zero.
• Usually the BA control center calculates ACE based upon tie-line flows; then the AGC module sends control signals out to the generators every couple seconds.
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017
Energy Systems Research Laboratory, FIU
Three Bus Case on AGC
Bus 2 Bus 1
Bus 3Home Area
266 MW133 MVR
150 MW
250 MW34 MVR
166 MVR
133 MW 67 MVR
1.00 PU
-40 MW 8 MVR
40 MW -8 MVR
-77 MW 25 MVR
78 MW-21 MVR
39 MW-11 MVR
-39 MW 12 MVR
1.00 PU
1.00 PU
101 MW 5 MVR
100 MWAGC ONAVR ON
AGC ONAVR ON
Professor O. A. Mohammed, EEL5285 Lecture Notes, Spring 2017