1. ECE 333 Renewable Energy Systems
Lecture 2: Introduction, Power Grid Components
Dr. Karl Reinhard
Dept. of Electrical and Computer Engineering
University of Illinois at Urbana-Champaign

2. Announcements Masters: MacKay: Homework 1: 1.1, 1.11, 2.6, 2.7, 2.8.
Read Chapter 1
Review Chapter 2 (as needed) for homework
MacKay:
Read Chapter 2, The Balance Sheet
Homework 1: 1.1, 1.11, 2.6, 2.7, 2.8.
Quiz 1: Thursday, Jan 25 based upon Homework 1

3. Energy Economics
Electric generating technologies involve fixed costs (costs to build them) and operating costs
Nuclear and solar high fixed costs, but low operating costs (though cost of solar has decreased substantially recently)
Natural gas/oil have low fixed costs but can have higher operating costs (dependent upon fuel prices)
Coal, wind, hydro are in between
A unit’s Capacity Factor (CF) also contributes significantly to Total Co$t

4. Ball park Energy Costs Capacity Factor (Usually expressed over a year)
Source: Steve Chu and Arun Majumdar, “Opportunities and challenges for a sustainable energy future,” Nature, August 2012, Figure 6

5. Natural Gas Prices 1997 to 2018
The Henry Hub is a distribution hub on the natural gas pipeline system in Erath, Louisiana. Due to its importance, it lends its name to the pricing point for natural gas futures contracts traded on the New York Mercantile Exchange (NYMEX).
(17 Jan 2018)
Marginal cost for natural gas-fired electricity ($/MWh) ~ x gas price

6. Coal Prices Vary Substantially
BTU content varies 8–15 KBtu/lb  Costs ~ $1 – 2/MBtu

7. Power System Structure
All power systems have 3 major components:
Load: Consumes electric power
Generation: Creates electric power.
Transmission/Distribution: Transmits electric power from generation to load.
Key Constraint:
“Electricity” can’t be effectively stored
at every moment in time,
net generation = net load + losses 6

8. Electric Power Systems
Electric utility: can range from quite small, such as an island, to one covering half the continent
4 major interconnected ac power systems in North America (60 Hz )
Smaller systems: microgrids, stand-alone, backup systems
Transportation:
Airplanes and Spaceships: (400 Hz, weight reduction)
Ships and submarines
Automobiles: dc with 12 volts standard

9. Large-Scale Power Grid Overview

10. Notation and Voltages
The IEEE standard is to write ac and dc in smaller case, but it is often written in upper case as AC and DC.
North American grid is 60 Hz (ac); most of the rest of the world is 50 Hz.
US the standard household voltage is 120/240, +/- 5%. Edison actually started at 110V dc.
European Union recently standardizing at 230V.
Japan’s standard voltage is 100V
Higher voltage provides more power,
but the trade off is greater electrical safety hazards

11. Loads Range < 1 W to 10’s 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
Loads characterized as resistive, inductive, capacitive (power factor)  important to system operation / co$ts 10

12. Ex: Daily Variation in California
FIGURE 1.17 (Masters, Gilbert M. Renewable and Efficient Electric Power Systems, 2nd Edition. Wiley-Blackwell, 11

13. Example: Weekly Load Variation12

14. Ex: Annual System Load
8720 13

15. Load Duration Curve
Common annual load representation 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
DEMAND (MW)
HRS
Load duration curve tells how much generation is needed 14

16. GENERATION 15

17. US Generator Capacity Additions
Total US Generation Capacity is about 1000 GW

18. Basic Steam Power Plant
Rankine Cycle: Working fluid (water) changes between gas and liquid
FIGURE 1.20 Basic fuel-fired, steam electric power plant. Masters, Gilbert M. Renewable and Efficient Electric Power Systems, 2d Ed. Wiley-Blackwell 17

19. Carnot Efficiency of Heat Engines
Heat engines use temperature differences to convert a portion of high temperature source heat (QH) into work (W) with output heat (QC)
Examples are fossil fuel generators, nuclear generators, concentrated solar generators and geothermal generator

20. Modern Coal Power Plant
FIGURE 1.21 Typical coal-fired power plant using an electrostatic precipitator for particulate control and a limestone-based SO2 scrubber.
Masters, Gilbert M. Renewable and Efficient Electric Power Systems, 2nd Edition. Wiley-Blackwell 19

21. Basic Gas Turbine Brayton Cycle: Working fluid always a gas
FIGURE 1.22 Basic simple-cycle gas turbine and generator.
Masters, Gilbert M. Renewable and Efficient Electric Power Systems, 2nd Edition. Wiley-Blackwell, 21/06/2013
Brayton Cycle: Working fluid always a gas
Most common fuel is natural gas
Typical efficiency is around 30 to 35%

22. Gas Turbine
Source: Masters

23. Combined Cycle Power Plant
FIGURE 1.23 Combined-cycle power plants have achieved efficiencies approaching 60%.
Masters, Gilbert M. Renewable and Efficient Electric Power Systems, 2nd Edition. Wiley-Blackwell.

24. Determining operating costs
In determining whether to build a plant, both the fixed costs and the operating costs (variable) are considered.
Once built, the decision of whether or not to operate the plant depend upon the operating costs:
fuel
operations and maintenance (O&M)

25. Heat Rate
Fuel costs are usually specified as a fuel cost, in $/Mbtu, times the heat rate, in MBtu/MWh
Heat rate = MBtu/MWh/efficiency
Example, a 33% efficient plant has a heat rate of 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 24

26. Fixed Charge Rate (FCR)
Power plant capital costs can be annualized by multiplying the total amount by a value known as the fixed charge rate (FCR)
The FCR accounts for fixed costs including loan interest, returns to investors, O&M costs, taxes, etc.
The FCR varies with interest rates; typically below 10%
For comparison purposes, FCR is typically expressed $/yr-kW 25

27. 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) 26

28. Coal Plant Example
Assume $4B capital costs for a 1600 MW coal plant having a 10% FCR and 8000 annual operating hours.
Assume a 10 Mbtu/MWh heat rate, 1.5 $/Mbtu fuel costs, and variable $4.3/MWh O&M costs.
What is the annualized cost per kWh?
Fixed Cost($/kW) = $4 billion/1.6 million kW=2500 $/kW
Annualized capital cost = $250/kW-yr
Annualized operating cost = (1.5*10+4.3)*8000/1000 = $154.4/kW-yr
Cost = $( )/kW-yr/(8000h/yr) = $0.051/kWh 27

29. Capacity Factor (CF)
Capacity Factor (CF) provides a measure of how much energy an plant actually produces compared to the energy if the plant ran at full capacity the full year
 The CF varies widely between generation technologies 28

30. Generator Capacity Factors
Source: (17 Jan 18)
 lower capacity factor means a higher cost per kWh 29

31. In the News
UI built its "solar farm" on 21 acres just south of Windsor and west of First Street
Farm has a 5.9 MW peak capacity, and is estimated to produce 7860 MWh per year
This gives it a capacity factor of 7860/(5.9*8760) = 15.2%
Will supply about 2% of the campus electric load
Project will be built and operated by Phoenix Solar for ten years, with UI buying all the output for about $1.5 million per year
Energy cost is $1.5million/7860MWh = $0.19/kWh
But after ten years UI takes ownership with no additional cost
Source: News-Gazette, January 21, 2015