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 reinhrd2@illinois.edu

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

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

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

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). https://www.eia.gov/dnav/ng/hist/rngwhhdW.htm (17 Jan 2018) Marginal cost for natural gas-fired electricity ($/MWh) ~ 7-10 x gas price

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

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

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

Large-Scale Power Grid Overview

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

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

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

Example: Weekly Load Variation 12

Ex: Annual System Load 8720 13

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) 0 1000 HRS 7000 8760 Load duration curve tells how much generation is needed 14

GENERATION https://www.eia.gov/energyexplained/index.cfm?page=electricity_in_the_united_states 15

US Generator Capacity Additions Total US Generation Capacity is about 1000 GW https://www.eia.gov/todayinenergy/detail.php?id=30112#

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

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

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

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%

Gas Turbine Source: Masters

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.

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)

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 24

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

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

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 = $(250 + 154.4)/kW-yr/(8000h/yr) = $0.051/kWh 27

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

Generator Capacity Factors Source: https://www.eia.gov/todayinenergy/detail.php?id=25432 (17 Jan 18)  lower capacity factor means a higher cost per kWh 29

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