EFS Chapter 5 Energy Analysis and Life-Cycle Assessment
Chapter 5: Energy Analysis and Life-Cycle Assessment
Introduction
Smart energy choices and investments are important for individuals, communities, and society.
Basic questions need to be addressed to make informed decisions.
Personal financial effects and energy savings information are necessary for individual decisions.
Global environmental effects and financial effects need to be compared.
Community investments should consider long-lasting effects and evaluate energy savings and costs.
Society should consider efficiency standards, renewable energy use, and subsidies for different energy sources.
Analytical Methods for Energy Decisions
Four basic analytical methods are introduced:
Life-cycle assessment
Energy analysis
Economic cost-effectiveness
Environmental assessment
Life-cycle Assessment
Fundamental to sustainability analysis.
Considers energy, economic, social, and environmental impacts from cradle to grave.
Provides a broad framework for energy analysis.
Energy Analysis
Determines and compares energy consumption and production of different options.
Can involve complex life-cycle net energy analysis.
Simple energy consumption or conversion efficiency calculations can be done.
Economic Cost-effectiveness
Puts energy analysis in terms of economic and financial costs and benefits.
Considers investment choices and limited financial resources.
Requires knowledge of energy needs, economic value of energy, capital and operating costs, and time value of money.
Environmental Assessment
Looks beyond economic effects and considers impacts on the natural and human environment.
Uses impact indicators such as greenhouse gas emissions, air pollutant emissions, land and water requirements, human health effects, etc.
Some measures can be put in economic terms, others cannot.
Principles of Life-Cycle Thinking and Sustainability Analysis
Decisions should consider costs and benefits over the long term.
Life-cycle cost, including operating cost, should be considered.
Full costs and benefits of acquiring, manufacturing, using, and disposing of a product should be considered.
Price of energy and products often does not include full costs.
Life-cycle cradle-to-grave thinking expands thinking backward and forward along the product development and disposal process.
McDonough and Braungart extend this thinking further with "cradle-to-cradle" and "the upcycle" concepts.
Life-cycle assessment can be applied to embodied energy in buildings and other products.
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Energy Analysis and Life-Cycle Assessment
Voluntary certification systems and labeling systems incorporate life-cycle costs and impacts
Examples include ISO 14000 family of standards, U.S. Green Building Council's LEED green building certifications, and green labeling systems in Europe
Life-cycle analysis assesses the performance of an activity or product over its life cycle
Measures of performance include energy use, economic cost, social effects, and environmental impact
ISO 14000 standards specify a four-step process for life-cycle analysis
Define goals and scope
Inventory impact activities
Assess impacts
Evaluate and interpret results
Life-cycle inventory involves tracking all flows in and out of the system from cradle to grave
"Gate-to-gate" addresses flow in and out for product manufacturing only
Impact indicators include energy used, carbon emissions, and pollutant emissions
Accurate inventory data and reliable coefficients are needed for life-cycle analysis
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Energy Analysis
Energy analysis applies energy engineering principles to measure, estimate, or predict energy consumption and efficiency
Energy analysis can be used to inform building design, product choices, and energy production
Energy analysis compares useful energy outputs with necessary energy inputs
Net energy analysis assesses indirect energy inputs
Units of energy and time, system boundary, and time period must be carefully considered in energy analysis
Specific metrics used in energy analysis include useful energy output, direct input energy, total indirect input energy, indirect continuous energy costs, and one-time energy costs
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Energy Analysis and Life-Cycle Assessment
Indirect input energy takes into account the energy required to produce the direct input energy and the conversion systems used
Equation for indirect energy input: EI = ts E˙ IC + EIOT
EI: total indirect input energy
E˙ IC: continuous indirect energy inputs
EIOT: one-time indirect energy inputs
ts: lifetime of the system
Diesel generator example: direct input energy is the diesel fuel per year, indirect input energy takes into account the energy required to produce the diesel fuel and the generator system
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Energy for Sustainability
Energy needed in the "fuel cycle" to extract, refine, and transport petroleum and its diesel product to the site of the generator
Energy needed to manufacture the generator and transport it to the points of sale and use
Energy to operate and maintain the generator
Energy to dispose of the generator after its useful life
Solar photovoltaic plus battery system
Direct input energy is sunlight (E˙ D = 0)
Indirect energy input is the energy needed to manufacture the photovoltaic modules, batteries, and other components and their transport and installation on site (EIOT)
Maintenance of the system is a continuous cost (E˙ IC)
Direct Conversion Efficiency (η)
Describes the efficiency of a system to convert direct input energy to output energy
Can be used to compare options with common starting and ending points in the energy conversion process
Cumulative direct conversion efficiency is the product of component efficiencies from the same start point to the same end point
Example: Fuel-cell car vs. battery electric car
Fuel-cell car: ηcumulative = 0.134 (13.4%)
Battery electric car: ηcumulative = 0.252 (25.2%)
Limitations of direct conversion efficiency when comparing systems with different starting and ending points
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Energy Analysis and Life-Cycle Assessment
Direct conversion efficiency for a diesel generator and a photovoltaic battery system
Diesel generator: η = 0.25 (25%)
PV system: η = 0.166 (16.6%)
Other metrics to consider indirect energy and differences in energy sources and systems
Energy Return on Energy Investment (EROI)
Compares useful output energy to indirect input energy
Indicates how much energy other than direct fuel energy input must be invested to get a unit of useful energy
Can be expressed as total EO divided by EI or annual E˙ O divided by annualized E˙ I
Table 5.1: Comparing Direct Conversion Efficiency for Fuel-Cell and Battery-Electric Vehicles
Page 8: Energy for Sustainability
EROI (Energy Return on Investment) must be greater than 1
If EROI is less than 1, the system takes more indirect input energy to produce useful output energy
Higher EROI is better
Analysts argue that modern society must have:
EROI above 3 for individual energy systems and sources
EROI above 10 for all energy to achieve a high quality of life
EROI depends on basic assumptions and data inputs, making it difficult to compare different studies
EROI assumes all energy is the same in terms of quality and source, which is a fundamental flaw
EROI analyses of different energy sources and systems have proliferated in recent years
Charles A. S. Hall and Cutler Cleveland are seen as the founders of EROI research
Fossil fuel EROI is declining
Fossil fuel EROI declining (Table 5.2)
Studies have shown diminishing returns of energy investment in fossil fuel production
Early days of oil production had low indirect energy investments and high EROI
U.S. oil and gas production had an EROI of 100 in 1930
Coal production had an EROI of 100 in 1950
Depletion of resources has led to the need for deeper and farther extraction, increasing energy requirements
By 2000, oil and gas EROI dropped to 20, by 2007 to 11
By 2007, coal EROI dropped to 60
Unconventional fossil fuels require more energy to extract and process, reducing EROI
Canadian oil sands EROI estimates range from 3 to 5
More fossil fuel combustion is needed to produce useful fuels, leading to increased carbon emissions
Fuel EROI figures and electricity production options (Table 5.2)
Fuel EROI compares fuel energy output value with indirect energy input value
Most studies do not include input energy for transport, processing, refining, or conversion to useful energy
EROI studies of electricity production options consider added inputs and losses
Coal power with scrubbers and combined-cycle natural gas electricity have EROI of 5
Nuclear power EROI is estimated at 5-8
Hydropower EROI is very high at 40-60
Wind and solar PV electricity have increasing EROI due to improved energy efficiency in production
Wind EROI is 20 and solar PV EROI improved from 7 in 2000 to 16 in 2013
Ethanol EROI estimates are low, ranging from 0.8 to 4.8 for corn ethanol
Cellulosic switchgrass ethanol EROI is 8 and sugarcane ethanol is 9
Biodiesel EROI from soy is about 5.5
Difficulty in comparing results
Assumptions of indirect energy inputs vary between studies, making it difficult to compare results
"Meta" studies have attempted to aggregate results under common assumptions
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Energy Analysis and Life-Cycle Assessment
EROI researchers use graphical form to communicate data and trends
The "net energy cliff" is shown in Figure 5.3, which plots EROI against net energy delivered to society
As EROI declines, net energy as a percentage of total energy extracted declines exponentially and falls precipitously for EROI <5
EROI values for selected sources are given in Table 5.2
U.S. oil and gas production has a declining EROI, while solar PV has an improving EROI
Assumptions in EROI studies should be carefully stated and include an energy flow diagram, system boundaries, energy inputs and outputs, data needs and sources, and how they are used in EROI calculations
Net Energy (NE) or Energy Balance
Net energy (NE) compares useful output energy to input energy using the difference rather than the ratio
NE is related to EROI
Table 5.2 shows EROI values for selected energy sources and systems
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Energy Payback Time (EPBT)
EPBT is the time it takes for an energy system to recover its one-time input energy with output energy
EPBT is particularly useful for renewable energy systems like wind and photovoltaics
EPBT is equivalent to ts/EROI
Example of EPBT for PV modules:
Crystalline silicon PV modules: EI = EIOT = 5600 kWh/kWp
Thin-film copper indium diselenide (CIS) modules: EI = EIOT = 3100 kWh/kWp
Page 11: Energy Analysis and Life-Cycle Assessment
The kWp of the module occurs at peak sun (1 kW/m2)
Typical average value for solar energy falling on a site in the United States is 1700 kWh/m2/year
Each kWp will produce 1700 kWh/year on average for the United States
System losses accounted for by a performance ratio (PR) of 0.8
EPBT (Energy Payback Time) calculated for crystalline silicon PV modules is 4.1 years
Expected life of these modules is 30 years
EROI (Energy Return on Investment) calculated for crystalline silicon PV modules is 7
By 2013, EPBT of polycrystalline silicon PV systems decreased to less than 2 years, and EROI was calculated at 16
By 2015, typical commercial module efficiencies were 16%–18%
Page 11: Section 14.3.3 - Energy Balance of Bioethanol
See section 14.3.3 for a discussion of the energy balance of bioethanol
Page 11: Conclusion of Page 11
The efficiency of production of crystalline silicon PV modules has increased over time
EPBT and EROI have probably continued to improve
Page 12: Energy Audits, Energy Data Monitoring, and Energy Control and Management
Energy analysis requires good information
Best data come from physical monitoring of systems, energy consumption, and functions performed
Energy monitoring and control technologies are changing rapidly
Smart meters, data displays, web-based and phone app software, and Internet Wi-Fi controls are advancing
Energy monitoring can be as simple as reviewing monthly electric utility bills or jotting down car's odometer reading
Energy monitoring can be as complicated as installing a multifunction computer datalogger
New technologies and consumer products are rapidly changing the nature of energy data acquisition
Page 12: Energy Audits
Energy audits evaluate patterns and trends of energy consumption and identify efficiency opportunities
Auditing is applied to buildings, transportation fleets, and industrial processes
Three levels of energy audits: Walkthrough or visual assessment, Energy survey and analysis, Detailed analysis of capital-intensive modifications
Level 1 audit includes rapid assessment and helps scope out needed monitoring and analysis
Level 2 audit includes monitoring of historical utility billing data and identification of potential energy conservation measures (ECMs)
Level 3 audit goes beyond basic analysis and may use computer simulations and economic assessment of major modifications
Basic procedure for Level 1 and 2 audits includes preliminary walkthrough, analysis of billing data, review of specifications and information, facility walkthrough and diagnostics, monitoring of energy systems and equipment, synthesis of results and findings, identification of potential ECMs, economic analysis, and preparation of final report
Page 12: Conclusion of Page 12
Better data leads to better analysis and results, and better-informed decisions
Energy monitoring is an important component of an energy audit
Energy Analysis and Life-Cycle Assessment
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Energy utilities and companies monitor energy sales for billing purposes
Electric and natural gas utilities have cumulative kWh and gas meters on houses
Fuel oil distributors use flow meters to measure sale in gallons
Gas stations use flow meters to measure gallons bought at the pump
Utility bills are a source of energy monitoring data
Monthly record of consumption of natural gas (1 therm = 100,000 Btu, or about 100 cubic feet [ccf]) and electricity (kWh) and peak power demand (kW)
Can show variation from month to month, from heating to cooling season, from year to year
Can show changes in usage resulting from new appliances or energy conservation measures
Utilities provide online historical usage and billing data
Available in downloadable spreadsheet format or graphical form
More sophisticated methods have been developed to track and analyze utility bill data
Useful in evaluating efficiency interventions when other energy monitoring methods are not available
Examples include Princeton Scorekeeping Method (PRISM) and energy service vendors' tracking software and online services
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Data logging involves the use of meters and loggers to measure energy use and functions performed for energy analysis and evaluation studies
Commonly used meters are the same ones used by utilities for billing purposes
Submetering is used to obtain more detailed or site-specific data
Programmable communicating thermostats (PCTs) record information and communicate it to a web portal
"Run-time" meters measure the cumulative time equipment is on
Dataloggers store digital data retrieved from different sensors
Plug-load monitors measure the energy and power drawn by appliances connected to them
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Current transducers (CTs) are used to monitor electricity
Placed around a circuit wire to measure current flow
Voltage generated by the magnetic field is converted into an amperage reading
Internet of Things (IoT) brings products to monitor, display, and control energy use
Includes smart meters, programmable communicating thermostats, in-home displays, plug-load controllers, information hubs or gateways, smart appliances and lighting, and integration with solar power generation, storage, and electric vehicle charging
Examples of innovative products include Google's Nest PCT, Ecobee PCT, Samsung's SmartThings, Apple's HomeKit, Ceiva Gateway hubs and Homeview IHD, and Philips Hue lighting system
Page 16: Economic Analysis of Energy Systems
Minimizing energy use and maximizing efficiency is important for various reasons
Accelerating the use of clean, renewable energy sources
Reducing pollution and other impacts of conventional energy
Sustainable energy should be financially worth it for everyone to adopt
Economic analysis is a necessary first step to determine if certain options are worth pursuing
Energy analysis is the starting point, followed by economic analysis
Energy consumption and efficiency need to be quantified first
Economic value of energy can be determined by putting energy into monetary terms
Energy prices are set by the market, influenced by government policy
Government subsidies, taxes, and environmental policies affect energy prices
Energy prices have been volatile over the years
U.S. average residential electricity prices have increased at a steady rate from 2000 to 2016
Energy prices are used to calculate economic costs
Page 17: Life-Cycle Costing and Time Value of Money
Long-term commitments and future costs need to be considered in energy analysis
Example: Nuclear power requires considering plant construction, operation, fuel mining, enrichment, decommissioning, and waste disposal
Life-cycle cost analysis is important for personal decisions like buying appliances or lightbulbs
Choosing initially cheaper energy-consuming items can be more expensive over the product's life cycle
Time value of money recognizes that money has a time dimension
Future dollars are discounted to present value using a discount rate
Table 5.3 provides U.S. energy prices for retail gasoline, residential natural gas, and electricity from 2000 to 2016
Note: The transcript contains more information beyond page 17, but due to the token limit, only the information up to page 17 is included in the note.
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Compound interest equation:
F = P (1 + i)^n
P = present dollars
F = future dollars at year n
i = interest rate
Example: $100 investment with 4% annual interest rate for 10 years
Interest compounded annually
Table shows the growth of the investment each year
Calculating heating bill:
Comparison between the speaker's house and neighbor's house
Speaker's house:
Gas furnace, 80% efficient
Natural gas cost: $1.10 per therm
Calculation of natural gas cost per year
Neighbor's house:
Electric resistance, 100% efficient
Electricity cost: 11¢/kWh
Calculation of electricity cost per year
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Life-Cycle Economic Cost of Lightbulbs:
Efficiency standards for lightbulbs set by the Energy Independence and Security Act of 2007
Comparison of different types of bulbs and their costs
Calculation of the life-cycle cost of three options: incandescent, CFL, and LED bulbs
Normalization of the life of all three bulbs to 15,000 hours
Calculation of the life-cycle cost for each bulb type
Comparison of life-cycle cost savings of LED over incandescent and CFL bulbs
Suggestion to check current prices and redo the calculation
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Compound growth equation can be used to calculate future value
Formula: F = P (1 + i)n
Example: $100 in 10 years with a discount rate of 4%
Calculation: F = $100(1 + 0.04)10 = $148.02
Present value: P = $100 / (1 + 0.04)10 = $67.56
Time value of money is important for energy analysis with long time periods and high discount rates
Examples of present value calculations:
$100 in 10 years with a discount rate of 0.5%
Calculation: P = $100 / (1 + 0.005)10 = $95.13
$100 in 6 months with a discount rate of 10%
Calculation: P = $100 / (1 + 0.1)0.5 = $95.31
$100 in 10 years with a discount rate of 10%
Calculation: P = $100 / (1 + 0.1)10 = $38.55
Ignoring the discount rate for high discount rates and long time periods can lead to large errors
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Factors to consider when choosing a discount rate: prevailing interest rates, inflation rates, expected returns from alternative investments
Simple approach is appropriate due to uncertainties
Equation for discount rate: d = i - r
d: discount rate
i: interest rate
r: inflation rate for energy prices
Example of discount rate calculation for future years
Literature debates the appropriate discount rate for evaluating energy systems and programs
Economic measures of cost-effectiveness are important for driving investment in efficient and renewable energy systems
Several metrics used to assess economic cost-effectiveness and compare investments
Simple payback period (SPP) is a useful measure of cost-effectiveness
Calculation: SPP = IC / (AES * Pr)
IC: initial capital cost
AES: annual energy savings
Pr: energy price
Return on investment (ROI) is the inverse of SPP
Calculation: ROI = 100 / SPP
An ROI greater than 10% is considered a good investment
Page 22: Energy for Sustainability Solution Box 5.3 - Simple Payback Period of Low-Flow Showerheads
The author wanted to calculate the payback on replacing old high-flow showerheads with low-flow showerheads.
Each new showerhead cost $10.
The flow rates of the old and new showerheads were measured.
The old showerhead took 1 minute to fill a 5-gallon bucket, while the low-flow showerhead took 2.5 minutes.
The average shower time for the family was 10 minutes for 25 showers per week.
The gas water heater operated at 75% efficiency and the cost of natural gas was $1 per therm.
Energy analysis results:
Energy for old showerheads:
Flow rate = 5 gal/min
Flow time = 13,000 min/yr
Hot water flow = 65,000 gal/yr
Energy for hot water = 21.7 × 10^6 Btu/yr
NG energy for hot water = 28.9 × 10^6 Btu/yr
Energy for new showerheads:
Flow rate = 2 gal/min
Hot water flow = 26,000 gal/yr
Energy for hot water = 8.68 × 10^6 Btu/yr
NG energy for hot water = 11.56 × 10^6 Btu/yr
Energy savings: 17.34 × 10^6 Btu/yr
The Simple Payback Period (SPP) was calculated to be 0.173 years or 63 days.
The investment would be recovered by natural gas monetary savings in 2 months, after which the savings would continue to accrue.
Additional savings would come from reduced water bills.
Page 23: Energy Analysis and Life-Cycle Assessment
Return on Investment (ROI) of the investment in low-flow showerheads was calculated to be 580%.
Cost of conserved energy (CCE) and levelized cost of energy (LCOE) are useful economic measures.
CCE measures the cost per unit of energy saved, while LCOE measures the cost per unit of energy produced.
CCE is used for energy efficiency measures, while LCOE is used for energy production systems.
CCE and LCOE consider the time value of money through the capital recovery factor (CRF) using a discount rate.
CCE is calculated as IC × CRF + o&m AES.
LCOE is calculated as IC × CRF + o&m AEP.
Present value savings (PVS) calculates the total life-cycle dollar savings of the energy investment in present-day dollars.
PVS is calculated using the assumed discount rate (d) and the uniform present value factor (UPVF).
PVS can be compared with the total cost of the investment.
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PVS (Present Value Savings) formula: PVS = (AES × Pr – o&m) × UPVF
AES = annual energy savings
Pr = price of saved energy
o&m = annual operation and maintenance cost
UPVF = uniform present value factor
Calculate the PVS of the low-flow showerhead investment
Life of the showerheads: 20 years
Discount rate: 3%
o&m = 0
Sidebar 5.2 Economic Analysis Factors:
Compound Growth Factor (CGF)
Present Value Factor (PVF)
Capital Recovery Factor (CRF)
Uniform Present Value Factor (UPVF)
Solution Box 5.4 Cost of Conserved Energy of Low-Flow Showerheads:
Calculate the CCE (Cost of Conserved Energy) for the low-flow showerhead investment
Life of the showerheads: 20 years
Discount rate: 3%
o&m = 0
CRF = d(1 + d)n/[(1 + d)n – 1]
CCE = IC × CRF/AES
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Calculate UPVF (Uniform Present Value Factor)
Calculate PVS (Present Value Savings) using the formula: PVS = (AES × Pr – o&m) × UPVF
Calculate NPV (Net Present Value) using the formula: NPV = PVS − IC
Calculate B/C (Benefit–Cost) ratio using the formula: B/C = PVS/IC
Performing Economic Analysis with Spreadsheets:
Economic calculations can be tedious and complicated
Spreadsheets provide an easy way to perform economic analysis
Table 5.4 is a spreadsheet developed for energy and economic analysis
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Spreadsheet can be used for analysis and calculations
New data entries trigger automatic calculations
Assumptions can be easily changed and results can be seen without recalculating
Cost-effectiveness is defined as net positive economic value
Simple payback period should be less than the life of the investment
Cost of conserved energy (CCE) and levelized cost of energy (LCOE) should be less than current or expected energy price
Present value savings should be greater than cost of investment
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Cost-effectiveness is important for consumer choice and market penetration
Full life-cycle analysis includes assessment of environmental effects
Life-cycle analysis evaluates the environmental implications of energy and material options
Energy extraction, transport, and use have various impacts on the environment
Life-cycle analysis incorporates economic and environmental analysis
Environmental impact coefficients are used to calculate environmental costs of energy and materials
U.S. DOE's National Renewable Energy Laboratory (NREL) developed the Life Cycle Inventory (LCI) Database for life-cycle analysis
The LCI Database provides data for hundreds of products and processes
Note: The transcript contains more information, but these are the main ideas and supporting details.
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Using life-cycle inventory to estimate inputs and air emissions for vehicle operation
Example: driving a car 15,000 miles per year with 25 mpg
Data from Table 5.7
Excluding inputs and outputs for gasoline production
Data from Table 5.6
Procedure described in Solution Box 5.5
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Air pollution emissions from combustion of fossil fuels as severe environmental impact
Energy use accounts for 78% of air pollution emissions in the United States
19% from stationary sources (power plants)
60% from mobile sources (passenger vehicles)
Progress made in reducing emissions through technological controls
Air quality worse in global cities
Increasing attention to carbon dioxide and other greenhouse gas emissions from fossil fuels
"Carbon footprint" as an indicator of environmental impact
CO2 emission rates for various fuels listed in Table 5.9
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Emission rates for electricity generation
Table 5.10: rates for coal, oil, natural gas, and non-fossil fuel generation
Coal has highest emission rates for all pollutants
Natural gas has lower rates for CO2, NOx, and SOx
Wood and biomass generation similar to coal in NOx and 70% of coal's CO2
National averages may not be precise for specific locations
EPA's eGRID database provides emission rates for each state
Table 5.11: rates and energy source mix for four states in 2002 and 2014
Figure 5.7: fuel mix and CO2 emission rates for each state in 2012
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Environmental impacts of electricity depend on consumption and the source of power.
Example in Solution Box 5.6 shows this.
EPA's "Power Profiler" is an interactive online calculator that calculates impact based on zip code and monthly electricity use.
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There are many other environmental impacts of energy use besides air emissions.
Fossil fuel extraction and transport have various impacts, listed in Section 2.3.3.
Table 2.5 on the book website illustrates the wide range of impacts and their severity and risk.
More people are interested in determining their carbon footprint due to increased interest in global climate change.
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CO2 Emission Rates, Various Fuels
Motor gasoline: 19.6 pounds CO2 per gal
Distillate and diesel: 22.4 pounds CO2 per gal
Natural gas: 117.1 pounds CO2 per 103 ft3
Propane: 12.7 pounds CO2 per gal
Coal: 4931 pounds CO2 per short ton
Biomass: 0 pounds CO2 per unit
U.S. Average Emission Rates for Different Sources of Electricity
Coal: 1392 lb per MWh (2004), 982 lb per MWh (2016)
Natural Gas: 870 lb per MWh (2004), 1969 lb per MWh (2016)
Oil: 2202 lb per MWh (2004)
Biomass: 0 lb per MWh
Hydro: 0 lb per MWh
Nuclear: 0 lb per MWh
Wind: 0 lb per MWh
Solar: 0 lb per MWh
Geothermal: 0 lb per MWh
Electricity Emission Rates and Source Mix for Selected States
Washington
CO2 Emission Rate: 287 lb per MWh (2002), 225 lb per MWh (2014)
Source Mix: Coal (8%), Natural gas (1%), Nuclear (9%), Hydro (76%), Other renewable (6%)
California
CO2 Emission Rate: 633 lb per MWh (2002), 553 lb per MWh (2014)
Source Mix: Coal (2%), Natural gas (49%), Nuclear (19%), Hydro (17%), Other renewable (12%)
Virginia
CO2 Emission Rate: 1232 lb per MWh (2002), 877 lb per MWh (2014)
Source Mix: Coal (51%), Natural gas (10%), Nuclear (37%), Hydro (0%), Other renewable (2%)
West Virginia
CO2 Emission Rate: 2071 lb per MWh (2002), 1976 lb per MWh (2014)
Source Mix: Coal (98%), Natural gas (<1%), Nuclear (0%), Hydro (2%), Other renewable (0%)
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Reducing Carbon Emissions
Consumers can reduce emissions by:
Using energy efficiency and conservation
Installing on-site renewable energy systems
Buying "green power" from an electricity supplier
Carbon Footprint
Carbon calculators help assess carbon emissions
Ecological footprint approach calculates impact on the environment in terms of consumption of materials, energy, and generation of emissions and wastes
Carbon footprint focuses on CO2 emissions from energy and other consumption
Levels of Carbon Emissions
Scope or Tier 1: Direct emissions from household or facility
Scope or Tier 2: Indirect emissions from purchase of electricity, heat, or steam
Scope or Tier 3: Other indirect emissions from extraction, production, and transport of goods
Map Showing Electricity Fuel Mix and CO2 Emission Rates by State
Source: U.S. EPA, 2015
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Energy Analysis and Life-Cycle Assessment
Online carbon calculators have been developed
The best one is produced by the Cool-Climate Network at the University of California, Berkeley
It includes a detailed Scope 1, 2, and 3 calculator
It has a zip code–scale national map of average household CO2 emissions for travel, home, food, goods, and services
Summary
Several methods of life-cycle, energy, economic, and environmental analysis are important to compare energy and material options and make informed decisions
Energy analysis is important in understanding energy usage, efficiency, and production requirements
Economic analysis evaluates relative cost-effectiveness, with the simple payback period being the most straightforward technique
Discounting future savings is important for long time periods and high discount rates
Spreadsheets are useful for performing economic analyses with varying assumptions
Environmental assessment adds a sustainability dimension to energy and economic analysis
Assessing air and carbon emissions is more advanced than assessing other environmental impacts
Life-cycle analysis combines energy, economic, and environmental analysis to assess the broad impacts of energy and material options
Solution Box 5.6: Electricity Carbon Impacts Depend on Where You Live
Annual emissions attributed to electricity consumption in different households are calculated
Masters spends time in both Washington and California, so emissions are calculated for both states
Randolph lives in Virginia but is served by American Electric Power in West Virginia, so the West Virginia emission rate is used
Table 5.12 provides the solution results for emissions in different states and years
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UC Berkeley��s CoolClimate Network Household Calculator and CoolClimate Maps
UC Berkeley’s CoolClimate Network is one of the best online household carbon footprint calculators
It estimates direct and indirect carbon emissions from energy use, purchased electricity, food, goods, and services
Average values are given by zip code and are based on local utility source and census data
Personal household emissions can be calculated by inputting personal data on household size, income, energy use, vehicle mileage and fuel economy, diet, and levels of goods and services
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Impacts of Energy and Material Options
Life-cycle analysis assesses the impacts of energy and material options from cradle to grave or from resource acquisition to waste disposal
Life-cycle analysis is not yet fully integrated into common practice, but there have been recent developments in improved analytical tools and data
Market penetration of new energy-saving technologies tends to require short payback periods
Improved information, access to capital, and government policies can help overcome barriers to penetration of efficient and renewable energy technologies
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