Energy for SustainabilityRandolph & Masters, 2008

Chapter 5:Energy Analysis & Life-Cycle Assessment

Life Cycle Assessment “Sustainability” Analysis: energy, economic,

environmental “Cradle-to-Grave”

Check out this video on life cycle

http://www.storyofstuff.com/

Life Cycle Assessment: sometimes counter-intuitive

Energy

Waste

Life-cycle Assessment

Energy Analysis Economic Cost-effectiveness Environmental Assessment

Energy Analysis

Various metrics Efficiency (η) Energy return on investment (EROI) Energy payback time (EPT) Fossil fuel ratio (FFR) Petroleum input ratio (PIR) Net energy value (NEV)

Energy Balance

Eo = energy output (e.g., useful energy) Ed = direct energy input (e.g., fuel) Ei = indirect energy input

Eic = indirect energy – continuous (e.g., energy to produce fuel) Eiot = indirect energy – one-time (e.g., energy to make device)

ts = system life (used to convert Eiot to annual energy Eiot/ts)

Energy Analysis Metrics

Eo = energy output (e.g., useful energy) Ed = direct energy input (e.g., fuel) Ei = indirect energy input

Eic = indirect energy – continuous (e.g., energy to produce fuel) Eiot = indirect energy – one-time (e.g., energy to make device)

ts = system life (used to convert Eiot to annual energy Eiot/ts)

10 EE efficiency conversionDirect

d

o

1*0 EE

Eo* efficiencyenergy Overallid

Energy Analysis Metrics: Efficiency

Eo = energy output (e.g., useful energy) Ed = direct energy input (e.g., fuel) Ei = indirect energy input

Eic = indirect energy – continuous (e.g., energy to produce fuel) Eiot = indirect energy – one-time (e.g., energy to make device)

ts = system life (used to convert Eiot to annual energy Eiot/ts)

Metrics: Net Energy

i

o

EE EROI investmentenergy on returnEnergy

o

iot

EE EPBT mepayback tiEnergy

io EEvalueenergyNet Eo = energy output (e.g., useful energy) Ed = direct energy input (e.g., fuel) Ei = indirect energy input

Eic = indirect energy – continuous (e.g., energy to produce fuel) Eiot = indirect energy – one-time (e.g., energy to make device)

ts = system life (used to convert Eiot to annual energy Eiot/ts)

Metrics: Focus on Carbon, Petroleum

FFid

o

)E(EE FFR ratio fuel Fossil

o

Petroid

E)E(E PIR ratioinput Petroleum

Eo = energy output (e.g., useful energy) Ed = direct energy input (e.g., fuel) Ei = indirect energy input

Eic = indirect energy – continuous (e.g., energy to produce fuel) Eiot = indirect energy – one-time (e.g., energy to make device)

ts = system life (used to convert Eiot to annual energy Eiot/ts)

EROI for various energysources

Contradictory Studies on EROI, NEV of Corn-based Ethanol

Compare ethanol to gasoline: EROI not as important and Net Fossil Fuel

Farrell, et al., Science, 2006 Net Energy & Petroleum Input

Energy Input and Carbon Emissions

Getting Energy Use Data

Billing meters (e.g., gasoline pumps, electric, natural gas meters)

Monitor run-time: energy used = run-time (hrs) x energy/time

Submeters, data loggers

Dataloggers

Economic Analysis Economic value of energy: price

Volatility: Price of Gasoline in U.S., 1999-2007

Time value of money

$100

Time-value doesn’t matter much for short time periods and low discount rates

Present value of $100 Future dollars:a. d=4%, n=10 years

b. d=1%, n=10 years

c. d=10%, n=0.5 years

d. d=10%, n=10 years

Simple Payback Period (SPP)

Time to payback initial cost with energy savings

IC = initial cost (or cost difference when comparing options), $

AES = annual energy savings, energy units/year Pr = energy price, $/energy unit

(years) x Pr AES

IC SPP periodpayback Simple

Cost of Conserved Energy (CCE)

Cost per unit energy saved that can be compared to existing rates

1-d)-(1d)d(1 (CRF)Factor Recovery Capital n

n

CRF takes one-time payment and spreads it out over the lifetime (n) of the measure based on a discount rate (d)

Other Economic Factors

n)d1(1 (PVF) Factor ValuePresent

n

n

d)d(11-d)-(1 (UPVF) Factor Value Present Uniform

Other Economic Measures

What is Cost-effective?

SPP < life of measure CCE < current energy price PVS > IC NPV > 0 BCR > 1

SPP and Market Penetration

Conservation Supply Curve (CSC): plots cost per unit saved v. cumulative savings

CSC for U.S. electricity, 1990:each step is an efficiency measure

Economic Analysis Spreadsheet

Environmental Analysis

Energy Use Impact/energy Impact

Electricity depends on location

Carbon Footprint Calculator

Calculating Emissions and Offsets

Input energy use, spreadsheet calculates carbon emissions and “green tags” and trees to plant to offset emissions.