Energy Analysis Conventions Methods

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Supergen HiDEF/BSEBEC Training Workshop: Sustainability and the

Environment, University of Bath, 7-8 June 2010

ENERGY ANALYSIS: Conventions, Methods and Metrics

Geoff Hammond

Professor of Mechanical Engineering and Director

of the Institute for Sustainable Energy & the Environment(ISEE)

University of Bath (Email: [email protected])

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WHOLE SYSTEMS ANALYSIS IN THE ENERGY SECTOR

Interdisciplinary and integrated appraisal toolkit-

THERMODYNAMICS: energy, exergy, and exergoeconomic

analysis

ENVIRONMENTAL LIFE-CYCLE ASSESSMENT (LCA)

ENVIRONMENTAL COST-BENEFIT ANALYSIS (CBA) withcolleagues in Economics

______________________

ENERGY SECTOR RISK ASSESSMENT e.g., electricity networks

CARBON & ENVIRONMENTAL FOOTPRINTING e.g., cities,

communities, more electric pathways, and nations

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THERMODYNAMIC CONCEPTS AND TOOLS

FIRST AND SECOND LAW CONCEPTS

ENERGY QUANTITY EXERGY QUALITY

IDENTIFYING PROCESS IMPROVEMENT POTENTIAL

ENERGY ANALYSIS: CONSERVATION

EXERGY ANALYSIS: ENERGY (OR HEAT) CASCADING

It identifies scope for improvement potential; 80% injust three sectors of the UK economy - power

generation, space heating in buildings and transport

A Cautionary Note: Exergy analysis should not be elevated toa pivotal position

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ENTHALPY (H)

The energy content of a flow stream (or energy carrier) in laypersons terms. An extensive property of matter defined via

(1) There is an almost direct connection between the description

of the property and experimental measurements

(2) The mathematical manipulations associated with themeasurements involve elementary arithmetic

(3) The nearness to experience of the property makes it easy toaccept that its value is worth knowing

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( )1212 TTmcHH p =


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AN ENERGY BALANCE

Control Volume

Qe

Qother (or Wother)

Hin

Wuseful

Qb

T0


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ENERGY ANALYSIS: THE METRICS 1

Gross energy requirement (GER): The sum of all the primaryenergy [expressed as thermal energy (enthalpy)] required todeliver an artefact, good or service. Units: usually expressed interms of the quantity of primary energy per unit of mass output

(e.g., kJ/kg).

Process energy requirement (PER): The energy required todrive a particular process or 'unit operation'. Again co-products

would need to be treated as above. Units: usually expressed interms of energy quantities per unit mass of output (e.g., kJ/kg).

Energy requirement of energy (ERE): The sum of all the

primary energy requirements [expressed as thermal energy(enthalpy)] needed to produce one unit of delivered energy.Units: usually expressed in terms of the quantity of primaryenergy per unit of delivered energy (e.g., kJ/kJ).

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Energy intensity (EI): The primary energy required to producea given unit of good or service in monetary terms. Typical units:kJ/ (date) in the UK [and kJ/$ (date) in the USA]. When

referring to a national economy, the energy intensity is theprimary energy consumed per unit of Gross Domestic Product(GDP).

Net energy requirement (NER): The amount of energyavailable from a system after the deduction of the primaryenergy expended in creating the usable resource [i.e., thecalorific value - the GER]. Units: usually expressed in terms of

the quantity of energy (i.e., kJ, etc.).

NB: 'Energy cost - early expression for what is now preferablyreferred to as the GER, and still sometimes used colloquially.

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Level 4Capital

Level 3Raw Materials

for Inputs

Level 2Inputs toProcess

Level 1Direct Fuel

Use

EnergyTransformation

System

raw materialprocessing

fuelsenergyresources

ancillaryinputs

machines

tomakemachines

machines

final processmaking

economicproduct

economicproduct

Input / OutputTables

Input / OutputTables

Process

Analysis orInput / Output

Tables

ProcessAnalysis

Energy Analysis Methodology

Expanded Industrial System

transport

transport

LEVELS OF REGRESSION -

(GER)


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Energy gain ratio (EGR): The energy output of a system

divided by the gross energy requirement (or embodied energy),i.e., energy output over the system life/energy input forconstruction. The inverse of the ERE.

Energy payback period (EPP): The period that a device orsystem takes to repay the energy investment in its construction,i.e., energy input for construction/annual energy output, whenthe latter is constant over time. Units: time (e.g., months or

years).

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ENERGY ANALYSIS: SOME CONVENTIONS

Allocation between co-products: Some systems yield co-products, and then the energy inputs need to be apportioned

between them on the basis (for example) of mass, energycontent (calorific value), or monetary value of each co-product.

The opportunity cost convention of thermal inputs to

power generation: The electricity foregone by using primary orthermal energy in renewable or nuclear power generators inpreference to using them to produce electricity in conventionalfossil-fuelled power stations. Developed for energy analysis by

analogy with the use of the 'opportunity cost' concept ineconomics.

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EMBODIED ENERGY AND CARBON

Embodied energy (carbon) may be regarded as

the primary energy consumed (carbon released) toextract, process, transport, and produce a good (orservice).

It implies all the energy (carbon) requirementsassociated with the production of the good or service.

That includes the sum of the direct and indirect energyand carbon sources associated with the product oractivity, i.e., all energy and carbon flows must be tracedupstream to their origin.

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TOTAL

ENERGY

MINIMUM

ENERGY

PROCESSENERGY

EMBODIED ENERGY

EQUIPMENT SIZE

PRO

DUCT

ENERGY

G

(IDEALLIMIT)

MJ/kg

ENERGY USE IN PROCESS EQUIPMENT


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TO THERMODYNAMIC LIMIT

ENERGYMINIMUM

COSTMINIMUM

PROCESS + EMBODIED ENERGY (MJ/kg)

TO

TAL

COST

=CAPITAL+ENERG

Y

COSTS

/ kgC

ENERGY AND COST TRADE-OFF


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DETERMINING THE EMBODIED CARBON ASSOCIATED

WITH A PRODUCT OR SERVICE

Trace the energy requirement by fuel source for the typicalproduct or service in the UK

Estimate the carbon emanating from fossil fuel use (viacarbon coefficients)

Add additional carbon released/absorbed via other sources,i.e.,

Cement

Timber

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CARBON FOOTPRINTING: THE BASICS

Definition: The carbon footprint is a measure of the impactthat human activities have on the environment, and in particularon climate change. It is the amount of greenhouse gases (GHG)emitted through burning fossil fuels for electricity, heating, and

transportation in order to produce a good or service.

Standards

ISO 14040 & 14044 Environmental Life Cycle AssessmentPAS 2050 Life Cycle GHG Emissions of Goods & Services

Databases

Ecoinvent

Bath - Inventory of (Embodied) Carbon and Energy [ICE]

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THE CREATION OF THE ICEDATABASE

Created in support of a Carbon Trust and EPSRC-fundedresearch project the Carbon Vision Buildings Programme.

Aim: To produce an open-access, reliable database ofembodied energy and carbon for typical building materials

from cradle to gate.

It required values for the wide diversity of materialsassociated with buildings and construction.

this was considered this to be unavailable at the start ofthe project (in 2004).

Therefore we developed our own database

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THE INVENTORY OF CARBON & ENERGY (ICE)

An embodied energy and carbondatabase for building materials

ICEExcel andpdffiles created tosummarise data

Draws from over 250 references

Embodied energy & carboncoefficients ~ 400 selected values

Aim: Typical & usable marketproducts

Identifies primary & secondarymaterials

Available freely onlineBath


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THE FIVE SELECTION CRITERIA FOR ICEDATA

Source: Extracted from studies that are compliance withapproved methodologies/standards (e.g., ISO 14040 series

compliant).

System boundaries: Chosen to comply with cradle-to-gateembodiment. Non-fuel carbon emissions were included.

Origin (country) of data: The best available embodied energydata from around the world has been adopted, although a

preference was given to good quality UK sources.

Age of data: Modern sources were employed whereverpossible, because the fuel mix and carbon coefficients

associated with power generators has changed over time.

Embodied carbon: Preference given to data from LCAstudies, but otherwise estimates were made on fuel split.

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METHODOLOGICAL ISSUES

Recycling methodology

Recycled content (the adopted in the ICEinventory)

Substitution method (endorsed by the metals industry, e.g.,

Corus)

Other methods (i.e., the hybrid 50-50 method)

Carbon sequestration

Controversial whether to include or exclude?

The ICEdatabase presently excludes carbon sequestration

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VERIFICATION OF THE ICEINVENTORY

Validation of the dataset was initially undertaken throughapplication and comparison with embodied energy & carbon

estimates for whole buildings

Case Studies

Domestic buildings (see the following figures)

Non-domestic buildings

Comparison with BedZed estimates (BRE Data)

Embodied energy = ICEwas within 1%

Embodied carbon = ICEwas within 10%

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THE PRESENT STATUS OF THE ICEDATABASE

The ICEdatabase has been publicly downloadable via anonline website [see http://www.bath.ac.uk/mech-eng/sert/embodied/] since April 2007. Over 5000 copies had

been distributed worldwide by June 2009.

Feedback from professional users has played an importantpart in the choice of 'best values' for 'cradle-to-gate' embodied

energy & carbon from the range found in the literature.

The variation in published embodied energy & carbon datastems from differences in boundary definitions, age of the data

sources, and rigour of the original life-cycle assessments.

Data from the ICEinventory has been incorporated into anumber of carbon footprinting tools for products,

structures and activities by various industrial companies

and government agencies.

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INDUSTRIAL INTEREST IN EMBODIED ENERGY

AND CARBON

The ICEinventory has provided input data for 'carbon footprint'calculators and studies devised by organisations likeArup, BestFoot Forward, Buro Happold, Davis Langdon, dcarbon8, the EmptyHomes Agency, the Environment Agency, Halcrow, Hydrok UK,Masdar, and Wessex Water.

In the UK, the Governments Department for Environment, Foodand Rural Affairs (DEFRA) have recently asked for permission to

signpost the ICEdatabase from their own website, alongside theirannual update to the Department of Energy and Climate Change(DECC)/DEFRA greenhouse gas (GHG) conversion factors.

Hammond & Jones assisted the US National Trust for Historic

Preservation with the development of an embodied energyworkshop held in Washington DC (June 2009). The Trustanticipates that the adoption of the idea of embodied energy in USbuilding codes will readdress the balance away from thedemolition of historic buildings in favour of their refurbishment.

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Source: The New York Times, 31 March 2009


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BARRIERS TO THE MINIMISATION OF

ENERGY AND CARBON

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100

80

60

40

20

0

Existingenergy

use

Economicpotential Technical

potential Thermodynamicpotential

Energy saving potential

%


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CONCLUDING REMARKS

Energy analysis for part of a broader whole systems orsustainability appraisal framework for the evaluation of

energy resources and technologies on a life-cycle or

full-fuel cycle basis.

For a comprehensive assessment of the thermodynamicperformance of energy, the quality as well as the quantity of

the energy carrier needs to be considered. That stems from

2nd Law constraints, and leads to the use of exergy analysis.

Ideally these methods should be extended to embrace a

variety of disciplines (engineers and social scientists),together with modellers and policy analysts, working in

a process of co-production. Only then would they truly

encompass the three pillars of sustainable development.

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THANK YOU

Documents

Energy Analysis Conventions Methods