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In a resource-constrained world: Think exergy not energy

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When we think about energy, we consider it in terms of quantity. However, in a resource-constrained world, energy must also be appreciated from the point of view of quality, which is essentially a measure of its usefulness, or its ability to do work. In order to account for the quality and not just the quantity of energy, we need to measure exergy. Exergy analysis can be applied not only to individual processes, but also to industries, and even to whole national economies. It provides a firm basis from which to judge the effect of policy measures taken towards energy, resource and climate efficiency. In the future, consumers could be informed about products and services in terms of their exergy-destruction footprint in much the same way as they are about their carbon emissions. In its recent Opinion Paper ‘A Common Scale for Our Common Future: Exergy, a Thermodynamic Metric for Energy’, the former Science Europe Scientific Committee for the Physical, Chemical and Mathematical Sciences explained the concept of exergy and its application to energy efficiency. In doing so, the Committee reached out to policy makers to call for the formation of an International Exergy Panel to: 1. bridge the gap between the science of energy and energy policy, leading to the systematic use of the concept of exergy where appropriate; 2. provide an evidence-base for interrelated energy-, climate change and economic policies; 3. drive interdisciplinary research and development on the causes of exergy destruction and how we can minimise this destruction, from the molecular to the global scale; 4. guide the establishment of exergy destruction footprints for commodities and services; and 5. collaborate with the Intergovernmental Panel on Climate Change (IPCC ). Energy awareness is increasing within Europe through various initiatives, including the European Commission’s adoption of ‘A Framework Strategy for a Resilient Energy Union with a Forward-Looking Climate Change Policy’, a decade of EU Sustainable Energy Week (EUSEW) programmes addressing the EU’s sustainable energy agenda with stakeholders and the general public, and the historic 2015 Paris climate conference (COP21). In this context, the authors would like to take this opportunity to expand on the previous publication, and set out the benefits of applying exergy in a finite world in this brochure.
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IN A RESOURCE-CONSTRAINED WORLD:
THINK EXERGY,
NOT ENERGY
About Science Europe
Science Europe is an association of major European Research
Funding and Research Performing Organisations, founded in
October 2011 and based in Brussels. It supports its Member
Organisations in their efforts to foster European research
and to strengthen the European Research Area.
Further information: www.scienceeurope.org
Scientifically Independent Advice
to Science Europe
Science Europe is supported in its activities by a cross-
disciplinary Scientific Advisory Committee, composed of up
to 30 active researchers, who provide scientifically independent
advice on key European research policy topics and on the
implications of EU legislative and regulatory developments.
Further information: http://www.scienceeurope.org/sac
About the Authors
The former Science Europe Scientific Committee for the Physical,
Chemical and Mathematical Sciences (including Materials
Sciences), which ran from 2012 to 2015, was supported in its
activities related to Exergy by a working group comprising
the following experts:
 
 
 
and Technology
 
 
Energy Resources and Consumption, University of Zaragoza
 
Acknowledgment
The authors would like to express their special appreciation

Affairs at Science Europe, for her support and encouragement.
Date of Publication: June 2016
EXECUTIVE SUMMARY
When we think about energy, we
consider it in terms of quantity.
However, in a resource-constrained
world, energy must also be appreciated
from the point of view of quality,
which is essentially a measure of its
usefulness, or its ability to do work.
In order to account for the quality and
not just the quantity of energy, we need
to measure exergy.
Exergy analysis can be applied not
only to individual processes, but
also to industries, and even to whole
national economies. It provides a firm
basis from which to judge the effect of
policy measures taken towards energy,
resource and climate efficiency. In the
future, consumers could be informed
about products and services in terms of
their exergy-destruction footprint in much
the same way as they are about their
carbon emissions.
In its recent Opinion Paper ‘A Common
Scale for Our Common Future: Exergy,
a Thermodynamic Metric for Energy’,
the former Science Europe Scientific
Committee for the Physical, Chemical
and Mathematical Sciences explained
the concept of exergy and its application
to energy efficiency.1 In doing so, the
Committee reached out to policy makers
to call for the formation of an International
Exergy Panel to:
bridge the gap between the science
of energy and energy policy, leading
to the systematic use of the concept
of exergy where appropriate;
provide an evidence-base for
interrelated energy-, climate change-
and economic policies;
drive interdisciplinary research and
development on the causes of exergy
destruction and how we can
minimise this destruction, from the
molecular to the global scale;
guide the establishment of exergy
destruction footprints for
commodities and services; and
collaborate with the Intergovernmental
Panel on Climate Change (IPCC).
Energy awareness is increasing within
Europe through various initiatives, including
the European Commission’s adoption of ‘A
Framework Strategy for a Resilient Energy
Union with a Forward-Looking Climate
Change Policy’, a decade of EU Sustainable
Energy Week (EUSEW) programmes
addressing the EU’s sustainable energy
agenda with stakeholders and the
general public, and the historic 2015
Paris climate conference (COP21).
In this context, the authors would like
to take this opportunity to expand
on the previous publication, and set
out the benefits of applying exergy
in a finite world in this brochure.
3
4
EXERGY-BASED ENERGY
AND RESOURCE EFFICIENCY:
THE BASICS
The Need to Measure Energy and
Resource Efciency
The European Commission highlighted
seven societal challenges to reflect the
policy priorities of its ‘Europe 2020’
strategy. Out of these seven challenges,
at least four are directly related to the
availability of energy and resources:
Food security, sustainable agriculture
and forestry, marine and maritime
and inland water research, and the
Bioeconomy
Secure, clean and efficient energy
Smart, green and integrated transport
Climate action, environment,
resource efficiency and raw materials
If the aim is to improve energy and
resource efficiency, the question arises
of how to measure this. Of course, the
amount of energy and raw materials
that go into making something, or
that go into services such as heating,
communication, or transpor t, can be
easily measured. However, that does not
consider the quality of the energy nor the
© Shutterstock
Educators, researchers, policy makers,
stakeholders and citizens are urged to
consider energy and natural resources
on the basis of exergy, and in doing so
understand that:
exergy measures energy and
resource quality;
exergy-destruction footprinting
promotes improvements in industrial
efficiency;
exergy offers a common international
energy-efficiency metric;
optimal use of our limited mineral
resources can be achieved by the
application of exergy rarity; and
exergy should be integrated into
policy, law and everyday practice.
5
rarity of the materials used. In order to
account for the quality and not just the
quantity of energy, as well as factoring
in the raw materials used, we need to
measure exergy.
Exergy can be considered to be useful
energy, or the ability of energy to do
work. Exergy can be measured not
only for individual processes, but also
for entire industries, and even for whole
national economies. It provides a firm
basis from which to judge the effect
of policy measures taken to improve
energy and resource efficiency, and to
mitigate the effects of climate change.
Exergy as a Measure
of Energy Quality
The need to take the quality of energy
into account can be shown with a
simple everyday example (see Figure 1).
The energy contained in the movement
of air molecules in a 20m3 office at
20°C is more than the energy stored in
three standard 12V car batteries. While
you can only use the energy in the air
to keep yourself warm, you could use
the energy in the batteries to start your
car, cook your lunch, and run your
computer. The reason is that even if their
quantities were the same, the quality –
or usefulness – of the energy in the air
and in the batter y is different. In the air,
the energy is randomly distributed, not
readily accessible, and not easily used
for anything other than keeping you
warm. In contrast, the electric energy in
the battery is concentrated, controllable,
and available for all sorts of uses. This
difference is taken into account by
exer g y.
© Shutterstock
Figur e 1 Every day exampl e of exergy s howing (A ) batter y used to st art a car v ersus (B) a ir mole cules
in an offi ce used to he at the occ upant.
Thermodynamics is the Science
of Energy
The concept of exergy is inextricably
contained within the basic physical laws
governing energy and resources, called
thermodynamics. These laws cannot be
ignored: they are fundamental. Two of
the basic laws in thermodynamics need
to be considered:
First – Energy is conserved.
Second – Heat cannot be fully converted
into useful energy.
The second law concerns the concept of
exergy. Every energy-conversion process
destroys exergy.
Take for example a conventional fossil-
fuel power station, shown schematically
in Figure 2. Such a station transforms the
chemical energy stored in coal to produce
steam in a boiler, which is then converted
by a turbine into mechanical energy and
finally by a generator into electricity. In this
process, only 30–35% of the chemical
energy contained in the coal is converted
into electrical energy; the remaining
65–70% is lost in the form of heat.
Exergy analysis of this power generation
plant identifies the boiler and turbine
as the major sources of exergy loss. In
order to improve the exergy efficiency,
the boiler and turbine systems need to
be altered through technical design and
operational changes.
It is of utmost importance to look at the
exergy balance of processes. In fact,
we need to go much further: the exergy
balance of whole economies can and
should be routinely considered, as will be
shown later.
6
Coal
Pollution
Control
Steam
Boiler
Steam
Condenser
Combustion
Chamber
Exhaust
Gases
Pump Steam
Valve
Synchronous
Generator
AC
Power
Speed Control
Water
Cooling
Water
Steam
Turbine
Figure 2 Fossil-fuel powered steam turbine electricity generation.
Exergy as a Measure
of Resource Quality
Exergy can also be applied in order
to take the quality of resources into
account. A diluted resource is much
more difficult to use than a concentrated
one, as it first has to be collected
or refined. The measure to take the
concentration of a resource into account
is its chemical potential (or chemical
exergy). The chemical potential of pure
iron is much higher than the chemical
potential of an iron ore diluted by other
rocks.
An exergy consideration of any process
takes into account the chemical potential
of the resources used in the process.
The problem with chemical potentials,
however, is that it is only possible
to measure their difference. In order
to study the chemical potential of a
specific resource, a reference point is
needed. An interesting proposal as a
reference point for natural minerals is
the concept of ‘Thanatia’, a hypothetical
version of our planet where all mineral
deposits have been exploited and
their materials have been dispersed
throughout the crust.2 Using Thanatia as
a model, it is possible to determine the
exergy content of the Ear th’s resources.
By adding up all exergy expenditures,
the rarity of resources and their
products can be assessed.
7
© iStock.
Exergy Destruction in the Process
Industry
Industry is a large user of both material
and energy resources. Typically, an
industrial production process needs
the input of materials and of energy to
transform those materials into products.
Much of these inputs end up being
discarded: in the case of materials
as waste, and in the case of energy
as heat. This is exergy destruction,
since – recalling the Second Law of
Thermodynamics – not all inputs can be
fully recovered as useful energy.
Methanol, for example, is a primary
liquid petrochemical manufactured
from natural gas. It is a key component
of hundreds of chemicals that are
integral parts of our daily lives such as
plastics, synthetic fibres, adhesives,
insulation, paints, pigments, and
dyes. Before methanol production
even begins, 10% of the natural gas
is used to warm the chemical reactor.
Subsequently, during production
further reactor losses amount to
50%. This contributes to the exergy-
destruction footprint of methanol
production and of all its products.
8
© iStock.
How can we Increase the Energy
Efciency of Production?
While exergy destruction for any process
is never zero, it can be minimised. Every
process has a characteristic exergy-
destruction footprint. Knowledge of
this footprint can be used to rationalise
resource choices before production
begins and to monitor the use of energy
and resources during production. In a
full life-cycle approach, it can be used to
consider the total energy and resource
‘cost’ of a product: essentially its exergy-
destruction footprint.
An example of a process where reducing
exergy destruction can increase energy
efficiency is distillation. Distillation is
the most commonly applied separation
technology in the world, responsible for
up to 50% of both capital and operating
costs in industrial processes. It is a
process used to separate the different
substances from a liquid mixture by
selective evaporation and condensation.
Commercially, distillation has many
applications; in the previous example of
methanol production, it is used to purify
the methanol by removing reaction by-
products from it, such as water.
The conventional separation of chemicals
by distillation occurs in a column that
is heated from below by a boiler, with
the desired product (referred to as the
condensate) produced from a condenser
at the top, as illustrated in the left-hand
side of Figure 3. The exergy efficiency of
this distillation setup is about 30%.
The obvious question is whether the
same distillation results can be achieved
with a higher exergy efficiency by
operating the column differently. The
answer to that question is yes, as there
are better ways to add heat to the
column than by a boiler. The boiler and
condenser can be replaced by a series
of heat exchangers along the column,
such as on the right-hand side of Figure 3,
producing a more exergy-efficient
heating pattern. This arrangement
minimises the exergy destruction in the
system, reducing the exergy footprint
of the process. In this way, the same
product can be obtained with only 60%
of the original exergy loss. This of course
requires investment in replacing or
retrofitting the technology, but in the
long run such costs are compensated
by lower operating costs. Financial
benefits aside, the potential impact
of technological development driven
by exergy analysis on the energy
and material ef ficiency of industry,
is enormous.
9
Figure 3 Exergy destruction of 1025 kWh for the left hand side
distillation column compared with 673 kWh for the right hand
side [adapted from reference 3].
The Exergy Destruction Footprint
– Developing More Environmental-
friendly Technologies
When exergy analysis is performed on
a process, the exergy losses can be
identified and the exergy-destruction
footprint can be minimised. In the fossil-
fuel industry, for example, single- and
two-stage crude oil distillation are used
to obtain materials from crude oil for fuels
and for chemical feedstocks.
A single-stage system consists of a
single heating furnace and a distillation
column; a two-stage system adds
another furnace (to heat the product of
the first unit) and a second column.
Table 1 shows the comparison of
the exergy streams of these systems
and reveals a considerable reduction
in exergy losses and hence a higher
efficiency of the two-stage system.4
The two-stage system can be better
controlled than the one-stage system,
and comes closer to the minimal required
exergy in the best-case scenario. Adding
more stages gives even better control.
It is important to keep in mind that there
is no production without an exergy-
destruction footprint. A systematic
effort to reduce exergy destruction to a
minimum is an ideal to strive for when
developing more environmental-friendly
technologies.
Tabel 1 Exergy streams in single- or two-stage crude oil distillation systems.4 The feed and product streams are the same.
It is important to keep
in mind that there
is no production without
an exergy destruction
footprint.
SYSTEM 



STREAM OUT




ExErgy
EfficiEncy
( %)
Single stage 498.8 69.8 429.0 14.0
Two sta g e 352.0 110.9 241.1 31.5
10
A Large-scale Problem Needs
a Common-scale Solution
In 2013, industry accounted for 25% of
the EU’s total final energy consumption,5
making it the third-largest end-user after
buildings and transport. Over 50% of
industry’s total final energy consumption
is attributed to just three sectors: iron and
steel, chemical and pharmaceutical, and
petroleum and refineries.
Between 2001 and 2011, EU industry
reduced its energy intensity by 19%.5
However, significant efficiency potential
remains. As previous examples of
several industrial processes have shown,
exergy analysis offers a guide to the
development of more energy-efficient
technologies and provides an objective
basis for the comparison of sustainable
alternatives.
Energy analysis explains that electric and
thermal energy are equivalent according
to the First Law of Thermodynamics,
and that heating by an electric resistance
heater can be 100% efficient. Exergy
analysis, however, explains that heating
by an electric heater wastes useful
energy. When we know about this kind
of waste, we can start to reduce it by
minimising exergy destruction.
While the given examples have focused
on industrial processes, exergy analysis
can also tackle the energy and resource
efficiency of larger consumers of energy,
such as the buildings and transport
sectors. It is important to highlight
that exergy analysis can be used not
only to quantify the historical resource
use, efficiency and environmental
performance, but also to explore future
transport pathways, building structures
and industrial processes.
As explained in the Opinion Paper
‘A Common Scale for Our Common
Future: Exergy, a Thermodynamic
Metric for Energy’,1 a major roadblock
for implementing – or even finding –
solutions to our societal challenges
is the fact that energy and resource
efficiency are commonly defined in
economic, environmental, physical,
and even political terms. Exergy is the
resource of value, and considering it
as such requires a cultural shift to the
thermodynamic-metric approach of
energy analysis. Exergy provides an
apolitical scale to guide our judgement
on the road to sustainability. Exergy is
first step to a common-scale solution
to our large-scale problems.
SYSTEM 



STREAM OUT




ExErgy
EfficiEncy
( %)
Single stage 498.8 69.8 429.0 14.0
Two sta g e 352.0 110.9 241.1 31.5
11
ADOPTING EXERGY EFFICIENCY
AS THE COMMON NATIONAL
ENERGY-EFFICIENCY METRIC
Energy Efciency as a Key Climate
Policy: the Need to Measure
Progress with Exergy
Improving the efficiency of energy use
and transitioning to renewable energy are
the two main climate policies aimed at
meeting global carbon-reduction targets.
The 2009 Renewable Energy Directive6
mandates that 20% of energy consumed
in the EU should be renewable by 2020.
At the same time, the EU’s 2012 Energy
Efficiency Directive7 sets a 20% reduction
target for energy use.
Progress towards the renewable-energy
target is straightforward to measure,
since national energy use by renewable
sources is collected and readily available.
Indeed, for many citizens, the propor tion
of domestic electrical energy generated
from renewable sources appears clearly
defined on their electricity bills.
In contrast, national-scale energy
efficiency remains unclear and a
qualitative comparison of renewable
sources is lacking. A central problem is
that there is no single, universal definition
of national energy efficiency. In this void,
a wide range of metrics is inconsistently
adopted, based on economic activity,
physical intensity or hybrid economic–
physical indicators.
None of these methods are based on
thermodynamics, however, making
them inherently incapable of measuring
energy efficiency in a meaningful way.
As such, they are unable to contribute
to evidence-based policy making or
to measure progress towards energy-
efficiency targets. The EU is not alone,
there is currently no national-scale
thermodynamic based reporting of energy
efficiency by any country in the world.
Second-law thermodynamic efficiency
– in other words, exergy efficiency –
stands alone in offering a common scale
for national, economy-wide energy-
efficiency measurement, applicable
at all scales and across all sectors.
12
5.3
11.7
10.6
4.9
10.9
1.2
19.5
1.2
20.2
Legend
Gas [Mtoe]
Oil [Mtoe]
Coal [Mtoe]
Exergy losses [Mtoe]
Renewables [Mtoe]
Food & feed [Mtoe]
Heat [Mtoe]
Mech Drive [Mtoe]
Electricity [Mtoe]
Nuclear [Mtoe]
Gas
88.1
Coal products 3.3
Oil & oil products
53.6
Mech work
(Man labour) 0.01
Nuclear
16.2
Renewables 8.2
Food & Feed 0.9
Gas & gas products
51.8
Heat 1.1
Supplied food 0.2
Exergy coeff 10.6
1.0
10.1
0.4
15.1
TPES (199.4Mtoe)
Energy sector own use + TFC
(146.0Mtoe)
Useful work by end use
(30.9Mtoe)
Useful work by endsector
(30.9Mtoe)
1.8
0.2
20.0
9.4
46.4
41.5
2.3
3.3
Non Energy 12.9
0.6
Primary exergy (223.9Mtoe)
5.4
1.8
51.8
53.6
11.8
Coal
32.9
Oil
66.9
Residential/other 8.4
Industry 9.2
Energy sector 4.3
Exergylosses 179.1
Electricity
Generation
32.6
Direct Mechanical
work 10.0
Direct Heat 9.2
Electricity 11.7
Transport 9.0
Figure 4 shows a flow diagram from
primary exergy to useful work for the
United Kingdom for the year 2010.8
Energy supplied from coal, oil, gas,
renewables, and food and feed provides
the primary exergy. It is transformed into
ready-to-use energy, such as diesel or
electricity, which then provides ‘useful
energy’ through high-temperature heat,
mechanical drive, or electrical devices.
The useful energy is the last point of
common thermodynamic measurement
before it is exchanged for energy
services, such as thermal comfor t,
motion, or light.
The national exergy efficiency εNational
therefore represents the second-law
thermodynamic efficiency of the energy
conversion, defined in exergy terms as:
Figure 4 2010 United Kingdom Exergy flow chart: primary to final energy.8
εNational = (Sum of Useful Work ) / (Sum of Primary Exergy)
13
14
The Benets of Exergy-efciency
Reporting
Once this formal definition is in place,
reporting exergy-efficiency at a national
scale is not only desirable, but also
possible. Widespread use would enable
comparison between technologies,
sectors, and countries, enabling best
practice and energy-efficiency
opportunities to be identified. Figure 5
shows the aggregate exergy-efficiency
percentage of China, the United States
and the United Kingdom for the period
1971 to 2010.9 The figure shows an
increase in exergy efficiency in the United
Kingdom and China, while it remains
stagnant in the United States. Such
comparisons provide detailed insight into
the reality of current energy-efficiency
policies and their implementation in
everyday life.
In the 1970s and 1980s, Eurostat
collected national accounts of useful
energy. This accounting practice needs
to be reinstated. One of the downstream
benefits of formalising the national-
scale exergy-efficiency definition and
development of a consistent reporting
framework, is that it enables exergy
-efficiency to be included as part of the
overall policy-design process. Energy
use and efficiency can then be tracked
to view progress towards targets and
policies can be amended if the desired
energy reduction is not occurring.
It should not be misunderstood, however,
that the benefits of adopting exergy-
efficiency as the common national
energy-efficiency metric is to merely
satisfy a reporting exercise. In the words
of Fatih Birol, the International Energy
Agency’s Executive Director: “any
progress with climate change must have
the energy sector at its core or risk being
judged a failure”.10 The energy sector can
only be understood by applying second-
law thermodynamics, or exergy.
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
18.0%
20.0%
1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 2010
Exergy efficiency China-US-UK 1971-2010
China aggregate efficiency
Aggregate exergy efficiency %
US aggregate efficiency UK aggregate efficiency
Figure 5 Comparison of the exergy efficiency % of China, US and UK over time.9
NATURAL RESOURCE
CONSUMPTION
15
From Gaia to Thanatia: How to Assess
the Loss of Natural Resources
As technology today uses an increasing
number of elements from the periodic
table, the demand for raw materials
profoundly impacts on the mining
sector. As ever lower grades of ore are
being extracted from the earth, the use
of energy, water and waste rock per
unit of extracted material increases,
resulting in greater environmental and
social impact. Globally, the metal sector
requires about 10% of the total primary
energy consumption, mostly provided
by fossil fuels. By 2050, the demand for
many minerals, including gold, silver,
indium, nickel, tin, copper, zinc, lead, and
antimony, is predicted to be greater than
their current reserves. Regrettably, many
rare elements are profusely used, with
limited recycling.
The loss of natural resources cannot
be expressed in money, which is a
volatile unit of measurement that is too
far removed from the objective reality
of physical loss. Neither can it be
expressed in tonnage or energy alone, as
these do not capture quality and value.
Exergy can solve such shortcomings
and be applied to resource consumption
through the idea of ‘exergy cost’: the
embodied exergy of any material, which
takes the concentration of resources into
account measured with reference to the
‘dead state’ of Thanatia (see Figure 8).
Thanatia – from the Greek “ ”,
the personification of Death – is
a hypothetical dead state of the
anthroposphere, conceiving an ultimate
landfill where all mineral resources are
irreversibly lost and dispersed, or in other
words, at an evenly distributed crustal
composition. If our society is squandering
the natural resources that the Sun and
geological evolution of the Earth have
stored, we are converting their chemical
exergy into a degraded environment
that progressively becomes less able to
support usual economic activities and
eventually will fail to sustain life itself. The
end state would be Thanatia, a possible
end to the ‘Anthropocene’ period. It does
not represent the end of life on our planet,
but it does imply that mineral resources are
no longer available in a concentrated form.
Figure 8 Evolution of Planet Earth to complete exhaustion.2
   
ConCrete 83.2 8,640 1.7
BriCks 3.8 620 2.7
MarBle 2.8 2,080 12
steel 4.1 11,800 47
aluMiniuM 0.1 1,360 249
16
The Price the Planet Pays
To put the situation in context, consider
the example of a hotel building in Greece,
with an exergetic lifecycle of construction,
use and withdrawal phases. Table 2
compares the exergy, embodied exergy
and composition of the total building for
selected materials.
The comparison of the embodied exergy
reveals that the main material used in
large quantities is concrete, which has
the lowest embodied exergy of the listed
materials (1.7 MJ/Kg), while aluminium
is the least used material but has the
highest embodied exergy (249 MJ/Kg),
due to the very high energy demand
during its production. In general, exergy
analysis finds that three quarters of the
building’s exergy consumption over
an 80-year life cycle, stems from the
period it is in use (heating, cooling,
lighting), while the remaining relates to its
construction period (material extraction,
process, transport).
The exergy concept can be applied to
the whole process involving a building,
not just the use of materials in its
construction, but also the energy use,
eventual demolition, and recycling.
While this example gives invaluable
insight into the environmental impact of
materials that we typically consume, it is
important to go further in appreciating
the cost of our living to our planet.
An Essential Approach to Making
Better Use of our Mineral Resources:
the Application of Mineral Exergy
Rarity
The exergy of a mineral resource as
calculated with Thanatia as a reference
can be measured as the minimum
energy that could be used to extract
that resource from bare rocks, instead
of from its current mineral deposit. This
is an essential approach, since the
European Commission’s Communication
‘Towards a Circular Economy: A Zero
Waste Programme for Europe,12 states
that “valuable materials are leaking from
our economies” and that “pressure
on resources is causing greater
environmental degradation and fragility,
Europe can benefit economically and
environmentally from making better use
of those resources.
Applied to minerals we can define a
‘Mineral Exergy Rarity’ (in kWh) as “the
amount of exergy resources needed to
obtain a mineral commodity from bare
Table 2 Exergy (GJ), embodied exergy (MJ/kg) and composition of the total building material (%) for selected materials
used in the lifecycle of a hotel [data extracted from reference 11].
   
ConCrete 83.2 8,640 1.7
BriCks 3.8 620 2.7
MarBle 2.8 2,080 12
steel 4.1 11,800 47
aluMiniuM 0.1 1,360 249
17
rocks, using prevailing technologies”.2
The ‘exergy rarity’ concept is thus able
to quantify the rate of mineral capital
depletion, taking a completely resource-
exhausted planet as a reference. This rarity
assessment allows for a complete vision
of mineral resources via a cradle-to-grave
analysis. Exergy rarity is, in fact, a measure
of the exergy-destruction footprint of a
mineral, taking Thanatia as a reference.
Given a certain state of technology, the
exergy rarity is an identifying property
of any commodity incorporating metals.
Hence, exergy rarity (in kWh/kg) may
be assessed for all mineral resources
and artefacts thereof, from raw materials
and chemical substances to electric
and electronic appliances, renewable
energies, and new materials. Especially
those made with critical raw materials,
whose recycling and recovery
technologies should further enhance.
Such thinking is a step towards “a better
preservation of the Earth’s resources
endowment and the use of the Laws of
Thermodynamics for the assessment
of energy and material resources as
well as the planet’s dissipation of useful
energy”. This message was launched in
the Brescia Appeal to the UN and the
EU of a group of thirty-one scientists
in the field of exergy.13 More than ever,
the issue of dwindling resources needs
an integrated global approach. Issues
such as assessing exhaustion, dispersal,
or scarcity are absent from economic
considerations. An annual exergy-
content account of not only production,
but of the depletion and dispersion of
raw materials would enable a sound
management of our material resources.
Unfortunately, similar to the problem of
inconsistent national energy-efficiency
measurement, there is also a lack
of consistency in natural-resource
assessment, which is necessary for
effective policy making.2 Integration
of exergy analysis into our daily lives
through laws and even taxes is long
overdue, but progress is slow.
© iStock.
INTEGRATING EXERGY ANALYSIS
INTO OUR DAILY LIVES
18
Exergy-based Law-making
As far back as 1974, the Congress
of the United States passed Public
Law 93.577, the Federal Non-Nuclear
Energy Research and Development
Act, to establish a national programme
for research and development in
non-nuclear energy sources, with the
governing principle that the potential for
production of net energy be analysed
and considered in evaluating the
potential of any proposed technology.14
In effect, this legislation states that
net energy, rather than conventional
economic analysis, should provide the
basis for prospective energy technologies.
As a result of this legislation, the net
energy yields of renewable and non-
renewable energy supply technologies
are now publically available.
Unfortunately, despite the fact that
exergy analysis has matured in the
intervening years, it has remained
largely confined to the academic world.
An exception is the canton of Geneva,
which in 2001 introduced a new article
featuring the exergy concept in their
energy law.
15 Geneva authorities require
city developers to include an exergy
approach in their project proposal.
The law applies to about 20% of total
developments in particular buildings
© iStock.
INTEGRATING EXERGY ANALYSIS
INTO OUR DAILY LIVES
19
or building areas used for apartments,
offices, and commercial premises,
representing close to 80% of
the energy consumption of new building
developments. In practice, an internet
framework allowing users to calculate
their efficiency indicators was set-
up. Today, the law seems to be fully
implemented with energy efficiency
featuring heavily within the building
application process.16
The Cost of a Recycling Policy –
a Cautionary Tale
Recycling contributes significantly
to the preservation of natural resources.
At least, that is what policy and
legislation leads us to believe. However,
exergy analysis shows that well-intended
legislation may actually not have the
desired effects.
Since recycling technology itself requires
materials and energy input, both of which
contribute to the depletion of natural
resources, it is important to evaluate
the efficiency of the whole recycling
chain to determine its actual benefit.
Exergy analysis allows evaluation and
optimisation of any recycling system’s
environmental performance on a
fundamental basis, capturing efficiency
in the system as a function of physical,
metallurgical, and thermal processing,
and of the quality of reclaimed materials.
Such studies have shown that the high
recycling quotas for end-of-life vehicles
as required by EU legislation appear
to be totally erroneous, since they are
based on first-law arguments.17 The
present stringent legislation is violating
fundamental thermodynamics and
contrary to its intention, is potentially
damaging the environment.
Charging Exergy Loss, not Energy
Use – Radical Thinking or Just
Common Sense?
One of the leading proponents of the
1974 US Federal Non-Nuclear Energy
Research and Development Act, Senator
Mark Hatfield, interpreted the Act as
a step towards replacing money with
energy as the standard of value. While
still some way off from an ‘energy
currency’, there have been repeated calls
for an energy-based tax as an incentive
for exergy and resource conservation.
Current EU rules for taxing energy
products and electricity are laid down in
the Energy Tax Directive 2003/96/EC,18
which entered into force in 2004 with
the aim of reducing distortions caused
by divergent national tax rates, removing
competitive distortions between mineral
oils and other energy products, and
creating incentives for energy efficiency
and emission reductions. However, as
the taxation rates are based on volume,
rather than energy content, products
with lower energy content, such as
renewables, carry a heavier tax burden
than the fuels they are competing with.
Encouragingly, in 2011, the European
Commission presented a proposal to
revise the rules on taxation of energy
products in the EU, in order to reflect
CO2 emissions and energy content
(€/GJ), rather than on volume.
The following year, however, the
European Parliament voted against
20
© iStock.
the draft Energy Taxation Directive,
stating that it was not a good moment
to increase energy taxes in a time of
economic austerity and high fuel costs.
The European Council has had several
debates on the topic since 2012, but has
not yet released an official position on
the matter.
In the beginning of 2015, the
Commission withdrew the proposal,
because, in the words of First Vice-
President Frans Timmermans at the
Presentation of the 2015 Commission
Work Programme to the European
Parliament, “the Council has watered
it down so it no longer meets our
environmental objectives of taxing fuel
in a way that reflects real energy content
and CO2 emissions”.19
As previously demonstrated, the
second-law thermodynamics
consideration of energy has the
advantage that it can be applied with a
common measurement scale to natural
resources, fuels and products. It can
be applied to individual processes,
to industries, and to whole national
economies. It provides a firm basis
from which to judge the effect of policy
measures taken towards energy, and
resource and climate efficiency.
There is little doubt that the Energy Tax
Directive 2003/96/EC inadequately
supports the EU’s current energy and
climate change policies. However, is the
economic crisis and national-interests-
driven rejection of its proposed revision
a missed opportunity, or rather a timely
opening for a radical common-sense
thermodynamics approach to taxation
on energy?
It is time to charge for exergy use rather
than for energy use. In the future,
consumers should be informed about
products and services in terms of
their exergy content and destruction
footprints in much the same way as they
are about carbon emissions, and pay the
price accordingly. That gives a scientific
basis for charging for loss of valuable
resources.
CONCLUDING REMARKS
AND RECOMMENDATIONS
Thermodynamics is the science of
energy. Exergy measures useful energy.
Exergy efficiency is the real efficiency
of an energy system or process. To this
end, and compared with conventional
first-law thermodynamics energy
approaches, the second-law exergy
approach can identify and quantify
the causes of inefficiencies. Exergy is
therefore the right metric to value energy
use and resource scarcity.
In December 2015, world leaders signed
a historic climate agreement in Paris.
For the first time, all countries agreed
to play their part in keeping the global
temperature increase below 1.5°C. But
the Paris negotiations may turn out to
have been the easy part. Any progress
with climate change must tackle energy
use. Decision-makers must see beyond
economic and national interests to chart
a new course of radical climate policies
based on the science of energy.
With this in mind, the authors make the
following recommendations:
The teaching of concepts related
to exergy in schools and
universities
The promotion of the exergy
concept, with policy makers and
energy stakeholders taking a lead
in informing the public
The introduction of exergy
destruction footprints to give a useful
basis for work on energy efficiency
improvements
The reintroduction of national useful
energy accounting
Taxation of excess exergy destruction
footprints to drive the development of
more energy efficient technology
Use of exergy rarity to monitor the
earth’s mineral resources
The creation of accounts of exergy
destruction footprints and exergy
rarity to support the IPCC in finding
measures to mitigate climate changes
The EU has a moral responsibility
to show the same leadership in
implementing the Paris agreement as it
did in making the agreement possible.
The climate crisis was not solved in
Paris: the COP21 was just one step in
the right direction. The second step
requires the common sense and courage
to implement exergy as the rightful metric
for energy and natural resource use.
As wisely said by Howard Scott in 1933:
“It is the fact that all forms of energy, of
whatever sort, may be measured in units
of ergs, joules or calories that is of the
utmost importance. The solution of the
social problems of our time depends
upon the recognition of this fact. A dollar
may be worth - in buying power - so
much today and more or less tomorrow,
but a unit of work or heat is the same in
1900, 1929, 1933 or the year 2000.”20
21
References
1. Science Europe Scientific Committee for the Physical, Chemical and mathematical
Sciences, “A Common Scale for Our Common Future: Exergy, a Thermodynamic Metric
for Energy, http://scieur.org/op-exergy
2. A. Valero Capilla and A. Valero Delgado, “Thanatia: The Destiny of the Earth’s Mineral
Resources, A Thermodynamic Cradle-to-Cradle Assessment”, World Scientific Publishing:
Singapore, 2014.
3. S. Kjelstrup, D. Bedeaux, E. Johannessen, J. Gross, “Non-Equilibrium Thermodynamics
for Engineers”, World Scientific, 2010, see Chapter 10 and references therein.
4. H. Al-Muslim, I. Dincer and S.M. Zubair, “Exergy Analysis of Single- and Two-Stage Crude
Oil Distillation Units”, Journal of Energy Resources Technology 125(3), 199–207, 2003.
5. SET-Plan Secretariat, SET-Plan ACTION n°6, DRAFT ISSUES PAPER, “Continue ef forts
to make EU industry less energy intensive and more competitive”, 25/01/2016,
https://setis.ec.europa.eu/system/files/issues_paper_action6_ee_industry.pdf
6. European Parliament. Directive 2009/28/EC of the European Parliament and of the Council
of 23 April 2009. Official Journal of the European Union L140/16, 23.04.2009, pp. 16–62.
7. European Parliament. Directive 2012/27/EU of the European Parliament and of the Council
of 25 October 2012 on energy efficiency. Official Journal of the European Union L315/1,
25 .1 0.2012.
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US and UK aggregate exergy efficiencies 1960 –2010”, Environmental Science and
Technology 48, 9874–9881, 2014.
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and future energy demand: An exergy efficiency and decomposition analysis”, Applied
Energy 155, 892– 903, 2015.
10. Presentation of the “World Energy Outlook - 2015 Special Repor t on Energy and Climate”,
presented by the International Energy Agency’s Executive Director Fatih Birol at the EU
Sustainable Energy Week, 2015.
11. C.J. Koroneos, E.A. Nanaki and G.A. Xydis, “Sustainability Indicators for the Use of
Resources –The Exergy Approach”, Sustainabilit y 4, 1867–1878, 2012.
12. http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A52014DC0398
13. Appeal to UN and EU by researchers who attended the 12th biannual Joint European
Thermodynamics Conference, held in Brescia, Italy, from July 1, International Journal of
Thermodynamics 16(3), 2013.
14. FEDERAL NONNUCLEAR ENERGY RESEARCH AND DEVELOPMENT ACT OF 1974,
Public Law 93–577, http://legcounsel.house.gov/Comps/Federal%20Nonnuclear%20
Energy%20Research%20And%20Development%20Act%20Of%201974.pdf
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in a local law on energy”, Energy, 33, 130–136, 2008.
22
Colophon
June 2016
‘In a Resource-constrained World: Think Exergy, not Energy’: D/2016/13.324/5
Author: Science Europe
For further information, please contact office@scienceeurope.org
© Copyright Science Europe 2016. This work is licensed under a Creative Commons
Attribution 4.0 International Licence, which permits unrestricted use, distribution,
and reproduction in any medium, provided the original authors and source are
credited, with the exception of logos and any other content marked with a separate
copyright notice. To view a copy of this license, visit http://creativecommons.org/
licenses/by/4.0/ or send a letter to Creative Commons, 444 Castro Street, Suite 900,
Mountain View, California, 94041, USA.
BY
16. http://ge.ch/energie/
17. O. Ignatenkoa, A. van Schaika and M.A. Reuterb, “Exergy as a tool for evaluation of the
resource efficiency of recycling systems”, Minerals Engineering, 20(9) 862–874, 2007.
18. European Parliament. Directive 2003/96/EC of the European Parliament and of the Council
of 27 October 2003. Official Journal of the European Union L283/51, 27.10.2003.
19. http://europa.eu/rapid/press-release_STATEMENT-14-2723_en.htm
20. H. Scott, “Technology smashes the price system, an inquiry into the nature of our present
crisis”, Harpers Magazine, Jan. 1933.
23
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Exergoeconomic analysis is a tool used to identify hidden costs associated with a machine or a system that cannot be identified using typical cost management techniques applied in the industry. While exergoeconomic analysis finds applications in power system innovations and optimization, it has not yet been harnessed by the manufacturing industry to reduce operating costs. The purpose of this study is to use exergoeconomic analysis to identify hidden costs in manufacturing processes, with a focus on the industrial beverage mixer system. The study proposes a methodology of identifying the hidden financial losses in the system and recommends modifying the systems operation and design as a measure to reduce costs and increase profitability. Thermodynamic and economic data for the study were obtained from manufacturing plants. An exergy cost analysis was performed using thermoeconomic analysis software. Exergoeconomic values and variables were obtained using equations based on extant literature. The results reveal that the mixer possesses a low exergoeconomic factor of 5.50% owing to the high irreversibility of the H 2 O reservoir, flow-mix reservoir, and carbonator. The total hidden cost of the system equaled 733.04 $/h, of which 99.0% is contributed by the mixer. Improvements to the deaeration technique for the H 2 O reservoir of the mixer component, as well as the H 2 O treatment procedure, can reduce the irreversibility of the H 2 O reservoir and the hidden costs.
Article
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There are very few useful work and exergy analysis studies for China, and fewer still that consider how the results inform drivers of past and future energy consumption. This is surprising: China is the world's largest energy consumer, whilst exergy analysis provides a robust thermodynamic framework for analysing the technical efficiency of energy use. In response, we develop three novel sub-analyses. First we perform a long-term whole economy time-series exergy analysis for China (1971–2010). We find a 10-fold growth in China's useful work since 1971, which is supplied by a 4-fold increase in primary energy coupled to a 2.5-fold gain in aggregate exergy conversion efficiency to useful work: from 5% to 12.5%. Second, using index decomposition we expose the key driver of efficiency growth as not 'technological leapfrog-ging' but structural change: i.e. increasing reliance on thermodynamically efficient (but very energy intensive) heavy industrial activities. Third, we extend our useful work analysis to estimate China's future primary energy demand, and find values for 2030 that are significantly above mainstream projections.
Article
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National exergy efficiency analysis relates the quality of primary energy inputs to an economy with end useful work in sectoral energy uses such as transport, heat and electrical devices. This approach has been used by a range of authors to explore insights to macro-scale energy systems and linkages with economic growth. However, these analyses use a variety of calculation methods with sometimes coarse assumptions, inhibiting comparisons. Therefore, building on previous studies, this paper firstly contributes towards a common useful work accounting framework, by developing more refined methodological techniques for electricity end use and transport exergy efficiencies. Secondly, to test this more consistent and granular approach, these advances are applied to the US and UK for 1960 to 2010. The results reveal divergent aggregate exergy efficiencies: US efficiency remains stable at around 11%, whilst UK efficiency rises from 9% to 15%. The US efficiency stagnation is due to "efficiency dilution", where structural shifts to lower efficiency consumption (e.g. air-conditioning) outweigh device-level efficiency gains. The results demonstrate this is an important area of research, with consequent implications for national energy efficiency policies.
Article
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Global carbon dioxide (CO2) emissions reached an all-time high in 2010, rising 45% in the past 20 years. The rise of peoples’ concerns regarding environmental problems such as global warming and waste management problem has led to a movement to convert the current mass-production, mass-consumption, and mass-disposal type economic society into a sustainable society. The Rio Conference on Environment and Development in 1992, and other similar environmental milestone activities and happenings, documented the need for better and more detailed knowledge and information about environmental conditions, trends, and impacts. New thinking and research with regard to indicator frameworks, methodologies, and actual indicators are also needed. The value of the overall indicators depends on the production procedure of each material, and indicates their environmental impact. The use of “exergy indicators” based on the exergy content of materials and the use of the second law of thermodynamics in this work presents the relationship between exergy content and environmental impact.
Book
The book describes in a simple and practical way what non-equilibrium thermodynamics is and how it can add to engineering fields. It explains how to describe proper equations of transport, more precise than used so far, and how to use them to understand the waste of energy resources in central unit processes in the industry. It introduces the entropy balance as an additional equation to use, to create consistent thermodynamic models, and a systematic method for minimizing energy losses that are connected with transport of heat, mass, charge, momentum and chemical reactions. © 2010 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.
Book
Is Gaia becoming Thanatia, a resource exhausted planet? For how long can our high-tech society be sustained in the light of declining mineral ore grades, heavy dependence on un-recycled critical metals and accelerated material dispersion? These are all root causes of future disruptions that need to be addressed today. This book presents a cradle-to-cradle view of the Earth's abiotic resources through a novel and rigorous approach based on the Second Law of Thermodynamics: heat dissipates and materials deteriorate and disperse. Quality is irreversibly lost. This allows for the assessment of such depletion and can be used to estimate the year where production of the main mineral commodities could reach its zenith. By postulating Thanatia, one acquires a sense of destiny and a concern for a unified global management of the planet's abiotic resource endowment. The book covers the core aspects of geology, geochemistry, mining, metallurgy, economics, the environment, thermodynamics and thermochemistry. It is supported by comprehensive databases related to mineral resources, including detailed compositions of the Earth's layers, thermochemical properties of over 300 substances, historical energy and mineral resource inventories, energy consumption and environmental impacts in the mining and metallurgical sector and world recycling rates of commodities.
Article
Recycling contributes significantly to the natural resources preservation. However since recycling technology at the same time requires primary materials and energy input, both contributing to the natural resources depletion, it is important to evaluate the resource efficiency of the whole recycling chain to determine the actual benefit of recycling. For such an evaluation exergy analysis can be used by calculation of the exergy efficiency as an indicator for the resource efficiency of the recycling chain. In this paper exergy analysis is added as a metric to the fundamental recycling system optimisation model developed previously by the authors. This addition allows evaluation and optimisation of the recycling system environmental performance on a fundamental basis, capturing exergy efficiency in the system as a function of physical, metallurgical and thermal processing and the quality of recyclates. Several car recycling scenarios have been evaluated using the fundamental recycling system optimisation model. The results reveal the influence of legislatively required recycling/recovery quotas and recycling system architecture on the environmental benefits of recycling. The results suggest that legislation does not represent the best exergy and resource efficiency of the system supporting the view that the present stringent legislation for end-of-life vehicle recycling is violating fundamental thermodynamics.
Article
Extending the exergy concept to practitioners and policy makers is still a major challenge. Recently the “Canton of Geneva” in Switzerland introduced a new law governing the procedures of attribution of building permits for new or retrofitted city areas. Authorities were asked to define a procedure including the calculation of an exergy indicator to be quantified in each file concerning large projects submitted for acceptance. This paper summarizes the problem definition, a clarification of the limits expected from the exergy indicator as well as the spreadsheet tool and the tables used to facilitate this quantification both for heating and air conditioning. For simplification the overall system was divided into a superstructure formed by four subsystems including the room convector, the plant of the building, a possible district heating and cooling plant and an external power plant. Three temperature ranges were considered for the building distribution networks both in heating and cooling. Ten different technology combinations were considered ranking from the lowest heating exergy efficiency with nuclear electricity and joule heating to the best efficiency with hydroelectricity and District heating electric heat pumps using lake water.
DirectiveEu of the European Parliament and of the council of 25 October 2012 on energy efficiency
  • European Parliament
European Parliament. Directive 2012/27/Eu of the European Parliament and of the council of 25 October 2012 on energy efficiency. Official Journal of the European union L315/1, 25.10.2012.
Exergy analysis of Single-and two-Stage crude Oil Distillation units
h. al-muslim, i. Dincer and S.m. Zubair, "Exergy analysis of Single-and two-Stage crude Oil Distillation units", Journal of Energy resources technology 125(3), 199-207, 2003.
SEt-Plan actiOn n°6, DraFt iSSuES PaPEr, "continue efforts to make Eu industry less energy intensive and more competitive
  • Set-Plan
  • Secretariat
SEt-Plan Secretariat, SEt-Plan actiOn n°6, DraFt iSSuES PaPEr, "continue efforts to make Eu industry less energy intensive and more competitive", 25/01/2016, https://setis.ec.europa.eu/system/files/issues_paper_action6_ee_industry.pdf