\

Renewable and Sustainable Energy Reviews

PERGAMON 1 "0887# 124Ð175

Sustainable energy development

Naim H[ Afgana\\ Darwish Al Gobaisib\ Maria G[ Carvalhob\
Maurizio Cumoc
a
Instituto Superior Tecnico\ Lisbon\ Portu`al
b
International Foundation for Water Science and Technolo`y\ Abu Dhabi\ UAE
c
University of Rome {{La Sapienza||\ Rome\ Italy

Abstract

The paper presents an overview of sustainable energy development and is aimed to emphasize
the important aspects relevant to this activity[ A short introduction\ related to the present
energy outlook with a survey of available data\ is presented[ This gives the possibility to assess
the motivation for a sustainable energy development[
Special attention is devoted to the de_nition of sustainability and its generic meaning[ In this
respect\ particular attention is devoted to the discussion of di}erent aspects of sustainability in
the present world[ In order to present an engineering approach to the sustainable development\
attention is devoted to the review of sustainability criterions as they have to be introduced in
the future products[
The main emphasis is given to review a potential development in the energy engineering
science which may lead to a sustainable energy development[ Seven major areas are listed with
speci_c problems and their relevance to the sustainable energy development[ This includes the
following areas ] energy resources and development ^ e.ciency assessment ^ clean air tech!
nologies ^ information technologies ^ new and renewable energy resources ^ environment
capacity ^ mitigation of nuclear power threat to the environment[
The education system is the milestone for any economic development[ In this respect\
sustainable energy development will require special attention to be devoted to the new devel!
opment of the education system[ The distance learning education system is envisaged as the
potential option for the knowledge dissemination of the new energy technologies[ Þ 0887
Elsevier Science Ltd[ All rights reserved[

0[ Introduction

Energy resources have always played an important role in the development of the
human society ð0Ł[ Since the industrial revolution\ energy has been a driving force for

 Corresponding author[ Tel[] 99240 0 7307971 ^ fax ] 99240 0 7364434 ^ e!mail ] nafganÝnavier[ist[utl[pt

0253Ð9210:87 , ! see front matter Þ 0887 Elsevier Science Ltd[ All rights reserved[
PII ] S 0 2 5 3 Ð 9 2 1 0 " 8 7 # 9 9 9 9 1 Ð 0
125 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

modern civilization development[ Technological development and consumption of

energy\ along with the increase in the world population\ are interdependent[ The
industrial revolution\ especially to the momentum created by the change from recipro!
cal engines to the great horsepower of steam engines in the late nineteenth century\
which brought about a revolution in dynamics*began a drastic increase both in
consumption and population of the world ð1Ł[
The history of life on the Earth is based on the history of photosynthesis and energy
availability ð2Ł[ The history of such a planet lies in the capture of solar energy and its
conversion by photosynthesis in plants and phytoplankton as organic molecules of
high energy content[ The plants convert this energy into other organic compounds
and work by biochemical processes[ Photosynthesis counteracts entropy increase and
degradation since it tends to put disordered material in order[ By capturing the
solar energy and decreasing the planetary entropy\ photosynthesis paves the way for
biological evolution[
Boltzman ð3Ł\ one of the Fathers of modern physical chemistry\ wrote\ in 0775\ that
the struggle for life is not a struggle for basic elements or energy\ but a struggle for
the availability of negative entropy in energy transfer from the hot Sun to the cold
Earth[ In fact\ life on the Earth requires a continuous ~ux of negative entropy as the
result of the solar energy captured by photosynthesis[ The Sun is an enormous
machine that produces energy by nuclear fusion and o}ers planet Earth the possibility
of receiving large quantities of negative entropy[ Every year the Sun sends 4[5×0913
joules of energy to the Earth and produces 1×0900 tons of organic material by
photosynthesis[ This is equivalent to 2×0910 joules:year[ Through the billions of years
since the creation of the planet Earth this process has led to the accumulation of an
enormous energy in the form of di}erent hydrocarbons[ Most of the fossil fuels belong
to the type of material where molecular binding is due to Van der Waal|s potential
between every two molecules of the same material[ Mankind|s energy resources rely
heavily on the chemical energy stored in the fossil fuel[ Table 0 shows assessed energy
resources ð4Ł[
Energy and matter constitute the earth|s natural capital that is essential for human
activities such as industry\ amenities and services in our natural capital as the inhabi!
tants of the planet Earth may be classi_ed as ]

Table 0
World non!renewable energy resources in 0884

North Latin
America America West Asia Middle
Total CPE a a Europe Africa Paci_c East
098toe ) ) ) ) ) ) )

Oil 84 00[4 3[8 02[4 2[1 6[8 1[6 45[2

Gas 74 30[4 7[2 2[6 2[4 5[0 5[1 15[6
Coal 429 35[5 15[5 9[5 8[7 6[4 78 9[99
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 126

, Solar capital "provides 88) of the energy used on the Earth#

, Earth capital "life support resources and processes including human resources#
These\ and other\ natural resources and processes comprise what has become known
as {natural capital| and it is this natural capital that many suggest is being rapidly
degraded at this time[ Many also suggest that contemporary economic theory does
not appreciate the signi_cance of natural capital in techno!economic production[
All natural resources are\ in theory\ renewable but over widely di}erent time scales[
If the time period for renewal is small\ they are said to be renewable[ if the renewal
takes place over a somewhat longer period of time that falls within the time frame of
our lives\ they are said to be potentially renewable[ Since renewal of certain natural
resources is only possible due to geological processes which take place on such a long
time scale that for all our practical purposes\ we should regard them as non!renewable[
Our use of natural material resources is associated with no loss of matter as such[
Basically\ all earth matter remains with the Earth but in a form in which it can not
be used easily[ The quality or useful part of a given amount of energy is degraded
invariably due to use and we say that entropy is increased[
The abundant energy resources in the early days of the industrial development of
modern society have imposed the development strategy of our civilization to be based
on the anticipated thinking that energy resources are unlimited and there is no other
limitations which might a}ect human welfare development[ It has been recognized
that the pattern of the energy resource use has been strongly dependent on the
technology development[ In this respect it is instructive to observe ð5\ 6Ł the change
in the consumption of di}erent resources through the history of energy consumption[
Worldwide use of primary energy source since 0749 is shown in Fig[ 0 ð5Ł[ F is the
fraction of the market taken by each primary!energy source at a given time[ It could

Fig[ 0[ Market penetration of primary energy sources[

127 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

be noticed that two factors are a}ecting the energy pattern in the history[ The _rst is
related to the technology development and\ the second\ to the availability of the
respective energy resources[ Obviously\ this pattern of energy source use is developed
under constraint imminent to the total level of energy resources consumption and
re~ects the existing social structure both in numbers and diversity ð7\ 8\ 09Ł[ The world
energy consumption is shown in Fig[ 1 ð00Ł[
Looking at the present energy consumption pattern\ it can be noticed that oil is a
major contender\ supplying about 39) of energy[ Next\ coal supply is around 29)\
natural gas 19) and nuclear energy 5[4)[ This means that the current fossil fuel
supply is 89) of the present energy use[ In the last several decades\ our civilization
has witnessed changes which are questioning our long!term prospects[ Fossil fuel\
non!recyclable is an exhaustible natural resource that will be no more available one
day[ In this respect it is of common interest to learn how long fossil fuel resources
will be available\ as they are the main source of energy for our civilization[ This
question has attracted the attention of a number of distinguished authorities\ trying
to forecast the energy future of our planet[ The Report of the Club of Rome {{Limits
to Growth||\ published in 0861 ð01Ł\ was among the _rst ones which pointed to the
_nite nature of fossil fuel[ After the _rst and second energy crisis\ the community at
large has become aware of the possible physical exhaustion of fossil fuels[ The amount
of fuel available is dependent on the cost involved[ For oil\ it was estimated that the
proven amount of reserves has\ over the past twenty years\ leveled o} at 1[1 trillion
barrels produced under ,19 per barrel[ Over the last 049 years we have already used
up one!third of that amount\ or about 699 billion barrels which leaves only a remaining
0[4 trillion barrels[ If compared with the present consumption\ it means that oil is

Fig[ 1[ World energy consumption[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 128

Fig[ 2[ Residual life forecast of energy resources[

available only for the next 39 years[ Figure 2 shows the ratio of the discovered
resources to the yearly consumption for the fossil fuels ð00Ł[
From this _gure it can be noticed that coal is available for the next 149 years and
gas for the next 49 years[ Also\ it is evident that as much as the fuel consumption is
increasing\ new technologies aimed at the discovery of new resources are becoming
available\ leading to a slow increase of the time period for the exhausting of the
available energy resources[
It is known that the energy consumption is dependent on two main parameters\ the
amount of energy consumed per capita and the growth of population[ It has been
proved that there is a strong correlation between the Gross Domestic Product and
Energy consumption per capita[ Figure 3 shows the economic growth and energy
consumption for a number of countries\ in 0889 ð01Ł[
There are a number of scenarios which are used for the forecast of the world
economic development[ With the assumption that the recent trend in the economic
development will be conserved in the next 49 years and considering the demographic
forecast in the increase of human population\ as shown in Fig[ 4 ð02Ł[
Future energy consumption could be calculated\ as shown in Fig[ 5 ð03Ł[
Compared with the available resources it is easily foreseen that the depletion of the
energy resources is an imminent process which our civilization will face in the near
future[ Nevertheless\ whatever is the accuracy of our prediction methods and models\
it is obvious that any inaccuracy in our calculation may a}ect only the time scale but
139 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 3[ Economic growth and energy consumption[

not the essential understanding that the energy resources depletion process has begun
and requires human action before adverse e}ects may irreversibly enforce[
Natural resources scarcity and economic growth are in fundamental opposition to
each other[ The study of the contemporary and historical beliefs showed ð04Ł\ that ]
"0# natural resources are economically scare\ and become increasingly so with the
passage of time ^ "1# the scarcity of resources opposes economic growth[ There are
two basic versions of this doctrine[ The _rst\ the Malthusian\ rests on the assumption
that there are absolute limits ^ once these limits are reached the continuing population
growth requires an increasing intensity of cultivation and\ consequently\ brings about
diminishing returns per capita[ The second\ or Ricardian version\ views the dim!
inishing returns as current phenomena re~ecting the decline in the quality of resources
brought within the margin of a pro_table cultivation[ Besides these two models\ there
is also the so called {Utopian case| where there is no resources scarcity There have
been several attempts to apply these models to the energy resources in order to
N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 130

Fig[ 4[ Demographic forecast of human population[

Fig[ 5[ Future energy consumption forecast[

131 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

de_ne the correlation between speci_c energy resources and economic growth[ The
substantial questions related to the scarcity\ its measurement and growth are ] "0#
whether the scarcity of energy resources has been and:or will continue to be mitigated
and "1# whether the scarcity has {de facto| impacted the economic growth[ An analysis
based on the relative energy prices and unit costs has been applied to natural gas\
bitumen coal\ anthracite coal and crude oil[ The U[S[A[ analysis in this respect can
serve as the indication for the future trend in a world scale[ Using two measures of
scarcity*unit cost and relative resource price change in the trend of resource scarcity
for natural gas\ bitumen coal\ anthracite coal and crude oil\ over three decades are
shown in Fig[ 6 ð5Ł[
It can be noticed that each of the energy resources has become signi_cantly scarcer
during the decade of the 0869s[ The situation reversed itself during the 0879s[ The
change that took place\ has implications for future economic growth the extent that
resources scarcity and economic growth are interrelated\ even if it was not proven
that short!term energy resources scarcity ~uctuation has substantial implications on
long term economic growth[ The need for an active involvement in allocating scare\
non!renewable energy resources has become obvious\ considering its potential e}ect
on economic growth[

Fig[ 6[ Scarcity factor for fossil fuels[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 132

1[ Environment

Primary energy resources use is a major source of emissions ð06\ 07\ 08\ 19Ł[ Since
fossil fuels have demonstrated their economic superiority\ more than 77) of primary
energy in the world in recent years has been generated from fossil fuels[ However\
exhaust gases from combusted fuels have accumulated to an extent where serious
damage is being done to the world global environment[ The accumulated amount of
CO1 in atmosphere is estimated at about 1[64×0901t[ The global warming trend from
0899Ð0889 is shown in Fig[ 7 ð10Ł[
The future trend of the carbon dioxide concentration in the atmosphere can be seen
in Fig[ 8 ð10Ł[
It is obvious that the further increase of CO1 will lead to disastrous e}ects on the
environment[ Also\ the emission of SO1\ NOx and suspended particulate matters will
substantially contribute to exasperate the e}ect on the environment[
On a world scale\ coal will continue to be a major source of fuel for electric power
generation[ Many developing countries\ such as China and India\ will continue to use
inexpensive\ abundant\ indigenous coal to meet growing domestic needs ð11\ 12\ 13Ł[
This trend greatly increases the use of coal worldwide as economies in the other
developing countries\ continue to expand[ In this respect the major long!term environ!
mental concern about coal use has changed from acid rain to greenhouse gas emis!
sions*primarily carbon dioxide from combustion[ It is expected that coal will
continue to dominate China|s energy picture in the future[ The share of coal\ in
primary energy consumption is forecast to be no less than 69) during the period
0884Ð1909[ In 0882\ China produced a total of 0[003 billion tons of coal ^ in 1999 it is
planned 0[4 trillion and 1909 it will be 1[9 trillion[ Since China is the third largest
energy producer in the world\ after the U[S[A[ and Russia\ its contribution to the
global accumulation of CO1 will be substantial if the respective mitigation strategies
are not adopted[ The example of China is instructive in the assessment of the future

Fig[ 7[ Global warming trend*0899Ð0889[

133 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 8[ Carbon dioxide concentration change forecast[

development of developing countries and their need for accelerated economic devel!
opment[

2[ Sustainability

It has been shown that energy resources are the bricks for building our civilization
ð14Ł[ Their polyvalent use has o}ered a service to human society\ leading to the
welfare commodity for a decent level of human life[ Sadly\ however\ production and
consumption of energy are going hand in hand with less than welcome side!e}ects[
This is the reason why society has recognized the importance of intelligent energy use
with a sensibility that the required energy services be provided as clean and e.cient
as possible[ Crucial importance is added due to the rapid growing world population
and the need for accelerated economic development of developing countries[ This is
the reason why energy takes a centre stage in the debate surrounding one of today|s
main dilemmas ] how to combine economic development with a habitable environment
in a world that is undergoing rapid changes as a result of population growth and
economic development of the developing part of the world[
Lately\ in a few years\ {sustainability| has become a popular buzzword in the
discussion of the resources use and environment policy[ The word sustainability has
a Latin root*sustinere*meaning {{to hold up|| by world inhabitants\ present and
future ones[ Before any further discussion of the subject\ it is necessary to de_ne and
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 134

properly assess the term we are going to use[ It should be emphasized that the
de_nition is needed in order to clarify the concepts[ So what is sustainability< Among
the terms most often adopted there are the following ]
"a# for the World Commission on Environment and Development "Brundtland Com!
mission# ð15Ł ] {{development that meets the needs of the present without com!
promising the ability of future generations to meet their own needs||[
"b# for Agenda 10\ Chapter 24 ð16Ł ] {{the development requires taking long!term
perspectives\ integrating local and regional e}ects of global change into the
development process\ and using the best scienti_c and traditional knowledge
available||[
"c# for the Council of Academies of Engineering and Technological Sciences ð17Ł ]
{{it means the balancing of economic\ social environmental and technological
considerations\ as well as the incorporation of a set of ethical values||[
"d# for the Earth Chapter ð18Ł ] {{The protection of the environment is essential for
human well!being and the enjoyment of fundamental rights\ and as such requires
the exercise of corresponding fundamental duties||[
"e# Thomas Je}erson\ Sept[ 5 0778 ð29Ł ] {{Then I say the Earth belongs to each
generation during its course\ fully and in its right no generation can contract debts
greater than may be paid during the course of its existence||[
All _ve de_nitions stand for the emphasis of a speci_c aspect of sustainability[
De_nitions "a# and "e# imply that each generation must bequeath enough natural
capital to permit future generations to satisfy their needs[ Even if there is some
ambiguity in these de_nitions\ it is meant that we should leave our descendants the
ability to survive well and meet their own needs[ Also\ there is no speci_cation in
which form resources are to be left and how much is needed for the future generations\
because it is di.cult to anticipate the future scenarios[
De_nitions "b# and "c# are more political pleas for the actions to be taken at global\
regional and local levels in order to stimulate the United Nations Organization\
Governments and Local Authorities to plan development programs in accordance
with the scienti_c and technological knowledge[ In particular\ it should be noticed in
de_nition "c# the ethical aspect of the future development actions to be taken to meet
sustainable development[
De_nition "d# is based on religious beliefs\ paying responsibility and duty towards
nature and the Earth[ In this respect it is of interest to enlighten that the Old
Testament\ in which the story of creation is told is a fundamental basis for Hebrew
and Christian doctrines of the environment[ In the world of Islam\ nature is the basis
for human consciousness[ According to the Koran\ while humankind is God|s vice!
regent on Earth\ God is the Creator and Owner of nature[ But human beings are his
trusted administrators\ they ought to follow God|s instructions\ that is\ acquiesce to
the authority of the Prophet and to the Koran regarding nature and natural resources[

3[ Sustainable development

Since the Brundtland Commission\ in its 0876 report\ Our Common Future\ warned
of the growing threat to the Earth from pervasive world poverty\ environmental
135 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

degradation\ disease and pollution\ it has become indispensable for the scienti_c
community to pay increasing attention to the subjects related to these problems[
Five years later the United Nations Organization Conference on Environment and
Development was held in Rio de Janeiro[ An unprecedented number of world leaders
met to discuss and map the road to sustainable development[ Among the Documents
adopted at the Rio Conference is the {Agenda 10|\ a blueprint of how to make
development socially\ economically and environmentally sustainable[ Agenda 10 calls
on governments to adopt national strategies for sustainable development[
Sustainable development focuses on the role and the use of science in supporting
the prudent management of the environment and for the survival and future devel!
opment of humanity ð20\ 21\ 22\ 23Ł[ It is recognized that scienti_c knowledge should
be applied to articulate and support the goals of sustainable development\ through
scienti_c assessment of current conditions and future prospects for the Earth system[
The program areas which are in harmony with conclusions and recommendations
of this International Conference on an Agenda of Science for Environment and
Development into the 10st century are ]
"a# Strengthening the scienti_c bases for sustainable management ^
"b# Enhancing scienti_c understanding ^
"c# Improving long!term scienti_c assessment ^
"d# Building up scienti_c capacity and capability[
It is essential for the implementation of this program that it be focused on the long!
term perspectives and the global changes of life support systems[ In particular\ there is
a need for a constant interaction with governmental\ industrial\ political\ educational\
cultural and spiritual authorities participating in the realization of the program[ It is
of crucial importance that\ in the realization of the program\ an active role be given
to scientists from developing countries[ Since the major part of the population increase
is expected in the developing part of the world\ the participation of scientists from
developing countries will bridge de_ciencies in dealing with the problems which are
imminent to their environment by an academic approach[
Sustainability development has even become a political movement with a strong
connotation related to the existing di}erences among continents\ regions and coun!
tries ^ its strength should be seen in the promotion for the salvage of the planet\ the
only place for our human civilization[ In this respect\ the determination of the
interested parties\ including the United Nations Organizations\ government organ!
izations\ non!government organizations and religious organizations\ to recognize
sustainable development as the path for the creation of the future of new generations\
is a guarantee for the economic prospectives and social development[
There are several ways in which the ideas of sustainable development are presented
and interpreted[ Ecocentric interpretations indicate a conspicuous degree of reference
to ecosystems[ Anthropocentric interpretation tends to put humans at the centre of
the issues[ Others such as biocentric interpretation focus on the protection of the
elements of the biosphere[ Our main concern in this general setting is energy\ and
whatever we do for and with energy may be re~ected in any of the above mentioned
perspectives and interpretations[ While this concern for sustainability in the energy
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 136

sphere should include considerations at the global level\ more importantly\ there is
the need to look at it as a regional issue in the overall global scenario[ There are
several perspectives on this[ Figures 09 and 00 attempt to distinguish sustainable and
unsustainable development[

4[ Energy sustainability criterions

There has been a number of attempts to de_ne the criterions for the assessment of
the sustainability of the market products[ In this respect the Working Group of the
UNEP on Sustainable Development has come out with qualitative criterions for the
assessment of the product design ð24\ 25Ł[
Having these criterions as bases\ we would like to introduce them as a speci_c
application in the energy system design[ In this consideration\ energy system is taken
as the entity which should comply with sustainability criterions[
Energy System design is de_ned as ]

4[0[ Strate`ic desi`n

Strategic design will require holistic planning that meets and considers all inter!
related impacts e[g[\ logistic\ space planning and resource planning[ As regards the
energy system\ it may be interpreted as ] mixed energy concept with optimization of

Fig[ 09[ The consequences of unsustainable development[

137 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 00[ Sustainable development[

local resources\ urban and industrial planning with transport optimization\ use of
renewable energy sources[

4[1[ Optimized desi`n

The design optimization of the energy system means the selection of the structure
and design parameters of a system to minimize the energy cost under conditions
associated with available materials\ _nancial resources\ protection of the environment
and government regulations\ together with safety\ reliability\ availability and main!
tainability of the system[

4[2[ Desi`n of dematerialization

This will imply that the energy system\ plant and equipment are designed with
optimal use of information technology in order to prevent duplications\ prevent
operational malfunction\ and assure rational maintenance scheduling[ Dema!
terialization in the design may be seen as the introduction of knowledge based systems\
use of virtual library\ digitized video\ use of on!line diagnostic systems\ development
of new sensor elements and development of new combustion technologies[

4[3[ Desi`n of lon`evity

A complex energy system is commonly composed of di}erent subsystems and

individual equipment elements[ It has been recognized that the life time of the elements
and subsystems is not equal[ In this respect\ optimal selection of the life cycle for
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 138

elements and subsystems may lead to the retro_tting procedure which will re~ect the
need for the sustainable criterion application[ Examples for this criterion can be seen
as ] modular design of subsystems\ standardization of elements\ lifetime monitoring
and assessment\ co!ordination of suppliers and buyers[

4[4[ Life cycle desi`n

This will mean that the energy system and its subsystems have to be designed to
meet sustainability through every stage of the life cycle[ It is known that the energy
system is designed to work under di}erent conditions in order to meet load changes\
environment change\ social changes\ etc[ It is obvious that there will be di}erent cycles
for each of the mentioned time scale processes[ In this respect the system has to ful_l
its function without failing to meet sustainability requirements[ As an example\ we
can see ] water cooling temperature change\ social change may lead to the requirement
to decrease the load to meet sustainability criteria\ building pumping power stations
for energy saving at night\ period of thermal power plant technical minimum etc[

5[ Energy sustainable development

In order to reach the goals indicated by the sustainable energy development the
e.ciency conversion use has to meet several criteria ð26Ł[ The potential for e.ciency
improvement is generally underestimated[ Most of the energy conversion systems
consider e.ciency improvement as a separate process and their analysis re~ects only
the potential improvement of the process but not the potential for the e.ciency
improvement obtained by an exergy analysis of the energy system[ Fossil fuel energy
resources use is mostly conversion to heat by the combustion processes[ Since the
combustion process is taking place at temperatures between 899Ð0299>C and over
39) of heat is used at low temperature\ it is vital to take into consideration the
thermodynamic assessment of the e.ciency in order to bring in line energy conversion
processes and energy demand to obtain the optimum fuel utilization[
In the de_nition of sustainability\ it is of substantial importance to envisage its
broad aspect which composes versatility of the components to be taken into con!
sideration ð27\ 28\ 39Ł[ In this respect\ wholeness of sustainability has to include
de_nitions of those components which are linked to speci_c parameters to be taken
into consideration of the assessment of sustainability of speci_c situations in global\
regional and local environments[ There are a number of characteristic entities which
will be used to de_ne the wholeness of sustainability ] life diversity\ natural resources\
environment capacity\ population increase\ social disturbances and ethic changes[
It is out of the scope of this writing to dwell on all characteristic entities for
sustainability de_nition[ Energy is one of the essential commodities required for
human life and is a}ecting the sustainable wholeness in its total change ð30Ł[ For this
consideration we will focus our attention only on those characteristic entities which
are in direct correlation with energy sustainability measurement[ In this group are
included ] "i# natural resources ^ "ii# environment capacity ^ "iii# population increase[
149 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Each of these entities has to be de_ned with speci_c parameters which can be
used to determine characteristic indictors for global assessment[ The possible use of
indicators is characterizing the changes which are determined by the maximum values
technically feasible[ It is re~ecting the di}erence between the state of the entity with
the maximum availability and respective current state of the entity[ If applied to the
individual energy resources there is a di}erence between known maximum exploitable
resources with known technologies and current resources to be obtained with present
technological capacity[ Possible changes are functions of the technological devel!
opment in the resource discovery[ This implies that there are two means for the
increase of the resources\ i[e[\ by additional capital investment for the discovery and
by new technology for the resource discovery[
In the assessment of sustainability\ the current consumption change has to be taken
into consideration which is re~ecting the current consumption change in the reference
time period[ In order to form some kind of resource indicator for sustainability
measurement a ratio between the current change and the maximum potential change
has to be established[ Its trend will give the measuring parameter for the resource
depletion in time[ It is known that the current consumption of energy resources
strongly depends on the e.ciency of their use\ which may be classi_ed in two groups[
The _rst one is the possible e.ciency increase due to the change in the e.ciency of
primary energy source conversion and the second one is due to the change in the
e.ciency of the _nal energy use[
A number of authoritative studies have presented forecasts for the energy supply
in the 10st century[ Conclusions drawn from this analysis have become a driving force
for the development of the plan for the sustainable energy supply system[ Even if a
number of options are taken into consideration\ common issues are the following ]

5[0[ Prevention of the ener`y resources depletion with scarcity index control

Whichever scarcity model is used\ the energy resource scarcity is in direct relation
to the social production output[ In this respect\ the e.ciency of resources use and
technology development are of fundamental importance[ It is obvious that the
e.ciency of the energy resource use is a short!term approach\ which may give a return
bene_t in the near future ð31Ł[ As regards the technology development\ long term
research and development is needed[ In some cases it will require respective social
adjustments\ in order to meet requirements of the new energy sources[
The availability of energy resources is limited by two factors ] capital to be invested
in prospecting of new resources and prospecting technologies for energy resources[
From recent experience it was learned that there is a direct correlation between
capital invested in prospecting and the amount of the available reserves[ It was proved
that a _xed amount of 07 ,:t is needed for new energy reserves[ In many developing
countries this is a limiting factor for the availability of energy resources[
The prospecting technology is composed of three phases[ The geological subway
based on the real prospecting and respective diagnostic techniques for electromagnetic
waves detection[ The resolution of the instrument employed is one of the limitations\
and is under consideration for further development[
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 140

The second phase of prospecting technology is related to software for the design of
the resource body based on the ultrasonic scattering or earthquakes generated by
local explosions[ The main limitation in the development of new software is the speed
and memory size of computers[ It can be expected that with the further development
of computer technology this problem will be overcome[ Also\ new numeric schemes
will substantially contribute to the accuracy and time expectation for the prediction
of the size of resources body[
From the beginning of energy resources exploration\ drilling technology was the
limitation to the achievement of new resources[ The development of drilling tech!
nology has marked a direction for the discovery of new resources[ A recent example
with new drilling technology has led to a gas resource in the Mexican bay[ Also\
North Sea gas resources are the result of a new o} shore drilling technology[ The
same has been proved in the discovery of new gas resources in Algeria[ Deep sea
drilling has become one of the global issues which may remove the scarcity problems
of energy resources for the next few centuries[ It should be mentioned that two thirds
of the earth surface is covered by deep sea so that the breakthrough in deep!sea
technology may lead to a substantial change in the energy resource picture in the
world[

5[1[ Ef_ciency assessment

The potential improvement of the energy conversion process is a driving force for
its development ð32Ł[ In the assessment of the conversion process a promising tool is
the exergy analysis of the energy system[ The exergy analysis is based on the maximum
potential availability and its use for the assessment of the conversion process[ By
de_nition\ the exergy is parameter for the validation of the e.ciency of the energy
conversion process and system[ Taking into account the law of thermodynamics\ the
technology improvement appears as a signi_cant factor responsible for an entropy
change in the energy system[ The application of the principle of Carnot therefore
allows to determine an absolute limit to any transformation of the deposit of free
energy ð33\ 34Ł[
Following the _rst energy crisis\ many countries have organized an energy e.ciency
assessment campaign with the aim of improving e.ciency and gain!saving which has
contracted the increase of energy price[ It was proved that this approach has resulted
in the increase of e.ciency of energy use between 09Ð19) in a number of European
countries[ The main emphasis has been given to the evaluation e.ciency of di}erent
technologies and utilizations of energy[
The e}ort directed to the evaluation of the technological processes for energy
saving is of great importance ð35\ 36Ł[ A new development of products is also under
consideration for the minimum use of energy[ In accordance with one of the criteria
for sustainable development\ products have to meet the requirement related to the
minimum use of energy[ A favourable example for this achievement is the development
of a new lighting system with ~uorescent lamps and which\ in comparison with
traditional bulbs\ have a saving of about 39)[
Cogeneration of heat and electricity is one of the potential means to improve the
141 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

e.ciency of the energy resource utilization[ Cogeneration plants in conjunction with

the desalination in regions where water and energy are needed are an example[ Figure
01 shows a schematic representation of cogeneration in desalination plants ð37Ł[
Recent projects with gas _red cogeneration plants have demonstrated extremely
high e.ciency ð38Ł[ The increased gas resources may lead to further development of
highly e.cient power plants for electricity production[ The cogeneration will play a
special role in the development of new energy systems[

5[2[ Clean air technolo`y development

The combustion process is an irreversible thermodynamic process with a high

degree of availability losses in the energy conversion cycle[ In this respect there is a
potential opportunity to increase the energy conversion e.ciency by improving the
combustion process[ There are a number of potential combustion technologies which
might lead to an e.ciency increase of the combustion process[ Among those there
are ]

5[2[0[ Catalytic combustion

The low temperature catalytic combustion of lean natural gas mixtures represents an
e}ective method for heat generation ð49Ł[ Coexistence with reactant catalysts enhances
the chemical reaction but is stechiometrically independent of the reactant[ Among the
processes of catalysis there is the absorption into the catalysis reaction at the catalyst
surface and the liberation of the chemical products[ Zeolite is a catalyst widely
used in the chemical industry[ Detailed behaviour of the catalyst has not been fully
understood[ In particular it is expected that the catalytic combustion may lead to an

Fig[ 01[ Schematic representation of desalination plant[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 142

Fig[ 02[ Schematic representation of fuel cell[

e.cient use of the fuel cell[ Figure 02 shows a schematic representation of the catalysis
of platinum in a fuel cell[
The catalysis mechanism at the interface between electrode and electrolyte ensures
the electron transfer from the input hydrogen molecule to the electron metal[ The
search for low cost alternatives has not been very successful but lately the good
performance of some of active composition of La\ Ni\ Co\ O "LSNC powder# leads
to promising expectations[

5[2[1[ Fluidized bed combustion

A recent progress in the ~uidized bed combustion has led to substantial developments
of this new energy system ð40Ł[ In the combustion in ~uidized beds the coal is depressed
in a mass of its ashes and absorbent lime and the process is developed at a temperature
of 749>C[ There are two types of boilers ] bubbling and circulating "Fig[ 03#[
The bubbling alternative o}ers a good thermal design[ In principle\ this is a clean
option for electricity generation with medium and good quality coal[ The energy
e.ciency of a bubbling boiler in the Rankine cycle with steam turbines\ is similar to
that of the conventional pulverized coal power plant[
A 249 Mwe bubbling atmospheric ~uidized bed power plant is an option with a
very good performance with medium and high quality coal[
The second alternative of the ~uidized bed combustion power plant is the circulating
~uid design\ o}ering a high degree of operating ~exibility in coal quality use[ It is a
complex design\ which includes fuel chambers\ large cyclone\ recovery boiler and\ in
some cases\ outer ash cooler[ This option reduces the energy e.ciency compared to
present pulverized coal plant[ A factor contributing to these problems signi_cantly is
143 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 03[ Fluidized bed boiler types[

the high electric energy consumption in auxiliary services\ particularly for the ven!
tilator for recirculation[ The e.ciency of the existing circulating ~uidized bed plants
is about 29)[ A 149 Mwe plant is in operation with low quality coal[ The use of
circulating ~uidized bed boiler technology is rapidly increasing due to the ability to
burn low grade coal\ while meeting the required NOx\ SOx and particulate emission
requirements[
The pressurized ~uidized bed combustion boiler is an option o}ering a 09) increase
in e.ciency over conventional pulverized coal _red plants[ It is a compact plant with
moderate speci_c investment using high quality material and it is conceived for
medium and good quality coal[

5[2[2[ Low NOx burners

The present\ advanced energy technology is focused to reach further improvements
in the emission control ð41Ł[ In principle there are two approaches ] the _rst one\ by
reorganization of combustion processes in the burners and the second one\ by post!
combustion processes in the furnace[
In order to minimize SOx\ NOx and particulate emissions a new burner design is
envisaged to meet the requirements for minimization of initial NOx formation[ It is
expected that the new burners will reach 269Ð389 mg:Nm2 in properly designed new
furnaces ð42Ł\ which is the limit for present emission control[
Further NOx reduction can be achieved through furnace staging[ Here the boiler
combustion zone is opened close to the stechiometric chemistry condition and the
balance of air is added in the upper furnace through an over_re airport[ NOx emission
can be lowered through post!combustion technologies such as selective catalytic
reduction[ NOx is reduced with molecular nitrogen and water and by reduction with
ammonia in presence of a catalyst[
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 144

Numerical modeling of the processes in combustion chambers has become impor!

tant in design and analysis of tools ð43\ 44Ł for improving air distribution in power
plant burners[ Numerical modeling allows the analysis of designs for optimal modi!
_cations of turning vanes\ ~ow splitters\ perforated plates and burner shrouding[
Also\ numerical models of boiler furnaces ð45Ł are available as computational ~uid
dynamic software which allows practical analysis of power plant furnace behaviour
with minimum emissions of SOx\ NOx and particulate[ Retro_tting of existing power
plants with advanced combustion technologies will lead to substantial increases of
e.ciency and minimize emission\ to the environment ð46\ 47Ł[ Figure 04 shows a
typical low NOx burner[

5[2[3[ New boiler desi`ns

Coal _red boiler power plants will continue to be one of the major contributors in
the future[ Modern pulverized coal!_red systems presently installed generate power
at net thermal e.ciency ranging from 23Ð26)\ while removing up to 86) of uncon!
trolled air pollution emissions[ A new generation of pulverized coal!_red boiler tech!
nologies currently under development\ which will permit a generating e.ciency in
excess of 31)[ In this respect\ further development is needed for improvements in
reducing emissions and expanding operability[ To achieve a high thermal\ special
attention has to be devoted to the load cycling operation[ In this respect a low!
emission boiler system in development is based on the diagnostic monitoring of
process parameters and expert systems[
The development of high performance power systems is an ultimate goal for upgra!
ding pollution control with corresponding combustion system improvements and the

Fig[ 04[ Low NOx burner[

145 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

control of SOx\ NOx through the implementation of new burner design and post
combustion emission control[ Also\ the implementation of the boiler numerical codes
for the determination of process parameters will be used as a tool for the e.ciency
control and early diagnostic function monitoring[ This improvement in heat and mass
transfer research ð48\ 59\ 50\ 51Ł has substantially contributed to new boiler designs
and will lead to the increase of availability of modern power plant systems ð52Ł[ Figure
05 shows a schematic representation of new boiler design[

5[3[ Development of intelli`ent ener`y systems

The recent development of arti_cial intelligence has opened the possibility to utilize
those achievements in the energy sustainable development[ There are three major
paths\ namely ] expert system development in energy engineering ^ new control based
on fuzzy logic and respective reasoning ^ intelligent thermal system design[

5[3[0[ Expert system in ener`y en`ineerin`

The expert system development in energy engineering is focused in two directions ]
expert system for energy system design and knowledge!based for on!line diagnostic
ð53\ 54\ 55\ 56Ł[ It has been shown that the expert systems for energy system design
can be e.cient tools in the selection\ optimisation and assessment of power plant
design[ Also\ expert system logic can be used in energy system planning\ including
optimization of the energy system\ re~ecting the potential use of renewable energy
sources[ An example of expert system use in the design of thermal equipments is
demonstrated by the heat exchanger design ð57Ł[ Further developments of knowledge!

Fig[ 05[ New boiler design[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 146

based systems for the design of energy systems will promote an increase of e.ciency
and reliability[
The knowledge!based system for the fault diagnostic in energy systems has proved
to be a powerful tool for the evaluation of system parameters in order to forecast a
potential malfunction of system elements[ Figure 06 shows a schematic representation
of an expert system for fouling assessment[
There are several attempts which have proved the possibility of knowledge!based
systems in the diagnostic of thermal power plants[ The e.ciency monitoring and
respective logistic evaluation of diagnostic parameters has been demonstrated to be
a good and reliable tool for the advanced diagnostic of operational de_ciency[ The
boiler fouling and tube leakage knowledge!based system prototypes demonstrated
the possibility of the detection of processes leading to the degradation of power plant
e.ciency ð55Ł[ The diagnostic systems are based on on!line monitoring of diagnostic
variables and their fuzzi_cation for the reasoning retrieval of the cases representing
diagnostic results[

5[3[1[ Fuzzy lo`ic control

The new fuzzy logic control system is demonstrated to be a qualitatively e.cient
system for the on!line control of energy systems ð58Ł[ While similar model!based
control systems designs are trial and error\ the knowledge!based controller is {ad hoc|
at the present time[ A gap exists between solid theoretical results such as stability\
controllability etc[ A real!time implementation of intelligent control systems uses
fuzzy logic\ neural networks\ general algorithms\ expert systems etc[ A common
de_nition of fuzzy control system is that it emulates a human expert[ Under this
situation\ the knowledge of a human operator would put in form of a set of fuzzy

Fig[ 06[ Knowledge!based system for power plants[

147 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

linguistic rules[ These rules would produce an approximate decision\ like a human
would[ Figure 07 shows a block diagram of fuzzy control systems[

5[3[2[ Intelli`ent ener`y systems

The present world has learned that some basic assumptions are not valued and so
requires a new approach for adjustment to its future development[ There have been
world scale meetings emphasising the need for the economic order to meet con!
temporary development within the limits recognised by irreversible changes in energy
resources and environment capacity[
New measurements called {indicators of sustainability| are designed to provide
information for understanding and enhancing the relationships between the economic
energy use\ and environmental\ and social elements inherent in long!term sustain!
ability[
There are di}erent terms used in the consideration of the product design[ The
{clean| design is used in the widest sense of all management as well as technical
decisions related to speci_cation\ planning and development of products not just
technical processes designed by engineering[ The {eco|!design refers to the processes
of systematic incorporation of environmental life cycle consideration into product
design[
{Intelligent product| design comprises the speci_cations re~ecting resource life cycle\
environmental cycle\ product!life cycle\ end of life and clean design[ The generic
design procedure to be adopted for the intelligent product design of the thermal
equipments require the de_nition of indicators for the assessment and optimization
of the speci_c design[
In order to provide the design criteria re~ecting complex requirements imposed by
the intelligent design\ it is necessary to de_ne the respective indicators to be used in
the evaluation of the speci_c design of thermal equipment ð69\ 60Ł[ These indicators
should be based on the optimization of the e.ciency of respective thermal equipment\
resource use assessment and validation\ environment capacity use and degradation\

Fig[ 07[ Block diagram of fuzzy control system[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 148

Fig[ 08[ Scheme of intelligent energy system[

modular structure with multipurpose elements\ end of life assessment and economic
justi_cation of speci_c designs[ Figure 08 shows a schematic presentation of an
intelligent energy system[
In order to evaluate the validation of the indicators the thermal equipment will be
used[ In this respect\ the criteria will be adapted for the speci_c thermal equipment[
It is aimed to develop the algorithm with the indicators to be used for the assessment
of design[ The assessment will be made for a number of selected products presently
on the market to be evaluated within the frame of the criteria for intelligent design[

5[4[ New and renewable ener`y sources "NRES#

Besides the possibility o}ered by the e.ciency improvement of processes in power

generating units\ there is a great challenge to increase the e.ciency of energy systems
by introducing energy mixed systems[ The energy system includes power or heat
generating units\ energy transport systems\ energy storage systems and energy end!
use systems[ From the energy resources point of view\ there are a number of options
which might be taken into consideration for the optimization of the energy system[
In this respect\ high interest is shown in the potential use of the renewable energy
resources as power or heat!generating unit in the energy system[ The imminent
advantages of the renewable energy resources due to their availability and low cost
impact\ are promoting the renewable energy source to be included in the energy
system[
159 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Renewable energy sources\ by de_nition\ meet the requirements of sustainability[

It is therefore expected that the long!term energy strategy will rely on renewable
energy resources[ The total availability of renewable energy resources is very large[
This picture re~ects the presently available technologies in the _eld of renewable
energy resource use and exploitation ð60\ 61Ł[ Very promising alternatives are envis!
aged with the promotion of new technologies under development[

5[4[0[ Solar ener`y resources

Solar energy can be exploited in three main modes ]
, by enhanced absorption of solar energy in collectors\ which provide low!grade heat ^
, by using re~ecting devices to concentrate the solar energy in a heat carrier\ which is
then used to generate electricity ^
, by converting sunlight directly into electricity[
Solar energy resources do not have clear limits[ The annual in~ux on the Earth surface
is 09\999 times as large as the current human energy consumption ^ the fraction
reaching the land surface is 2999 times as large and even 24) of this would make
0999 times more energy than we demand today[ As we can see\ the resource of solar
energy is huge but diluted[ In the literature\ it is assessed that the feasible tool use of
solar energy from the technical standpoint is about ð63Ł ]
Thermal solar for 069 Mtoe:year
Decentralized electric solar for 349 TWh:year
Network electric solar for 129 TWh:year
In the local resources evaluation for these three solar systems one could take into
consideration their minimum and maximum capacity to be installed[ From the present
status of the development the following capacity can be taken into consideration
Minimum ] Maximum ]
Thermal solar 049 kW 79 MW
Decentralized electric solar 29 kW 4699 kW
If the mean insulation for the speci_c location is taken into consideration then the
respective values for the land to be used will be obtained[ For this purpose\ it will be
used qR  4[3 kWh:m1:day so that the following extension of land is required for the
speci_c use of the solar energy ]
Minimum land ðm1:kWeŁ
Thermal solar 19Ð24
Decentralized electric solar 25Ð79
It should be mentioned that for insulation lower than qR  3 kWh:m1:day\ it might
be di.cult to adopt the same method of validation[
Solar energy use is presently demonstrated in three options ] solar thermal\ solar
photovoltaic and solar power plant[ Solar thermal energy production plant has
reached an industrial level and is available on the market in many countries ð64\
65\ 66Ł[ There are a number of designs di}erentiated with respective e.ciency and
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 150

sophistication of the material used[ Solar thermal option is mostly available for the
hot water production units[ It is also demonstrated for air heater and climatization
units[ Since it has reached maturity\ it is not expected major breakthrough in this
_eld\ which might a}ect its potential use[ Water heater units are available in the
market with the following ranges ]
Temperature range ð>CŁ
Unglazed ~at plate collectors ³39
Glazed ~at plate collectors 39Ð099
Vacuum tube collectors 049Ð199
The solar thermal is anticipated to cost 7!8 U[S[ cents:GJ in the medium term[ In
the long term this could come down to 3Ð5 U[S[ cents:GJ[
The solar photovoltaic system is also in its demonstration stage\ with a number of
various applications[ It has been demonstrated in three levels\ i[e[\
Power
Ubiquitous solar cell not _xed
Solar unit for electronic application 49 WÐ0 kW
Solar units for irrigation 4Ð59 kW
The _rst level is not an energy intensive application and has no signi_cance for its
consideration for the energy source strategy point of view[ The second option is being
used as the only energy source in remote areas and has been demonstrated as a reliable
energy source[ It ranges in power production from 49 WÐ0 kW and is commercially
available at competitive prices[ Figure 19 shows schematic representation of Solar
power plant[
For the third option\ there have been a number of demonstration projects which
have proved its feasibility for rural areas[ Even\ the energy available from the grid for
many countries is lower than the energy produced by a photovoltaic unit\ and the
di}erence in energy may be compensated by the additional capital investment needed
for a new grid construction for remote areas[
Solar power plants are in the stage of development[ They are available as photo!
voltaic cell modular units and can be installed when the power demand requires a
system augmentation[ As demonstrated\ the modular power ranges between 49 kW
and 0 MW[ Solar power plants with concentrators are still in the development stage
and will not be considered in the technical assessment of the solar energy utilization
ð66\ 67Ł[
Solar plant power 49 kWÐ0 MW
Present estimate of photovoltaic solar plant electricity ranges from a cost of 12Ð22
U[S[ cents:kWh[ It is expected that in the medium term this cost will be as low as 1[1Ð
1[3 U[S[ cents:kWh ð68Ł[

5[4[1[ Geothermal ener`y resources

Resources exploitable at current energy prices correspond to aquifers in narrowly
localized volcanic zones ð79\ 70Ł[ Presently installed and in construction plants reach
151 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 19[ Solar power plant[

a total electrical capacity of 6099 MW "high enthalpy energy#[ Low enthalpy hot
water to be used directly for heating is estimated to about 02 Mtoe:year[ These two
groups of geothermal energy systems are speci_ed by the temperature and ~ow
capacity of the individual well[ From experience\ the following limits are adopted ]
Min[ temperature ð>CŁ Min[ capacity ðm2:hŁ
High enthalpy geothermal 89 1899
Low enthalpy geothermal 24 0999
Particular resources evaluations will require a speci_c assessment of the respective
aquifer volume in order to estimate uncertainty in the lifetime of the geothermal
energy system to be built[ It is expected that the volume of the aquifer should exceed
several times the capacity needed for the respective system lifetime[ In the local
resource evaluation for the geothermal system it should be included also the land
required for the brine to be deposited during the lifetime of the plant[
Geothermal utilization is commonly divided into two categories ] electric pro!
duction and direct application[ Figure 10 shows the minimum production temperature
in a geothermal _eld that is required for di}erent utilizations[
Conventional electric power production is limited to ~uid temperatures above
039>C but a considerably lower temperature may be used with the application of
binary ~uids[ Geothermal electric energy plants have reached their maturity and have
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 152

Fig[ 10[ Minimum production temperature in geothermal _eld[

proved to be very reliable sources of energy[ They are used in 10 countries\ with a
total world installed capacity of 5906 MW distributed over 229 individual turbine
generator units[ The geothermal power plants are built in four versions\ i[e[\ direct
steam plants\ ~ash steam plants\ binary plants and hybrid plants[
Direct steam plants are used with vapour dominated resources[ Steam from pro!
duction wells is gathered and transmitted via pipelines directly to a steam turbine[ In
most direct steam plants the capacity of the turbine is greater than 4 MW[ Typical
schematic representation of direct steam plant is shown in Fig[ 11[
Flash steam production is used when the ~uid\ in the geothermal reservoir is
pressurized hot water or a mixture of liquid and vapour at the well head[ It is designed
153 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 11[ Direct application of geothermal energy[

in two modi_cations\ i[e[\ with single ~ash steam unit and dual ~ash units[ A single
~ash plant is a simple ~ash unit[ The ~ashing process takes place between the reservoir
condition and the power plant[ The ~ash usually occurs in the well at the point where
the geo~uid pressure falls to the saturation pressure corresponding to the temperature
and composition of the geo~uid[ A signi_cant improvement in resource utilization
can be achieved by adding a secondary ~ash process[ Instead of being discharged\ the
liquid that is removed from the separator is subjected to another pressure drop in
which additional steam is released[ The lower pressure steam is admitted to the turbine
at an appropriate stage and generates additional power[
Binary plants are used when it is not advisable to allow the geo~uid to come in
contact with the power production equipment\ i[e[\ the turbine\ for danger of scaling\
corrosion or e}ects of large quantities of non!condensable gases[ In basic turbine
system\ the hot liquid enters a vapour generator where it transfers heat to a secondary
~uid[ The working ~uid is chosen to provide good thermodynamic matches to geo~uid
and obtain a high utilization e.ciency\ safety and economy[
Besides the basic binary cycle there are two cycles\ which exhibit a higher e.ciency ]
a dual pressure system and a dual!~uid system[ In dual pressure binary plants the
turbine receives the working ~uid at two pressure levels[ Either two separate turbines
or a dual admission turbine may be used[ Optimized dual!pressure binary plant can
have 04Ð14) higher brine utilization compared to the basic binary plant geo~uid
temperature of 84Ð049>C[ The dual ~uid binary plant is a system with two binary
loops\ each of them with a particular ~uid[ The key for producing a high e.ciency
cycle\ is to couple the two loops by means of a recuperator in which the heat otherwise
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 154

wasted\ from the upper loop is transferred to the lower loop in su.cient quantity to
provide the evaporation for the lower cycle working ~uid[
Hybrid plants are described so far and combined in various ways to achieve a higher
e.ciency or to overcome the potential problems related to geo~uid characteristics[
The following are examples of hybrid plants ] direct steam:binary units and ~ash
steam:binary units[
There are three classes of turbine power units used in geothermal plants ]

"a# 29Ð39 MWe

"b# 4Ð09 MWe
"c# 9[1Ð9[4 MWe

The power rating for the respective geothermal power cycles are ]

Direct steam plant 4Ð39 MWe

Flash steam plant 0Ð24 MWe
Binary plant 9[91Ð9[4 MWe
Hybrid plant Not yet available

The ideal inlet temperature for house heating is about 79>C\ but with the application
of large radiators with heat pumps or auxiliary boiler\ the thermal water with a
temperature of only a few degrees above the ambient temperature can be used ben!
e_cially[
It uses mostly known technology and straightforward engineering[ It is estimated
that the installed thermal power\ that uses geothermal ~uids for direct non!electric
application\ is over 00\274 MWt\ with a total energy production of 20[0901 Kcal[ This
was achieved with a ~ow rate of about 73\999 kg:s at an average load factor of 25)[
These data do not include all uses where the inlet temperature is below 24>C[ This
also excludes _sh farms using warm water at the scale of tens of MWt[ This further
more ignores most of the heat pump installations\ which have a growing market for
space heating and cooling and will become the largest application of geothermal
energy systems[ Such application of heat pumps reduces the energy consumption by
29) when compared with air source heat pumps and more than 59) when compared
with electric or fossil fuel heating and cooling[ There are two parameters\ which are
relevant for the assessment of the geothermal energy for non!electric applications\
namely ] ~uid temperature and ~uid ~ow rate[ As regards the temperature range for
non!electric geothermal energy use\ there are three options ]

Temp range >C

"a# Heating 19Ð79
"b# Drying 79Ð059
"c# Chemical processes 049Ð199

Fluid ~ow rate is strongly dependent on the respective application capacity[ In this
155 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

respect a rough estimate of the power range for the mentioned applications is the
following ]
Power range ðMWtŁ
"a# Heating 09Ð14
"b# Drying 0Ð09
"c# Chemical processes 09Ð099
For each geothermal well temperature\ the respective ~ow rate can be determined
and the number of boreholes is estimated in order to meet the speci_c requirement[
Technologically the geothermal energy application for non!electric use has been
demonstrated in a number of countries[ The available know!how for di}erent appli!
cations has proved its maturity so that\ within the de_ned parameters it can be
considered as a demonstrated entity in the technological assessment of NRSE[
Electricity production from geothermal sources cost is around 3 U[S[ cents:kWh
and for the heat generation the cost is around 1 U[S[ cents:kWh ð68Ł[

5[4[2[ Biomass ener`y resources

Biomass provide about 03) of the world energy or about 14 million barrels of oil
equivalent per day "Mboe:day# ð71\ 72\ 73Ł[ It is the most important source of energy
in developing countries[ In general\ it is rather di.cult to estimate biomass resources
because they are strongly dependent on natural vegetation[ Detailed analysis shows
that if it is assumed 24 GJ:capita the consumption for developing countries\ the land
required per capita with biomass yield 1\ 4 and 09 t:ha:year\ will be 0[9 and 9[1
ha:capita\ respectively[ It is estimated that for biomass use for energy production a
minimum of 4 t:ha:year yield would be needed and it could be used in an area where
local energy consumption is substantially below the average for developing countries[
Commodities such as lighting\ water for people\ water for livestock and irrigation are
of primary interest for the biomass electricity production[ As was shown\ cooking gas
also is estimated for the potential consumer of biomass energy[
In the local resources assessment for biomass energy\ main emphasis is given to the
land needed and yields of biomass production[ The second requirement is strongly
dependent on the geographical location and may substantially vary in di}erent
locations[ For example ] in tropical regions the yield is 05 t:ha: a\ while in subtropical
the yield is 11 t:ha y[ So\ the parameters to be used in the assessment of biomass local
resources are ] local demand for land and yield of biomass production[
Biomass energy production can be obtained through di}erent routes for biomass
conversion processes[ The great versatility of biomass as a feedstock is evident from
the range of wet to dry materials\ which can be converted into various solid\ liquid
and gaseous fuels using biological and thermochemical conversion processes[ Solid
fuels are wood\ charcoal\ crop and forestry residual\ agroindustrial and municipal
wastes and briquettes[ Biomass derived liquids are mainly ethanol and methanol[
Gases are mainly biogases from anaerobic digesters\ gasi_ers!producing gases which
can be used for electricity generation and\ possibly\ coupled to e.cient gas turbines[
There are two main branches of biomass conversion\ i[e[\ bioconversion process
and thermal process\ The bioconversion processes are alcoholic fermentation and
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 156

anaerobic fermentation[ The thermal processes are pyrolysis and combustion of the
biomass[ In this analysis\ priority will be given to those technologies which are
demonstrated in industrial scale and could be used as reference for the technological
assessment of their maturity[ In this respect\ bioconversion technology for the ethanol
production falls into a category of technologies which are presently commercially
available[ For the ethanol production there are three options ]
Capacity ðl:dayŁ
Micro system ³199
Mini system 199Ð19\999
Macro system ×19\999
Among these options\ the mini system is ideal from the technical\ economical\ social
and environmental standpoint[ It appears to be a highly viable solution to the liquid
fuel energy problem\ especially for developing countries[ The second option in biocon!
version technologies is biogas production[ Biogas production is a well!known tech!
nology based on anaerobic fermentation[ There are a vast number of technical systems
used for biogas production[ From this analysis it is omitted the biogas production
facility based on a primitive technology for individual use[
Pyrolysis and combustion processes are based on high temperature conversion
processes with partial or full combustion of biomass fuel[ They are used for charcoal
of heat production\ depending on the process of biomass conversion[ The charcoal
production plant has not proved its maturity and is not yet available as commercial
technology[ Cooking stoves are presently commercially available as a combustion
technology based product[ There are three sizes of the wood fuelled thermal energy
plants in cottage\ medium and large industry processes and enterprises[ The com!
bustion process of biomass is not substantially di}erent from the combustion of
any solid fuel[ This implies that specially designed boilers are used for the biomass
combustion plants[ In this respect there are a variety of boiler designs\ which may
serve this purpose[ In particular there is a great interest for the waste incineration
boiler as energy source[ Figure 12 shows schematic representation of typical biomass
power plant[
It is expected in the medium term\ that at a biomass cost of 1 U[S[ cents:GJ the
electricity produced will reach 09Ð04 U[S[ cents:kWh ð68Ł[

5[4[3[ Wind ener`y resources

The world technically exploitable resources are estimated about 299 TWh:year ð74\
75Ł[ They are rather heterogeneous and strongly dependent on geographical location[
It was recognized that the most economical turbines are those with a rating between
0Ð249 kW[ This means that the wind velocity at the potential location of the wind
power plant should be a minimum of 5[4 m:s with an availability of 14Ð39)[ In this
respect\ the wind energy to be used for electricity production will depend on the single
unit production of the speci_c size but the total installed capacity may be dependent
on local demand or grid capacity[ Grid connected turbines in the form of wind farms
are a forthcoming entity for the wind use for electricity production[ In connection
with this approach the land occupied by wind farms is to be taken into consideration
157 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 12[ Biomass thermal plant[

as local resource of the speci_c location[ It is estimated that 3Ð7 MW could be installed
on 0 km1[
In de_ning the resource conditions for the wind energy utilization the following
parameters are needed ]

"a# average wind velocity at the speci_c location

"b# probability distribution of wind velocity[

Wind turbine technology is available in two arrangements of the rotor\ in relation

to the direction of the wind\ i[e[\

"a# Horizontal!axis wind turbine

"b# Vertical!axis wind turbine[

The horizontal!axis wind turbine in which the direction of the wind is parallel to
the axis has been technologically developed[ At present\ horizontal!axis wind turbine
generators represent approximately 84) of the capacity installed in wind plants[ The
developed wind turbine plants presently in operation and new turbine could be
classi_ed in the following three categories ]

Capacity Diameter ðmŁ

"a# Small!size wind turbines 099 kW ³19
"b# Medium!size wind turbines 099 kWÐ0 MW 19Ð49
"c# Large!size wind turbines ×0 MW ×49
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 158

Small sized wind turbine generators are used in a large number of applications[
Most of these applications are limited to the supply of isolated dwellings ] pumping\
desalination\ and integration with diesel\ storage\ integration with other renewable
energy sources[ In all these applications the storage capacity is an essential factor[
Medium size wind turbine generators are commercially available and grid connec!
ted[ Figure 13 shows an average size wind turbine installed in the European Com!
munity in the period 0875Ð0881[
The con_guration of the plant is conventional and the blades are made of glass _bre
reinforced plastic or laminated wood bound by epoxy resin with a power regulation by
adjusting the pitch of the blades[ The technology of large!size wind turbine generators
is still in the developmental stage[ Prototypes of the capacity up to 3 MW and rotor
diameters up to 099 m are available in some countries[ The obtained results have
con_rmed the substantial feasibility of large wind generators but have also shown
that these machines are still far from being competitive with medium!size machines[
Lowest current electricity cost from wind resources is 5 U[S[ cents:kWh ð68Ł[

Fig[ 13[ Wind turbines[

169 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

5[4[4[ Hydro ener`y resources

It is estimated that the gross theoretical productivity of hydro energy is about 29
million GWh:year with an exploitable production of about 02 million GWh:year ð76\
77Ł[ The present production of the existing plants is of the order of 1[1 million
GWh:year[ The main reason for the large discrepancy between exploitable and present
production is the _nancing capacity of the countries[ The average percentage of hydro
electric energy production is for developed countries 6) and for developing countries
43)[
In many countries\ emphasis is given to the utilization of the small!scale hydropower
potential[ The total capacity of the mini:micro power plant is about 0[4) of the total
installed hydropower potential[ An equal amount of small!scale plant capacity is
currently in the planning stage[
Inventories of suitable hydropower sites have been established for many areas and
a vast catalogue of the exploited sites is available[ The best sites have already been
explored[ There is still a lack of knowledge of the potential of small plant sites[
As for any hydraulic turbine\ the parameters to be known in the assessment of
the speci_c location are the available hydrostatic pressure and the water ~ow rate[
Hydrostatic height is usually constant for mini:micro hydropower plants[ The water
~ow rate is a very sensitive parameter for small hydropower plants[ It varies seasonally
and sometimes daily[ Knowing the respective accumulation\ the minimum ~ow rate
can be established[ In order to obtain reliable data of the water ~ow for a small
turbine hydropower plant\ a rough estimate of the accumulation volume has to be
determined and divided by dry season time[ Small hydropotential plants can be
grouped in three classes ]

Flow rate ðm2:hŁ Height ðmŁ

Small hydro power plant 4Ð0999 09Ð299
Mini hydro power plant 9[4Ð49 1Ð099
Micro hydro power plant 9[1Ð2 1Ð49

The hydro energy conversion technology is a mature technology[ The long!term

development of hydro turbines has reached a state where commercially available
hydro turbines of all sizes can be purchased in accordance with the respective resource
potential[ Large hydro turbine plants have been in operation for decades in a number
of countries[ Demonstration of modern small hydropower plants has been achieved
in many countries[ These achievements have o}ered experience and practical training
to test the value of the small hydro power development to be used in rural and remote
locations[
According to UNIPEDE classi_cation there are three types of hydropower plants ]

Power ðkWŁ
Small power plants ³09\999
Mini power plants ³1999
Micro power plants ³499
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 160

Technically there are three main types of hydro turbines\ depending on the water ~ow
rate and available height
Height ðmŁ
Kaplan turbines 1Ð19
Francis turbines 4Ð199
Pelton turbines 49Ð0999[
In Kaplan turbines\ a mechanical momentum is produced by helical blades formed
to develop a pressure di}erence at the front and rear surface of the blades[
The Francis turbine is designed to uptake the water radial ~ow through _xed blades
into rotating blades on the turbine rotor[
The Pelton turbine is designed in the form of one!row double spoon blades exposed
to the injected water stream[
The diagram shown in Fig[ 14 gives the possibility to select the respective hydro
turbine type in accordance with the available ~ow rate and potential height[ It also

Fig[ 14[ Selection of hydro turbine[

161 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

shows the power of the respective turbine to be obtained for the speci_c parameters
of the respective location[

5[5[ Environment capacity for combustion products

Sustainability is closely related to the environment capacity of our plant[ It has

been shown that natural processes in the biosphere possess the maximum rate of
change[ This rate of change exceeds by orders of magnitude the contemporary rates
of the parameters de_ning the anthropogenic impact to the environment and by four
orders of magnitude\ the mean rate of change of the parameters de_ning the geo!
physical processes ð78Ł[ The concentration and the rate of change of chemicals involved
in the biochemical cycles may be characterized by the changes of organic and inorganic
carbon[ The capacity of biologically active organic and inorganic carbon chemical
species in the environment is equal and ten times larger than their annual primary
production[ Therefore it may be expected that this resource of environment capacity
could be considered in the next ten years\ if only synthesis or decomposition of organic
matter is taking place[ This means that all life processes will end[
The ~uxes of the organic material produced by the synthesis and decomposition
processes in the biosphere are within the accuracy of one hundredth percent of the
anthropogenic ~uctuation resulting in the environment in the geological time scale[
This slow change in the environment in the geological time scale can be compensated
by biological processes leading to the biosphere control of the chemical composition
of the environment[ It is known from the Le Chatelier principles that any external
perturbation of the equilibrium state of a system will induce the process to compensate
for these perturbations[ The compensation of the perturbations in the environment
can be obtained by the synthesis and decomposition of organic processes in the
biosphere[ Since the preservation of the biosphere is a}ecting the biodiversity of our
planet\ it is of primary interest in long!term evolution\ to have the control of the
organic processes in the biosphere[ For this reason\ the preservation of the biosphere
is the main requirement for the global ecological security for the sustainable devel!
opment of our planet[
In order to observe the sustainability of the environment\ the ecological system has
to be monitored and followed with modern methods and techniques[ It is obvious
that an interdisciplinary approach is needed to understand all aspects of the changes
which are introduced by human activities[ In this respect the world energy system is
responsible for the production and emission of a number of chemicals which are
proven to have adverse e}ects on the environment[
The energy use is a major source of emissions[ In the same time it is essential to the
economic and social development for improved quality of life[ There have been
recognized several threats as signals for potential hazard to the environment[ The
emission of air pollutants is usually considered in three groups\ i[e[ ] carbon dioxide\
nitrogen oxide\ and sulphur oxides[
The adverse e}ects of the emission gases are recognized by two processes ] the
greenhouse e}ect\ leading to global warming and depletion of the ozone layer in the
stratosphere[ Global warming is observed by the increase of the mean earth tempera!
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 162

ture[ It can be noticed that recent changes in concentration of CO1 in the atmosphere
are correlated with the changes in the global temperature[ This has led a number of
specialists in the _eld to conclude that the damage is irreversible[ Figure 15 shows the
estimated trend of CO1 production[

5[6[ Miti`ation of nuclear power threat to the environment

Besides the e}ects of energy systems on the environment\ by the emission of ~ue
gases in the atmosphere due to the combustion of organic fuels in power production
plants\ there are possibilities which are imminent to some old power plant systems to
have hazardous e}ects on the environment in a very short time with long lasting
consequences[ Nuclear power plants are very bene_cial in the light of greenhouse
e}ects because they have no exhaust gases ð89Ł[ But it is known that present nuclear
power reactors have the potential to be enormous sources of radioactivity emission[
Besides a}ecting their immediate surroundings\ these hazardous events may lead to
regional and global threats to the environment[ The low probability of this kind of
event has been the only barrier to the disastrous event to spread its consequences to
the global environment[ Examples recently learned are requiring di}erent approach
to face and master potential hazardous events[ Human society is not in a position
to lean its existence on man!made probability actions without possibility for any
correction[
Opponents of nuclear energy outline two points that are crucial for them ] the
possibility of major radiological releases following accidents and the heavy inheritance
of long lasting radioactive waste for future generations[ Obviously\ both these points
are very relevant for the sustainability development of this form of energy[ Let us

Fig[ 15[ OECD Scenario for CO1 emission[

163 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

discuss these separately[ Major accidents may be generated by a reactivity excess

"Chernobyl# ð80Ł\ or by a loss of coolant "Three Mile Island# ð81Ł or by a loss of
~owrate or by anticipated transients without the interruption of the nuclear chain[
Even if the chain reaction during the accident has been broken with a prompt insertion
of control rods\ the radioactivity decay residual heat\ if not adequately removed to a
heat sink\ may cause the melting of the core threatening the integrity of the reactor
vessel[ Against these possible accidental chains a {defence in department| strategy has
been developed with three main lines ] a {preventive line|\ a {protective line| and a
{mitigative| line[ This strategy worked at the Three Mile Island accident with external
releases of few curies of radioactivity\ but did not work at Chernobyl due to its
absence of external containment and many other design de_ciencies[
Present reactor designs for the second line of defence have a majority of {active|
safety systems and a minority of {passive| ones[ An {active| system needs an external
energy supply for intervention and a {passive| one is based on physical laws like
natural convection\ thermal dilation\ stress!strain relations\ etc to operate ð82\ 83Ł[
The present trend of designers is to increase the percentage of passive safety systems
to counteract the possible accidental chains\ proposing the so called {advanced passive|
reactors for a transition period from the _rst to the second generation of nuclear
reactors[ This trend is also associated with a preference of a deterministic approach
instead of the more scienti_c probabilistic one\ for better gaining the acceptability of
common people who often remember the old saying {if it can happen\ it will happen||[
A design of the second generation of nuclear reactors with 099) passive safety
systems already exists\ i[e[\ the MARS "Multi!purpose Advanced Reactor inherently
Safe#[ Figure 16 shows a schematic representation of the MARS reactor ð86Ł[
This reactor has been conceived for small electric networks and for co!generation
purposes\ to increase the overall e.ciency and multiply the possibilities of utilization[
It is modular and assembled in small parts that are totally built and controlled\ with
quality assurance produced in factories[ In this way the construction time is shortened\
the related cost reduced\ and the assembly procedures inverted in order at the end of
useful life\ to guarantee an easy and total decommissioning of the metal pieces[ All
these characteristics meet the requirements of sustainability[
The second point of the fear of nuclear opponents\ related to the long lasting
wastes\ is still opened to interesting solutions[ It is possible to separate the long!life
radionuclides "actinides# from other radioactive _ssion products[ The actinides may
be recycled in {ad hoc| reactors and converted in the radionuclides of the "i[e[\ short
life# radionuclides[ The radionuclides with long lasting lifetime can be converted into
short life isotopes by their mutation through nuclear reactions in high ~ux nuclear
reactors or in a coupled device of subcritical nuclear reactor in which a beam of high
energy particles are injected by means of a powerful accelerator[ The total amount of
long lasting wastes will be substantially reduced so as to be conveniently placed in
suitable geological formations\ which remained dry and intact for millions of years in
the past[
A device of this type has been recently proposed by Rubbia and co!workers ð84Ł\
with a subcritical fast reactor cooled by lead in natural convection\ fed by spallation
neutrons generated by a beam of protons accelerated until 0 GeV[ Figure 17 shows a
N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 164

Fig[ 16[ Multi!purpose advanced reactor inherently safe "MARS#[

165 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

Fig[ 17[ Energy ampli_er[

 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 166

schematic representation of the conceptual design of this fast neutron operated high
power energy ampli_er[

6[ Energy education and sustainability

The contemporary development of information technology has substantially con!

tributed to the promotion of new means of dissemination of information and its
multiple use[ The set of information itself is a value which may be taken as the entity
representing the individual system[ The thermodynamic approach to the information
has de_ned it as the state variable which de_nes the system[ It has been shown that
the information is the extensive variable of the system and is equal to the logarithm
of the number of information[ The similarity of the information and entropy of the
physical system has led to the use of {negentropy| as the parameter which describes
the respective system[ With the development of the information theory and the
respective concept of information system\ it becomes obvious that the socio!economic
system can be described with the approach used in thermodynamics[ It was recognized
that the socio!economic system goes through changes from one state to other states
similarly as in thermodynamic system[ This has led to the de_nition of socio!economic
system including information as the extensive parameter of system\ de_ned as the
negentropy[ The information may have di}erent forms and the knowledge is one of
them generated by the scienti_c and technological research[ The knowledge is trans!
ferred by the education system[ In this respect the scienti_c and technological devel!
opment from one side and education system from the other side can contribute to the
information exchange in any socio!economic system[ So\ we can consider socio!
economic changes in the two processes\ i[e[\ the generation of information by scienti_c
and technological development and the exchange of information by the education
process[ In this case\ to have the harmony in the global system\ between the use of its
resources and at the same time to take care of the preservation of ð85\ 86Ł environment\
it is of paramount interest to the development of science and technology and the
education process in achieving this goal[ Also\ we can say that the sustainable devel!
opment of our civilization will require besides using immediate action to preserve
resources and environment capacity for future generations to devote a substantial
attention to the science and technology development as well as the development of
the education process[ The science and technology development has to be focused on
these problems which will a}ect the consumption of available material resources and
environment capacity[
In the development of the sustainability issue there are three fundamental dimen!
sions which have to be taken into consideration in the assessment ] knowledge dis!
semination\ science and technology development and exploration of new resources[
The knowledge dissemination implies the development of the respective education
system which will meet increasing demand for continuous refreshment of the knowl!
edge in order to follow the contemporary development of new technologies[
Life!long education is presently recognized as a continuous learning activity to
follow the needs of modern society ð85\ 86Ł[ It can be seen as the education system
167 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

with di}erent levels in accordance with the aim\ need and individual perception
capability[ In particular\ the aim of lifelong education is diversi_ed by speci_c require!
ments of the professional scope[ These programs of lifelong education could be aimed
to increase the fundamental knowledge of the speci_c subject or to the design or
technical operation guidance for the respective equipment\ system or structure[ The
need for lifelong education may come from the individual desire for the increase of
his:her competency and also can be the result of the organized UniversityÐIndustry
programs for the upgrading of the workforce ð87\ 88Ł[ Finally\ the individual per!
ception capacity may require additional help in adapting himself:herself to the normal
working condition[
There are di}erent educational schemes which are suitable for an organized
approach to lifelong education[ Distance learning has been introduced in the edu!
cation system as the associate system to bridge di.culties arising from the lack of
space for all those wishing to enter the higher education institution[ In this respect\
distance learning education methodology has proved advantageous which is of interest
to be exposed to the public at large in order to be evaluated through its application
in lifelong education[ In particular\ it becomes relevant to take advantage of modern
communication systems\ which are o}ering great possibilities to convey information
to any distance\ as desired[ If the information to be transferred is adequately organized
and structured\ the messages will become the knowledge needed to be adapted for the
learners[ For this reason\ education and training\ coupled with the recent development
in telematics\ is opening a new venue for the revolutionary changes in the higher
education system[
It is also recognized that the present education system is too rigid to accommodate
new challenges of the lifelong education system ð099Ł[ To assimilate the distance
learning education with a modern information technology and its prominence at this
time\ it is important to realize the changes in relationships between higher education
and society[ It is obvious that the present status of the higher education system will
no longer enjoy a monopoly on the provision of learning service[ Its eminence is
blurred by the increasing competency of other institutions penetrating in the education
service[ Distance learning education with multimedia background has risen to pro!
minence because it has the potential to address the social changes imminent to modern
society as an alternative education system[ The new distance learning systems will
accommodate the time and space of the part!time learner\ giving the opportunity to
those outside metropolitan areas without the prominent education institution to have
access to high quality education and to be exposed to outstanding professional
specialists in the speci_c _eld[
In a number of countries it was proved that the distance learning methodology is
a powerful tool for the dissemination of knowledge of di}erent levels[ The devel!
opment of an in!house training and education capacity by business and other agencies
not only signals the rise of importance for the changes of training and education
methodology\ but also re~ects a dissatisfaction with the ability of mainline public
institutions to provide adaptive\ ~exible relevant and problem centred approaches to
training and education*at a reasonable cost[
Particular attention has to be devoted to postgraduate education\ which is socially
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 168

independent and can be organized without the personal interaction between the
teacher and the learners and learners among themselves\ as it is necessary for under!
graduate education[ In the context of the need for e.cient and appropriate timing of
postgraduate education\ the demand and perspective of multimedia distance learning
education is of high expectation[ Technology oriented postgraduate education pro!
grams will be linked into regional\ national and international networks and will be a
great possibility for the integrated education environment\ leading to the demo!
cratization of the world education system[ The postgraduate engineering education
in many contemporary education programs is printed to the continuation of the
undergraduate education with emphasis on the fundamental knowledge to be learned
or gives the deep knowledge related to speci_c systems\ objects or entities[ This
subdivision will o}er two types of postgraduate education programs\ namely\ the
subject oriented and the object oriented postgraduate education programs[
The modern development of information technology is o}ering a challenge for its
use in the education process[ The multimedia information telematics is one of the new
achievements\ which is opening a possibility to use the distance learning methodology
for postgraduate education[ A limited number of quali_ed teachers for the speci_c
subjects of modern technology is one of the limitations for the knowledge dis!
semination in the _eld\ needed for the promotion of economic development The
scarcity of competent teachers in specialized disciplines can be adequately subsidized
by the respective use of distance learning methodology\ which will allow the exposition
of the valuable professionals in the _eld to larger audiences[ If consideration is given
to the future need for postgraduate education\ it becomes obvious that a new lifelong
education system is needed to meet the constantly increasing demands for higher
education in di}erent engineering _elds[

6[0[ Ener`y and environment en`ineerin` education

The energy and environment problems in the contemporary world are the chal!
lenging engineering _elds requiring the constant increase of our attention in order
to meet the increasing demands and also face the potential adverse e}ects on the
environment[ In this _eld\ a new strategy is in development which compulsorily
requires the respective e.ciency of the systems\ increases the global energy system
structure use of new and renewable energy sources\ meets a new social aspect of the
energy and environment[ Also it will better understand in depth all consequences
which possibly promote global changes in the environment[ These requirements could
only be met with the respective education systems which will be able to accommodate
the needs for an increasing number of specialists with a high level of education\
capable of understanding in depth all energy and environment problems ð090Ł[ It is
becoming obvious that the present energy and environment engineering education
system is facing di.culties in many countries to meet forthcoming demands[ Even
more\ in a number of developing countries this problem is open and will require
outside assistance to be overcome[ In this respect\ the future energy development
strategy has to include the development of the respective energy education system\
which will ensure its promotion and practical application[ It is of paramount interest
179 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

to the society to combine its e}ort in the economic development with the change in
the structure of the education system[
Engineering education is closely linked with economic development ð091Ł[ The
promotion of new technology advances by the use of information technology is
important to the further development of the engineering education ð092Ł[ In particular\
the increase of the engineering knowledge body leading to the larger number of the
engineering specializations is only the tip of the iceberg of the problem in engineering
education[ In this respect\ energy and environment engineering education is of primary
interest for modern society[ For this reason\ it is needed to look for the new achieve!
ments in the education methodological developments[ Particular emphasis in this
respect has to be given to postgraduate education in order to ensure the bene_ts
coming from the development in the di}erent _elds of science and technology[
E.ciency\ reliability\ new energy sources and environment are among those issues
of energy engineering which are to be recognized as the main driving forces to increase
the demand from the energy systems[ The e.ciency of the energy systems has been
recognised since Sady Carnot de_ned the Second Law approach for its assessment[
In this respect\ it has become important to understand the quality of energy in order
to obtain the maximum from a potential source of energy[ Exergy analysis has become
a powerful tool for the engineering evaluation of the respective energy system[ The
Second Law e.ciency assessment requires knowledge about principles of exergy
analysis\ technical characteristics of the respective system and equipment[ The correct
e.ciency evaluation of the system will also require a social aspect of the energy cost\
which includes the environment interaction with the respective energy system[
The reliability and safety of the energy systems have become main issues of the
adverse e}ects which might have regional\ national and global e}ects[ It is a complex
issue which requires in!depth knowledge about the system ] its functionality and
limitations[ This knowledge is required at di}erent stages of the energy system devel!
opment including design\ construction and operation[ The risk evaluation is a speci_c
issue\ which has to be introduced at each stage of the development[ Learning about
reliability and safety aspects of the energy system requires a high degree of sophis!
tication of all the subjects to be taught in the normal engineering curriculum[ It is
known that any malfunction of the energy system leading to the degradation of
reliability and the decreasing safety margins of the system is a result of complex
processes\ which are time dependent and interrelated[ This implies that in order to
gain the knowledge needed for the assessment of reliability and safety of the energy
system\ the engineering education programs should include time and space dependent
processes with the respective mathematical and numerical tools to be used in modern
computer systems[
New and renewable energy sources are based on modern achievements in physics
and chemistry[ So\ it is important to the new energy sources assessment and evaluation
to have respective knowledge in these _elds[ In particular\ the engineering aspect of
the new and renewable energy sources should be emphasized in order to introduce
them into the strategy of the energy system development[ It is obvious that the energy
engineering education has to re~ect the needs for the competitive evaluation of these
sources of energy[ For this reason it is necessary to design energy education programs\
 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175 170

taking into consideration the need for society to introduce the new energy sources in
everyday life[
The increased environmental concern in modern society has led to the inter!
nationally recognized requirements for higher attention to the adverse e}ects of
human activity towards its surrounding[ In this respect\ the energy!producing systems
have been called for special attention to introduce the di}erent kinds of measures to
prevent consequences leading to the degradation of the environment[ In view of the
impact of energy systems on the environment\ increased emphasis is given to the
assessment of such impacts at the stage of energy programming and the project design
in order to take into consideration environment problems caused by the energy
production\ transport and consumption[ Besides updating traditional curriculums in
energy engineering with the environment aspect of the problem\ it is necessary to
include subjects such as biology and social sciences in energy engineering curriculums[
It has to be emphasized that the engineering education aspect has to be developed
and introduced in the energy programs[

6[1[ Lifelon` education in ener`y en`ineerin`

It is known that the need for upgrading professional capability of the manpower
in engineering is the result of constantly growing demand for the increase of e.ciency
of technical systems and increasing awareness of the environment problems ð093\ 094Ł[
The organized e}ort is streamed to meet challenges for the bene_ts obtained with a
new approach to future technical systems and their incorporation in the human
environment without adverse e}ects[ One of the lines in this e}ort is a new lifelong
education system[ In order to meet this requirement the distance learning education
methodology o}ers the advantages proved to be cost e}ective and revealing new
features to be enjoyed as the incentive challenge for the learners[ In particular\ it
seems appropriate to focus the attention to advantages which are of common interest
for the public at large[ In this respect\ the distance learning with multimedia is
proved to be easily accommodated for the on!job training for the IndustryÐUniversity
cooperation[ The education programs could be designed for speci_c needs and adapted
in the on!job environment with limited teaching assistance[
As a milestone of further progress in the process of large!scale extension of the
application of scienti_c and technical achievements\ university and other educational
institutions should attach importance to the development of postgraduate engineering
education closely related to the technology research centers[ In this respect\ the
distance learning with the multimedia education used in an appropriate environment
can prove to be cost!e}ective[ The multi!use of teaching material with a limited
number of professionals in many cases has shown to be adaptive to the learner|s
demands and wishes[ As most of the postgraduate education programs are closely
linked to the speci_c technology developments\ it is of great interest to the design
respective courses having in mind the customer interest and local environment[ The
energy engineering postgraduate courses in this respect has to be aimed to meet the
recent strategic demands in the modern development of the global energy system[ The
variety of options for the speci_c programs will require a polyvalent approach in the
171 N[H[ Af`an et al[:Renewable and Sustainable Ener`y Reviews 1 "0887# 124Ð175

design of the respective postgraduate energy engineering program ð095Ł[ It will have
to accommodate the di}erent discipline!oriented modules\ to be used in the con!
struction of multiple options as required by the individual learners[ With this
approach\ it will be possible to launch the individual education programs\ which are
to be custom!made to the speci_c needs of the individual learners or their employers[
This will lead us to take full advantage of the multimedia environment and if connected
with the recent development in telematics may lead to the formation of a global
engineering education system[ This means that future learners will have the oppor!
tunity to connect themselves to any available education programs in the world network
designed as a part of the global system[ In this respect\ lifelong engineering education
is at the beginning of network formation\ which will\ similarly to the existing Internet
or similar global network\ o}er the education commodity to any individual wishing
to increase his:her competency in the speci_c _eld of interest[

7[ Conclusions

It is shown that present energy strategy requires adaptation of new criteria to be

followed in the future energy system development[ No doubt there is a link between
energy consumption and environment capacity reduction[ This is an alarming sign\
which recently has become the leading theme for our near and distant future[ Together
with social aspects of future economic development\ it is of paramount interest for
modern society to implement the world leaders adopted resolutions before it is too
late[
Modern engineering science has to be oriented to those areas which may directly
assist in our future energy planning[ In this respect\ it is a demanding need that our
attention be oriented to the global aspect of energy development[ Modern technologies
will help to adopt essential principles of sustainable energy development[ With the
appropriate renewable energy resources introduction in our energy future and relief
of nuclear energy threat\ it will be possible to comply with the main principles to be
adopted in the sustainable energy strategy[
In order to promote sustainable energy development\ the respective education
system is required[ It is recognized that the present energy education system cannot
meet future demand for knowledge dissemination[ It is shown that the potential
option for the future education system is distance learning with multimedia telematic
systems[

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